The throttle and non-return valve KO-T

is intended for the continuous of selffiling of the descented casing string with the drilling mud or the cement mortar. This valve prevents reverse motion of the drilling mud from the back-pipe space in the string at the cementation of it. In addition the valve serves as a stopping device for the separating cementing plug. The use of the non-return valve allowes to perform the descent of the casing pipe string with the location of the valve ball over the seat or without the ball. As a result it is possible to provide selfclosing of the string by the mud drilling. The throttle and non-return valve KO is manufactured with trapezoidal thread (OTTM), with heigh-hermetical joint(OTT) and Buttress- thread .