PR-746-22204-R01 Review of Technologies to Enable In-situ Valve Service to Reduce Methane Emissions

Leaking gas industry valve stem seals are recognized as a substantial source of atmospheric methane, which is a greenhouse gas. Newly proposed regulations include methane alongside volatile organic compound emissions, with leak detection and repair requirements. If a leak is identified a first attempt at repair must occur no later than five calendar days after identification, or else be justifiably delayed. The objective of this report is to review valve technology and methods used to address in-situ valve stem leak repair that offers an economical solution with reduced service disruption. A wide variety of valves are employed in natural gas facilities, with valve stems that rotate or translate, and with seals ranging from packings to O-rings. Low emissions valve designs are available, but turnover of legacy valves is slow. Precise causes of failures are not well documented, although stem misalignment, intrusive dirt, and corrosion may exacerbate seal damage. Injection of lubricants and sealants into the valve packing or seal area offers the simplest remedy for leakage control. However, more work is required to identify optimal sealants for each application and to predict durability of the repair using injection. Safety must be assured where seals must be replaced, but there are varying practices in addressing isolation of the seal area from high pressure gas. Where double block (or isolation) and bleed are required, knowledge of the valve main seal design is essential. Blowdown of line sections may be required, but the methane release is of concern. Methods exist to capture or else oxidize the methane. Opinions on the protection offered by backseating of gate valves varies. Improved understanding and practice will require comprehensive record keeping on the history of each valve, permitting analysis and quality improvement using the resulting operations database. This is key to recommendations in a future roadmap that includes study of failure modes and optimized use of sealants. Monitoring success of repairs would be better served by measuring leak rate than concentration. Record keeping and better understanding of failures and success of repair approaches also support decisions on immediate versus deferred repair, use of sealants, and on whether a valve should be replaced or repaired. Hardware and practice innovations are anticipated in response to leak detection and repair requirements.