POWER TONG

CLE DE VISSAGE A COMMANDE PNEUMATIQUE

English Abstract

A power tong (1) for rotating a tubular (40) in wellbore
operations, the power tong comprising an outer case (2), a rotary
(3) rotatably mounted in the outer case (2) for rotating a tubular
(40), apparatus (4) for rotating the rotary (3) to rotate the tubular
(40), at least one active jaw (8) movably mounted on the rotary (3)
and displaceable relative thereto to grip the tubular (40), the at least
one active jaw (8) having a gripping element (15) for contacting
the surface of the tubular (417), and wherein one of said active jaw
(8) and said rotary (3) is provided with a cam (27) and the other
with a cam follower ( 19), characterized by pre-load apparatus (28,
29) interconnected directly or indirectly between the at least one
active jaw (8) and the rotary (3) for, in use, displacing said active
jaw (8) with respect to said rotary (3) so that the active jaw is
cammed into gripping engagement with the tubular (40) and so inhibit
relative rotation between said active jaw (8) and said tubular (40) on
subsequent rotation of said rotary (3).

French Abstract

L'invention porte sur une clé de vissage à commande pneumatique (1) qu'on utilise pour faire tourner un matériel tubulaire (40) dans des opérations de forage. Cette clé de vissage comprend un boîtier extérieur (2), un élément rotatif (3) monté sur axe dans le boîtier extérieur (2) pour faire tourner un matériel tubulaire (40), un appareil (4) pour actionner l'élément rotatif (3) faisant tourner le matériel tubulaire (40), au moins une mâchoire active (8) mobile montée sur l'élément rotatif (3) et pouvant être déplacée par rapport à celui-ci pour serrer le matériel tubulaire (40), ladite mâchoire active (8) comportant un élément de préhension (15) qui vient au contact de la surface du matériel tubulaire (40). La mâchoire active (8) et l'élément rotatif (3) sont munis l'une d'une came (27) et l'autre d'un galet de came (19) caractérisés par des appareils de préchargement (28, 29) jumelés directement ou indirectement entre la mâchoire active (8) et l'élément rotatif (3) pour déplacer ladite mâchoire active (8) par rapport audit élément rotatif (3) pour déplacer ladite mâchoire active (8) par rapport audit élément rotatif (3) pendant l'utilisation, de sorte que la mâchoire active soit amenée à verrouiller le matériel tubulaire (40) et empêcher ainsi une rotation relative entre la mâchoire active (8) et le matériel tubulaire (40) lors d'une rotation subséquente de l'élément rotatif (3).

Claims

8
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A power tong for rotating a tubular in wellbore
operations, the power tong comprising:
an outer case;
a rotary rotatably mounted in the outer case for rotating
a tubular;
apparatus for rotating the rotary to rotate the tubular;
and
at least one active jaw movably mounted on the rotary and
displaceable relative thereto to grip the tubular, the at
least one active jaw having a gripping element for
contacting the surface of the tubular, and wherein one of
said active jaw and said rotary is provided with a cam and
the other with a cam follower; and
pre-load apparatus interconnected directly or indirectly
between the at least one active jaw and the rotary for, in
use, displacing said active jaw with respect to said rotary
so that the active jaw is cammed into gripping engagement
with the tubular and so inhibit relative rotation between
said active jaw and said tubular on subsequent rotation of
said rotary.
2. A power tong as claimed in claim 1, further comprising
at least one passive jaw secured to the rotary for
facilitating the gripping of the tubular.
3. A power tong as claimed in claim 1 or 2, wherein said
pre-load apparatus comprises a first piston and cylinder
assembly:

9
4. A power tong as claimed in claim 2, wherein said first
piston and cylinder assembly acts between said active jaw
and said passive jaw.
5. A power tong as claimed in claim 3, where said first
piston and cylinder assembly acts between said active jaw
and said passive jaw.
6. A power tong as claimed in any one of claims 2 to 4,
further comprising a second passive jaw secured to the
rotary for facilitating the gripping of the tubular.
7. A power tong as claimed in claim 6, wherein said pre-
load apparatus further comprises a second piston and
cylinder assembly arranged to act between said active jaw
and said second passive jaw.
8. A power tong as claimed in any one of claims 1 to 5,
further comprising a control system for selectively
activating the pre-load apparatus and selectively
controlling the application of a pre-load to the at least
one active jaw.
9. A power tong as claimed in claim 6 or 7, further
comprising a control system for selectively activating the
pre-load apparatus and selectively controlling the
application of a pre-load to the at least one active jaw.
10. A power tong as claimed in claim 9, wherein said
control system comprises a control valve for permitting
fluid to flow from a fluid reservoir under pressure to a
selected one of the first and second piston and cylinder
assemblies and for selectively permitting fluid from the

10
other of said piston and cylinder assemblies to flow back
to the fluid reservoir.
11. A power tong as claimed in any one of claims 1 to 10,
wherein said active jaw comprises a jaw holder, a carrier
mounted on said jaw holder and a gripping element mounted
on said carrier.
12. A power tong as claimed in claim 11, wherein said
gripping element is releasably connected to the carrier.
13. A power tong as claimed in claim 11 or 12, wherein the
carrier is releasably connected to the jaw holder.
14. A power tong as claimed in any one of claims 1 to 13,
wherein the gripping element is flexible for conforming to
an exterior shape of the tubular.

Description

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POWER TONG
During the construction, maintenance and repair of
oil and gas wells various operations require the connec-
tion~and disconnection of successive lengths of threaded
tubulars such as pipe, casing, or tubing. Tools known
as tongs are used to "make" and "break" such connec-
tions.
Certain known power tongs have a body, a rotary
rotatably mounted in said body and at least one active
jaw which, in use, is pushed against a pipe in the
rotary and grips it for rotation with the rotary. In
one common arrangement the pushing action is generated
by a cam member which is bolted to the rotary and is
shaped so that the active jaw is cammed against the pipe
on rotation of the rotary relative to the active jaw in
one sense and is released on rotation of the rotary
relative to the active jaw in the opposite sense.
With known power tongs high torques, for example
50,000 ft.lbs, are often applied to tubulars.
It will be appreciated that if the active jaw is
not applied to the tubular with sufficient force the
tubular will slip.
Because activation of the active jaw relies on
rotation of the rotary relative to the active jaw there
is a period when the active jaw may become entrained
with the rotary and rotate a small distance relative to
the tubular before the active jaw is fully applied.
Whilst this is of little consequence for many types of
tubulars this is extremely detrimental for certain
tubulars, particularly those which have special surface
coating which may be torn away.
In WO 92/18744 the present applicant discloses a
tong having a rotary with an active jaw which can be
applied by hydraulic rams prior to rotating the rotary.
However, this arrangement cannot readily be adapted to

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the myriad of tongs in the field which rely on cams to
displace the active jaw into engagement with the tubu-
lar.
According to the present. invention there is provi
ded a power tong for rotating a tubular in wellbore
operations, the power tong comprising
an outer case,
a rotary rotatably mounted in the outer case for
rotating a tubular,
apparatus for rotating the rotary to rotate the
tubular,
at least one active jaw movably mounted on the
rotary and displaceable relative thereto to grip the
tubular,
the at least one active jaw having a gripping
element for contacting the surface of the tubular,
and wherein one of said active jaw and said rotary
is provided with a cam and the other with a cam follow-
er, and
pre-load apparatus interconnected directly or
indirectly between the at least one active jaw and the
rotary for, in use, displacing said active jaw with
respect to said rotary so that the active jaw is cammed
into gripping engagement with the tubular and so inhibit
relative rotation between said active jaw and said
tubular on subsequent rotation of said rotary.
The gripping element may be formed as an integral
part of the jaw although the jaw will normally comprise
a jaw holder on which the gripping element is mounted.

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For a better understanding of the present invention
reference will now be made, by way of example, to the
accompanying drawings, in which:-
.Fig. 1 is a simplified plan view of one embodiment
of a tong in accordance with the present invention;
Fig. 2A is a simplified plan view of the active jaw
holder and the two passive jaw holders which form part
of the tong shown in Fig. 1;
Fig. 2H is a simplified plan view of the active and
passive jaws which form part of the tong shown in Fig. 1
and which comprise the active and passive jaw holders
shown in Fig. 2A with their respective gripping elements
mounted thereon;
Fig. 2C is a section taken on line 2C-2C of Fig.
, 2A;
Fig. 2D is a section taken on line 2D-2D of Fig.
2A;
Fig. 3A is a simplified plan view of an alternative
jaw assembly being applied to a tubular (shown in cross
section);
Fig. 3H is a front view of a gripping element which
forms part of a passive jaw shown in Fig. 3A;
Fig. 3C is a section of a detail of Fig. 3A;
Fig. 3D is a front view of the detail of Fig. 3C;
Fig. 4A shows the jaw assembly of the tong of Fig.
1 mounted on a tubular before the application of pre-
loading force;
Fig. 4B shows the jaw assembly of the tong of Fig.
1 mounted on a tubular after the application of pre
loading force;
Fig. 5A is a side view of a second embodiment of a
gripping element;
Fig. 5H is a plan view of the gripping element
shown in Fig. 5A;
Fig. 6A is a side view of a third embodiment of a

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gripping element;
Fig. 6B is a plan view of a gripping element shown
in Fig. 6A; and
Fig. 7 is a perspective view of a modified active
j aw .
Referring to Fig. 1 of the drawings there is shown
a power tong which is generally identified by the refer-
ence numeral 1.
The power tong 1 comprises an outer case 2 which
accommodates a rotary 3 which can be rotated by a hy
draulic motor 4.
The rotary 3 accommodates a jaw assembly 5 which
comprises two passive jaws 6 and 7 and an active jaw 8.
The passive jaws 6 and 7 and the active jaw 8 each
comprise a jaw holder and a gripping element removably
mounted thereon.
As shown in Fig. 2A the passive jaw 6 and 7 and the
active jaw 8 comprises jaw holders 9, 10 and 11 respect-
ively each of which is provided with stops 12 to inhibit
circumferential displacement of their respective grip-
ping elements 13, 14, 15 (Fig. 2B).
As can be seen from Fig. 2D the jaw holder 9 is
provided with holes 16 to facilitate attachment of the
gripping element 13. Similarly, the active jaw 8 is
provided with holes 17 to facilitate attachment of the
gripping element 15 (Fig. 2C). In addition, the active
jaw 8 is provided with two aligned bores 18, each of
which can accommodate a pin which is held in position by
a circlip 20 which supports a cam follower in the form
of a roller 19 shown in dotted lines in Figs. 2B and 2C.
Figures 3A-3D show an alternative jaw assembly to
the jaw assembly shown in Figs. 2A-2D. Parts having
similar features to parts shown in Figs. 2A-2D have been
identified by the same reference numeral with the addi-
tion of an apostrophe. The essential difference is that
T 1 _ i

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the gripping elements 13', 14', 15' are mounted on
respective carriers 21, 22, 23 which are mounted on
their respective jaw holders 9', 10', 11'.
The carrier 21, 22 and 23 protect the jaw holder
9', 10' and 11' in the event that the gripping elements
13', 14', 15' are worn down.
Each carrier 21, 22, 23 is provided with dovetail
keys 24 which slide in corresponding dovetail slots 24a
in their corresponding jaw holder.
Similarly, each gripping element 13', 14', 15' is
provided with dovetails 25 which slot into corresponding
dovetail slots in their respective carriers.
Turning now to Figs. 4A and 4B the passive jaws 6,
7 are bolted to the rotary 3 which is provided with a
cam 26 having a ramming surface 27.
The active jaw 8 is mounted in the rotary 3 with
its rollers (cam followers) 19 engaging the ramming
surface 27.
A first hydraulic piston and cylinder assembly 28
is pivotally connected between the passive jaw 6 and one
end of the active jaw 8 whilst a second hydraulic piston
and cylinder assembly 29 is pivotally connected between
the passive jaw 7 and the active jaw 8.
The first hydraulic piston and cylinder assembly 28
and the second hydraulic piston and cylinder assembly 29
are connected to a control 'system which comprises hy
draulic lines 30 and 31, a spool valve 32 operable by a
lever 33, a reservoir 34, a bleed valve 35, a pump 36
actuable by an air supply 37, a pneumatic accumulator
38, and non-return valves 39.
As shown in Fig. 4A the air supply 37 is switched
off and the active jaw 8 is shown spaced from the tubu-
lar 40.
For the purpose of this explanation it will be
assumed that it is desired to tighten ("make up") a

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joint by rotating tubular 40 clockwise. Air supply 37
is actuated and pump 37 pumps hydraulic fluid through
hydraulic line 30 to expand the second piston and cylin-
der assembly 29. At the same time hydraulic fluid in
the first piston and cylinder 28 returns to the reser-
voir 34 via hydraulic line 31. Contraction of the first
piston and cylinder 28 is facilitated by a return spring
in the first piston and cylinder assembly 28 as shown.
The expansion of the second piston and cylinder assembly
29 displaces the active jaw 8 relative to the cam sur-
face 27 so that the rollers 19 roll along the cam sur-
face 27. This urges the active jaw 8 against the tubu-
lar 29 with a force determined by the pressure of the
air supply or a pressure relief valve (not shown) in
parallel with bleed valve 35.
At this point the active jaw 8 and the passive jaws
6 and 7 are in full engagement with the tubular 40. The
rotary 3 may then be rotated to rotate the tubular 40.
The control system may be mounted on the rotary 3
for rotation therewith, the air supply 37 being connec
ted to the pump 36 as and when needed, the pneumatic
accumulator 38 helping compensate for any seepage.
In order to release the active j aw 8 , the bleed
valve 35 may be opened to allow hydraulic fluid to flow
through hydraulic line 30 back to the reservoir 34.
If it were desired to unscrew ("break") a joint
then, starting from the position shown in Fig. 4A the
spool valve 32 would be displaced to the right and the
pump 36 actuated. The first piston and cylinder assemb-
ly 28 would expand and the second piston and cylinder 29
assembly contract. The anti-clockwise movement of the
active jaw 8 relative to the rotary 3 would cause the
rollers 9 to roll along the cam surface 27 and the
active jaw 8 to be urged into gripping engagement with
the tubular 40 prior to activation of the rotary 3.

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a
The gripping elements 13, 14, 15 may take the form
of teeth although they preferably comprise the appli-
cants "non-making jaws". A particularly suitable grip-
ping element is disclosed in WO 98/34004.
The gripping elements can be made of a wide variety
of materials, for example aluminium, zinc, copper,
brass, bronze or soft steel. Optional teeth may be
provided. The surface of the gripping elements may be
covered to conform generally to the shape of the tubu-
lar, for example as,shown in Figs. 5A and 5B or of a
tighter radius of curvature as shown in Figs. 6A and 6B.
If desired the gripping elements may be flexible or may
comprise a plurality of rigid elements laid side by
side. Although not recommended, it is conceivable that
the gripping element could be formed integral with a jaw
holder.
Fig. 7 shows a modified active jaw 8" which, in
addition to comprising a jaw holder 11" and a gripping
element 15" is also provided with rods 41 and 42 to
facilitate attachment of the first and second piston and
cylinder assemblies thereto.
* *
Various modifications to the arrangement disclosed
are envisaged, for example the first piston and cylinder
assembly 28 and the second piston and cylinder 29 could
be replaced by a single double acting piston and cylin-
der assembly. Similarly, a single piston and cylinder
assembly could be used and moved from the position of
the first piston and cylinder assembly 28 and the second
piston and cylinder assembly 29 for breaking or making
joints as desired.

Representative Drawing