Pressurized sheave mechanism for high pressure wireline service

Abstract

A pressure containing wireline sheave mechanism having a sheave body defining an opening within which is received a sheave housing which cooperates with the sheave body to define a circular internal sheave chamber which is exposed to operating pressure such as well pressure during well servicing activities. A split sheave having an external wireline groove is located within the internal chamber and is rotatably supported at its inner periphery by bearings. During operation of the wireline sheave mechanism lubricant is supplied to the inner periphery of the internal sheave chamber at a location adjacent the bearing and at a lubricant pressure exceeding well pressure to prevent well pressure induced migration of contaminants from the wireline groove of the sheave to its bearings. Seals on each side of the internal sheave chamber establish sealing between the sheave body and sheave housing and cause well pressure induced force acting on the sheave housing to be substantially confined to hoop stress so that the sheave mechanism is protected against significant pressure induced internal side loading. This permits the sheave mechanism to be of relatively small dimension and of relatively lightweight construction without and sacrifice from the standpoint of pressure containing capability.