Minimizing Fugitive Emissions
To protect the environment and improve health and safety, industrial and governmental bodies have established more stringent fugitive emissions limits that are providing more demanding challenges for plant Leak Detection and Repair (LDAR) programs. This in turn creates new challenges for the sealing technologies intended to prevent them.
Controlling fugitive emissions requires a holistic approach to the flanged joint. This includes the flanges, gasket, studs and nuts, installation procedure and routine maintenance. Seal failure is not always a gasket failure. Any weak element in this jointing system can lead to fugitive emissions or more significant and possibly catastrophic leaks, even with the best quality gasket. The most effective programs start with training of both regular maintenance personnel and contract or temporary personnel employed for turnarounds or outages.
Correct selection of gasket style and material is critical to maintaining seal integrity for the entire plant operating cycle, between planned shutdowns. Initially, some gaskets produce a very tight seal, but eventually as the joint relaxes the seal integrity is impacted. Thermal cycling can increase the rate and severity of the joint relaxation, whilst high temperatures can cause oxidation of graphite materials which may create leakage paths and seal failure. Using the most appropriate gasket design and materials initially will minimize the total cost of the flanged joint and prevent costly repairs or plant outages, whilst improving health and safety and limit any impact upon the environment.
Finally, the performance of the joint must be monitored over its intended service life to detect any changes in leak rate. Performing a controlled re-torque may extend the life of the flanged joint and avoid a costly shutdown