As we continue to “dumb down” RAGAGEPs to take away OSHA/EPA’s ability to cite fundamental engineering failures found in processes handling HHC/EHS, the issue of “conflicting requirements” continues to be troubling. As my Anhydrous Ammonia clients learned firsthand last year, with the 7th edition of CGA 2.1, the RAGAGEP has some NEW requirements for pressure testing and leak testing piping. Although this was a revision, it was IN NO WAY necessary, and there is just a tiny (all pun intended) exception that conflicts with the pressure/leak testing requirements found in ASME B31.3 and 31.5.
Call me a pessimist, but I believe this revision was added to make the last sentence “allowable” rather than simply referencing the RAGAGEPs the standard already references (B31.3 and 31.5). They wanted to sneak in these ten (10) little words, which is a clear VIOLATION of ASME B31.3, 345.4.1, and 345.5.3.
The new content that CGA 2.1 now allows (conflicting with ASME B31.3/B31.5)…
(emphasis by me)
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5.6.10 After assembly of the complete piping system, including appurtenances and components. the piping system shall be proven free of leaks by performing a leak test at not less than the normal operating pressure of the system. Using anhydrous ammonia as a test medium shall be permitted. |
In my early days of working with NH3, a phrase uttered under our breath was “farmer testing.” No offense to the farmers who use NH3, but in the middle of a 1,000-acre cornfield at 2:00 a.m., there are LIMITED resources AND LIMITED exposures (only farm hands), so leak testing piping/hoses by allowing a small amount of NH3 to enter the system, then closing the valve and “sniffing around” the implement(s) to deploy the NH3 is all they can reasonably do.
But inside an industrial facility, including those that are only a storage and filling facility (i.e., bulk and nurse tanks), it is IMPERATIVE that the proper means and methods be used to leak-test our piping.
To demonstrate the conflicting requirements, here is what ASME B31.3 states. I should point out that CGA 2.1. references B31.3 three (3) times as the chosen piping RAGAGEP.
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345.4 Hydrostatic Leak Test 345.4.1 Test Fluid The fluid shall be water unless there is the possibility of damage due to freezing or to adverse effects of water on the piping or the process … 345.5 Pneumatic Leak Test 345.5.1 Precautions Pneumatic testing involves the hazard of released energy stored in compressed gas. Particular care must therefore be taken to minimize the chance of brittle failure during a pneumatic leak test. Test temperature is important in this regard and must 345.5.2 Pressure Relief Device A pressure relief device shall be provided, having a set pressure not higher than the test pressure plus the lesser of 345 kPa (50 psi) or 10% of the test pressure. 345.5.3 Test Fluid The gas used as test fluid, if not air, shall be nonflammable and nontoxic. |
Another question I have is about “leak testing” pressure requirements. How will we generate the NORMAL operating pressure by using NH3 gas within the process? Maybe we could meet this pressure on some vapor lines, but how do we generate NORMAL operating pressures AND CONTROL that pressure in the piping during the “leak test”?
I may be persuaded to allow NH3 to be used on a leak test AFTER maintenance on a VERY SHORT run of SMALL DIAMETER piping. But CGA does NOT LIMIT the use of NH3 gas, and I can just see some former clients using NH3 gas to test their entire process for leaks, and in my professional opinion, they will get what they are asking for.
99.99% of the time, this will be done in the name of saving $. Nitrogen is too expensive to use, and the facility will not have the means to CLEAN and DRY their compressed air (as that too costs $), so they will use this 10-word sentence to through caution to the wind and declare it safe because their chosen RAGAGEP allows it.