Globally, oil and gas producers seek ways to lower fugitive emissions for safety, environment and economic reasons. These are the unintended emissions of gases from pressurized parts of the production process.
At the upcoming April 30-May 3 Offshore Technology Conference in Houston, Emerson’s Amr Gado and Calvin Deng will present a paper, Pressure Relief Valves Fugitive Emissions Testing, on Thursday May 3 at 2:45pm as part of the Technical track, Striving Toward Safety Excellence in Offshore and Subsea Environments.
Their paper, written with Emerson colleague D. Emile Tezzo, provides an overview and look at the importance of fugitive emissions. They’ll review the existing emissions standards, and specifically their work with a leading oil & gas producers and third-party testing laboratory to develop a first-of-its-kind fugitive emissions testing program for pilot-operated pressure relief valves.
The major sources of regulations around fugitive emissions are the United States’ Clean Air Act and Germany’s TA-Luft. Valves are some of the most important devices to consider in a process when seeking to control and reduce emissions.
In the effort to create the testing program they looked to existing standards for valves with stems including:
- ISO 15848-1 & 15848-2 – Industrial valves – Measurement, Test and Qualification Procedures for Fugitive Emissions
- Shell MESC 77-300 and 77-312 – Procedure and Technical Specification for Type Acceptance Testing of Industrial valves – Fugitive Emissions Production Testing
- API 622 and 624 – Type Testing of Process Valve Packing for Fugitive Emissions Type Testing of Rising Stem Valves Equipped with Graphite Packing for Fugitive Emissions
Pressure relief valves (PRVs) differ in design by function and geometry from in-line valves They are self-contained with no stem and self-actuated by set pressure limits. Given these differences and no existing standards for PRVs, they worked to create a new test procedure for direct spring valves (conventional and thermal relief) and pilot operated valves. The other test parameters were for a range of 1″ to 10″ PRVs operating in a temperature range from -320ºF (-200ºC) to 1000ºF (540ºC) with test pressures up to 6000 psig with a pressure class up to ANSI Class 2500.
The team collaborated to recreate a test rig at the independent testing laboratory using helium as the test gas. Helium is ideal due to its small atomic mass (more prone to leak than gases with larger molecule sizes) and low concentration in the environment (easier to trace). Pressure is applied at the outlet for spring valves and one mechanical adjustment at room temperature and pressure is allowed—as it is for in-line valves.
The tests were performed on Anderson Greenwood pilot operated PRVs, Crosby direct spring-operated PRVs and OMNI portable thermal relief valves. A mass spectrometer leak detector and sample probe was used to measure for fugitive emissions at potential leak points including gasket joints, pipe and tube fitting connections, body flanges, etc. Based on the rating of the PRV, temperatures were cycled at the valve inlet from ambient temperature to 1000 ºF, back to ambient, down to -320 ºF, and then again back to ambient.
Here are the acceptance criteria from this testing process:
- Class A: 1.78 E-9 x gasket OD (mm)
- Class B: 1.78 E-8 x gasket OD (mm)
- Leakage above Class B is unacceptable
Make sure to catch their presentation if you’ll be at OTC. You can see some of these valves designed to meet fugitive emissions regulatory requirements in the OTC exhibit area in the Emerson booth #2261.
Visit the Offshore Technology Conference 2018 page on Emerson.com to get a free show pass.
