High Temperature Leak Sealant that Floats

[yamoffathoo]

The normally closed, 1500lb 10"nps wedge gate valve body/bonnet gasket is leaking 1200 psig and 500 degF subcooled water at about 1.5 lb/min.

The idea to plug this leak is to back seat the valve, hook a jacking pump to the packing blow-out line, close the valve and inject sealant. The inter-gate volume has a pressure equalizing line that exits the bottom of the body and is tied back into the process, so unless the sealant will float on water at these pressures and temperatures, it can escape.

I'm looking for success stories with temporarily sealing valves this way and what sealant worked best.

 

[unclesyd]

I Would contact the Furmanite People with your problem. They are not cheap but have the materials and know how to resolve your leak problem.

http://www.furmanite.com/

 

[yamoffathoo]

Furmanite, Team, CEDA, Sealweld...none have information on specific gravity at elevated temperatures and pressures of their exotic sealants.

 

[unclesyd]

How are you going to hold the sealant in the bonnet as the internal pressure will push any semi-solid out of the valve?

Something you might want to look at is a Syntactic Foam Product. These products could possibly allow you inject the material and let it set to bring in the microballoons in play to plug the leak.

Did you talk to anyone about boxing in the bonnet flange?
We have done this on Class 600 Globe Valves/

http://www.crgrp.com/technology/materialsportfolio/sialyte.s

html

http://www.synfoam.com/SynFoamHT.html

Do you have any deposits or broken bolts on the flange?
Either one of these conditions would preclude any attempt to plug the leak.

 

[yamoffathoo]

Uncle Syd,

Sorry for any confusion; the valve will be closed when sealant is injected into the body through the packing blow-out hole in the bonnet. Leakage flow presently enters the inter-gate volume through the pressure equalizing line, rises around the wedge and exits through the body/bonnet gasket. A sealant that floats will flow into the gasket leak paths under a 1200 psi pressure differential.

We are looking at injecting a castor oil carrier dosed with tiny graphite particles that have been shown to plug .001" wide stress corrosion cracks in stainless steel piping systems. The particles create log jams which effectively block flow until they are disturbed by system transients.

Peening the body/flange gap closed or applying a clamp have all been assessed as too risky because of the increased stud load from increased hydrostatic area.

Lack of maintenance resulting in loss of gasket resiliency is the culprit here.

 

[unclesyd]

Your last post ring a few bells. A product called Bar's Stop Leak, a mixture of Flake Graphite, Asbestos Fibers,w with and Soluble oil carrier was used to stop a leak in the cooling system of the first atomic submarine, Nautilus, prior to commissioning. it was still hold until the sub was decommissioned.
i pretty sure they don't add Asbestos fibers any more but you might call Bar's to see what they have now.
You could still add Asbestos Fibers to you mixture to enhance the leak plugging ability.

http://www.barsproducts.com/tech_sheet.htm

You may want to file this.
To help seal a valve bonnet we drilled and tapped the flanges at each bolt hole. To help hold the injected sealant we use soft iron bailing wire to help hold the sealant in the gap between flanges. The leak was sealed after only injecting sealant in 4 or 5 of the tapped holes. The sealant was a pasty compound that set up rather quickly.

These reason for asking about deposits or broken bolts was we had two incidents were caustic embrittlement was the cause of flange leaks. The leak sealing company was going to to replace the broken flanges and slug the remaining bolts down. This probably would have resulted in a catastrophic failure and fatalities.

All it takes is a good plan. Please keep the forum informed as to you progress.

 

[yamoffathoo]

The injection proposal was deemed too risky, process shut down and gasket replaced...thanks anyway.