Inside BOP-Kelly check valve is a constant-open type blowout protection assembly in drilling tool, as well kick happens, it can be closed and prevent fluid under ground from gushing up through the water hole in drilling column. In well control operation, if hose and high-pressure manifold is damaged, it can be replaced in safety under the valve being closes.
Upper check adopts left hand thread but the lower adopts right hand thread, and they are identical in structure of ball valve.
The rated working pressure of Kelly check valve should be equal to the rated pressure of BOP, the ID of check should be larger than (or equal to) the ID of Kelly rod, Max working pressure and test pressure should be tested according the requirement listed in the below table, Holding pressure for 3 minutes without leakage is considered as a qualified sealing test, appliance for check is up to 82 Deg. C. And the check wrench should stay the available/usable position.
Upper check valve consists of valve body, upper/lower seat, ball body, rotary-block, retainer, spring and non-metal seals etc.
Valve body is ASTM4140 forging, and the machinery properties after heat treatment can meet the requirementof API Spec 7.
Valve seat and ball body are made of heat-resistant stainless steel with abrasion and corrosion resistance.
The valve is single direction seal, as the valve is closed, under the co-reaction of fluid pressure under well and pre-load spring pressure, the ball body approaches to the back-seat quickly so as to create a seal. As for the sealing face of back-seat adds a PTFE nonmetal ring and reduce the compact of ball body to valve seat, So that it should have more reliable performance.
The surface of the valve body stamped with visiblesign of " open" or " close' indicates the open/close station of check valve obviously