Injected sealant flange clamp 1

[DrejzaVu]

Can a flange clamp with injected sealant considered permanent repair for a leak? According to API 570 Section 8.1.4 Nonwelded Repairs, such repairs are temporary and must be replaced at turnarounds or appropriate opportunities.

Is there any other standard or code that permits the use of such sealing technologies as permanent repairs?

Mark

 

[Cockroach]

I can't recall the exact specification, it may be API 6D or something of that nature, flanges loose their ANSI rating when a) material is removed, b) repairs involving heating beyond annealling temperature. The typical interpretation is no machining (material removal) or welding (heat application - PWHT, stress relax, etc) that would imply carbide migration in the ferrous matrix.

On the other hand, if you do a weld repair and get the flange NDE c/w chemical analysis, the engineer is permitted to certify such repairs as meeting the intent of manufacturing. Typically it is more cost effective to replace the flange since examination and testing costs far exceed the value of replacement.

I have never met an engineer who personally admitted recertifying a flange, I know for sure that I would not!

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[jte]

DrejzaVu-

I'd go with the API 570 approach. The flange clamp increases the load on the bolts (OD of sealing surface is now around the flange OD, not gasket diameter) so be sure to check that before installing flange clamps. For those of you who don't know what we're discussing, see

http://www.drshannonco.com/Plidco Flange+RepairRings.htm

for an example. Sooner or later the goop you injected will harden and crack or you'll get a thermal excursion which loosens it and you'll wind up having to re-inject the clamp. If the clamp has been on for a while, the injection ports may or may not work. If you can't get the clamp to seal you'll need to box the whole setup with a welded or bolted encapsulation.

The cost of removing the clamp, cleaning the goop off of the flanges (which should be undamaged), and putting a new gasket in is pretty small. That's the approach we take at our facility.

If the flange is a repeat offender, you might want to torque the bolts, add bellville (spring) washers, and/or run a piping stress analysis to be sure that you aren't loading the flange beyond their rating when you include the equivalent pressure due to tension or moment on the flanges.

A question for other flange clamp users out there: We always trash the clamps after they've been used. Does anyone refurbish and reuse their flange clamps or bolted boxes?

jt

 

[dmreeser]

I DON'T KNOW ABOUT THE CERTIFICATION OF FLANGES BUT WORKING IN A STEEL MILL I AM FAMILIAR WITH THE TEMPORARY REPAIR OF FLANGES WITH FLANGE CLAMPS AND INJECTION .THEY ARE AT BEST TEMPORARY AND SHOULD ONLY BE USED UNTIL THE LINE CAN BE ISOLATED AND REPAIRED.WE USE THEM ON OUR STEAM LINES AND FOUND OUT THAT THEY ARE EXPENSIVE,VERY TEMPORARY AND WHEN A SUBSTANCE IS INJECTED INTO THE CLAMP IT CAN ALSO ENTER THE PIPE ITSELF AND CAUSE OTHER PROBLEMS DOWN THE LINE.
DURING OUR LAST STEAM OUTAGE WE REMOVED 2 REPAIR BOXES,I PLAN ON TRYING TO SALVAGE THEM,I WILL LET YOU KNOW IF IT IS WORTH THE TROUBLE.