chillers
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f you’re running a molding plant without quality cooling water you’re basically taking a bath with a toaster. Trouble is, water-cooling systems are fairly complex and prone to a host of problems. Some are obvious and catastrophic while others are silent, creeping failures that slowly erode your plant’s productivity. Wanna avoid both kinds? Keep the following in mind.
PIPELINE TO CATASTROPHE Abrupt cooling failures are usually caused by issues relating to system design, equipment selection, or maintenance. A poor choice of system components during the planning stage can wreak havoc later on. “When designing a cooling system, the load needs to be tabulated to ascertain its cooling capacity limits,” said Al Fosco, global marketing manager with Frigel North America. “A load study can be performed to calculate the heat loads associated with each molding machine in the plant.” Planning can be made a bit easier by following a rule of thumb. “A water flow velocity should not exceed 10 feet per second,” said Mike Sinclair, regional sales manager with Berg Chilling Systems Inc. “If it does, it can create erosion at the elbows, and at valves and other 12
flow control devices, that can lead to failure. Also, everything eroded by the highvelocity water will move downstream and plug up your equipment.” One of the most catastrophic flow problems is a burst pipe — if a main header bursts, the system can empty quickly, inundating operators and equipment. It’s an outcome that can also be avoided by proper planning at the outset. “Most often, a burst pipe is caused by lack of proper support, such as a hanger failure,” said Al Fosco. “All piping must be supported to minimize stress. In addition, some pipe materials are more susceptible to failure than others.” Which is why picking the right material is so important. “PVC piping is a good option for an inexpensive, non-corrosive, non-reactive system — it doesn’t support bug growth and it doesn’t corrode — but it’s crucial to select Schedule 80 PVC rather than lighter-duty Schedule 40 PVC, which cracks and breaks easily,” said Mike Sinclair. “But with the decline in stainless steel prices, more and more plants are using Schedule 10 stainless steel in their large diameter piping, and this is probably the best all-round solution, as it’s extremely difficult to damage stainless steel.” The answer to the plastic or steel
Frigel North Photo Credit:
America
How to avoid cooling system meltdown By Mark Stephen, editor dilemma? Operate your system with procedures that prevent the pressure spikes known as “water hammer”. As a rule, prudent system design also includes provision for back-up pumping — preferably a pump scheme that permits automatic transfer to the back-up pump to keep the system operating when a failure occurs. One solution is a dualarm pump that incorporates two pumps in one casing. “It’s also important to have a comprehensive understanding of the cooling system design,” said Al Fosco. “Often, the system fails because a valve operates incorrectly — it either opens when it shouldn’t, or it may open too far, or not far enough. A valve may operate accidentally or even fail internally. Regardless, you’ll need to have a complete system drawing with valves and components identified and their locations noted for quick reference.”
WATERY GRAVE Once the cooling system has been designed, installed, and is up and running, a primary focus shifts to maintaining good water quality management. “Good water quality will ensure clean heat exchangers and corrosion-free piping, which will prolong the plant equipment’s
Canadian Plastics June 2015 www.canplastics.com
CPL Jun15 p12-15 Chillers.indd 12
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