Three-Way Valve Minimizes Dangerous Fugitive Emissions

N/Aytown, TX processing plant, engineers needed to replace a number of multiport 3-way valves in a liquid phosgene application. The German-manufactured valves that were in use performed adequately. However, parts and replacements for the German valves were expensive and a long leadtime was required for delivery. Plant management was also interested in upgrading the stem seals to better control fugitive emissions. Control of fugitive emissions was especially difficult because the process involved thermal cycling. The temperature varied from ambient to –30°F.

Working with the Special Products Group of Xomox (Houston), a 3-way sleeved plug valve (Figure 1) was modified with a patented, extended-stem packing design (Figure 2). The Tufline XP top seal was deemed especially appropriate because of its exclusive (and patented) thermal shrink-seal lip which helps control fugitive emissions. To control fugitive emissions during thermal cycling, a lip is machined in the interior bore of the bonnet of the Tufline XP Sleeved Plug Valve (Figure 3). Any radial shrinkage of the live-loaded PTFE packing causes the packing to compress tightly against this lip. This patented shrink-seal lip actually tightens the seal as the packing shrinks.

Primary top sealing is provided by the interaction of the plug, the full-circumferential PTFE sleeve, and the body. The extended live-loaded packing provides secondary, back-up sealing for superior control of fugitive emissions. The unique design included a special TFE/Grafoil double-packed stem. (Grafoil packing is a product of UCAR Carbon Co.) It was also a plus that Tufline was able to easily and economically match existing face-to-face dimension- and bolt-pattern requirements.

The new valves matched or exceeded the performance of the previously used German valves. For process applications, they are available in ANSI Classes 150, 300, or 600; with flanged or screwed ends; in multiport configurations; and with a monitoring port. The valves are also fire-tested to API 607, 4th Edition.

Plant management and engineers now breathe easier with improved assurance of compliance with EPA air quality regulations. Tufline and plant personnel have also developed a continuing partnering relationship. Plant engineers rely on continued valving support that is nearby, responsive, and economical.

The Xomox Special Products Group designs, manufactures, and modifies valves for:

• Unusual and difficult applications
• Greatly extended service life
• Dramatically reduced maintenance and repair frequency
• Extremely complex or compact processing systems.

According to Xomox, the Special Products Group engineers and sales representatives work with plant engineering personnel to get a firsthand understanding of special valving needs. They quickly respond with cost-effective proposals.

For more information, visit the Xomox <%=company%>.