Using plastic for compressed air piping
Contaminant-free compressed air piping systems continue to become increasingly important with the advent of industrial automation. This article discusses the benefits to using plastic piping, the limitations of certain plastics, the do's and don'ts of installation, joint drying times for 100 percent pressure testing, provides a sizing guide for main air lines and more.
"Plastics," the famous one-word line from the 1967 film "The Graduate," was said to be the key to the future. That prediction was never truer than today as it relates to compressed air piping systems. The technology for using plastic for compressed air systems ( Fig. 1 ) has been around for a number of years in Europe. Today, the use of plastic for clean compressed air systems has become widespread in the United States.
Contaminant-free compressed air systems have continued to become increasingly important with the advent of industrial automation. Assembly robots, packaging equipment, paint spraying, and pharmaceutical processing are just a few of the many applications that require clean compressed air.
Black iron or galvanized steel pipe commonly used for compressed air systems typically generates rust, corrosion, and other debris that can cause manufacturing problems. These contaminants are minimized or eliminated by using stainless steel or copper pipe. However, metal piping systems, particularly threaded systems, are still prone to leakage, which forces the use of larger, more expensive compressors. Also, stainless steel and copper, on an installed-cost basis, can be prohibitively expensive.
Low operating costs are possible with plastic in compressed air systems. Even if only a small percentage of threaded joints in a plant are leaking, this loss can amount to thousands of dollars per year, not counting any major leaks that may go unrepaired for long periods of time. The end result is lower efficiency and waste of valuable energy, which plastic piping can reduce.
Plastic piping manufactured for compressed air systems is a specifically designed thermoplastic, a specially engineered formulation of ABS that has been extensively modified. The result is a homogeneous shatter-resistant piping system with outstanding strength, ductility, and impact resistance. The ABS used conforms to Cell Classification 54322 as outlined by ASTM D-3965. A failure from over-pressurization or severe impact would merely result in a crack or split that would release the pressure harmlessly. No fragmentation of the pipe or fitting would occur ( Fig. 2 ).
Other thermoplastic piping materials, such as PVC and CPVC, are recommended for liquid service, but should never be used to convey compressed air. The use of PVC and CPVC in a compressed air system could result in a failure that would cause the rapidly decompressing air to fling sharp fragments of plastic through the air.
Plastic has proven to be ideal for compressed air and gas, based on four factors engineers take into consideration when specifying a system:
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Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.
There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.
But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.
Read more: 2015 Salary Survey