The prediction of liquid leak rates through packing seals

Abstract

Packing rings are the most sensitive member of packed stuffing boxes in pressurized mechanical assemblies such as valves and pumps. Their ability in dealing with pressure and temperature are not well established, making their long-term use in valves and compressors unpredictable. The wrong choice of the material, number of packing rings, incorrect installation and fluid incompatibility can lead to leakage failure and cause hazards to human and environment. Leakage of fluids (gas or liquid) in the nuclear or petrochemical industries often occurs in carrier lines, valves, and compressors. Such a situation can cause high risk and have drastic consequences on human health and safety and the environment. In these industries, accident reports indicate that fluid leakage is often related to valves. The sealing of valves is insured by packed stuffing boxes that requires a special attention by researchers in this field. The porous nature of packing rings is an open path for leakage. Unfortunately, the lack of standard tests and design procedures of stuffing box packings of valves is alarming and has been the subject of recent studies. In practice, a small amount of research has been conducted on fluid flow through packing rings, some of which cover numerical and analytical leakage predictions. There is definitely a need of experimental research in this field. In fact, the results of experimental tests can validate and confirm the accuracy of the predicted results and determine the robustness of the analytical and numerical models. In this research, a test rig was used to simulate the actual conditions of a valve packed stuffing box and lead us to simulate the leakage behavior at room temperature. This test rig was designed to measure gas or liquid leakage through packing rings under different compressive loads and fluid pressure. Different leakage measurement methods were used depending on the amount of leakage obtained with flexible graphite-based packing. This work aims at predicting leak rate through stuffing box packing rings; This is achieved by validation of the predictions with the experimental test results. In fact, the experimental tests have been performed to validate the analytical model and benefit the various industries with the results obtained under different operating conditions. Practically, the many parameters affecting leakage of packing rings have render the comparisons difficult to make. However, some parameters considered simultaneously have produced results close to reality. This work is based explicitly on the validation of a fluid flow analytical model based on several experimental leak measurements. The study on the packing ring materials starts with the determination their porosity parameters with a reference gas used in the developed fluid flow models to predict leak rates. Nitrogen gas was used as a reference gas to determine the pore size and their number in the packing ring porous structure. Finally, according to the findings, leakage through packing rings can be controlled and reduced, and its prediction is possible using the validated analytical models.

Date	24 Nov 2021
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Hakim A. Bouzid (Supervisor)