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PVC pipe not to be used in compressed air systems

October 1990

The Department of Labor & Industries warned consumers and employers in May 1988 that plastic-polyvinyl- chloride (PVC) pipe cannot be used in compressed air piping systems without risk of explosion. By law, employers must protect their workers by avoiding the use of unapproved PVC pipe in such systems. Existing compressed air systems that use PVC piping must be completely enclosed, buried or adequately guarded according to specifications approved by a professional consulting engineer. Only Acrylonitrile-Butadiene-Styrene (ABS) piping was approved for use with compressed air, provided it was marked on the pipe as approved for compressed air supply.

In October 1989, the Plastics Pipe Institute (PPI) amended their original recommendations for thermoplastic piping in the transport of compressed air and other gases. WISHA's (Washington Industrial Safety and Health Act) Division of Consultation and Compliance Services now will accept thermoplastic compressed air piping that meets the following guidelines (recommendation B, to the PPI 1972 recommendation):

"The Plastics Pipe Institute recommends that thermoplastic piping intended for the transport of compressed air or other compressed gases be buried or encased in shatter-resistant materials, unless the piping has been manufactured from materials which shall resist shatter-type failures under the anticipated conditions. Specifically, above ground installations of thermoplastic piping should only be made using products which have been suitably evaluated and which are recommended by the manufacturer for the particular intended service.

"It is recognized that while adequacy of strength is an important element in the safety of a compressed gas piping system, consideration must also be given to the nature of failure should accidental failure occur, whatever its cause. Above-ground piping which fails by shattering can present a serious hazard to personnel by the resultant flying shards, or pipe fragments, which are rapidly propelled by the released energy of the suddenly decompressing gas. Because the inclination of a material to fail by shattering is determined not only by the nature of the material, but by pressure, pipe and fitting dimensions, and by the nature of the gas, the evaluation of shatter resistance should consider all these and any other pertinent factors."

NOTICE TO EMPLOYEES: If you suspect that a pressurized PVC piping hazard exists, bring it to the attention on your employer. If you do not obtain satisfactory results, you may file a confidential complaint with the Department of Labor & Industries. Complaints are investigated promptly. Call the Department's toll free number at 1-800-423-7233.

NOTICE TO EMPLOYERS: If you have questions about the suitability of a material for air system piping, call the Department of Labor & Industries Regional Office for a free consultation.

 

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