Molten Sulfur Pipeline Integrity Assessment

[cwood3]

I ran across a situation yesterday that I haven't encountered before. A facility has a 2000' long 12" Std, Class 150 molten sulfur transfer pipeline. It operates at ~300F, less than 100 psig. The concern is that 3-4 years ago, it was noticed that the line had obviously undergone some thermal expansion, to the degree that some of the guide shoes moved off of the sleeper and more or less locked the line in place. The line is on "T" supports about 6' above ground. It is steam traced and is basically kept at 300F 24/7, sulfur transfer is periodic, not constant. The owner wants to correct the problem via performing a proper stress analysis. This will determine if the line was designed properly, if the supports were designed properly, or if neither was designed properly. They also want to know if there is the potential for the line being damaged or stressed in it's current state.

So after the stress analysis and taking the corrective action as far as piping and supports go, there ought to be some material integrity checks. Could be as simple as spot UT to verify wall thickness due to corrosion. All of the aforementioned is not a big dilemma. I was wondering about performing a hydro-test on the line after is fixed. This being a sulfur line, there's going to be a big mess inside it. What about the creation of sulfuric acid due to water + sulfur..? Any thoughts?

Thanks

 

[cwood3]

I know, strange, eh?

bump

 

[SJones]

If the principal issue has been one of stressing, what else suggests that corrosion should be addressed, other than by taking the tracing off for a CVI? Hydrotest should be a last resort driven by the expected degradation mechanism, or by regulation.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.