COMPRESSED AIR & PVC
Often we are asked about the use of PVC piping systems for use in compressed air transmission or testing. Our response has to be a thunderous - NO!
The following supports our position:
- The Plastic Pipe and Fittings Association notes in their PPFA Bulletin #4-80 (10/79) "Compressed air or inert gases should never be used for pressure testing plastic piping systems.
- "The Plastic Piping Institute issued Recommendation B - Thermoplastic piping for the transport of compressed air or compressed gases.
"The plastic pipe Institute recommends against the use of thermoplastic pipe to transport compressed air or other gases or the testing of such piping with compressed air or other compressed gases in exposed above ground locations, e.g. in exposed plant piping. It is recommended that all thermoplastic piping used to transport compressed air or other compressed gases be buried underground or encased in shatter-resistant materials. In designing thermoplastic piping to transport compressed air or other compressed gases, the strength at the operating temperature, the pressure, the energetics and the specific failure mechanism need to be evaluated." - Adopted January 19, 1972
- The American Society for Testing Materials has this draft proposal which will be added to the standards for PVC pipe and fittings.
"The products covered by this specification shall not be used in piping systems intended to store and/or to convey compressed air or other gases. Furthermore, these piping system products shall not be tested with compressed air or other gases unless recommended for such testing by the specific manufacturer, Additionally, the specific manufacturer making this recommendation shall provide a detailed procedure for such testing." - ASTM F17 - Project 90-95-01
Although the use of PVC for compressed air transmission may appear easy, and inexpensive, the dangers are real and immense. Water, like most liquids, is not compressible, therefore it cannot store energy. When a hydrostatic failure occurs, water is projected, but the shrapnel is not projected very far.
On the other hand, air and other gases are compressible. This can result in large amounts of stored energy. System failure could lead to a disastrous situation when this energy is released, sending shrapnel outward. Severe injury and damage can result.