recognized international standards. They can also be redesigned to any given customer’s specifications to ensure application suitability. “At least 80% of all valve leakage is from the stem. Test standards are therefore focusing in this area in particular.” According to Simpson, due to the large number of potential leak sources detecting valve leaks and repairing them are not always easy. From a cost perspective alone the impact of these leaks is severe while the environmental damage is extensive. Fugitive emissions also pose a real risk to workers and local communities proximity of industrial facilities.
Simpson says the industry is working hard to come up with solutions. Typical solutions include engineered packing sets typically using PTFE or elastomer sealing rings.
It is therefore essential that valve manufacturers and suppliers realise the dangers around fugitive emission and take extra measures to ensure their valves have secured stem seals to prevent them from leaking hazardous gas or vapour into the environment.
“Anti-extrusion elements from high modulus thermoplastic or metal is another option. Rings squeezed into a gland or ‘preset” using spring energized seals is also used.” Simpson says some manufacturers are opting to use multiple barriers to achieve low interface leakage – a move that was proving to be very successful.
These components, says Simpsons, can be tested at different temperatures with helium or methane test gas using the sniffing or vacuum method according to
“It has been found that greater leak-tightness can lead to increased wear and lower endurance levels so that needs to be kept in mind. All in all, there does, however, need to be further information to clarify what industry needs are.” He said improved collaboration between the industry and valve manufacturers was critical going forward to ensure that exact needs around fugitive emission were met.
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Pipes, Pumps and Valves Africa - May/Jun 2021