FIELD OF THE INVENTION
The subject invention relates to development of an improved drum shaft bush
extension to enhance the life of draw work's drum shaft in oil rig.
BACKGROUND OF THE INVENTION
An oil rig used for drilling wells for exploration or production of oil essentially
contains the following equipment:
1. Mast and substructure: which provides the basic support for the
equipment used for drilling and handling of various tools.
2. Hoisting and rotating equipment: These are equipment like the hoist also
known as the draw works, rotary, swivel and traveling block.
The draw works are used for the following activities.
a) Raising and lowering of mast and substructure during every rig
building and rig move.

b) Provide required rotating torque to the drill bit through the rotary
table and Kelly.
c) Raising and lowering of drill pipes using the traveling block in the
process of drilling and tripping operations.
d) Miscellaneous activities like torque tighting of drill pipe, breaking of
the pipe points. Fishing, surveying the drilled hole using various
instruments.
The drum shaft plays a key role in all of the above functions. The rotating speed
of the drum shaft is controlled by the main brake mounted on the drum shaft
itself. The braking activity is continuous during the operation of the oil rig.
Large amount of heat is generated due to the frictional force and needs to be
dissipated.
The brake flange used for this purpose has an integral water jacket (chamber)
through which oil circulation is facilitated. The supply of cooling water required
is provided through the hollow passage of the main drum shaft upto the length
where the brake flange is mounted.

Connectivity is provided by means of pipes and hoses with 100 % leak proof
joints.
In existing design, the drum shaft is provided with a groove for the 'O' ring which
prevents passing of water in the joined plane.
Over a period of time, 'O' ring groove gets damaged due to corrosion. The said
damage is due to the fact that the water used for cooling at rig sites is often of
very poor quality and is drawn from available ground sources near by.
In the process of continuous operation the 'O' ring groove gets damaged leading
to water seepage initially and consequently result heavy leakage. The water
thus leaked mixes with the oil which is flowing through another passage fpr
lubricating the chains and sprockets of the draw works. As a consequence this
drum shaft needs regular replacement of the damaged 'O' ring groove due to
corrosion, thus resulting both expensive and time consuming procedure.
The present invention has proposed to overcome the above difficulties of prior
state of art by employment of stainless steel bush inserted into bored shaft
instead of maintaining groove for the 'O' ring to prevent leakage of water in the
jointed plane.

No prior patent document was noticed in respect of such development of the
present invention.
DESCRIPTION OF THE INVENTIOM
One objective of the invention is to avoid such replacement of costly drum shaft
and save time consuming activity in such replacement and optimize run of the
drum shaft.
The said objective is carried through on employment of shaft bush extension
instead of the 'O' ring groove configuration of the drum shaft.
The proposed invention will be better understood from the following description
with reference to the accompanying drawings in which
Figure 1 represents a sectional elevation view of
the drum shaft with SS bush.

Figure 2 represents plan view of the drum shaft fixed with SS bush.
Figure 3 represents isolated view of the drum shaft
with SS bush with thread design.
In the Figures a hole (4) is a through hole bored in the drum shaft (2). A
stainless steel (SS) bush (1) with corresponding dimension is inserted into the
hollow bore (4) and adapted with the shaft (2) by threading (6) on drilling the
opening end of the shaft matching with outside diameter of the bush (1) and
thereafter welded all round at point (3) by Tungsten Inert Gas (TIG) welding at
the open face of the shaft. The whole setup of the drum shaft with the SS bush
is fastened through several keys (5) around the bored hole of the drum shaft.
Figure 3 in exploded view show how the said SS bush (1) is provided in the
bored hole of the drum shaft (2) with threading (6) with detailed manner of
attachment of the SS bush extension for connectivity with main brake and
related connections with pipes and hoses. The weld around the bush is made at
the open end portion of the threading (3) at the open end surface of the shaft on
which surface the bush (1) is adapted and extended beyond the said open
surface for connectivity.

Such adaptation of the SS bush extension shaft provide secured leak proof joints
of the drum shaft of an oil rig in operation with enhanced life of the drum shaft.
The scope and ambit of the invention as narrated herein is defined in the
encompassed appended claims.

We Claim:
1. An improved drum shaft of a rotating drum in a rotating and hoisting
device, the device known as draw work, and constituting a basic
component of an oil rig which oil rig further comprises a mast, and a
substructure, the rotating drum comprises a main brake mounted on the
drum shaft, and a mounting flange with in-built jacket for supplying
cooling fluid to dissipiate the heat generated during operation of the draw
work, the improvement is characterized in that a rear end of the drum
shaft susceptible to damage is provided with a hollow bore and an internal
threading, a bush formed of dissimilar material (stainless steel) weldably
attached to the hollow bore of the shaft with a portion of the threaded
area projecting beyond the flange joint which is further secured by
inserting a plurality of keys, and in that total length of the drum shaft with
bush extension is maintained identical to that of the existing shaft to
eliminate replacement of the associate components of the draw work.

ABSTRACT

TITLE: " AN IMPROVED DRUM SHAFT OF A ROTATING DRUM OF AN OIL RIG "
The invention relates to an improved drum shaft of a rotating drum in a rotating
and hoisting device, the device known as draw work, and constituting a basic
component of an oil rig which oil rig further comprises a mast, and a
substructure, the rotating drum comprises a main brake mounted on the drum
shaft, and a mounting flange with in-built jacket for supplying cooling fluid to
dissipiate the heat generated during operation of the draw work, the
improvement is a rear end of the drum shaft susceptible to damage is provided
with a hollow bore and an internal threading, a bush formed of dissimilar
material (stainless steel) weldably attached to the hollow bore of the shaft with a
portion of the threaded area projecting beyond the flange joint which is further
secured by inserting a plurality of keys, and in that total length of the drum shaft
with bush extension is maintained identical to that of the existing shaft to
eliminate replacement of the associate components of the draw work.