When out of round makes metal out of the question.
A natural gas plant in Texas had six, very specialized mainstream control valves that had unwavering steam leaks through the pressure seal cavity. The leaking increased with time. No matter what the team did in terms of resurfacing the cavity or changing the originally designed metal pressures seals, the steam kept leaking and the valves made an awful racket.
According to Rob Garlock, Fluid Sealing Engineering Specialist for EGC, the metal pressure seals within the valves were leaking so badly that there was a giant hissing noise in that area of the plant. A metal replacement would have required a massive amount of machining to bring the bonnet cavity up to speed. Instead, the plant called EGC.
Flexible graphite pressure seals were the ideal solution. However, “engineering was a challenge,” said Rob. “After careful measurement from the rebuild team, we only had a .320-inch bonnet neck height. Normally, we’ve got 1/2 to 2 inches, but this neck was extremely short. This time, the installed length of the seal was absolutely critical.”
Paying strict attention to the minimum and maximum conditions, EGC was able to come up with a singular design that would work for all 6 valves. “Had they used a metal seal, they would have had to make a specific seal for each application,” said Garlock. “We saved them a substantial amount of money doing it our way.”
The characteristics of flexible graphite to conform and compress were the key, even when out-of-round conditions persist. When high-density graphite is placed within the bonnet cavity and the bolts are tightened, it draws the bonnet up. Graphite literally can take the shape of the seal area in a way that metal seals cannot. It also works in oversize, steam cut and pitted bonnet cavities without the need for welding, grinding or refinishing.
In an email sent to Thom Jessup, EGC’s Sales Manager for Industrial Fluid Sealing Products, the plant’s team said: “Thanks for being the brain-child for Graphite seals. We took the unit 1 for a test drive today, and it was eerily quiet! Without the main steam blowing all over the place, it sounds like a different machine. Another huge thanks to the rest of the crew for setting us up with this fine product.”
Aside from being quiet, the VSG Pro is resilient, so it seals every time while rebounding after every pressure cycle. It won’t fuse to valve components and, after use, lifts right out of the valve. In time studies for valve maintenance, you can save nearly 75% installing graphite over metal. And every VSG Pro is custom engineered, manufactured and has a scheduled lead time of just 48 hours. Same day if necessary. See our site at www.egcgraphite.com or visit our microsite at www.outageseason.com for more information.
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