WATER TUBE BOILER HYDROSTATIC TEST

[perruolo]

Gentleman

We are close to start a plant Shutoff for maintenance. Client scope of work state carry out hidrostatic test in 4 water tube boiler (which have been in service)at 1.5 MAWP to detect leaks. However, NBCI Part 2 section 4.3.3 a) states that test pressure shall not be greater than MAWP stamped. How can this affect the integrity of Boiler??? What argument can I use to persuade the client to change their mind?

Thanks

MP

 

[metengr]

The NBIC in Part 3 allows the following;
Pressure tests shall be conducted using water or other liquid medium. The test pressure shall be the
minimum required to verify the leak tightness integrity of the repair, but not more than 150% of the
maximum allowable working pressure (MAWP) stamped on the pressure-retaining items, as adjusted
for temperature. When original test pressure included consideration of corrosion allowance, the test
pressure may be further adjusted based on the remaining corrosion allowance;

So, 1.5 X MAWP is indeed permitted for repairs and alterations. To check for leaks, the same approach can be used on small watertube boilers or fire tube boilers where nondestructive testing is difficult to establish wall thickness or to check for defects. The 1.5 X MAWP will find small leaks but that is about it. It will not cause a leak unless the defect or crack is near though-wall because the component material at room temperature still retains strength versus component material under pressure at elevated temperature. Another concern with 1.5X MAWP testing is that all pressure relief devices should be removed to avoid damage. This takes time and effort.

 

[perruolo]

metengr Thanks for your advise.

However we are not still repairing anything. We should first evaluate the actual condition of boiler and the take actions based on results. That´s why I mentioned NBCI Part 2 which required that pressure does not exceed MAWP stamped

 

[metengr]

perruolo;
I have seen many clients only use Part 3 of the NBIC to take advantage of elevated pressure testing (up to 1.5X MAWP) for condition assessment - no repairs or alterations. I agree you can and should use lower pressure.

If you are using the 2013 Edition of Part 2 of the NBIC here is what is stated for Liquid Pressure Testing;

4.3.1.2 LIQUID PRESSURE TESTING
Test pressure should be selected or adjusted in agreement between the Inspector and Owner-user.
The liquid test pressure shall not exceed the lesser of 150% of MAWP or test pressure established by the
original code of construction.

The pressure testing was revised to sync up with Part 3.