B31.1 - Hydro vs RT Exam

[JamusPSI]

Is there any stipulation that will allow RT to be substituted for hydro testing in a pipe that is designed for gravity flow and lo temp? Customer states it must be designed to B31.1 because this pipe is the core pipe in a double wall pipe scenerio.

 

[ColonelSanders83]

See below.

“137.3.2 Nonboiler External Piping. All nonboiler external piping shall be hydrostatically tested in accordance with para. 137.4. As an alternative, when specified by the owner, the piping may be leak tested in accordance with para. 137.5, 137.6, or 137.7. Lines open to the atmosphere, such as vents or drains downstream of the last shutoff valve, need not be tested”

“137.7.7 When specified by the owner, an initial service test and examination is acceptable, when other types of tests are not practical or when leak tightness is demonstrable by the nature of the service. One example is piping where shutoff valves are not available for isolating a line and where temporary closures are impractical. Others may be systems where during the course of checking out of pumps, compressors, or other equipment, ample opportunity is afforded for examination for leakage prior to full scale operation.”

You could make the case that provideing RT on the piping in question lowers the risk to the point that an in service leak test is adequet for the service. You could futher justify the lower test criteria if your calculated stresses for the system are signaificantly lower than the allowable stress for the line, again lowerin the risk. At the end of the day the test specified in B31.1 is a leak test only, not a strength test. For non-critical service Non-Boiler External Piping (NBEP) applications we perform an in service leak test with no problems. At the end of the day you must convince the owner this is adequete, if he refuses you are stuck with the full blown hydrotest. Its not a fight you can always win.

A question properly stated is a problem half solved.

Always remember, free advice is worth exactly what you pay for it!

http://www.ap-dynamics.ab.ca/

 

[vpl]

Colonel Sanders makes a very good point with his last sentence. In the end, you have to convince your client and do what was agreed to in the contract. If it's spelled out in the contract, you do it. If it wasn't spelled out, and the client insists, you can try quoting extra money to do the hydro. Of course, you have to balance the request for more money with how much you want the client's repeat business...



Patricia Lougheed

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