[MW:27755] Helium leak test in lieu of PT test for tube-to-tubesheet joints for ACHEs?

Dears, 

For tube-to-tubesheet joints in air cooled heat exchangers, can helium leak test be a substitute for PT test? One of our vendor have proposed helium leak test in lieu of PT test for tube-to-tubesheet joints.

Vendor have provided following justification,

We have offered a helium leak test after welding the tubes, in lieu of the requested liquid dye penetrant testing of the T/TS welds. We have found that the application process of spraying the liquid penetrant and developer through a plug hole using an aerosol can is ineffective as it is difficult to control the amount of chemicals being applied. we have even experienced on some jobs where excessive penetrant of developer solidifies giving false negative/positive results causing unnecessary rework or obscuring potential indications (leaks). if PT testing is desired over the helium leak testing, we can perform the testing at no charge, but will not guarantee or provide a report stating the results were acceptable. 

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