Ram-Type Blowout Preventer

Blowout preventers are used to maintain control of wells during drilling. Ram-type blowout preventers are used to close on the drill or pipe string to contain pressure in the well. At times it is necessary to strip or move the string through the closed rams. This stripping movement can severely wear or abrade the face of the resilient packers used in blowout preventer rams. Another reason the packers of ram-type blowout preventers are subject to wear is that to provide a seal they must tightly engage and conform to the irregular surface of the string when closed and such ability to conform causes the packers to be subject to pressure induced extrusion. The design of ram packers is thus a compromise to provide the needed conformity or feed of the resilient material with maximum abrasion and extrusion resistance.

Examples of prior ram-type blowout preventers can be seen in U.S. Pat. Nos. 2,883,141 and 3,692,316 which disclose the use of upper and lower packer plates designed to minimize extrusion damage. U.S. Pat. No. 4,323,256 discloses the use of a polytetrafluoroethylene insert in the face of the packer to minimize wear in stripping of the string through the packer. U.S. Pat. No. 2,194,258 discloses a ram-type blowout preventer having upper and lower plates of the packer which include a series of strips which are generally parallel to the ram axis and can move independently of each other to engage a drill or pipe string on which the rams have closed to provide a uniform support for the resilient packing material.

The present invention relates to an improved ram-type blowout preventer with an improved packer. The blowout preventer includes a housing with a bore therethrough and one or more pairs of opposed aligned ram guideways extending outward from the bore, a ram in each of the guideways, means for moving the rams in the guideways, a packer in the front of each of the rams having an upper plate, a lower plate and resilient packing means therebetween, said plates each having a drill or pipe string receiving recess and slots allowing the upper plate to flex about the axis of said bore or said recess and engage the string when the rams are closed about the drill or pipe string.

An object of the present invention is to provide an improved ram-type blowout preventer with improved ram packer means which seals effectively on a drill or pipe string to retain well pressure.

Another object is to provide an improved ram packer which is protected from extrusion damage.

Another object of this invention is to provide an improved ram-type blowout preventer with ram front packer plates that flex or conform to effectively engage the drill or pipe string passing through the blowout preventer.

These and other objects and advantages of the present invention are hereinafter set forth and explained with reference to the drawings wherein:

FIG. 1 is an elevation view, partly in section, of the improved blowout preventer of the present invention.

FIG. 2 is a plan view of the improved drill or pipe string receiving ram packer of the present invention in relaxed position with the ram not shown.

FIG. 3 is a plan view of two opposed packers of FIG. 2 with their rams not shown engaging a string and showing the flexing of the plates.

FIG. 4 is a sectional view of the packer taken along line 4--4 in FIG. 2.

Blowout preventer 10 includes housing 12 having bore 14 with ram guideways 16 extending outward from opposite sides of bore 14, with ram 18 in each guideway 16 and having means 20, such as a piston, connected to rams 18 by connecting rods 22, for moving rams 18 inward and outward in guideway 16. Each of rams 18 includes improved front packer 24. Groove 23 extends across the top of ram 18 and seal 25 is positioned therein to provide a seal extending from packer 24 on each side and across the top of ram 18, as is known in the art and shown in U.S. Pat. No. 3,102,709. While blowout preventer 10 shown in FIG. 1 only shows one guideway 16 it has two such guideways and each has substantially identical but opposed structure including ram 18.

As shown in FIGS. 2 and 4, packer 24 includes upper plate 26, lower plate 28 and resilient packing 30 between plates 26 and 28. Each of plates 26 and 28 include face or front recess 32, rear projections 34 and side portions 36 and 38. Also each of plates 26 and 28 has a plurality of slots 40 starting in holes 42 and extending to the front or rear surfaces of plates 26 and 28. It is preferred that slots 40 are substantially perpendicular to the surface on which they open. Holes 42 are provided to avoid any stress concentration in the plates.

The radius of recesses 32 is slightly larger than the radius of the string on which packer 24 is to seal. This allows plates 26 and 28 to flex and conform to the string 44. The closing and sealing action of a pair of packers 24 is shown in exaggerated form in FIG. 3.

As can be seen from the drawings, plates 26 and 28 are sufficiently flexible to move into close proximity to or into engagement with string 44 to provide a substantially continuous support of resilient packing 30 around string 44 whereby extrusion of resilient packing 30 is prevented.

With the improved support supplied by the improved flexible plates it is possible to use a resilient material for the resilient packing which flows or conforms readily to improve the sealing characteristics of the ram packers. Such material is preferred to be acrylonitrile-butadiene rubber, fluorocarbon rubber or similar solvent resistant rubber.