As we have discussed before, the PREFERRED pressure/leak testing method is hydrostatic. This is the “rule” for all of the ASME B31 series RAGAGEPs; however, for some odd reason, many businesses believe that pneumatic testing is “easier, cleaner, and cheaper” and will just perform their testing with little to no consideration for using hydrostatic methods. But B31.9, Utility Piping, has some very specific restrictions for using pneumatic testing on “plastic pipe,” and that is what I want to discuss in this article.
Here are also some BASELINE requirements for “pneumatic pressure testing” done under ASME B31 series (31.1 – 31.12):
The first choice is ALWAYS “hydrostatic testing,” as it is far safer than pneumatically testing piping, which many refer to as “creating a small bomb.” As shown below, there are several requirements that MUST be satisfied to use pneumatic testing instead of a hydrostatic test.
B31.9
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937.4 Pneumatic Testing
937.4.1 General.
Compressed gas poses the risk of sudden release of stored energy. For that reason, pneumatic testing shall be used only within the following limitations:
(a) The piping system does not contain cast iron pipe or plastic pipe subject to brittle failure. (see the types of plastics subject to brittle fracture failures below)
(b) The system does not contain soldered or solvent cement joints over NPS 2 (DN 50). (NOTE: most plastic pipe joinments have solvent cement joints)
(c) The test pressure does not exceed 150 psig.
(d) The system will be used in gas service, or for other reasons cannot be filled with water. (Water pipe is going to be in water service)
(e) Traces of a test liquid would be detrimental to the intended use of the piping. (Water pipe is going to be in water service)
The most common plastic pipes subject to brittle failure include:
- PVC (Polyvinyl Chloride): The most widespread rigid plastic pipe.
- CPVC (Chlorinated Polyvinyl Chloride): Similar to PVC but formulated for higher temperatures.
- ABS (Acrylonitrile Butadiene Styrene): Commonly used in drainage, but behaves similarly to PVC if subjected to pressure testing.
- UPVC (Unplasticized Polyvinyl Chloride): A highly rigid form of PVC.