When it comes to process cooling, few industries rely on the application of heat as much as the sintering process in powder-metal manufacturing. With temperatures in the high heat section of a sintering furnace reaching several thousand degrees Fahrenheit, the parts must be cooled dramatically before being handled by operators.
Sintering is a process by which metal particles are chemically bonded and formed by heat and pressure without reaching the point of total liquefaction. To accomplish this, powdered metal and alloy mixtures are compacted into near-net shapes, typically using a high pressure press. The compacted material then must be placed in a sintering furnace to improve the bonds and harden the material to the desired final specifications.
To expedite the temperature-reduction process, cooling towers commonly are used to circulate water through a jacket that cools the air surrounding the part. The most common type of cooling towers are constructed of galvanized steel. For sintering, metalworking and other industrial processes, these galvanized towers unfortunately are susceptible to corrosion and rust problems that can require ongoing maintenance. This can lead to expensive process downtime along with repair costs.
Structure Maintenance Solutions, Drawbacks
Phoenix Sintered Metals LLC, a powdered-metal part manufacturer, inherited a galvanized cooling tower when the company purchased its facility in Brockway, Pa. The tower was so corroded it was losing water — and expensive water treatment chemical — at an alarming rate. Patching was slowing — but not preventing — the losses.
“We were losing a lot of water out of the bottom of the cooling tower on a daily basis because of the leaks,” explains Josh Crawford, maintenance supervisor at Phoenix Sintered Metals.
For aging galvanized cooling towers, this scenario is not unique. Metal cooling towers are under constant attack by salt air or the caustic atmosphere of many industrial sites. Minerals in hard water as well as its pH level also can contribute to corrosion.
To combat the slow deterioration, plant personnel often are tasked with patching panels and holes. Eventually, the cooling tower is replaced. Even with diligent maintenance practices and cooling water chemistries, galvanized cooling towers typically must be replaced every 7 to 12 years.
“We were spending a lot of time trying to patch cracks in the floors. We were able to contain it a little bit but never able to completely stop it. As time went on, the cooling tower continued to rust, and the problem became worse,” adds Crawford.
The cooling tower, having been relocated from a shuttered, second location prior to Phoenix Sintered Metals LLC’s acquisition of the facility, was oversized for the current operation by about 60 percent. While this did not impact the unit’s cooling capability, an oversized unit adds to operating costs in terms of electricity to operate fans and pumps. Water replacement and specialized water chemistries costs also are higher.
Eager for a more permanent solution, Crawford contacted ProChemTech International Inc. to inspect and evaluate the system. Also based in Brockway, Pa., ProChemTech provides cooling water chemistry, systems design and engineering solutions. “The previous ownership used that tower for quite a few years,” says Bill Foringer, plant manager at ProChemTech. “Initially, [Phoenix Sintered] considered refurbishing it, but that isn’t cost effective when you need new fan, motor, base and pan — it can get quite expensive. So, at that point we started looking at new cooling towers.”
Engineered Plastic Cooling Towers
When asked to make a recommendation, ProChemTech suggested a high density polyethylene (HDPE) plastic cooling tower. Phoenix Sintered opted to purchase an HDPE tower from a manufacturer with a line of factory-assembled and modular plastic cooling towers in capacities up to 2,500 tons. Made from corrosionproof engineered plastic, the seamless-shell design does not have joints, seams, panels, gaskets, bolts, fasteners or caulking like conventional towers.
“What drew our attention right away is that we wouldn’t have to worry about the rusting of the shell,” says Crawford. “Granted, had we purchased a new, galvanized tower, it wouldn’t require much upkeep at first, but eventually it would get to that point where we would have those same issues.”
Phoenix Sintered selected an induced-draft tower. Crawford says he is impressed by the cost and length of warranty associated with plastic cooling towers. Because HDPE towers are unaffected by corrosives, they require little maintenance and provide a longer service life.
According to Crawford, the unit was installed in July of 2016 by a local contractor recommended by ProChemTech and has been working well since.