Determination of the force needed for closing a universal blowout preventer.pdf

DETERMINATION OF THE FORCE NEEDED FOR CLOSING A UNIVERSAL BLOWOUT PREVENTER I. V. Kostriba, A. T. Rasi-Zade, B. O. Frenkel, N. M. Barkhudarov, and V. P. Romanov UDC 622.245.73 621.891 The resistance at friction points exercises much influence on the force which acts in the direction of the plunger axis and is essential for packing deformation during universal blowout preventer closing. However, in the published reports [1-3] the coefficients of friction at the same points, which were furnished with no reference to the operating conditions, differ widely, which complicates blowout preventer design. For instance, the coefficient of friction is 0.02- 0.25 for packing friction with the walls of the blowout preventer housing, 0.03-0.25 on the surface between the plunger and the rubber part of the packing, and 0.15-0.7 on the support- ing front surface between the metallic inserts of the packing and the blowout preventer cover. According to [1-3], the total friction losses are 38, 35, and 70%, respectively. The cause of such a wide divergence of the values is that the real operating conditions were not given adequate consideration in the experimental investigations and in the determination of the coefficients of friction in the blowout preventer joints. In this paper we give a method and the results of determination of friction losses in the movable elements of a universal blowout preventer during its operation. In Fig. 1 we see that the balance of the forces acting on the plunger in the direction of its axis during the blowout preventer F cu + F~ + F c~ P = Psq + fr r fr (i) where P is the force due to pressure in the hydraulic blowout preventer control system; P sq is the force on the plunger for packing squeezing; cu F~ and F c~ Ffr r fr are the losses of the Fig. i. Theoretical diagram of action of forces on preventer plunger: i) preventer cover; 2) packing; 3) housing; 4) plunger; 5) seal gland. Translated from Khimicheskoe i Neftyanoe