U.S. patent number 3,561,526 [Application Number 04/854,836] was granted by the patent office on 1971-02-09 for pipe shearing ram assembly for blowout preventer.
This patent grant is currently assigned to Cameron Iron Works, Inc.. Invention is credited to Maurice J. Meynier, III, Leonard E. Williams, Jr..
United States Patent |
3,561,526 |
Williams, Jr. , et
al. |
February 9, 1971 |
PIPE SHEARING RAM ASSEMBLY FOR BLOWOUT PREVENTER
Abstract
A knife blade is carried by each of the two rams of the ram
assembly of a blowout preventer. The knife blades overlap when the
rams are closed with the cutting edge of one knife blade passing
just below the cutting edge of the other knife blade to shear a
pipe string extending through the preventer. Each knife blade
engages a seal member on the other ram, when the rams are closed,
to form two vertically spaced seals between the engaging faces of
the rams.
Inventors: |
Williams, Jr.; Leonard E.
(Houston, TX), Meynier, III; Maurice J. (Houston, TX) |
Assignee: |
Cameron Iron Works, Inc.
(Houston, TX)
|
Family
ID: |
25319641 |
Appl.
No.: |
04/854,836 |
Filed: |
September 3, 1969 |
Current U.S.
Class: |
166/55; 83/639.1;
137/68.14; 251/1.3 |
Current CPC
Class: |
E21B
29/08 (20130101); E21B 33/063 (20130101); Y10T
83/8858 (20150401); Y10T 137/1654 (20150401) |
Current International
Class: |
E21B
33/06 (20060101); E21B 29/00 (20060101); E21B
29/08 (20060101); E21B 33/03 (20060101); E21b
029/00 () |
Field of
Search: |
;166/.5,55,55.1 ;251/1
;137/67,68 ;83/639 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Brown; David H.
Claims
We claim:
1. A blowout preventer comprising a body having a pipe opening
therethrough, ram guideways extending laterally from opposite sides
of the pipe opening, a ram assembly comprising first and second
rams, each located in one of the ram guideways, and means for
moving the rams together to close off the pipe opening and for
moving the rams apart to open the pipe opening, each ram having a
knife blade attached thereto in position for the cutting edge of
the blade on one ram to pass just below the cutting edge of the
blade on the other to shear any pipe positioned in the pipe opening
when the rams are moved together to close off the opening, and seal
means on each ram positioned to engage and be compressed by the
knife blade on the other ram when the rams engage to form a
separate and independent seal between the knife blade on each ram
and the seal means on the other.
2. The blowout preventer of claim 1 in which the cutting edge of
each knife blade is generally concave, tapering inwardly from each
side toward the center, to cause the blades to tend to center the
pipe between the blades as the rams are moved together and to shear
the pipe progressively from the sides toward the middle of the
blades as the rams are moved together.
3. A ram assembly for positioning in ram guideways that extend
laterally from opposite sides of a pipe opening in the body of a
blowout preventer, comprising two rams for movement between an
engaged position closing off such pipe opening to a spaced apart
position opening such pipe opening to receive pipe, said rams
having oppositely facing surfaces that engage when the rams close
off the pipe opening, each said ram having a knife blade extending
laterally across said surface with its cutting edge projecting
therefrom, said blades being positioned on the rams for the cutting
edge of one blade to pass just below the cutting edge of the other
blade, when the rams are moved together through their respective
ram guideways, to shear pipe positioned in the pipe opening, and
seal means on the rams to seal off the pipe opening when the rams
are in engagement, said seal means including a seal member
extending laterally across the facing side surface of each ram to
be compressed by the knife blade on the other ram as the rams move
into engagement.
4. The ram assembly of claim 3 in which the knife blades taper
inwardly toward the center thereof to tend to center pipe
positioned between them and to shear the pipe progressively
inwardly toward the center of the cutting edge as the rams are
moved together.
Description
This invention relates to blowout preventers generally and, in
particular, to a ram assembly for a blowout preventer that will
shear pipe extending through the preventer, when the rams of the
assembly are moved together to close off the opening through the
preventer.
Shear rams are installed in preventers where there is a possibility
that it may be desirable to have the ability to cut the drill pipe
or tubing. This would be done, in most cases, only to prevent
irrevocable damage from being done to the well, the wellhead
equipment, or the drilling rig. For example, if while operating
offshore from a floating vessel, the anchor system should fail or
for some reason be unable to keep the vessel over the hole and a
string of pipe extends from the vessel into the hole; it would
probably be better to shear the pipe string at the wellhead rather
than to run the risk of damaging the wellhead or the vessel.
Shear ram assemblies for blowout preventers have been proposed
before. For example, see U.S. Pat. Nos. 2,919,111 and 2,969,838
which issued on Dec. 2, 1959 and Jan. 31, 1961, respectively. It is
the purpose of the rams described in these patents, as well as the
rams of this invention, to not only shear the pipe string, but also
to come together and form a seal between them and the preventer
body to close off the opening through the preventer after the pipe
has been sheared. The seal between the rams is formed by resilient
sealing members that are compressed between the rams. Cutting a
pipe string, such as a string of Grade E drill pipe, requires a
substantial amount of force to be applied to the rams and usually
the rams will flatten the pipe between them before they cut it. The
end of the pipe will be above the bottom of the hole or in tension
in most cases, so when it is finally sheared it will jump apart due
to the weight of the pipe string extending below the preventer. As
the pipe is flattened and sheared, it may be forced against one or
both of the sealing elements and damage them. Further, the pipe
could tear one or both elements as the pipe moves rapidly from
between the rams when sheared. The danger here is that the sealing
elements will be damaged to the extent that they will not seal and
this function of the rams will be lost.
Therefore, it is an object of this invention to provide a shear ram
assembly for a blowout preventer wherein the likelihood of damage
to the ram sealing elements is reduced, when the ram assembly cuts
a pipe string.
It is another object of this invention to provide a shear ram
assembly for a blowout preventer that forms two, vertically spaced,
pressure seals between the rams of the assembly, when the rams are
moved into engagement to provide two chances for a seal instead of
one.
It is another object of this invention to provide a shear ram
assembly for a blowout preventer that will cut the pipe after it is
flattened, from each side toward the middle of the flat sides of
the pipe, to reduce the cross-sectional area in shear at any given
time and the maximum force required to shear the pipe.
These and other objects, advantages, and features of the invention
will be apparent to those skilled in the art from a consideration
of this specification including the attached drawings and appended
claims.
In the drawings:
FIG. 1 is a view partially in elevation and partially in vertical
section of a blowout preventer equipped with the preferred
embodiment of the shear rams of the shear ram assembly of this
invention;
FIG. 2 is a view similar to FIG. 1 showing the shear rams closed
after having sheared a pipe string;
FIG. 3 is an isometric view of the ram assembly of FIGS. 1 and
2;
FIG. 4 is a top view of one of the rams of FIG. 3 and part of the
adjacent side of the other;
FIG. 5 is a vertical section through the rams of FIG. 4 taken along
line 5-5;
FIG. 6 is a top plan view of the rams as they move together with a
pipe string between them that is not in the center of the opening
through the blowout preventer; and
FIGS. 7, 8 and 9 show sequentially the rams moving together to
shear a pipe string.
The blowout preventer of FIG. 1 includes main body 11 through which
extends vertical bore or opening 12. This is the opening through
which pipe can pass through the preventer. Ram guide ways 13a and
13b extend laterally from opposite sides of bore 12. Flanges 14 on
the upper and lower sides of the body connect the preventer in the
wellhead stack in the conventional manner. The ram assembly of the
blowout preventer comprising first and second rams 15 and 16 are
located in ram guide ways 13a and 13b, respectively, on opposite
sides of pipe opening 12.
Means are provided for moving the rams into engagement to close the
pipe opening through the preventer and for moving them apart to
open up the opening therethrough. The means for moving each ram is
similarly constructed so only one such assembly will be described
in detail. As shown in FIG. 1, bonnet 17 is attached to body 11
across the open end of ram guideway 13a. Bonnet 17 includes body 18
and head 20. Bonnet body 18 and head 20 are connected by a
plurality of bolts 21 (FIG. 2). Bolts 22 releasably connect the
bonnet assembly to main body 11 of the preventer.
Piston 25, located in cylinder 19, is connected to rod 26. The rod
extends through bonnet body 18 and is releasably connected to ram
15. Hydraulic pressure on one side of piston 25 moves ram 15
laterally toward ram 16 and hydraulic pressure on the other side
will retract the ram to the position shown in FIG. 1. For a
complete description of this portion of the preventer, see U.S.
Pat. No. 3,272,222 entitled "Blowout Preventer" that issued Sept.
13, 1966 to Herbert Allen.
The piston and cylinder arrangement just described may not be able
to provide sufficient force to cause the shear rams to cut through
a particular pipe string. This may be due to the thickness of the
pipe or the lack of sufficient hydraulic pressure or both. If such
a situation is likely, the preventer can be modified to provide
additional force for shearing the pipe. As shown in FIGS. 1 and 2,
cylinder 28 and cylinder head 29 are attached to head 20 of the
bonnet by bolts 30. Piston 31 in cylinder 28 is connected to rod 32
with the rod extending through head 20 to engage or be connected to
piston 25 as desired. Fluid pressure acting against piston 31
produces an additional force for urging ram 15 toward ram 16.
Referring now to FIGS. 3, 4, and 5, rams 15 and 16 include main
bodies 35 and 36, respectively. The ram bodies are oval in vertical
cross section, which is the shape of ram guide ways 13a and 13b.
The rams, when positioned in the guide ways, have opposite faces 37
and 38 that engage and limit the distance the rams can be forced
together. Extending laterally across faces 37 and 38 are grooves 39
and 40. These grooves in turn are connected to grooves 41 and 42
that curve over the top of the ram bodies and along the sides
thereof to combine with lateral grooves 39 and 40 to provide a
continuous groove across the front face of the rams, part way down
the sides, and over the top. Sealing elements 43 and 44 are located
in grooves 41 and 42, respectively. Sealing elements 45 and 46 are
located in grooves 39 and 40 and extend laterally across opposite
faces 37 and 38 of the rams. Also located in grooves 39 and 40 are
knife blades 47 and 48.
The knife blades project from faces 37 and 38 of the rams and are
positioned to overlap when the rams are moved into engagement, as
shown in FIGS. 2 and 5. In FIG. 5, the rams are shown just before
they move into engagement with the knife blades just beginning to
overlap. Seal elements 45 and 46 are each positioned to engage the
knife blade carried by the other ram, i.e., as shown in FIG. 5,
knife blade 47 on ram 15 will engage and compress seal member 46,
when the rams are moved together. Knife blade 48 on ram 16 will
engage and compress seal member 45. Thus, vertically spaced seals
are formed between the rams. This provides two chances for a seal
to be formed between the mating faces of the rams or, stated
another way, both sealing elements would have to be damaged by the
pipe to keep a seal from being established between the rams.
The cutting edge of knife blade 47 is its lower outer edge 47a. The
cutting edge of knife blade 48 is the upper outer edge 48a. As the
rams move together, knife edge 47a passes just above knife edge 48a
to shear any pipe string located in the pipe opening of the
preventer. The knife blades are held in grooves 39 and 40 by bolts
49 and 50, respectively, as shown in FIG. 5.
Seal elements 45 and 46, which are made of a resilient material
such as rubber, are compressed between the knife blades and the
back of the grooves in which they are located. This compression
causes each seal element to form tight seals along the back, top,
and bottom of the groove in which it is located as well as to seal
between the element and the knife blade. This compression and the
accompanying deformation is transmitted to seal members 43 and 44
in side and top grooves 41 and 42 to hold them in sealing
engagement with rams guideways 13a and 13b.
The cutting edges of knife blades 47 and 48 are generally concave,
tapering inwardly from each side toward the center, as shown in
FIG. 6. So shaped the blades will tend to urge pipe such as pipe
string 51 shown in FIG. 6, toward the center of the blades as the
blades are moved together by the rams.
There is another advantage in providing this shape for the cutting
edges. The actual shearing of the pipe usually begins after the
blades have flattened the pipe. This flattening is shown
sequentially in FIGS. 7, 8, and 9. The actual cutting operation
begins when the blades and pipe are as shown in FIG. 9. The cutting
starts from each narrow side, which is probably split
longitudinally by this time, and moves progressively inwardly from
both directions toward the center as the blades move together. This
reduces the actual cross-sectional area being sheared at any one
time and reduces the actual force required to shear a given pipe
string.
From the foregoing description of one embodiment of this invention
by way of example, it will be seen that this invention is one well
adapted to attain all of the ends and objects hereinabove set
forth, together with other advantages which are obvious and which
are inherent to the apparatus and structure.
* * * * *