Cautions Areas

USE OF COMPRESSED AIR OR GAS WITH GF Harvel PVC/CPVC PIPING PRODUCTS

GF Harvel's PVC and CPVC piping products are "rigid" thermoplastic materials. As a result, GF Harvel does not recommend the use of PVC or CPVC piping products for the testing, transport, or storage of compressed air or gases. The compressibility of air and/or other gases result in tremendous amounts of stored energy, even at lower pressures. Should a failure occur in a compressed air or gas system for any reason (i.e. improper assembly, mechanical damage etc.) the failure mode will be very dramatic in nature due to the physical characteristics of the rigid piping in combination with the immediate release of this stored energy. Under these conditions, the velocity created by rapidly escaping air and the resultant failure mode can throw shards of plastic in multiple directions (i.e. shrapnel/projectiles). This scenario creates a substantial hazard to personnel and property within the vicinity of the piping should a failure occur. Several cautionary statements and alerts against the use of rigid PVC/CPVC piping for use with compressed air or gases are available through the Plastic Pipe Institute (PPI), American Society for Testing and Materials (ASTM), various other trade organizations, manufacturers, safety codes, as well as several State and Federal Agencies (i.e. OSHA).

The following statements currently appear in our published literature:

"GF Harvel recommends against the use of its thermoplastic piping systems for transport or storage of compressed air or gases. Trapped air must be removed from liquid piping systems so that no air remains locked in the system when pressure is applied to the liquid. Excessive surge pressure must be avoided. Surge pressure can develop if liquid movement through the pipe is near maximum velocities and valves are closed abruptly. Maximum velocity is generally considered to be 5 feet per second."

"Compressed air or other gases should never be used in testing. Extreme care should be used to assure complete venting of all entrapped air when filling the system with water or other liquids used in testing. Whether a hydraulic hand pump or available water line pressure is used, any slow build-up of gauge pressure on a completely liquid filled line shows some entrapped air in the system. Pressure should be immediately released and the line re-bled. Failure to do this can lead to a catastrophic failure when the decompressing gas suddenly accelerates the solid water column if a faulty joint separates."

"CAUTION: PVC and CPVC piping systems are not recommended for compressed air lines. Improper installation, especially poor cementing techniques can lead to an abrupt release of tremendous stored energy. Shattering of pipe and fittings is then apt to occur at directional changes and at points where the system is rigidly restrained due to the instantaneous whipping action imparted by the escaping air. Internal surface cracks, due to the stress, can be initiated which will tend to propagate and cause shattering, hairline or pinhole cracks over a period of time. There is also evidence that certain additives to system lubricants will initiate internal stress cracking which will again lead to similar failure over extended periods of time."

Warning! The use of rigid thermoplastic plastic piping in compressed air or gas applications can result in severe bodily injury or death.

Use of Plastic Pipe to Construct Launching Devices

It has been brought to our attention that plastic piping products are being used to construct launching devices commonly known as "Spud Guns". GF Harvel does not recommend nor approve these or similar devices. Devices of this type are extremely dangerous regardless of the type of piping materials used to build them.

GF Harvel does not recommend the use of our PVC or CPVC piping products for the testing, transport, or storage of compressed air or gases. The compressibility of air and gas results in tremendous amounts of stored energy, even at lower pressures. Should a failure occur in a compressed air or gas system, the failure mode will be very dramatic in nature due to the physical characteristics of the rigid plastic piping in combination with the immediate release of this stored energy. Under these conditions, the velocity created by rapidly escaping air and the resultant failure mode can throw shards of plastic in multiple directions (i.e. projectiles). This scenario creates a substantial hazard to personnel and property within the vicinity of the piping should a failure occur. Several cautionary statements and alerts against the use of rigid PVC/CPVC piping for use with compressed air or gases are available through the Plastic Pipe Institute (PPI), American Society for Testing and Materials (ASTM), various manufacturers, safety codes, as well as several State and Federal Agencies (i.e. OSHA). It should also be noted that these types of devices are considered illegal by many State laws.

In addition to the obvious risk of bodily harm involved with the handling of flammable/explosive materials of combustion, plastic pipe utilized in this application is subject to failure for the following reasons:

  • The failure mode of rigid thermoplastic piping under these use conditions will be very dramatic. The rapid release of the pressure build-up associated with the combustion gases can result in the instantaneous rupture of the pipe wall and/or attached components. This will result in shards of plastic (shrapnel) rapidly escaping at high velocity.
  • Temperatures created as the result of the ignition of flammable substances can quickly exceed the thermal properties of the piping, thereby greatly reducing its physical properties and making it more susceptible to failure.
  • Shock loads associated with the combustion of the flammable substance can quickly exceed the design capabilities of the plastic piping.
  • The sudden pressure rise associated with combustion can quickly exceed the pressure bearing capacity of the piping.
  • Chemical compatibility issues with certain flammable substances can cause stress cracking and premature failure of the plastic.

Warning! The use of plastic piping in these types of devices can result in severe bodily injury or death.