CONJUNTO E APARELHO DE VALVULA DE SEGURANCA DE GAS DE ELEVACAO,E PROCESSO PARA ABRIR UMA VALVULA DE SEGURANCA DE GAS DE ELEVACAO

摘要

A lift gas safety valve has a compound valve closure assembly which will close automatically upon loss of hydraulic control pressure, and which can be reopened and maintained in the open position by the application of hydraulic control pressure at a relatively low pressure level. A primary valve closure member is slideably mounted onto a valve stem for movement to a seated position on the valve body in which a lift gas flow passage is closed, to an unseated position in which the lift gas flow passage is opened. A bypass flow passage is formed between the stem and the primary valve closure member for establishing fluid flow communication between the lift gas flow passage and the outlet port when the primary valve closure member is in its seated position. The auxiliary valve closure member is mounted onto the valve stem for movement from a seated position on the primary valve closure member to an unseated position for selectively closing and opening the bypass flow passage. According to this arrangement, when the auxiliary valve closure member is moved to its open position, the pressure differential across the safety valve is equalized, thereby permitting the main valve closure member to be unseated by the application of hydraulic control fluid at a relatively low pressure level.