Kelly Cock Valve
Kelly valve also named kelly cock or drill pipe safety valve, which is located within the drill string that allow for free-passage of drilling fluid without pressure loss. It is a hand control valve in drill string circulating system and it is one of the effective tools to prevent blowout.
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Kelly valve is specifically designed for effective control of blow outs and/or mud loss control. It can be divided into upper kelly cock valve and lower kelly cock valve. The upper kelly cock is connected between lower end of swivel and upper end of kelly; the lower kelly valve is connected between lower end of kelly saver sub. The kelly valve can be opened on or closed off by only turning the special operating wrench at 90° according to indicating direction. During drilling operation, both upper and lower Kelly cocks should be connected to prevent accident during drilling operation.The sealing principle for Kelly valve is that the ball is positioned and provided with proceeding stress by the lower seat supported by spring load and a close seal between ball and ball seat is provided. During normal drilling operation, the hole is kept unblocked by turning the stem to be "on" position; In case of kick or blowout, turn the operating stem to be "off" position to close off the internal bore of drill string, the kick or blowout accident is avoided due to a high pressure sealing situation between ball and ball seat.
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