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Avoiding Tank Disasters The Do’s and Don’ts for a Safe Shop

Preventing Electroplating PLATING Tank Catastrophes – 18

Architectural Powder POWDER Coatings Mean Growth – 22

Optimizing Wash System PRETREAT Spray Patterns – 26

Choosing the Right Vapor CLEANING Degreasing Method – 36 A property of Gardner Business Media NOVEMBER 2018 / VOLUME 83 / NO. 2 PLATING

Preventing Electroplating Tank Catastrophes

Process tanks are a necessity, providing critical service to About 75 percent of process plating and pickling operations, yet they have often been implicated in facility accidents, leaks, catastrophes and tank users have reported fires. Associated risks can threaten both worker safety and groundwater contamination, draining profit and a compa- tank failures. Here’s how ny’s reputation. It is said that a prudent man learns from his experience to avoid them. but a wise man learns from the experience of others, and the intent of this article is to provide you, the reader, with the opportunity to become wiser without experiencing your own major loss. Rather than focus on technical or scientific issues, we will share actual experiences we have encountered over the BY CURTIS GOAD GOAD COMPANY past 40 years in the finishing industry. Since no “silver bullet” tank material exists, and any tank is only as good as its weakest element, tanks should not be viewed as a commodity nor taken for granted. About 75 percent of process tank users have reported experiencing tank leaks. Proper material selection, and taking advantage of advances in fabrication/welding methods and technologies can greatly reduce premature failure.

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Tank Safety Tips

Properly plank tanks before working Leave spills for cleanup later. Clean up DO overhead. DON’T spills immediately to avoid an accident.

Engage in horseplay around tanks. Make sure that a properly functioning, A splash or trip could give you a bad self-contained breathing apparatus and DON’T DO chemical burn. an operator trained in its use are avail- able for emergency rescue. Climb out over, lean over or walk on tank Make certain that all equipment is DON’T rims or anodes rods. Slipping into a tank DO properly locked out/tagged out before is a leading cause of very serious injuries. working.

Climb into a tank or enter a confined DON’T space without employing the buddy Inspect tanks and piping for leaks, system, ensuing proper ventilation and DO corrosion and deflection (bowing). fully complying with your plant’s confined space rules.

Ever lift a bag or drum of chemicals Here are tips for avoiding a tank failure, including DON’T above the tank rim. The entire contents best practices and what not to do. could fall in, causing a blowup.

Exposure and Environmental Liability drips will amount to gallons of acid over time. One drip per Although tank leaks can often be repaired, the associated minute equals one gallon per week (364 gallons over seven lost production and loss of chemicals can be costly. In a years), so even one drip per hour over seven years would recent survey, 67 percent of facilities reported having had create six gallons of acid. In this case, the actual quantity a leak that resulted in major cost or burden, and 18 percent it took to dissolve the steel is irrelevant; whatever the have experienced catastrophic tank failure in the past. amount, it was enough to fully corrode the steel. These latter companies reported dire consequences: worker exposure, overcoming of secondary containment, and envi- ronmental or clean-up liability. Poor welding is a common cause of tank failure. Welding machines provide the highest strength welds, and plastic shops should have quality assurance programs and quali- fied welders based on AWS b2.4 standard specification for plastic welding. Hand welds are tedious and require intense focus, and since welding large tanks requires long hours or days of welding, tiredness and reduced concen- tration are likely. The fewer hand welds—both in terms of linear feet and number of passes—the better. But tank welds are not the only source of tank failure. In one instance, a well-built seven-year-old polypropylene tank that had never leaked before experienced a side wall blowout due to hidden structural steel corrosion caused by acid drips at the tank’s top rim. A fume collection hood had been mounted on the tank rim, and the plastic encapsu- lating the steel structure evidently had been compromised. Fortunately, the wall of this tank full of acid blew out over Hot fumes will condense to liquid, and even extremely slow a weekend, when no one was at or near the tank.

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Hidden corrosion under the encapsulated polypropylene caused this catastrophic failure and tank wall blowout.

Fortunately, this incident happened over a weekend, when Steel tanks can have either a patented bonded lining no one was near the heated tank full of acid. Had someone (no problematic hand welds with seam strips) or been on the catwalk next to the tank when the wall blowout a machine-welded box liner dropped into it. We occurred, we can only imagine the consequences. have never heard of this type of tank experiencing a complete wall blowout. The steel exterior can be lined, Suggestions for Preventing Similar Catastrophes which allows for easy spark testing, or covered with • Monitor the deflection or bowing of tank walls. Use a a clear, see-through vinyl that protects the steel yet laser measurement device and shoot the laser beam allows visual inspection for corrosion. from one end of the wall to its other end. If you have to move out from the edge to get to the other end, that Polypropylene Tanks Rated Worst distance represents how much the wall has deflected In a discussion of tank catastrophes, we would be remiss or bowed. Full tanks want to be round, so structure if we did not address plastic tank fires. When we started is required to stiffen the wall, and without structure fabricating machine-built polypropylene (PPL) tanks in the (see images), the plastic itself can break apart. Note early 1980s, we thought they were great, and so did our that the tank needs to be filled to its operating level in customers—until a devastating process line fire at a captive order for the deflection to be properly measured. shop. It turns out, of 30 plastics tested, polypropylene • Visually inspect the integrity of the structural steel was rated the worst in terms of fire hazard. PPL has been itself. This may sound easy to do, but often a visual called “diesel fuel in the solid state,” because it is almost all inspection is not possible because the steel is encap- hydrocarbon, and it burns with a maximum heat-release sulated in plastic to prevent it from corroding from chemical splashes or from the atmosphere itself. In addition, if lateral hoods or a catwalk or other items are at the tank, the deflection described above may be difficult to measure. Spark testing may be a possibility, and DC spark testing, rather than AC spark testing, is the safest method, but it requires grounding to the steel, which complicates matters. Another option (except in the case of stainless steel) is to use a large on/off welding magnet to check if the mild steel has been eaten away. If the steel is still there, a strong magnet will connect to it, even through the plastic encapsulation. • Consider using solid-wall steel tanks over free- This tank measuring approxiamately 15 feet tall by 12 feet in standing plastic tanks with an encapsulated structure. diameter failed in the shop.

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The tank at left is lined with carbon steel and has 100 percent sealed clear vinyl exterior protection. The PPL tank above has a steel structure, insulation and clear vinyl protection. rate approaching that of gasoline. Temperatures as high as only to have the vessel burst from the added pressure. 1,093°C (2,000°F) are reached, sufficient to cause steel to • A large, steel-lined zinc-nickel plating tank lost all of lose strength and for buildings to collapse. Plus, firefighting its precious contents when it was accidentally drained. is made more complex by the presence of hazardous mate- Frank Altmayer, educational director of the National rials. Some plants have been a total loss. Association for Surface Finishing, advises against drain Loss-prevention data sheets from FM Global Property valves in plating tanks. recommend using “noncombustible construction for all • A PVDF tank, which earns it place as among the best pickling and electroplating tanks, fume collection and for acid service, is repurposed for a high-pH solution— exhaust equipment, and ducts.” The requirements for fire its Achilles heel—and fails. Don’t assume a great tank protection sprinkler systems, hose streams (500 gallons per can hold any solution; instead rely on the expertise of minute), water supplies, alarms and interlocks, containment your supplier. systems, and minimum one-hour fire separation between • An anodizer was using a caustic etch tank along with combustible plastic tanks and the surrounding occupancy a domed side tank to collect and separate the sludge. are exhaustive, costly and stringent. The etch solution produced a large amount of foam Polyvinyl chloride (PVC), chlorinated PVC (CPVC) and containing hydrogen gas, which accumulated in the polyvinylidene fluoride (PVDF) all offer excellent fire prop- dome of the tank; only a small pipe ventilated the erties, as they are among the least easily ignitable plastics dome. A spark from an unknown source at the etch and are self-extinguishing; they will not continue burning tank (probably metal against metal from the hoist work unless a large, continuous heat source is applied to them. bar) set off the hydrogen in the foam, and the clarifi- They also have low flame-spread ratings due to drastically cation tank took off like a rocket, blasted through the lower heat-release ratings. Tests have shown that burning wall of the building and landed in the parking lot, flat- PPL releases 14 times more heat than burning PVC. tening an unoccupied car.

Avoiding Human Error Our advice is this: Please learn from the experiences and Of course, the ever-present human element can result in tank catastrophic failures of others; be wiser because of their losses failures, too. Here are some examples we have encountered: and not your own. • A worker added air at the inlet of a slow-draining plastic cylinder in a treatment system to speed up the draining, Curtis Goad is president of Goad Co. Visit goadco.com.

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