Out of Round? No Problem!

A valve was over-pressurized in a west coast nuclear power plant.  It led to an extreme condition called out-of-round in the pressure seal cavity.  They called the manufacturer but there was no way to machine the cavity back to accepting a metal seal. And, it would take 20 weeks to get an identical valve. Knowing that the plant couldn’t wait that long, the OEM called EGC.

When the EGC engineers checked out the 15”, 900 lb. main steam header shut-off valve, they found that out-of-round was only part of the problem.  It was oversized, coned and ballooned.

So, the engineers went to work.  They understood that Thermafoil® high-density graphite is extremely flexible when it comes to sealing a high-pressure application with these conditions.  They know that they can bend, mold and reshape what is standard into something that’s truly an art form.

EGC carefully measured and crafted a 16”, capped VSG pressure seal that would fit within the valve cavity.  “With a graphite pressure seal, the end caps are designed to flare-out to contain the graphite”, says Rob Garlock, EGC’s Pressure Seal Engineer.  “This means that they will mold to the shape of the valve body ID once the seal is put under load, even if it is out-of-round or egg shelled. And if the graphite needs to fill any scratches, grooves or imperfections it will flow to these points under load to seal them and prevent leakage.”

The plant reported zero leakage and no failures since the VSG was installed.  EGC pressure seals remain the preferred choice at this facility.