Sulfuric Acid Line Leakage

[Nabeel Ahmed Qureshi]

At our site, we handle 95% H2SO4. Few days back we faced a leakage from a 2'' fillet weld joint connected to 3'' main header. We usually do RT of all but welds to ensure their integrity however DPT is only done for Fillet weld joints. There are quite a few number of fillet joints which seems vulnerable after this incident. Can some body let me know how to ensure the integrity of remaining such fillet joints. We plan to conduct hydrotest of entire piping above design to testify the circuit fit for use. Would it be enough or we shall plan something else?
Regards
NAQ

[arcpro]

Nabeel,
Weld joints in critical / hazardous services are inspected one step ahead from other services. Many a times designers avoids such weld joints which cannot be radiographed with ease or if such joints are included in the system then inspection protocols are set more stringent as compared to other piping networks.
Fillet welds in hazardous services must be undertaken with following inspection protocols:
1. Fit-up must be checked before commencement of welding
2. DPT after first pass should be undertaken
3. DPT after final pass
4. Fillet size verification

This protocol shall be followed for every fillet weld under hazardous services.

[qaisarabbas]

For health assessment of remaining joints, you should do RT for Butt weld joints & Hydrotesting for both Fillet & Butt welds.
UFD may also be tried on fillet welds.

[mechcolor]

For piping fillet welds inspection, you always remain short of taking advantage from most conventional and useful techniques like radiography and ultrasonic. But you can still try magnetic particle testing on fillet welds in addition to penetrant testing.
The best way to control any defects in new welds is to adopt the strategy suggested by arcpro.
For the welds in service, you may carry out magnetic particle and obviously strength test of whole piping.

[octane]

Thanks...
Good information.