Industry:
Across Industries

Engineering Specialties Used:
Finite Element
Heat Transfer
Thermal Stress

Situation:
California law requires facilities with certain process streams to limit the amount of product “leaking” to the environment through gaskets and packings. The released products are called “fugitive emissions” and exceeding permitted limits can result in large fines. A facility had very large diameter valves which regularly exceeded their fugitive emission limits. Valve replacement was considered to be cost prohibitive and there was no guarantee new valves would meet the

very strict requirements. Several attempts were made to eliminate the problem with a trial-and-error approach. None were successful and one even resulted in a small fire.

Solution:
A two-dimensional axisymmetric finite element model (FEM) was built to understand the temperature distributions and thermal displacements during operation. A fluid analysis was performed using closed-form empirical equations to determine fugitive emission rates. These results compared favorably with the plant’s experience. A remediation design was prepared and tested using the same analytical approach to demonstrate compliance with regulatory limits. The parts were built and installed. The facility has not had a fugitive emission exceedence since. (Note: the analysis was also used to show why the parts passed a hydrotest in the shop but leaked in the field.)