Valve Designs and Test Results

The original sleeved plug valve is the most basic. Typically the stem seal is a PTFE diaphragm with a back up metal diaphragm. This type of valve exhibited test results showing emissions of slightly over 100 ppm at the stem seal. The XP version of the sleeved plug valve has a set of PTFE packing rings on an extended plug stem. These valves showed test results of approximately 25 ppm. The severe service valve is a valve usually with a multi-piece plug and stem to compensate for side loading on the stem as a result of actuation. This type of valve typically has a separate adjustment for the stem seal and the in-line plug seal. The results for this valve came in with fugitive emissions in the 10-15 ppm range. These valves are often rated as good, better and best and usually priced accordingly. All sleeved plug valves tested were less than the 500 ppm EPA guideline and 100 ppm or less. Process Ball Valves may be comprised of several different body designs, one piece, two-piece or three-piece and have soft seats often made from PTFE of modified PTFE. The stem and ball are usually separate parts. The stem is usually fitted with a set of PTFE or grafoil packing rings. The testing of Process Ball Valves yielded an average result of approximately 150 ppm for valves with PTFE packing.