Dynamic behavior and difference pressure control of difference pressure regulator for dry gas seals

Abstract

As a result of the research work based on comprehensive numerical and experimental studies, an analytical method for predicting direct action gas difference pressure regulator (DPR) characteristics for dry gas seal (DGS) system allowing to build up from the possible mode of dynamic instability and to ensure the maintenance of required difference pressure for the overall operating range of compressor has been developed. The method of static and dynamic characteristics analysis of the regulator is based on solving equations of the mass flow rates and the forces acting on the slide valve balances, the single-mass dynamic model of the movable part and the mass flow rates balance in the upper and lower chambers with the use of the analytical methods of the automatic control theory (ACT). The experimental verifications of the single-seated and the double-seated DPR designs with the inlet pressures of 9.28, 6.98, 5.0, 3.2 MPa have been satisfactory agreed with the calculation results. So at difference pressure on a slide valve more than 2.4 MPa with constant external actions, a loss of stability of the movable part of the DPR may occur. The damping chamber with the laminar flow restrictor, at a suitable choice of its geometry, provides the necessary attenuation of the vibration process. The conductivity of the feeding channel has a significant influence on the static characteristics of the DPR. Under the condition of the inlet restrictor significant resistance, it is provided a rather narrow range of the variations for the difference pressure across the slide valve.