Gross-leak test

Pressurize unit with nitrogen to 200 kpa and perform a low-pressure gross leak test. Correct any leaks found PF/Operations team ... 

Fine and gross leak tests should be conducted in accordance with the requirements and procedures for the specific test conditions for the device. Combinations of fine and/or gross leak testing can be conducted in sequence or at the same time. 

Before connecting the pump sub-assembly into the system, set up the pump with hoses connected on the inlet and outlet and turn the pump on, feeding it water. Observe the action of the pump to get a feel for it and notice if there are any leaks. Such a test is limited because there will not be back pressure from the whole system (unless you provide for that), but this test will indicate any gross leaks. 

Fine and gross helium leak testing will detect any marginal or bad seals through which moisture and other contaminants can enter the package. 

After work which involves breaking joints on a solvent recovery unit, the plant should be pressure tested before being returned to service. This test need not be done to a pressure over that specified for the bursting disc since it is to detect gross leaks which cannot be corrected by pulling up joints while the plant is operating. 

Cumulative Helium Leak Detection (CHLD) is a variation on conventional leak detection that allows for gross and fine leak testing in the same pass and the potential for helium-leak detection at leak rates several orders of magnitude lower than with conventional leak-detection methods. 

The hydrostatic test is, in one sense, a method of examination of a vessel. It can reveal gross flaws, inadequate design, and flange leaks. Many beheve that a hydrostatic test guarantees the safety of a vessel. This is not necessarily so. A vessel that has passed a hydrostatic test is probably safer than one that has not been tested. It can, however, stiU fail in service, even on the next appheation of pressure. Care in material selection, examination, and fabrication do more to guarantee vessel integrity than the hydrostatic test. 

If H0 is rejected, a two-stage procedure is initiated. First, a list of candidate biases and leaks is constructed by means of the recursive search scheme outlined by Romagnoli (1983). All possible combinations of gross errors (measurement biases and/or process leaks) from this subset are analyzed in the second stage. Gross error magnitudes are estimated simultaneously for each combination and chi-square test statistic calculations are performed to identify the suspicious combinations. We will now explain the stages of the procedure. 

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