Any introductory course starts out with a brief history of the subject, and this article will be no different. According to a technical report of the International Nickel Co., Ltd., Joseph Shore applied for a patent for nickel plating in 1840; however, it was not until 1842, in Frankfort, Germany, that Böttger succeeded in depositing nickel from a solution of nickel ammonium sulfate.1
One of the first United States patents was granted to Adams in 1869 for a solution of nickel ammonium chloride, and in 1878 Weston obtained a patent for the addition of boric acid to nickel plating solutions. Several patents were granted for various bath improvements, until O.P. Watts developed a rapid nickel plating bath in 1916. This nickel plating bath is still predominantly used throughout the world and was the first to make it possible to exceed current densities of 5 asf by a factor of 10.
Nickel plating solutions based on sulfamate solutions were introduced by Cambi and Piontelli in a report for the Lombard Institute of Sciences.
Types of Nickel Plating Solutions
Sulfate Solutions. The most common nickel plating bath is the sulfate bath known as the Watts bath. Typical composition and operating conditions are shown in Table I. The large amount of nickel sulfate provides the necessary concentration of nickel ions. Nickel chloride improves anode corrosion and increases conductivity. Boric acid is used as a weak buffer to maintain pH.
The Watts bath has four major advantages: 1) Simple and easy to use; 2) Easily available in high purity grades and relatively inexpensive; 3) Less aggressive to plant equipment than nickel chloride solutions; and 4) Deposits plated from these solutions are less brittle and show lower internal stress than those plated from nickel chloride electrolytes.
High Chloride Solutions. Chloride baths have an advantage over sulfate baths in deposition speed; not necessarily in current density, but in improved current distribution.
All-Chloride Solutions. The advantages of all-chloride nickel plating solutions include the following: 1) Low voltage; 2) Good polishing characteristics; 3) Heavy coatings can be deposited; 4) Low pitting; 5) Improved cathode efficiency; and 6) No need to cool the plating solution. See Table I for composition and operating parameters.
However, there are disadvantages to this bath as well: 1) Highly corrosive; 2) Nickel chloride is sometimes less pure than nickel sulfate (particularly important in bright nickel plating); 3) Mechanical properties of the deposit are not as good as those from the Watts bath.
Fluoborate Solutions. In nickel fluorborate baths, the electrolyte is maintained at a pH of 2.0-3.5 using fluoroboric acid. Metal content is maintained at up to 120 g/liter of nickel, which is much higher than in a Watt's bath. Because of this, higher current densities are necessary.
Nickel coatings deposited from this type of bath have properties similar to those deposited from Watt's baths; however, these coatings are usually specified for heavy nickel applications and electroforming.
Anode dissolution in a nickel fluoborate bath not containing chloride is better than in a nickel sulfate solution with nickel chloride.
Disadvantages of fluoborate baths include the following: 1) High cost of chemicals; 2) Throwing power less than that of sulfate solutions.
Sulfamate Solutions. This bath is based on the nickel salt of sulfamic acid, and the pH is adjusted using sulfamic acid, nickel oxide or carbonate. When intensive agitation is used in solutions with a high nickel concentration, current densities up to 500 asf can be achieved.
Nickel coatings from this type of bath usually have very low stress values and high elongations. Another advantage is that it is possible to operate the sulfamate bath without difficulties related to anode dissolution at low chloride levels or even without chloride. The principle advantage of this bath is that it can be operated at nickel concentrations of 180-200 g/liter. This allows for the use of high current densities without losing the properties of the coating.
Types of Nickel Plating
Bright Nickel. Bright nickel plating baths are used in the automotive, electrical, appliance, hardware and other industries. Its most important function is as an undercoating for chromium plating, helping finishers achieve a smooth bright finish as well as a significant amount of corrosion protection.
Table I—Composition and Operating Parameters
Nickel Plating Baths
Composition
Watts
High Chloride
All Chloride
Fluoborate
Sulfamate*
Nickel Sulfate (oz/gal)NiSO4 • 6H2O
20-40
32
Nickel Chloride (oz/gal)NiCL2 • 6H2O
6-12
12
32
0-3
Nickel Fluoborate (oz/gal)ni(SO3HN3)2 • 4H2O
45-60
Boric Acid (oz/gal)
4-6
4-5
4
4
4-6
pH Range
2.0-5.2
2.0-2.5
0.9-1.1
3.0-4.5
3.5-4.5
Temperature (F)
90-160
100-160
100-145
90-160
90-140
Current Density (asf)
10-60
10-60
50-100
50-100
5-260
Anodes
Nickel, bagged, cast rolled, depolarized or carbon type
Filtration
Continuous, turnover once every 1-4 hr
*This bath is used in electroforming as well as situations where a low stress/no stress deposit is needed. It allows you to deposit a lot of nickel in a shorter period of time. The sulfamate nickel is more expensive than other types of nickel baths.
Bright nickel plating baths use combinations of organic agents to achieve bright nickel deposits. There are two classes of these organic additives. The first class is the aromatic sulfonic acids, sulfonamides and sulfonamides that contain the functional group =C-SO-2. Saccharin is a widely used example of this type of brightener. Nickel deposits plated using these additives are mirror bright initially; however as the nickel builds, brightness diminishes. This first class of brighteners incorporates sulfur into the bright nickel, reducing corrosion resistance.
Brighteners in the second class, also called levelers, have inorganic metal ions and organic compounds. These may include butynediol, coumarin, ethylene cyanohydrin and formaldehyde. These are used as leveling agents because they increase surface smoothness as the nickel deposit thickness increases.
Semi-Bright Nickel. At first, coumarin was used to obtain a high-leveling, ductile, semi-bright and sulfur-free nickel deposit from a Watts nickel bath. However, coumarin-free solutions are now available. A semi-bright nickel finish is semi-lustrous, as the name implies. However, it was specifically developed for its ease of polishing and buffing. Or, if subsequently bright nickel plated, buffing can be eliminated. Brightness and smoothness are dependent on operating conditions (see Table I).
The reason semi-bright nickel finishes are so easily buffed and/or polished is that the structure of the deposit is columnar, whereas the structure of a bright nickel finish is plate-like (lamellar). However, the structure can be changed with additives, a change in pH, current density or even an increase in solution agitation. This is not a problem unless it affects properties such as internal stress.
Internal stress can be compressive or tensile. Compressive stress is where the deposit expands to relieve the stress. Tensile stress is where the deposit contracts. Highly compressed deposits can result in blisters, warping or cause the deposit to separate from the substrate. Deposits with high tensile stress can also cause warping in addition to cracking and reduction in fatigue strength.
Watts baths and high-chloride type baths can produce high tensile stress. During bright-nickel plating, stress-reducing additives are used, but these codeposit sulfur materials that affect the physical and/or engineering properties of the deposit. Saccharin is often used as a stress reducing agent. Nickel sulfamate baths can deposit pure low-stressed finishes without using additives.
Other Types of Nickel. To obtain other types of finishes such as satin nickel, organic additives are used and deposition conditions are altered. Deposits from a Watts bath are usually 7-10 mm thick, with the appearance dependent on the temperature and/or pH. At higher temperatures and a pH of 4.5-5.0, nickel deposits are matte. At 122F and a pH of 2.5-3.5, deposits are bright.
Black nickel plating is lustrous and has a black or dark gray color. Plating is done with little or no agitation. Occasionally it is necessary to remove hydrogen gas (bubbles) from the part's surface using wetting agents. The pH of the bath ranges from 5-6, and the temperature varies from ambient to 140F. Current density remains at approximately 0.5 A/dm2.
The coatings average 2 mm thick and corrosion resistance is limited, therefore they are usually lacquered or coated with oil or grease. If the black nickel must have good corrosion resistance, an undercoating such as bright or dull nickel, zinc or cadmium is necessary.
Barrel Nickel Plating
Barrel plating solutions are relatively similar to rack plating solutions; however, operating conditions may differ, although not radically. The pH is usually maintained at about 4, unless plating zinc diecasting, in which case a pH higher than 4 may be necessary. However, anode corrosion is better at a lower pH, and anode area is limited. The anode area should be as large as possible to avoid the liberation of oxygen and chlorine.
Temperatures can vary for barrel nickel plating from 86-104F for some solutions and 104-140F for others. Current density can also vary. For a typical barrel, approximately 24-32 inches long and 16 inches in diameter, the load is 300-600 amps per load or between 1-1.5 A/dm2. Other considerations are the barrel loading, surface area and coating thickness.
There are some special considerations for barrel plating: 1) Parts must be able to move about freely in the barrel; 2) Precise surface preparation is essential, including thorough rinsing; and 3) When the electrolytes are used to full capacity, low-current-density treatment should be used continuously.
Properties of Nickel Deposits
Thickness. Corrosion resistance is often intimately related to the thickness of the coating; however, the functional requirements of the coating are also important. Micrometer readings are used most often to determine coating thickness. ASTM standard B487 describes a method of measuring coating thickness based on metallographic examination of cross-section of the plated part. Other ASTM tests include ASTM B530 and ASTM B504. The ASTM web site (www.astm.org) has information on the tests mentioned in this article.
Hardness. Certain addition agents, such as saccharin or napththalene sulfonic acid, can increase the hardness of a nickel deposit. Wetting agents may also increase hardness. Nickel deposits plated from Watts nickel baths, sulfamate or fluoborate baths can rise to 650 HV (HV is Vickers hardness). Heavy nickel baths produce deposits with hardnesses between 250-350 HV.
Hardness is not only a result of addition agents but is also affected by the plating bath composition, temperature, current density and other operating conditions. ASTM B578 is a test for the microhardness of plated coatings.
Ductility. Ductility can be measured using two ASTM test procedures, B489 and B490. Ductility can also be measured using a tensile testing machine; however this test is specific to measuring plated thin foils.
Information about other properties such as adhesion, brittleness, dull deposits and burning are covered in PFOnline's Nickel Troubleshooting Guide which is this month's online exclusive (for the url see the contents page).
This primer by no means even scratches the surface of nickel plating. There have been volumes written on the subject. It is hoped that this article will give you some information on the basics and some reference materials as to where you can go to find more information about the process.
Wednesday, July 8, 2009
Thursday, June 18, 2009
Betting It All on Plating Automation
Two years ago, National Plating Corp.was a small plater in the highly competitive Cleveland area when young Mark Palik, National's third-generation owner, made an all or nothing multimillion-dollar bet on a new highly automated zinc-chloride barrel line. He wanted to take on the area's high-volume platers in the automotive and fastener fields and their rock-bottom prices.
Mark's grandfather, John Palik, started the company in 1946 as a copper, nickel and chromium plating shop. He was aggressive, building the company up to a peak of 60 employees by the late '50s. Active in the industry, John won national awards and was the first president of the National Association of Metal Finishers. He retired in 1970, selling the company to his son Dave who was active in the business. Unlike John, however, Dave was more cautious and decided to downsize the business. He traded off the semi-automatic chromium line for a 10-station cyanide-based zinc barrel line. He was quite content being a much smaller shop with steady, profitable work and fewer frustrations.
By the mid '80s, things were changing. The plating industry was challenged by EPA requirements and the need for expensive waste treatment improvements. Dave Palik had had enough. He did not want to adjust to all these changes; he'd rather sell the company and find a quieter life-style.
When Mark, then a 20-year-old photographer working in California, heard about his father's desire to get out of the business, he decided to give it a shot. "I told him I would come back here and try it for at least the summer," he laughed, "and here I am, eleven years later!"
NATIONAL PLATING'S big line can turn out 20,000 lbs of parts in an hour.
When Mark took over National Plating in 1987, it was time to either commit to big improvements or risk losing the business. For the Palik family, each generation had reacted to its times, applied its own philosophy and been successful in its own way.
It was a small shop at that time, with about eight employees. Mark's plan was clear: respond to this challenge and clean up its act. He immediately began to expand the business and within two years had tripled sales. Today, it employs 40 people.
How did he finance these early expansions? "Hard work," is his quick answer. "We've always had handy people and our own welders. It is not rocket science to build a plating tank. We even built a few of our own barrels at one time. Building your own equipment is a distinct advantage, not something many can do."
The big leap forward. The decision to launch the new line was made two years ago. Business was good, and Mark again wanted to expand. Cost efficiency was the key philosophy behind this major move. "Where prices are going in this industry, it doesn't make sense for anybody with conventional equipment to tackle large volumes of work. We needed to build a line that was so productive and cost efficient that I could run work at the going rate."
MARK PALIK checks the coating thickness using equipment capable of measurements within approximately 1%.
Like the movie Field of Dreams, Mark's theory was "If you build it, they will come." When people asked, however, if he had lined up work for this new line, he had to admit that he had not, but he did have two or three big accounts in mind. "There was no doubt in my mind that when we showed them we could turn massive volumes quickly with better QC and SPC levels than they were getting, they would at least give us an opportunity to be a second source," he explained. "That's all we would need to earn more of their business."
Has it worked? "Yes," he replied with a grin. "Although it was not as easyas I thought it would be." He knew that even with the ups and downs of demand in this business, any plater doing automotive work would have to meet that industry's tough ISO and QS 9000 requirements with the QC and SPC his company had in place.
He was right. This has helped attract new business. "Since we jumped on the large-volume bandwagon, our volume has increased over 300%, sales have doubled, and we were just getting started! We are running the line at about three-fourths capacity now and expect to hit full capacity by year's end. I do not know of any barrel plating line that is more productive."
Because the company did much of the work itself, Mr. Palik pointed out that the investment was probably half what it would have cost had it been engineered and installed by an outside firm. "Although there's no other U.S. barrel line quite like this," he said. "I visited a similarly automated one in Canada that cost more than $4 million."
Another philosophy Mark Palik has always employed is no third shift, even at the busiest of times. He feels that operating around the clock seven days a week cannot be done without sacrificing quality. "We run two shifts five days a week," he said, "eight to twelve hours per shift, depending on how busy we are, and always have available capacity. If we get too busy while running two twelves, we'll just run a Saturday and get caught up."
Features of the new line. Here are the key features that make this new zinc plating line unique and efficient:
Rectification: The line has individual rectification for each plating station. "This gives us the versatility to plate one barrel at 1,000 amps," Mr. Palik explained, "and follow it up with a 100-amp load, thus tailoring plating current to the surface area of the part in each barrel."
Stainless tanks: Another major commitment was to use only stainless steel tanks rather than lined steel tanks. A major initial expense, yes, but one that pays off in reliability and ease of maintenance in the end.
Automatic hoists: Four automatic high-speed hoists were designed and built in-house. They cost about $20,000 each to build, which was a big savings over having to buy them outside.
Barrel automation: With automated barrel handling, the results are consistent cycle to cycle, not varying shift to shift. "Our chromates are constantly on conductivity meters with pumps automatically controlling concentration," he noted. "It is the same every time: concentration, submersion time and end result. On a manual line, you can have an operator counting out the submersion timing and being either faster or slower than the guy on the next shift." The barrels have automatic locking doors. Operators load the barrel and when it turns in one direction, the door locks closed. After processing, turn the barrel the other way, and the door opens and the barrel dumps. This is much faster than standard barrel doors that require manually removing four or five clamps from the door each time you load and unload.
Solution processing: Maintaining bath chemistry is the key to quality control, and here Mr. Palik relies on statistical process control methods and constant monitoring, including daily testing of metal content and chemistry levels. "We use SPC to constantly maintain all chemistry levels," he said. "Everything is charted on the computer. If we got some blistering on a part we ran two months ago, for example, we can go back to our SPC charts and see exactly where our chemistry levels were the day we ran it." Pavco Inc., Cleveland, Ohio, is the main proprietary chemical supplier, and has been instrumental in providing technical support. "Once a week the supplier does an analysis of basically everything we do daily, including a check on the proprietary chemicals, which we cannot do. It can also troubleshoot any problems with its much more sophisticated analytical equipment."
BELT DRYER handles parts carefully.
Thickness testing: Three on-line eddy current testers monitor coating thickness within approximately 5%. This is supplemented by an X-ray test machine that can measure coatings to within approximately 1% on the more complicated surfaces, like parts with threads.
Ventilation: Ventilation is another area of emphasis. "We've spent a lot on ventilation," Mr. Palik recalled. "It is not just having adequate exhausting, you also need to be bringing in more fresh air than you exhaust. We have a big air-makeup unit on our roof, pumping air in and pumping it out. That was a code requirement for us to move into this building. Another was that not only did our chemical storage rooms have to be sprinkled with fire doors, but everything in the building had to be fully sprinkled."
Drying: Here Mr. Palik committed to a belt dryer for his new plating line. Why? "Easier part handling and more pounds per hour than a centrifugal dryer," he replied. "It is less labor intensive and less chance of any violent motion harming the parts. In centrifugal dryers, sometimes parts can kick out, rattle around and get distorted."
Baking and post treatment: Post treatments offered include all the usual plus black chromate, olive drab, bright dipping, lacquer and wax. The new line also offers full capacity baking to help relieve any hydrogen embrittlement of heat-treated parts induced in the plating process.
Help up the learning curve. "You can be two lifetimes in this business and still get stumped. When we do, our supplier can come in with sophisticated equipment, tear apart the plating chemistry and find out what is in the bath that is causing an unusual problem. With our own lab, we are pretty self-sufficient for the day-to-day things, but every once in a while oil or something a new customer is using can cause problems. Many companies are cutting costs by using recycled oil in their manufacturing process. We have probably the best cleaning system around, but can still get something crazy in there now and then. You can bandage many problems by simply throwing in brighteners, but we would much rather analyze the problem and correct it."
AUTOMATED barrels move down the zinc plating line.
Those plating shops serving the auto industry are facing a requirement that all Tier Two suppliers be ISO 9000 registered by year's end. Mark Palik sees that, too, as an opportunity. "We plan to be registered by then," he says. "We're half-way there already."
Although plating demand in the Cleveland area has slacked off since he committed to this new line, Mr. Palik remains optimistic. Once he convinced a few big-volume customers that his small shop was moving into the big time, it didn't take long for the news to spread. "People started talking about the line and the job we were doing for them," he recalled. "Soon people I had called months ago started calling back. Our reputation started paying off."
source http://www.pfonline.com/articles/129804.html
Mark's grandfather, John Palik, started the company in 1946 as a copper, nickel and chromium plating shop. He was aggressive, building the company up to a peak of 60 employees by the late '50s. Active in the industry, John won national awards and was the first president of the National Association of Metal Finishers. He retired in 1970, selling the company to his son Dave who was active in the business. Unlike John, however, Dave was more cautious and decided to downsize the business. He traded off the semi-automatic chromium line for a 10-station cyanide-based zinc barrel line. He was quite content being a much smaller shop with steady, profitable work and fewer frustrations.
By the mid '80s, things were changing. The plating industry was challenged by EPA requirements and the need for expensive waste treatment improvements. Dave Palik had had enough. He did not want to adjust to all these changes; he'd rather sell the company and find a quieter life-style.
When Mark, then a 20-year-old photographer working in California, heard about his father's desire to get out of the business, he decided to give it a shot. "I told him I would come back here and try it for at least the summer," he laughed, "and here I am, eleven years later!"
NATIONAL PLATING'S big line can turn out 20,000 lbs of parts in an hour.
When Mark took over National Plating in 1987, it was time to either commit to big improvements or risk losing the business. For the Palik family, each generation had reacted to its times, applied its own philosophy and been successful in its own way.
It was a small shop at that time, with about eight employees. Mark's plan was clear: respond to this challenge and clean up its act. He immediately began to expand the business and within two years had tripled sales. Today, it employs 40 people.
How did he finance these early expansions? "Hard work," is his quick answer. "We've always had handy people and our own welders. It is not rocket science to build a plating tank. We even built a few of our own barrels at one time. Building your own equipment is a distinct advantage, not something many can do."
The big leap forward. The decision to launch the new line was made two years ago. Business was good, and Mark again wanted to expand. Cost efficiency was the key philosophy behind this major move. "Where prices are going in this industry, it doesn't make sense for anybody with conventional equipment to tackle large volumes of work. We needed to build a line that was so productive and cost efficient that I could run work at the going rate."
MARK PALIK checks the coating thickness using equipment capable of measurements within approximately 1%.
Like the movie Field of Dreams, Mark's theory was "If you build it, they will come." When people asked, however, if he had lined up work for this new line, he had to admit that he had not, but he did have two or three big accounts in mind. "There was no doubt in my mind that when we showed them we could turn massive volumes quickly with better QC and SPC levels than they were getting, they would at least give us an opportunity to be a second source," he explained. "That's all we would need to earn more of their business."
Has it worked? "Yes," he replied with a grin. "Although it was not as easyas I thought it would be." He knew that even with the ups and downs of demand in this business, any plater doing automotive work would have to meet that industry's tough ISO and QS 9000 requirements with the QC and SPC his company had in place.
He was right. This has helped attract new business. "Since we jumped on the large-volume bandwagon, our volume has increased over 300%, sales have doubled, and we were just getting started! We are running the line at about three-fourths capacity now and expect to hit full capacity by year's end. I do not know of any barrel plating line that is more productive."
Because the company did much of the work itself, Mr. Palik pointed out that the investment was probably half what it would have cost had it been engineered and installed by an outside firm. "Although there's no other U.S. barrel line quite like this," he said. "I visited a similarly automated one in Canada that cost more than $4 million."
Another philosophy Mark Palik has always employed is no third shift, even at the busiest of times. He feels that operating around the clock seven days a week cannot be done without sacrificing quality. "We run two shifts five days a week," he said, "eight to twelve hours per shift, depending on how busy we are, and always have available capacity. If we get too busy while running two twelves, we'll just run a Saturday and get caught up."
Features of the new line. Here are the key features that make this new zinc plating line unique and efficient:
Rectification: The line has individual rectification for each plating station. "This gives us the versatility to plate one barrel at 1,000 amps," Mr. Palik explained, "and follow it up with a 100-amp load, thus tailoring plating current to the surface area of the part in each barrel."
Stainless tanks: Another major commitment was to use only stainless steel tanks rather than lined steel tanks. A major initial expense, yes, but one that pays off in reliability and ease of maintenance in the end.
Automatic hoists: Four automatic high-speed hoists were designed and built in-house. They cost about $20,000 each to build, which was a big savings over having to buy them outside.
Barrel automation: With automated barrel handling, the results are consistent cycle to cycle, not varying shift to shift. "Our chromates are constantly on conductivity meters with pumps automatically controlling concentration," he noted. "It is the same every time: concentration, submersion time and end result. On a manual line, you can have an operator counting out the submersion timing and being either faster or slower than the guy on the next shift." The barrels have automatic locking doors. Operators load the barrel and when it turns in one direction, the door locks closed. After processing, turn the barrel the other way, and the door opens and the barrel dumps. This is much faster than standard barrel doors that require manually removing four or five clamps from the door each time you load and unload.
Solution processing: Maintaining bath chemistry is the key to quality control, and here Mr. Palik relies on statistical process control methods and constant monitoring, including daily testing of metal content and chemistry levels. "We use SPC to constantly maintain all chemistry levels," he said. "Everything is charted on the computer. If we got some blistering on a part we ran two months ago, for example, we can go back to our SPC charts and see exactly where our chemistry levels were the day we ran it." Pavco Inc., Cleveland, Ohio, is the main proprietary chemical supplier, and has been instrumental in providing technical support. "Once a week the supplier does an analysis of basically everything we do daily, including a check on the proprietary chemicals, which we cannot do. It can also troubleshoot any problems with its much more sophisticated analytical equipment."
BELT DRYER handles parts carefully.
Thickness testing: Three on-line eddy current testers monitor coating thickness within approximately 5%. This is supplemented by an X-ray test machine that can measure coatings to within approximately 1% on the more complicated surfaces, like parts with threads.
Ventilation: Ventilation is another area of emphasis. "We've spent a lot on ventilation," Mr. Palik recalled. "It is not just having adequate exhausting, you also need to be bringing in more fresh air than you exhaust. We have a big air-makeup unit on our roof, pumping air in and pumping it out. That was a code requirement for us to move into this building. Another was that not only did our chemical storage rooms have to be sprinkled with fire doors, but everything in the building had to be fully sprinkled."
Drying: Here Mr. Palik committed to a belt dryer for his new plating line. Why? "Easier part handling and more pounds per hour than a centrifugal dryer," he replied. "It is less labor intensive and less chance of any violent motion harming the parts. In centrifugal dryers, sometimes parts can kick out, rattle around and get distorted."
Baking and post treatment: Post treatments offered include all the usual plus black chromate, olive drab, bright dipping, lacquer and wax. The new line also offers full capacity baking to help relieve any hydrogen embrittlement of heat-treated parts induced in the plating process.
Help up the learning curve. "You can be two lifetimes in this business and still get stumped. When we do, our supplier can come in with sophisticated equipment, tear apart the plating chemistry and find out what is in the bath that is causing an unusual problem. With our own lab, we are pretty self-sufficient for the day-to-day things, but every once in a while oil or something a new customer is using can cause problems. Many companies are cutting costs by using recycled oil in their manufacturing process. We have probably the best cleaning system around, but can still get something crazy in there now and then. You can bandage many problems by simply throwing in brighteners, but we would much rather analyze the problem and correct it."
AUTOMATED barrels move down the zinc plating line.
Those plating shops serving the auto industry are facing a requirement that all Tier Two suppliers be ISO 9000 registered by year's end. Mark Palik sees that, too, as an opportunity. "We plan to be registered by then," he says. "We're half-way there already."
Although plating demand in the Cleveland area has slacked off since he committed to this new line, Mr. Palik remains optimistic. Once he convinced a few big-volume customers that his small shop was moving into the big time, it didn't take long for the news to spread. "People started talking about the line and the job we were doing for them," he recalled. "Soon people I had called months ago started calling back. Our reputation started paying off."
source http://www.pfonline.com/articles/129804.html
Fasteners and Finishes
What happened to cadmium? Once the premier coating for corrosion and lubricity, cadmium has faded greatly in automotive use and is predicted to be outdated soon. The reason stems from two major drives in automotive marketing. The first was the decline and final restriction of the coating in overseas vehicles. The EEC (European Economic Community) passed regulations that limited the percentage of toxic metals, including cadmium, to amounts that seemed extreme to American eyes. A strictly adhered to timetable eliminated cadmium in paints (usually yellow, red and white are cadmium based), plastics (used mainly as ultraviolet stabilizers and for a variety of other reasons) and finally for plating. The EEC allowed that if a strong case in the area of safety, etc. could be made for its use, then cadmium could be allowed. However, since the European car manufacturers were building without cadmium, the presence of cadmium in the same components built in America was not justifiable. Back in the States the companies that did not have significant export markets did not worry about the impending ban. Farm, heavy equipment and truck markets were involved almost from the start. The major use of cadmium in automotive applications was as a plating on all metal prevailing torque nuts (locknuts). A drive was on for a substitute plating before the ban's cutoff date. The problem of disposal of plating sludge had been an increasing one for several years as more and more of the authorized landfills closed their gates to cadmium sludge. The price to dispose of the sludge rose so high that most platers began to charge back to their customers a surcharge when cadmium was requested. The EPA and other groups began to circulate reports about the potential hazards of cadmium in the ecosystems and the effects of heavy metals on the human fetus.
This soon led to the second drive to eliminate automotive cadmium. The Title III Act was passed with its list of banned and to-be-banned chemicals. Major OEMs, with the automotive companies leading the way, wanted to create an image of concern. The potential harm was from the plating chemicals and effluent not the finished plating; however, the concern was that some might rub off. It may be perceived that the problem was due to the demand of the OEMs for the dangerous platings. In the spirit of being a good neighbor, the automotive companies would no longer ask for cadmium plating on fasteners.
The search for a substitute was a race against time. Research into any reasonable and some very unreasonable alternatives proceeded. After six or seven months, the list of unacceptables has grown to more than 160, and the ones with promise stood at three or four. Among the rejected ideas were multiple layered plating/organic/lube coatings, an organic so strong that it caused rabbits to go blind within minutes of exposure, and some exotics whose cost placed them within the reach of governmental agencies only. One of the good guys was tin plate. Unfortunately, it was also prone to metal embrittlement, came from some unstable countries and was expensive.
The other alternatives were Magni Corporation's Dorryltone® (later replaced by Dorrylflake) and Dacromet® series of coatings from Metal Coatings International. These last two had the properties that were needed for locknuts. They showed narrow torque bands (for good control in assembly) were readily available, easily applied, economical and non-toxic. One of these two was chosen by the various companies.
This is about where the situation stands today. Some complaints about various aspects of these substitutes have arisen, especially in the areas of corrosion vs. thickness and the fact that the new coatings do not have the same torque/tension values (it takes more torque to produce the same tension, or the new finish is not as slippery as cadmium). While these seem to be the choice of the moment, work is being done on various friction modifiers to increase lubrication. One drawback to these fluids is that they tend to wash off, are not present in reuse situations and require extra labor steps. Topcoats on the two forerunners have also improved the products and further developments look promising.
Cadmium remains available, for a price, in local markets. The surcharge also remains and varies as disposal charges fluctuate. Military remains the largest single customer for cadmium today. Long storage times of assembled components and harsh conditions make the use of cadmium a must in some areas. Hammering the fuse of an atomic bomb that has been in storage for 15 years, to service it, is one place where cadmium would be a first-choice coating for this engineer.
This soon led to the second drive to eliminate automotive cadmium. The Title III Act was passed with its list of banned and to-be-banned chemicals. Major OEMs, with the automotive companies leading the way, wanted to create an image of concern. The potential harm was from the plating chemicals and effluent not the finished plating; however, the concern was that some might rub off. It may be perceived that the problem was due to the demand of the OEMs for the dangerous platings. In the spirit of being a good neighbor, the automotive companies would no longer ask for cadmium plating on fasteners.
The search for a substitute was a race against time. Research into any reasonable and some very unreasonable alternatives proceeded. After six or seven months, the list of unacceptables has grown to more than 160, and the ones with promise stood at three or four. Among the rejected ideas were multiple layered plating/organic/lube coatings, an organic so strong that it caused rabbits to go blind within minutes of exposure, and some exotics whose cost placed them within the reach of governmental agencies only. One of the good guys was tin plate. Unfortunately, it was also prone to metal embrittlement, came from some unstable countries and was expensive.
The other alternatives were Magni Corporation's Dorryltone® (later replaced by Dorrylflake) and Dacromet® series of coatings from Metal Coatings International. These last two had the properties that were needed for locknuts. They showed narrow torque bands (for good control in assembly) were readily available, easily applied, economical and non-toxic. One of these two was chosen by the various companies.
This is about where the situation stands today. Some complaints about various aspects of these substitutes have arisen, especially in the areas of corrosion vs. thickness and the fact that the new coatings do not have the same torque/tension values (it takes more torque to produce the same tension, or the new finish is not as slippery as cadmium). While these seem to be the choice of the moment, work is being done on various friction modifiers to increase lubrication. One drawback to these fluids is that they tend to wash off, are not present in reuse situations and require extra labor steps. Topcoats on the two forerunners have also improved the products and further developments look promising.
Cadmium remains available, for a price, in local markets. The surcharge also remains and varies as disposal charges fluctuate. Military remains the largest single customer for cadmium today. Long storage times of assembled components and harsh conditions make the use of cadmium a must in some areas. Hammering the fuse of an atomic bomb that has been in storage for 15 years, to service it, is one place where cadmium would be a first-choice coating for this engineer.
Monday, June 8, 2009
Choosing Pumps and Filters
Platers and finishers have special requirements compared to the average user of pump and filtration equipment. The solutions are toxic, precious, expensive and corrosive. A certain amount of thought goes into the specification of each component.
Each person in the company has concerns and requirements when selecting pumps and filters. However, each may have a different opinion about the application and equipment. It is important to consider all of the concerns.
Facility manager's concerns.
What are the utility requirements, such as the amp draw of the mo-tors, voltage requirements, power consumption?
Shop air requirements at scfm or psi?
Dimensions of the equipment or a footprint?
Maintenance manager's concerns.
What is required for proper installation?
In addition to items purchased, what components, such as pipe, fittings, valves, electrical components, switches, etc. are needed?
What type of pump is best for the particular application?
Will the pumps be mounted inside or outside the tank?
Questions about in-tank vertical pumps that need to be addressed.
How will chemicals and fumes affect the motors?
Will the motor's coating withstand the harsh environment without peeling and contaminating the solution?
Will the motor bearings hold up? Are the bearings sealed or unsealed and what service is required for them?
What is the service factor of the motors?
Are they insulated for chemical duty?
Will the pumps introduce air into the solution?
Are drip shields available for the motors?
Are all wet-end components compatible with each constituent of the chemical being pumped?
Can the pump run dry without damage?
In electroless plating where the metal tends to plate out and deposit on plastic, can the wet-end components of the pump withstand the effects of stripping solution?
What temperature range will the pump withstand without damage?
What are the psi to temperature ratios the pump will operate under?
Will the pump run against a closed discharge without damage? How long? Will the internal components warp under heat?
Questions to ask when considering a vertical pump mounted outside the tank.
Will the pumped liquid be kept in the pump column or will it pump up the column when under a closed discharge?
Does the pump have a port seal at the mounting plate to protect the motor bearing from corrosive fumes?
What spare parts should be kept in inventory?
Are there any parts susceptible to wear, and what preventive maintenance is needed to keep the pump running at its optimum?
When repairs are necessary, can the pump be removed and repaired at the shop, or does it need to be shipped back to the factory?
Are there factory authorized dealers in the area?
What are the return authorization procedures?
How long is the pump warranty, and what is covered?
Are there any special tools needed for disassembly and repair?
Does the pump have a parts list and operating instructions?
1. TYPICAL VERTICAL pump installations.
In addition to most of the preceding vertical pump concerns, there are more concerns relating to out-of-tank pumps.
The horizontal pump may be a magnetic-driven sealless centrifugal pump, a direct-drive single- or double-seal centrifugal pump, a self-priming centrifugal pump, an air-diaphragm pump or any of a number of other types.
Each of these pumps presents different concerns for the maintenance manager in addition to the concerns presented by the in-tank pumps. The list sometimes seems endless, but each concern is legitimate and must be answered.
What are the Net Positive Suction Heat (NPSH) factors of each pump and application involved?
Is a "flooded suction" to the pump available? If so, is the liquid being pumped or introduced to the suction casing by gravity? With flooded suction available, priming is unnecessary. If not available, either manual priming would be necessary or a priming chamber should be considered.
Can the pump handle abrasives or be run dry? For how long?
The magnetic-driven sealless pump may be considered if the solution contains precious metals or has a low specific gravity (1.4 or lower) or the impeller was trimmed to handle the specific gravity. Magnetic-driven pumps totally isolate the process solution. Since they do not have mechanical seals, packing rings or shaft lip seals, they are referred to as sealless or leakproof. This added measure of safety could reduce environmental concerns and help the user stay within EPA regulations. However, magnetic-driven pumps should never be used with electroless plating solutions or cleaners containing ferrous metal fines. The particles will adhere to the magnet and act like a grinding wheel, eventually destroying the pump.
The mechanical-sealed pump with a single mechanical seal might be considered if the solution is not extremely toxic or contaminated with abrasives, and where slight leakage due to wear or failure of the seal would not present a problem. If temperatures greater than 140F are anticipated, or the solution contains abrasives, a double water flushed seal should be considered to cool and flush the abrasives off the process seal to prevent premature failure.
Pumps with priming chambers are effective when piping from the process tank is plumbed over the side of the tank, and gravity does not introduce liquid to the suction of the pump. If the pump were to be mounted higher than the liquid level in the tank, caution would need to be exercised and the NPSH would need to be calculated and applied. Pumps with priming chambers require priming only at initial startup.
Air-diaphragm pumps are usually the choice for waste treatment to pump heavy or abrasive sludges. These pumps may be used whenever NPSH calculations reveal a shortcoming in centrifugal pumps. With air, the maintenance manager's additional concerns might be as follows.
Is sufficient shop air available to operate the pumps, or will an additional compressor be required?
Would the pumps need oil lubrication for the ball check valves? Are the oil lubrication components standard with the pump, or do they need to be purchased separately?
What noise levels are expected by the pulsation of the pump? Is a muffler included?
Are pulsation dampeners needed on either the pump inlet or discharge plumbing to reduce vibration? Are they included with the pump?
Positive displacement pumps, such as peristaltic, gear or metering pumps, involved in most of the prior mentioned considerations and the addition of bypass pressure-relief valves may be required on the pump discharge.
2. TYPICAL SOLUTION flow patterns using eductor agitation.
Process engineer or chemist's concerns.
Will the chemistry or operation of the process be changed by the operation of the pump, filtration or agitation system? If so, in what ways? Will filtering particles from the solution result in a smoother deposit?
Will the pumps introduce air into the solution that may adhere to the flat surfaces of parts?
Will increased solution flow give better throwing power in low-current-density areas?
Can plating time be reduced?
Will stratification in any area of the process tank be reduced and particles swept off the tank bottom by the agitation?
Will more or less brightener or chemicals be needed because of the increased agitation?
If anode bags are used or curtains installed in front of the anodes, will there be a detrimental effect on the finish due to particles being forced by the pump agitation through the bag and into the solution?
Will the filtration rate be sufficient to remove the particles before they cause roughness on the plated parts?
A turnover rate of 10 to 20 times per hour may be needed to achieve the particle removal speed necessary to prevent this condition from occurring.
The plater's concerns.
Are the pumps, filters, plumbing, valves, agitation eductors or any of the other components such as hoses, etc., in the way?
The anodes must not be shaded with added equipment in front of them that decreases the exchange of positive/negative ions interacting in the bath.
If internal or external auxiliary anodes are needed on occasion, there must be room for immediate insertion and removal without obstruction.
Would the pump suction or discharge interfere with plating?
The shop owner, CEO or general manager's concerns are the bottom line and the greatest return on investment. Concerns may be the following.
Can we get along without it? If not, how did we get along without it until now?
What is the justification for adding or replacing the equipment?
How much will the installation or the additional and/or replacement equipment cost?
How long is the pay back?
Some of the previously cited decision-makers with their various concerns may also have a staff than can influence the decisions. Every member of the staff may have questions about the application. Therefore, whether the selection of the product begins with shop maintenance workers or the CEO, the majority of these concerns need be addressed. Satisfying the needs of the various personnel before selecting the system helps avoid problems.
Filtration media. After the pumps have been specified and turnover agreed upon, filtration media should be considered, if necessary. There are several effective filtration media available that will remove particulates from 100 microns down to submicron levels. The degree of automation required for the use of the equipment should be considered as well.
Media choice is left to the user. However, based on successful installations and past experience, the supplier will usually offer alternative methodologies such as depth-wound filter cartridges, flat paper or cellulose discs, horizontal or vertical plates, bags, cleanable sleeves, disposable fabric or backwashable permanent media. Each media has its pros and cons.
String-wound depth cartridge is the choice of filtration for the average plater because of its simplicity, high-solids-holding capacity and wide range of porosities available to remove progressively smaller particles. A 10-inch by two-and-a-half-inch diameter cartridge is equal to three-and-a-half sq ft of surface media.
For instance, when filtering iron from nickel, acid zinc or cadmium solutions, a filter with dimensions previously described and 15 micron retention will easily hold eight ounces of iron before loading. Sized at one cartridge per 50 gal of plating solution with a suitable pump to achieve an initial solution turnover rate of twice per hour, eight to 12 weeks between cartridge changes is not uncommon. For just a small extra capital investment, the filter chamber size could be doubled and two ten-inch filters per 50 gal of solution could provide 16 to 24 weeks between filter changes.
If mainly iron is filtered, the cartridges can be backwashed or soaked in a dilute acid solution to redissolve the iron. Also, an alkaline cleaner solution could be used to remove some oil and soil buildup in the filter. They could then be carefully rinsed and neutralized for several reuses prior to landfill disposal. If a spare change of filters is kept in stock, one set can be on-line while the other is soaked for reuse. Typically, two to four cartridges of 50 to 100 micron retention per 100 gal work best on cleaners.
One of the most common objections to using string-wound depth filters is that they are too bulky for landfill compared to disc bags. However, whenever any bulky material is sent to landfill for disposal, it is usually processed through a shredder or compactor first. Because of this, depth filters are no more of a problem to dispose of than any other media. Incineration may be considered in the future because polypropylene supports combustion and used cartridges can be used to reduce fuel costs.
Filter cartridges are also available in other configurations such as pleated material, melt-bonded poly-propylene free of organic sizing agents and a number of others, including membranes for electronic grade use. These membranes will filter down to 0.1 micron nominal or absolute, if necessary.
Carbon impregnated fibers as well as granulated carbon filter cartridges are also available in the same size configuration and may be mixed selectively with the other filter cartridges in the filter chamber to achieve carbon adsorption of unwanted organics. Where heavy dirt loads are encountered, it is recommended that the solution be filtered first and then carbon treated in a separate chamber downstream on a bypass.
Disc filter sets, composed of paper, polypropylene or cellulose fiber, are another type of filter media used in industry. The discs may be used alone with paper, or precoated with filter aid to achieve a faster and finer micron retention of the particulate filtered. The downside to discs is their low-solids-holding capacity. They need to be cleaned or serviced often, compared to depth-wound string filters. In heavy particulate applications such as acid zinc or cadmium plating with high iron content, daily cleaning is common, especially on barrel lines.
Wheel platers are the connoisseurs of disc filtration systems. They like them because of their rapid filtration of fine particulates. They buff and polish between steps in many shops, so introduction of buffing compound into the plating bath is common. However, since most buffing compound contains animal fat and greases, carbon needs to be used on the precoat of the discs to remove this organic contamination. When using powdered carbon on the discs, the brighteners in the acid copper and bright nickel baths need to be replenished continuously. If bulk granulated carbon is used on a by-pass in a separate chamber downstream from the filter discs, brightener depletion is much slower.
Bag filters are used in electroless nickel and copper plating because autocatalytic baths have a tendency to plate out on any surface they contact. Bags are the easiest filters to use in these applications, since they are a surface-type media. When they are plated with metal, the operator can see the plate-out and service the bags. When discs or depth filters are used in an enclosed chamber, the operator cannot see the plate-out. Plate- out of the entire bath could occur if the problem is not detected and corrected immediately.
Also, bags are a favorite where high loading of coarse solids occurs, such as in acid dip tanks and running water rinses. If the solution is not slimy and does not coat the bag surface, then the bag will load as vacuum cleaner bag does. However, alkaline cleaner baths are usually slimy, so the particles they contain blind off the bag surface quickly, requiring frequent service. On cleaner or acid dip tanks where oil contamination is a problem, an additional coalescing filter cartridge installed downstream of the bag filter may remove the oil. Auto-gravity filters are also ideal for this application.
Coalescing cartridges will separate any dissimilar liquids with a difference in specific gravity of 0.09 or greater. The prefilter removes the unwanted particulate so the coalescing filter will last indefinitely as long as no particulate is introduced. The oil coalesces from tiny droplets into large ones that float to the top of the water in the chamber. This oil can be manually or automatically bled off. A recycler can then recycle the concentrated oil.
Permanent-media filtration systems are a choice of platers for unattended operation and where disposable filter media or the labor to change it is objectionable. When used in a suitable system, the plating solution is kept clean and the filter media is restored to a clean state each time the system automatically backwashes itself. The up side of this system is that it operates in the top 20 pct of the filtration flow range at all times as compared to non-backwashed media where flow diminishes as the media loads. The backwashable sand filtration system is also an excellent choice for polishing clarified wastewater from the treatment system. A key advantage of the backwashable pressure filtration system is that it cleans itself automatically.
Disposable fabric filtration systems are often referred to as automatic indexing gravity filters. They use an array of tanks, conveyors, pulleys, motors, pumps and float level controls to index disposable filter media over a stationary conveyor. This type of system effectively removes particulates from phosphating solutions, carbonized deposits from quench oil, copper fines from printed circuit board deburring operations and high-solids solutions. The micron retention of the available fabric ranges from one to 125 microns.
Recessed plate filter presses are used in about every precipitation wastewater treatment plant to dewater the underflow of clarifiers. A typical tube-type or slant-plate clarifier with an inverted pyramid bottom or cone achieves approximately 0.5 pct solids on the bottom. If a flat bottom is used and a sludge rake or scraper sweeps the bottom of the clarifier, three pct solids may be achieved if proper flocculation and settling occur. However, the slurry still needs to be thickened to eight or nine pct solids through a sludge thickener before pumping through a filter press, otherwise a much larger press would be needed and would be cost prohibitive.
Where liquids having extremely high solids, usually five to 10 pct, need to be dewatered, an air-diaphragm pump operated from 60 to 90 psi usually is the choice to transfer the thickened slurry through the filter press. The polypropylene filter plates have recessed cavities of one-half to three-quarter inch each with a 20 micron polypropylene filter cloth. As the plates are sandwiched together under pressure, every pair of plates provides a one to one-and-a-half-inch cavity to retain the solids as the slurry is pumped through the plates. This type of filtration system is capable of achieving 30 to 35 pct solids with standard filter cloths. Using membrane-type filter cloths with high psi pumps, solids of up to 60 pct have been achieved. However, the cost of this type of system is much greater than the standard filter press.
Capacities of one-half to 50 or more cubic feet are readily available and applications may be sized accordingly. The general rule of thumb in sizing a filter press for the average plating or printed circuit shop is two-cu-ft capacity minimum for every 25 gpm flow through the clarifier. This sizing arrangement will usually provide a full eight-hour shift before dumping is necessary. The time required to dump and clean a filter press is minimal, usually 15 to 20 min by one worker.
Carbon purification is the choice of platers to adsorb organic contamination from plating solutions, rinses, etches and cleaners.
If total purification is required in a batch treatment, the solution is transferred to a treatment tank and temperature raised above 140F. Hydrogen peroxide is sometimes added to the solution. Three to 12-and-one-half lbs of powdered carbon per 100 gal of solution are added, stirred and allowed to sit four to eight hours. The carbon will settle to the bottom, along with the adsorbed contaminants. The clean liquid can be decanted or pumped back to the process tanks through a filtration media. The carbon sludge is then batch treated and disposed of with the rest of the hazardous waste.
The frequency of the batch carbon treatment procedure may be greatly reduced by circulating the plating solutions continuously through a chamber containing granulated carbon. In this way, a constant balance of brighteners to achieve uniform ductility will be achieved.
An effective way to accomplish purification is to install a separate canister containing granular carbon on a bypass with a valve controlling the flow. After the solution has passed through the filter chamber to remove particulates, a portion (about five to 20 pct) may be directed through the granulated carbon on a continuous basis to remove the unwanted organics and then through a coalescer to remove oil. Granular carbon will remove organic breakdown products of the brighteners as well as oil, grease, etc., without stripping the brightener system.
The canisters holding the carbon have either fine mesh screens or fine retention depth filters of one to three microns to trap any carbon attempting to exit the vessel. This type of granulated carbon canister is also widely used as a portable system on a cart with its own pump, hoses, valves, etc., to recirculate solutions needing carbon treatment.
Caveat Emptor. An experienced sales application consultant will attempt to gather the pertinent data for the application to satisfy all of the concerns of the team involved in the purchase. The ultimate goal is to have a successful installation.
MSDS supply the chemical composition of the materials and must be obtained wherever possible. These documents contain information as to flash points, toxicity and the constituents. It is essential that the chemical compatibility, pH, pressure, temperature, limitation and flow performance curves be researched for the pumps, filters and components of the applications. You also must determine what type and amount of solids are to be removed and how fast. And, are abrasives present or oil or dissimilar liquids that need to be separated? All of this data must be used to select the material and components for the application.
In the end, the rule of Caveat Emptor (let the buyer beware), usually applies. If you let the application consultant make the recommendation, and purchase the product recommended, a reputable manufacturer will stand behind the product. Real products applied to real applications repeatedly offer the customer the greatest assurance and the most peace of mind that the proper product and application have been recommended.
Each person in the company has concerns and requirements when selecting pumps and filters. However, each may have a different opinion about the application and equipment. It is important to consider all of the concerns.
Facility manager's concerns.
What are the utility requirements, such as the amp draw of the mo-tors, voltage requirements, power consumption?
Shop air requirements at scfm or psi?
Dimensions of the equipment or a footprint?
Maintenance manager's concerns.
What is required for proper installation?
In addition to items purchased, what components, such as pipe, fittings, valves, electrical components, switches, etc. are needed?
What type of pump is best for the particular application?
Will the pumps be mounted inside or outside the tank?
Questions about in-tank vertical pumps that need to be addressed.
How will chemicals and fumes affect the motors?
Will the motor's coating withstand the harsh environment without peeling and contaminating the solution?
Will the motor bearings hold up? Are the bearings sealed or unsealed and what service is required for them?
What is the service factor of the motors?
Are they insulated for chemical duty?
Will the pumps introduce air into the solution?
Are drip shields available for the motors?
Are all wet-end components compatible with each constituent of the chemical being pumped?
Can the pump run dry without damage?
In electroless plating where the metal tends to plate out and deposit on plastic, can the wet-end components of the pump withstand the effects of stripping solution?
What temperature range will the pump withstand without damage?
What are the psi to temperature ratios the pump will operate under?
Will the pump run against a closed discharge without damage? How long? Will the internal components warp under heat?
Questions to ask when considering a vertical pump mounted outside the tank.
Will the pumped liquid be kept in the pump column or will it pump up the column when under a closed discharge?
Does the pump have a port seal at the mounting plate to protect the motor bearing from corrosive fumes?
What spare parts should be kept in inventory?
Are there any parts susceptible to wear, and what preventive maintenance is needed to keep the pump running at its optimum?
When repairs are necessary, can the pump be removed and repaired at the shop, or does it need to be shipped back to the factory?
Are there factory authorized dealers in the area?
What are the return authorization procedures?
How long is the pump warranty, and what is covered?
Are there any special tools needed for disassembly and repair?
Does the pump have a parts list and operating instructions?
1. TYPICAL VERTICAL pump installations.
In addition to most of the preceding vertical pump concerns, there are more concerns relating to out-of-tank pumps.
The horizontal pump may be a magnetic-driven sealless centrifugal pump, a direct-drive single- or double-seal centrifugal pump, a self-priming centrifugal pump, an air-diaphragm pump or any of a number of other types.
Each of these pumps presents different concerns for the maintenance manager in addition to the concerns presented by the in-tank pumps. The list sometimes seems endless, but each concern is legitimate and must be answered.
What are the Net Positive Suction Heat (NPSH) factors of each pump and application involved?
Is a "flooded suction" to the pump available? If so, is the liquid being pumped or introduced to the suction casing by gravity? With flooded suction available, priming is unnecessary. If not available, either manual priming would be necessary or a priming chamber should be considered.
Can the pump handle abrasives or be run dry? For how long?
The magnetic-driven sealless pump may be considered if the solution contains precious metals or has a low specific gravity (1.4 or lower) or the impeller was trimmed to handle the specific gravity. Magnetic-driven pumps totally isolate the process solution. Since they do not have mechanical seals, packing rings or shaft lip seals, they are referred to as sealless or leakproof. This added measure of safety could reduce environmental concerns and help the user stay within EPA regulations. However, magnetic-driven pumps should never be used with electroless plating solutions or cleaners containing ferrous metal fines. The particles will adhere to the magnet and act like a grinding wheel, eventually destroying the pump.
The mechanical-sealed pump with a single mechanical seal might be considered if the solution is not extremely toxic or contaminated with abrasives, and where slight leakage due to wear or failure of the seal would not present a problem. If temperatures greater than 140F are anticipated, or the solution contains abrasives, a double water flushed seal should be considered to cool and flush the abrasives off the process seal to prevent premature failure.
Pumps with priming chambers are effective when piping from the process tank is plumbed over the side of the tank, and gravity does not introduce liquid to the suction of the pump. If the pump were to be mounted higher than the liquid level in the tank, caution would need to be exercised and the NPSH would need to be calculated and applied. Pumps with priming chambers require priming only at initial startup.
Air-diaphragm pumps are usually the choice for waste treatment to pump heavy or abrasive sludges. These pumps may be used whenever NPSH calculations reveal a shortcoming in centrifugal pumps. With air, the maintenance manager's additional concerns might be as follows.
Is sufficient shop air available to operate the pumps, or will an additional compressor be required?
Would the pumps need oil lubrication for the ball check valves? Are the oil lubrication components standard with the pump, or do they need to be purchased separately?
What noise levels are expected by the pulsation of the pump? Is a muffler included?
Are pulsation dampeners needed on either the pump inlet or discharge plumbing to reduce vibration? Are they included with the pump?
Positive displacement pumps, such as peristaltic, gear or metering pumps, involved in most of the prior mentioned considerations and the addition of bypass pressure-relief valves may be required on the pump discharge.
2. TYPICAL SOLUTION flow patterns using eductor agitation.
Process engineer or chemist's concerns.
Will the chemistry or operation of the process be changed by the operation of the pump, filtration or agitation system? If so, in what ways? Will filtering particles from the solution result in a smoother deposit?
Will the pumps introduce air into the solution that may adhere to the flat surfaces of parts?
Will increased solution flow give better throwing power in low-current-density areas?
Can plating time be reduced?
Will stratification in any area of the process tank be reduced and particles swept off the tank bottom by the agitation?
Will more or less brightener or chemicals be needed because of the increased agitation?
If anode bags are used or curtains installed in front of the anodes, will there be a detrimental effect on the finish due to particles being forced by the pump agitation through the bag and into the solution?
Will the filtration rate be sufficient to remove the particles before they cause roughness on the plated parts?
A turnover rate of 10 to 20 times per hour may be needed to achieve the particle removal speed necessary to prevent this condition from occurring.
The plater's concerns.
Are the pumps, filters, plumbing, valves, agitation eductors or any of the other components such as hoses, etc., in the way?
The anodes must not be shaded with added equipment in front of them that decreases the exchange of positive/negative ions interacting in the bath.
If internal or external auxiliary anodes are needed on occasion, there must be room for immediate insertion and removal without obstruction.
Would the pump suction or discharge interfere with plating?
The shop owner, CEO or general manager's concerns are the bottom line and the greatest return on investment. Concerns may be the following.
Can we get along without it? If not, how did we get along without it until now?
What is the justification for adding or replacing the equipment?
How much will the installation or the additional and/or replacement equipment cost?
How long is the pay back?
Some of the previously cited decision-makers with their various concerns may also have a staff than can influence the decisions. Every member of the staff may have questions about the application. Therefore, whether the selection of the product begins with shop maintenance workers or the CEO, the majority of these concerns need be addressed. Satisfying the needs of the various personnel before selecting the system helps avoid problems.
Filtration media. After the pumps have been specified and turnover agreed upon, filtration media should be considered, if necessary. There are several effective filtration media available that will remove particulates from 100 microns down to submicron levels. The degree of automation required for the use of the equipment should be considered as well.
Media choice is left to the user. However, based on successful installations and past experience, the supplier will usually offer alternative methodologies such as depth-wound filter cartridges, flat paper or cellulose discs, horizontal or vertical plates, bags, cleanable sleeves, disposable fabric or backwashable permanent media. Each media has its pros and cons.
String-wound depth cartridge is the choice of filtration for the average plater because of its simplicity, high-solids-holding capacity and wide range of porosities available to remove progressively smaller particles. A 10-inch by two-and-a-half-inch diameter cartridge is equal to three-and-a-half sq ft of surface media.
For instance, when filtering iron from nickel, acid zinc or cadmium solutions, a filter with dimensions previously described and 15 micron retention will easily hold eight ounces of iron before loading. Sized at one cartridge per 50 gal of plating solution with a suitable pump to achieve an initial solution turnover rate of twice per hour, eight to 12 weeks between cartridge changes is not uncommon. For just a small extra capital investment, the filter chamber size could be doubled and two ten-inch filters per 50 gal of solution could provide 16 to 24 weeks between filter changes.
If mainly iron is filtered, the cartridges can be backwashed or soaked in a dilute acid solution to redissolve the iron. Also, an alkaline cleaner solution could be used to remove some oil and soil buildup in the filter. They could then be carefully rinsed and neutralized for several reuses prior to landfill disposal. If a spare change of filters is kept in stock, one set can be on-line while the other is soaked for reuse. Typically, two to four cartridges of 50 to 100 micron retention per 100 gal work best on cleaners.
One of the most common objections to using string-wound depth filters is that they are too bulky for landfill compared to disc bags. However, whenever any bulky material is sent to landfill for disposal, it is usually processed through a shredder or compactor first. Because of this, depth filters are no more of a problem to dispose of than any other media. Incineration may be considered in the future because polypropylene supports combustion and used cartridges can be used to reduce fuel costs.
Filter cartridges are also available in other configurations such as pleated material, melt-bonded poly-propylene free of organic sizing agents and a number of others, including membranes for electronic grade use. These membranes will filter down to 0.1 micron nominal or absolute, if necessary.
Carbon impregnated fibers as well as granulated carbon filter cartridges are also available in the same size configuration and may be mixed selectively with the other filter cartridges in the filter chamber to achieve carbon adsorption of unwanted organics. Where heavy dirt loads are encountered, it is recommended that the solution be filtered first and then carbon treated in a separate chamber downstream on a bypass.
Disc filter sets, composed of paper, polypropylene or cellulose fiber, are another type of filter media used in industry. The discs may be used alone with paper, or precoated with filter aid to achieve a faster and finer micron retention of the particulate filtered. The downside to discs is their low-solids-holding capacity. They need to be cleaned or serviced often, compared to depth-wound string filters. In heavy particulate applications such as acid zinc or cadmium plating with high iron content, daily cleaning is common, especially on barrel lines.
Wheel platers are the connoisseurs of disc filtration systems. They like them because of their rapid filtration of fine particulates. They buff and polish between steps in many shops, so introduction of buffing compound into the plating bath is common. However, since most buffing compound contains animal fat and greases, carbon needs to be used on the precoat of the discs to remove this organic contamination. When using powdered carbon on the discs, the brighteners in the acid copper and bright nickel baths need to be replenished continuously. If bulk granulated carbon is used on a by-pass in a separate chamber downstream from the filter discs, brightener depletion is much slower.
Bag filters are used in electroless nickel and copper plating because autocatalytic baths have a tendency to plate out on any surface they contact. Bags are the easiest filters to use in these applications, since they are a surface-type media. When they are plated with metal, the operator can see the plate-out and service the bags. When discs or depth filters are used in an enclosed chamber, the operator cannot see the plate-out. Plate- out of the entire bath could occur if the problem is not detected and corrected immediately.
Also, bags are a favorite where high loading of coarse solids occurs, such as in acid dip tanks and running water rinses. If the solution is not slimy and does not coat the bag surface, then the bag will load as vacuum cleaner bag does. However, alkaline cleaner baths are usually slimy, so the particles they contain blind off the bag surface quickly, requiring frequent service. On cleaner or acid dip tanks where oil contamination is a problem, an additional coalescing filter cartridge installed downstream of the bag filter may remove the oil. Auto-gravity filters are also ideal for this application.
Coalescing cartridges will separate any dissimilar liquids with a difference in specific gravity of 0.09 or greater. The prefilter removes the unwanted particulate so the coalescing filter will last indefinitely as long as no particulate is introduced. The oil coalesces from tiny droplets into large ones that float to the top of the water in the chamber. This oil can be manually or automatically bled off. A recycler can then recycle the concentrated oil.
Permanent-media filtration systems are a choice of platers for unattended operation and where disposable filter media or the labor to change it is objectionable. When used in a suitable system, the plating solution is kept clean and the filter media is restored to a clean state each time the system automatically backwashes itself. The up side of this system is that it operates in the top 20 pct of the filtration flow range at all times as compared to non-backwashed media where flow diminishes as the media loads. The backwashable sand filtration system is also an excellent choice for polishing clarified wastewater from the treatment system. A key advantage of the backwashable pressure filtration system is that it cleans itself automatically.
Disposable fabric filtration systems are often referred to as automatic indexing gravity filters. They use an array of tanks, conveyors, pulleys, motors, pumps and float level controls to index disposable filter media over a stationary conveyor. This type of system effectively removes particulates from phosphating solutions, carbonized deposits from quench oil, copper fines from printed circuit board deburring operations and high-solids solutions. The micron retention of the available fabric ranges from one to 125 microns.
Recessed plate filter presses are used in about every precipitation wastewater treatment plant to dewater the underflow of clarifiers. A typical tube-type or slant-plate clarifier with an inverted pyramid bottom or cone achieves approximately 0.5 pct solids on the bottom. If a flat bottom is used and a sludge rake or scraper sweeps the bottom of the clarifier, three pct solids may be achieved if proper flocculation and settling occur. However, the slurry still needs to be thickened to eight or nine pct solids through a sludge thickener before pumping through a filter press, otherwise a much larger press would be needed and would be cost prohibitive.
Where liquids having extremely high solids, usually five to 10 pct, need to be dewatered, an air-diaphragm pump operated from 60 to 90 psi usually is the choice to transfer the thickened slurry through the filter press. The polypropylene filter plates have recessed cavities of one-half to three-quarter inch each with a 20 micron polypropylene filter cloth. As the plates are sandwiched together under pressure, every pair of plates provides a one to one-and-a-half-inch cavity to retain the solids as the slurry is pumped through the plates. This type of filtration system is capable of achieving 30 to 35 pct solids with standard filter cloths. Using membrane-type filter cloths with high psi pumps, solids of up to 60 pct have been achieved. However, the cost of this type of system is much greater than the standard filter press.
Capacities of one-half to 50 or more cubic feet are readily available and applications may be sized accordingly. The general rule of thumb in sizing a filter press for the average plating or printed circuit shop is two-cu-ft capacity minimum for every 25 gpm flow through the clarifier. This sizing arrangement will usually provide a full eight-hour shift before dumping is necessary. The time required to dump and clean a filter press is minimal, usually 15 to 20 min by one worker.
Carbon purification is the choice of platers to adsorb organic contamination from plating solutions, rinses, etches and cleaners.
If total purification is required in a batch treatment, the solution is transferred to a treatment tank and temperature raised above 140F. Hydrogen peroxide is sometimes added to the solution. Three to 12-and-one-half lbs of powdered carbon per 100 gal of solution are added, stirred and allowed to sit four to eight hours. The carbon will settle to the bottom, along with the adsorbed contaminants. The clean liquid can be decanted or pumped back to the process tanks through a filtration media. The carbon sludge is then batch treated and disposed of with the rest of the hazardous waste.
The frequency of the batch carbon treatment procedure may be greatly reduced by circulating the plating solutions continuously through a chamber containing granulated carbon. In this way, a constant balance of brighteners to achieve uniform ductility will be achieved.
An effective way to accomplish purification is to install a separate canister containing granular carbon on a bypass with a valve controlling the flow. After the solution has passed through the filter chamber to remove particulates, a portion (about five to 20 pct) may be directed through the granulated carbon on a continuous basis to remove the unwanted organics and then through a coalescer to remove oil. Granular carbon will remove organic breakdown products of the brighteners as well as oil, grease, etc., without stripping the brightener system.
The canisters holding the carbon have either fine mesh screens or fine retention depth filters of one to three microns to trap any carbon attempting to exit the vessel. This type of granulated carbon canister is also widely used as a portable system on a cart with its own pump, hoses, valves, etc., to recirculate solutions needing carbon treatment.
Caveat Emptor. An experienced sales application consultant will attempt to gather the pertinent data for the application to satisfy all of the concerns of the team involved in the purchase. The ultimate goal is to have a successful installation.
MSDS supply the chemical composition of the materials and must be obtained wherever possible. These documents contain information as to flash points, toxicity and the constituents. It is essential that the chemical compatibility, pH, pressure, temperature, limitation and flow performance curves be researched for the pumps, filters and components of the applications. You also must determine what type and amount of solids are to be removed and how fast. And, are abrasives present or oil or dissimilar liquids that need to be separated? All of this data must be used to select the material and components for the application.
In the end, the rule of Caveat Emptor (let the buyer beware), usually applies. If you let the application consultant make the recommendation, and purchase the product recommended, a reputable manufacturer will stand behind the product. Real products applied to real applications repeatedly offer the customer the greatest assurance and the most peace of mind that the proper product and application have been recommended.
Fasteners and Finishes
The plating source is often the blame for many automated assembly problems. The manufacturer requests a coating or plating of a certain type from the finisher. When the manufacturer receives the final product he runs off with it, only to call back in a few days to say that the plating is clogging up the assembly process. When the problem involves recalls and expensive warranty costs, the manufacturer may want a percentage paid by the finisher. This month's column talks about the interfaces of finishes with automated assembly tooling, processes and materials.
Automated processes are of two types. The high-tech version is completely controlled by robotic function. The other involves feeder tubes and fancy tools, but has a human operator somewhere in the process. Robotic installation requires that a shipment of material be 100 pct free of foreign material. This is one of the major complaints that assemblers have about finishers in general. Mixed parts occur because some stick in the barrels and are dragged over, stock is mixed in the plant by accident, and sometimes they come mixed to the finisher from the heat treater. Receiving inspection should be a basic requirement of all plating operations.
Robots function tirelessly, but they have an I.Q. of about 15. Installation of a bolt without threads or the wrong size will be attempted. If the part doesn't go in the hole, the robot stops and the system goes down. Mixed stock will not function in automated systems. If the problem is excessive (beyond the point where a simple sorting could separate the parts), special high-speed sorting can be performed. Some companies guarantee 100-pct no-mix conformance, but it costs. The additional charges may have to be passed on to the manufacturer. A small percentage of mixes are generally not a problem unless the assembly process is fully robotic.
While some complaints may be forthcoming, human operators will just toss aside incorrect and damaged parts. The major concern is where the parts jam feed lines and bowls. Then the downtime can be as much as 30 pct, and the manufacturer will come looking for compensation.
The type of finish applied often causes feed and assembly problems. Oil-based coatings tend to coat the plastic feed tubes and clog the system, stopping the flow of parts and the line process. While one common plant solution is to increase the feed pressure, the cure is worse than the problem. The parts tend to break loose suddenly and shoot out the feed tubes at high velocity.
Many new coatings are metallic-based paints. The flaking off of pieces in feed hoppers causes a poor finish on the part, leading to early corrosion. It also causes feed tube and assembly problems with the plating dust. In many areas, the airborne metallic particles are not allowed by OSHA and local environmental regulations. One study on the amount of time that parts spend in a vibratory-type feed hopper showed that not all the parts were fed out after 30 minutes. The last part in several cases took about 45 minutes to clear the bowl. That is a lot of time to be banging around. In addition to flaking and dusting, the likelihood of parts being nicked or otherwise damaged is great. Soft platings are especially prone to damage.
If the part has a recessed head drive, is of a small diameter with fine pitch threads and/or has an integrated washer, it is not a candidate for the thick organics and metallic coatings so popular today. Numerous companies running production coatings today will quote exceptions to the specification if asked to run this type coating on a "problem" part. Sorting for defects associated with these concern areas will use up as much as 35 pct of available labor.
It is a good practice to ask how the parts are going to be used when they arrive for plating. Uses that have potential for poor assembly and fit or will be hopper fed should be discussed with the customer to see if an alternate coating would be acceptable. Parts that are slated for robotic assembly should have a rider attached to the order requesting full sorting and 100 pct no-mix requirements, with an additional charge for this process.
Automated processes are of two types. The high-tech version is completely controlled by robotic function. The other involves feeder tubes and fancy tools, but has a human operator somewhere in the process. Robotic installation requires that a shipment of material be 100 pct free of foreign material. This is one of the major complaints that assemblers have about finishers in general. Mixed parts occur because some stick in the barrels and are dragged over, stock is mixed in the plant by accident, and sometimes they come mixed to the finisher from the heat treater. Receiving inspection should be a basic requirement of all plating operations.
Robots function tirelessly, but they have an I.Q. of about 15. Installation of a bolt without threads or the wrong size will be attempted. If the part doesn't go in the hole, the robot stops and the system goes down. Mixed stock will not function in automated systems. If the problem is excessive (beyond the point where a simple sorting could separate the parts), special high-speed sorting can be performed. Some companies guarantee 100-pct no-mix conformance, but it costs. The additional charges may have to be passed on to the manufacturer. A small percentage of mixes are generally not a problem unless the assembly process is fully robotic.
While some complaints may be forthcoming, human operators will just toss aside incorrect and damaged parts. The major concern is where the parts jam feed lines and bowls. Then the downtime can be as much as 30 pct, and the manufacturer will come looking for compensation.
The type of finish applied often causes feed and assembly problems. Oil-based coatings tend to coat the plastic feed tubes and clog the system, stopping the flow of parts and the line process. While one common plant solution is to increase the feed pressure, the cure is worse than the problem. The parts tend to break loose suddenly and shoot out the feed tubes at high velocity.
Many new coatings are metallic-based paints. The flaking off of pieces in feed hoppers causes a poor finish on the part, leading to early corrosion. It also causes feed tube and assembly problems with the plating dust. In many areas, the airborne metallic particles are not allowed by OSHA and local environmental regulations. One study on the amount of time that parts spend in a vibratory-type feed hopper showed that not all the parts were fed out after 30 minutes. The last part in several cases took about 45 minutes to clear the bowl. That is a lot of time to be banging around. In addition to flaking and dusting, the likelihood of parts being nicked or otherwise damaged is great. Soft platings are especially prone to damage.
If the part has a recessed head drive, is of a small diameter with fine pitch threads and/or has an integrated washer, it is not a candidate for the thick organics and metallic coatings so popular today. Numerous companies running production coatings today will quote exceptions to the specification if asked to run this type coating on a "problem" part. Sorting for defects associated with these concern areas will use up as much as 35 pct of available labor.
It is a good practice to ask how the parts are going to be used when they arrive for plating. Uses that have potential for poor assembly and fit or will be hopper fed should be discussed with the customer to see if an alternate coating would be acceptable. Parts that are slated for robotic assembly should have a rider attached to the order requesting full sorting and 100 pct no-mix requirements, with an additional charge for this process.
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