Eurovalve: Stable Operation of Spring-loaded Safety Valves in Gas Service Through Damping and Internal Modifications

Abstract

The stable operation of safety valves is required for the adequate protection of chemical plants. Instabilities like flattering and chattering of safety valves have caused severe damage to plants in the past. The publication introduces the results of the Eurovalve project investigated at the CSE Center of Safety Excellence.
Various models for safety valves are presented along with the equations used for numerical solution. It is shown that the stability of safety valves cannot be precisely pre-determined with the models currently available. Therefore, two methods of improving the stability that require the modification of the valve are proposed.
One such solution is the addition of different types of dampers to the safety valves. Measurements have been conducted to investigate the effect of friction dampers, and the results are analysed. The stability of the safety valve improves, but the safety valve reseating pressure drops below what is permissible by the standard. Simulations are used to test the effect damping on the system, showing that the analysed safety valve opens in a stable manner with a damping that reaches the critical damping of the spring mass-damper system.
The other possible solution presented in this paper is the modification of the force acting on the safety valve disk. The theoretical effects of modifying the safety valve disk are evaluated by varying the effective area of the safety valve. Limits for the effective area are derived based on the requirements of the international standards. Four different cases are examined within and out of these limits, showing that further investigations are necessary to adhere the standards.