Most engineers, technical personnel and installation professionals involved with valve design and installation will inevitably need to consider a stationary seal at some point in their career. Stationary seals are everywhere in industry and unavoidable where valves are used. Bonnet gaskets, multi-piece valve body seal gaskets and flange connection gaskets are the most common stationary seals encountered. The problem, though, is that gaskets generally are never given the design and maintenance attention they require.
Mechanical engineers, technologists and technicians receive anywhere from a paragraph to perhaps a section’s worth during their three- to four-year journey toward obtaining their degree or diploma. As students, only a handful may be lucky enough to see a gasket during a work training placement while the majority may have only seen references on drawings or bills of materials. Gaskets are a critical component in reducing fugitive emissions and having a better understanding of their complexity and application will make all gasket-related personnel more successful.
Gasket requirements are typically evaluated based on pressure and temperature limits of the valve or system design, on media applications where the valve may be used most often, and sometimes on the level of tightness that the overall valve or system is being designed to meet. These are certainly the highest profile criteria to evaluate. However, gasket manufacturers’ data would indicate that gaskets are considered far too late in the valve or system design process.
Being considered late in the design process can sometimes limit the available gasket material choices and the level of tightness that can be achieved. Sealability, chemical compatibility and blowout resistance can all be compromised when gaskets are not given proper consideration at the correct stage in the evaluation process.
Typical gasket data used for common evaluation consists of gasket factors (m&Y), maximum pressure (blowout resistance), minimum and maximum temperature limits, chemical resistance information, and creep resistance values. This type of information is commonly found on manufacturers’ and distributors’ websites, but it is only intended for standard, non-critical or non-enhanced applications. Common gasket data can work, however, it is not enough when having a fugitive emissions conversation. To reduce fugitive emissions to levels being targeted by modern governments and regulations, enhanced gasket data and gasket manufacturer involvement is a key element and is critical to sealing success.
Internal gasket manufacturer data analytics can provide OEMs with significantly enhanced seal performance of their products, allowing then to achieve tighter closures to meet evolving emissions regulations. One of the major tools at the gasket manufacturer’s disposal is enhanced gasket factors using mechanical and leakage criterion. These enhanced gasket factors include PVRC ROTT (Gb, s, Gs), EN 13555 / EN 1591 (Qmin(L), QSmin(L), Qsmax) and DIN E 2505 / DIN E 28090 (σVU/L, σBU/L, m/L). All of these factor sets take into account system tightness and leakage that is not inherent in the classic m&Y factors. Additionally, gasket manufacturers use load-unload curves, hot creep relaxation data, finite element analysis, cross-discipline installation experiences, other and similar applications, and overall gasket familiarity and selection experiences. Working with a gasket manufacturer can provide faster and better solutions, reduced analytical costs, better safety, and better valve or system leakage performance.
Performance-based Standards: A Call to Action
Currently there are not many performance-based standards for gasket materials. Existing testing standards are primarily for quality control purposes and quick physical property analysis and comparison. In 2002, the Fluid Sealing Association (FSA) developed a performance standard for comparison of non-metallic flat gaskets, which was later adopted by ASTM as standard F2716: Standard Practice for Comparison of Non-metallic Flat Gaskets in High Pressure Saturated Steam. This ASTM standard is very good for evaluating various non-metallic gaskets for long-term use as the test’s “pass” criteria is 2,000 test hours and is commonly run for 8,000 hours or longer.
Several new and hybrid styles of gaskets have emerged on the market in the last 10 years and existing standards do not evaluate these products well. As a result, OEMs and end-users are not able to easily determine suitability and often will not be the first to use them. These new technologies are very good and ready to meet current and emerging ultra-low emissions requirements. However, acceptable performance standards need to be established to ensure safe and reliable performance in the field.
A staple gasket group used in the valve industry is semi-metallic gaskets. These commonly include spiral wound, kammprofile and corrugated metal insert gaskets. As leakage qualification standards on this product group do not exist, the FSA Gasket Division Technical Subcommittee is currently developing a leakage performance standard for semi-metallic gaskets that will eventually use methane gas as a test media. The FSA is looking for additional gasket manufacturers and gasketing professionals to contribute to the development of this important qualification standard in order to capture all facets of ultra-low emissions requirements and gasketing technologies.
Emerging emissions regulation requirements are more achievable in the near-term than most recognize, and compliant gasket technology has already been developed. To meet these new initiatives, it is essential to fully analyze the application and emissions requirements along with the existing current sealing materials to understand what is and is not working. Furthermore, it’s important to apply enhanced gasket data and analyze various scenarios for applicability and apply gasket manufacturer recommended installation procedures. Once the analysis is complete, it can be tested and validated through live installation whenever available.
New technology costs are not prohibitive as gaskets are one of the lowest cost components in any system. Gasket manufacturer members of the Fluid Sealing Association are ready to work with any group looking for improvements in leakage containment. The FSA provides non-commercial advice and training for the best practices of the selection and use of fluid sealing products to meet modern environmental regulations.
The Fluid Sealing Association is a trade association focused on promoting a safe, clean environment for society and a safe work places for employees. Member companies are involved in the production and marketing of a wide range of fluid and air sealing devices primarily targeted at the energy and industrial process markets. We support the development of related standards and provide education in the fluid sealing area.