FRICTION KELLY BAR

Friction Kelly bar is another type kelly of bar, which the external key is composed of 3 or 6 wear -resistant strip without pressunrizing point.This kelly bar can form pressure force when the kelly bar is rotary.can produce peripheral force and the rotary passing down the pressure force,can produce the friction force.This kelly bar has the advantage of opeerating sample .drilling deep,but with less pressure transmission.So this kelly bar is suitable for the soft and silt layer.