The Valve Manufacturers Association held its annual Technical Seminar & Exhibits at the Hilton NASA Clear Lake in Houston, March 8-9. More than a dozen speakers presented on a variety of topics that centered on “Prevailing Challenges and Solutions for the Oil & Gas/Petrochemical Industries.” Following is the next article in this series.
David Bayreuther, vice president of engineering, Metso Automation USA, is a member of the U.S. team of experts working on revision of ISO-15484 and is also participating on a task force developing new API fugitive emissions standards. He presented a comprehensive analysis of the current state of affairs, starting his discussion saying, “We are nowhere near close to an industry-wide solution.”
In addition to safety risks, and product and economic loses, fugitive emissions contribute to air pollution and climate change. The rate of fugitive emissions in the U.S. has been estimated to be in excess of 300,000 tons per year. The EPA is concerned with 42 gaseous emissions, among which are greenhouse gases, which are the significant output from power plants and refineries. The rate of fugitive emissions from European refineries alone ranges from 600 to 10,000 tons per year and this is despite the many current valve emissions standards, including:
- ANSI/ISA S93.00.01
- ANSI / FCI 91-1
- TA-Luft VDI 2440
- ISO-15848-1 and -2
- Shell SPE 77/300
- Shell SPE 77/312
- API-624 (pending)
There are more regulations to follow, and they basically put the onus of proof on the manufacturer as end users around the globe push to satisfy their needs within standards organizations. This results in standards that vary widely based on the individual experience and perceived needs, which ultimately result in very high cost in both expense and time to the valve industry.
In general, overall emissions are attributed to the following primary types of sources:Equipment leaks, process venting, evaporation losses, disposal of waste gas streams (e.g., by venting or flaring), and accidents and equipment failures.
Valves top the list of leakers
Valves are the highest percentage of leakers and make up more than 90% of the process components that must be checked for leaks. Typically 50 to 60% of emissions from a plant are attributed to valves and approximately 85% of VOC emissions are from valves controlling gas streams. The typical breakdown of emissions by valve types is:
- Regulating control valve: 70%
- Automatic gate valve: 27%
- Gate valve: 26%
- Globe valve: 20%
- Plug valve: 20%
- Ball valve: 1%
Bayreuther addressed the question of why it is that less than 1% of the valves in gas service account for the majority of emissions from a plant. Part of the problem is that one successful test is no guarantee of future or consistent results. Successful results in a laboratory do not translate to success in actual service. The thermal stresses, vibrations, effects of corrosion (both within the system and from outside atmospheric conditions), and mechanical wear that the components are subjected to account for the development of leaks and the unwanted emissions.
He asked, “What are standards committees trying to accomplish? There has been a tremendous decline in FE during last 20 years, but industry is focused on trying to write standards.” While there are various tests for various types of valves and much emphasis on the accuracy of the tests, the question remains, what is the appropriate test? Helium vs. methane? Temperature? Number of thermal cycles? Test pressure? Should they be allowed to retighten the packing before and during the test? Leakage amounts are ridiculously low and that’s what the committees are dealing with.
An oversight in this whole equation is the fact that pumps and compressors are among the largest contributors to FEs, and they don’t have any standards.
Bayreuther stated that current standards are not serving our industry, and much time and expense has been wasted. ISO is still going the wrong direction but is widely used because it is the only well known option. API is taking a more realistic approach, but has fallen behind and is at risk of losing out to ISO. Large end-users are frustrated so they are writing their own standards. So far, the EPA has not taken a firm stance, but as soon as API 622 comes out, it may become involved.
Ultimately, emissions to the environment are controlled by the plant operators but manufacturers can assist by providing designs that are suitable for the thermal, pressure, and mechanical cycles a valve may experience in service.
ABOUT THE PRESENTER: David Bayreuther has 30 years experience in the valve and automation industry. He is a graduate of Northeastern University and holds a Masters Degree in Mechanical Engineering. His career started as an engineer for U.S. Navy valves on nuclear submarines, and he joined Metso Automation nearly 20 years ago. He holds several patents and is active in standards development organizations. Bayreuther is a member of the VMA Technical Committee and previously served as vicechairman and chairman.