Fugitive emissions are unintended emissions of gases or vapors from pressurized plant components. These emissions have been a concern for operators of oil and gas facilities and their regulatory bodies for a long time.
Fugitive emissions can be hazardous, can contribute to atmospheric pollution, and can represent an economic loss for the facility. As the number of potential leak sources at large industrial facilities can be numerous and difficult to identify, controlling fugitive emissions is particularly challenging. One particularly challenging potential source of fugitive emissions is pressure relief valves (PRVs).
Emerson’s Emile Tezzo and Amr Gado described an approach for fugitive emissions testing for pressure relief valves at the Emerson Exchange 2017 conference. Emile opened noting that the presentation would focus on the Anderson Greenwood and Crosby pressure relief valve brands. Regulations for fugitive emissions are becoming stricter and companies are more aware of the brand and their corporate social responsibilities in the communities in which they operate.
Fugitive emissions are pollutants leaked into the air and can come from equipment, pipelines, seals, valves, connectors, pumps etc. The majority of these emissions come from valves. The U.S Environmental Protection Agency and TA Luft in Germany are two countries with strict regulations covering fugitive emissions.
There are no widely adopted standards for fugitive emissions for pressure relief valves. A pressure relief valve is self-contained and self-actuated unlike regular valves. Amr explained that they started with a customer’s manual valve test standards and use these as a starting point for pressure relief valves. These standards had both pressure and temperature cycling.
They focused the temperature cycling on the inlet of the valve and used liquid nitrogen for the cold cycle and a heater for the hot cycle. The valve is fugitive emission compliant if it passes the test from ambient to cryogenic back to ambient to high temperature and back to ambient. The valve was pressurized with helium to make the test more rigorous given the small helium molecule size versus other bigger molecules such as methane. A sensor “sniffs” for helium to see if any leaks occur through the temperature cycle.
Because of this type testing with a major oil & gas producer, the American Petroleum Institute took note of this test procedure for the development of future fugitive emissions standards for pressure relief valves. As a type test, this testing must be repeated on a periodic basis.