Tandem Seals For Near Zero Hydrocarbon Emissions

Lecturepg. 49More stringent regulatory limits are being placed on gaseous emissions from pumps handling hydrocarbon fluids. For example, new pumps in the Los Angeles Basin are required to have ear zero emissions. The EPA is proposing a pump emission category of no detectable emissions (NDE), defined as being less than 50 ppm. Single seals have been developed that result in emission levels below 1,000 ppm, sufficient to meet regulations for existing equipment but not those for new pumps in the Los Angeles area. In response to these emission regulations, laboratory testing has been conducted on tandem mechanical seal arrangements in which the primary seal operated on propane and the secondary seal on various barrier fluids. Secondary seal emission rates of volatile organic compounds, on optimized seal designs, were determined to be well below 50 ppm. These results demonstrate that tandem mechanical seals provide an effective alternative to double seals and sealless pumps in the drive to achieve near zero emission rates for pumps handling light hydrocarbons