SHUTOFF VALVE FOR GAS WELL AND METHOD OF OPERATION THEREOF Russian patent published in 2007 - IPC F16K3/04 E21B34/06 F04B47/00 

FIELD: gas industry, particularly pipeline fittings adapted to automatically shutoff gas well fluid flow as fluid pressure increases to threshold value, namely shutoff valves to be built in production strings.

SUBSTANCE: shutoff valve comprises body with seat and sealing means. Sealing means control unit has spring-loaded rod with axial channel installed in the body so that it may slide in axial direction and defines annular cavity along with the body. The annular cavity receives power agent for rod operation. Support members of the structure, which take rod spring force and cooperate with mating support surfaces of the body and the rod are identical to seat surfaces of the body and the rod and may be installed at any rod end in dependence of valve operating regime. Removable profiled bush is installed in axial rod channel inlet. Removable profiled bush has cross-section selected in dependence of valve operating regime. Annular cavity may simultaneously seal operating agent supply channels. Method for valve operation involves installing hydraulically operated valve in production string nipple; passing gas fluid flow via hollow spring-loaded valve rod and retrofitting thereof to obtain automatic mechanical valve operated by fluid flow passing from well. In the case of emergency well shutoff hydraulically operated valve is removed from nipple, converted into automatic mechanical valve, for instance by sealing operating liquid supply channels, which deliver operating liquid in working cavity of executive mechanism, and rearranging support members taking rod spring force and cooperating with mating support surfaces of the body and the rod from the first rod end to another one. Replaceable profiled bush is arranged in inlet part of axial rod channel, wherein the bush has cross-section selected to provide upward rod movement and sealing means closing as gas fluid flow velocity head exceeds designed level. After that O-rings are alternated if necessary and valve is repeatedly installed in production string nipple. To save time automatic mechanical valve converted from hydraulically operated one is installed instead of demounted hydraulically operated nipple.

EFFECT: simplified well maintenance and decreased losses associated with valve repair and maintenance.

2 cl, 6 dwg