FIELD OF THE INVENTION
The present invention generally relates to an apparatus for making welding
locations on cylindrical pipes for welding thereon a plurality of carrier plates.
More particularly, the invention relates to a device for marking welding locations
on four sides with equal-spacing on the circumference of a cylindrical pipe used
in main steam line of high pressure boilers.
BACKGROUND OF THE INVENTION
Carrier plates are used in the main steam pipe line in high pressure boilers.
These pipe lines extend from boiler outlet to turbine inlet and having straight
portions as well as bends. Both straight pipes and bends are provided with
carrier plates. At a particular place, according to design requirements, four
members of carrier plates are to be welded exactly at 90 deg to each other. The
thickness of the carrier plate varies from 20mm to 50mm and the height of the
carrier plates is generally around 55 mm. The length of the carrier plate varies
from 120 mm to 200 mm. These carrier plates are resting on semi circular
clamps which in turn are supported by hanger rods with spring loaded assembly
to permit vertical thermal expansion. A prior art assembly of carrier plate with
cylindrical pipe line is shown in figure -1. The outside diameter of the pipe varies
from 219 to 600 mm.
The required four sides marking in the bend pipe is not possible without using a
crane for rotating the bend pipe every 90 deg to position the carrier plate for
subsequent welding. The pipe material is low alloy steels and particularly in case

of P 91 grade material, the carrier plate is to be pre heated to a temperature of
200 deg C to 250 deg C which is also to be maintained for the pipe material
before fit up for welding to avoid thermal cracking. Hence it is very difficult at a
time to maintain proper distance, root gap (distance between the bottom of the
carrier plate and top surface of the pipe) and straightness of the carrier plate
because these activities are carried out by holding it in hand only. Further, the
carrier plate is to be maintained at 250 deg C during welding and it is very
difficult to hold the carrier plate with hand gloves.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a device for
marking welding locations on four sides with equal-spacing on the circumference
of a cylindrical pipe used in main steam line of high pressure boilers.
Another object of the invention is to propose a device for marking welding
locations on four sides with equal-spacing on the circumference of a cylindrical
pipe used in main steam line of high pressure boilers, which allows welding of
the carrier plate with an orientation between the carrier plates exactly at 90 deg
to each other.
A further object of the invention is to propose a device for marking welding
locations on four sides with equal-spacing on the circumference of a cylindrical
pipe used in main steam line of high pressure boilers, which enables to maintain
root gap of 2 mm between the carrier plate and a curved surface of the pipe.

A still further object of the invention is to propose a device for marking welding
locations on four sides with equal-spacing on the circumference of a cylindrical
pipe used in main steam line of high pressure boilers, which eliminates holding fe
the carrier plate by hand during tack welding process.
SUMMARY OF THE INVENTION
Accordingly, there is provided a device for marking welding locations on four
sides with equal-spacing on the circumference of a cylindrical pipe used in main
steam line of high pressure boilers.
The device consists of:
- a circular ring having an inner diameter on which four holes drilled
diametrically opposite to each other maintaining an angle of 90 deg
between the hole centres, each of the holes accommodating at least
one hexagonal head nut permanently;
- four pipe clamping stud assembly inserted on all the four holes
simultaneously to clamp the pipe being concentric to the circular ring;
- a sliding plate vertically movable along a rectangular slot on a fixed
slotted plate welded on the circular ring;
- a locking plate assembly welded on four sides equally-spaced in front
of the circular ring for positioning along the up and down motion;

wherein the sliding plate assembly having plates on either end and the
carrier plate is placed in between a plurality of guide plates and tightened
equally on both sides by the carrier plate locking nut,
wherein the pipe is preheated to ensure heating of the circular pipe to a
length equal to the carrier plate, and wherein the tack welding is carried
out when the said length of pipe and carrier plate attain the required
temperature .
After the welding, the device can be taken out by loosening the lock nut of the
carrier plate and that of the sliding plate and finally loosening the pipe clamping
stud. By this invention, the disadvantages mentioned in the prior art are
eliminated and without physical marking , the welding of carrier plate is
completed with less effort, without use of crane for the pipe holding and also the
time required is only one tenth of the time required for prior art method.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - Circular pipe with carrier plates used in the main steam line of high
pressure boilers.
Figure 2 - The device with carrier plate and circular pipe in position.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
According to the present invention, a circular pipe (09) is concentrically
positioned by equally adjusting at least one pipe clamping stud (01) on four sides
so that the circular ring (03) is concentric with the circular pipe (09). At least one
carrier plate (04) is positioned on the circular pipe (09) by holding the carrier
plate (04) in between a plurality of guide plates (06) and tightened by a carrier
plate locking nut (05). Now, the carrier plate (04) can be moved on either
directions, the top and bottom carrier plates are moved up and down and the left
and right carrier plates are moved horizontally. The root gap as required, is
made by the movement of a sliding plate assembly (2) on all directions equally
and locked by a sliding plate lock nut (07) provided in a locking plate assembly
(08). By this device now without much difficulty described in the prior art,
preheating and tack welding can be done. The device can be withdrawn after
preheating and tack welding by loosening the sliding plate lock nut (07) and pipe
clamping stud (01).

WE CLAIM
1. A device for marking welding locations on four sides equal-spacing on the
circumference of a cylindrical pipe used in main steam line of high
pressure boilers, comprising:
- a circular ring having an inner diameter on which four holes drilled
diametrically opposite to each other maintaining an angle of 90 deg
between the hole centres each of the holes accommodating at least
one hexagonal head nut permanently;
- four pipe clamping stud assembly inserted on all the four holes
simultaneously to clamp the pipe being concentric to the circular ring;
- a sliding plate vertically moving along a rectangular slot on a fixed
slotted plate welded on the circular ring;
- a locking plate assembly welded on four sides equally-spaced in front
of the circular ring for positioning along the up and down motion;
wherein the sliding plate assembly having plates on either end and the
carrier plate is placed in between a plurality of guide plates and tightened
equally on both sides by the carrier plate locking nut,

wherein the pipe is preheated to ensure heating of the circular pipe to a
length equal to the carrier plate, and wherein the tack welding is carried
out when the said length pipe and carrier plate attain the required
temperature .
2. A method to guide and support carrier plate work pieces (04) placed
equally at 90 deg to each other on an outer periphery of a cylindrical pipe
(09) forming main steam line of steam boilers with pre determined root
gap of 2 mm for welding, the method comprising the steps of:
- positioning a device as claimed in claim 1, on the pipe (09) at required
place where the carrier plate (04) is to be welded;
- positioning at least four carrier plates (04) in such a way that the
centre of the carrier plate (04) coincides with the centre of the sliding
plate assembly (02) and locked using a carrier plate locking nut (05);
- loosening the slide plate lock nut to touch the carrier plate (04) bottom
surface with the pipe (09) and then simultaneously moving outwards
all the four carrier plate (04) to maintain the root gap of at least 2mm
by lifting the sliding plate assembly (02) based on a graduation
marked on it and tightened with the sliding block nut (07).

3. The device as claimed in claim 1, wherein the carrier plates (04) are
positioned simultaneously at all four places in one plate plane to weld
with the pipe (09) used for hanging the the main steam pipes by resting
on the carrier plates on the circular clamps.

ABSTRACT

The invention relates to a device for marking welding locations on four sides
equal-spacing on the circumference of a cylindrical pipe used in main steam line
of high pressure boilers, comprising a circular ring having an inner diameter on
which four holes drilled diametrically opposite to each other maintaining an angle
of 90 deg between the hole centers each of the holes accommodating at least
one hexagonal head nut permanently; four pipe clamping stud assembly inserted
on all the four holes simultaneously to clamp the pipe being concentric to the
circular ring; a sliding plate vertically moving along a rectangular slot on a fixed
slotted plate welded on the circular ring; a locking plate assembly welded on four
sides equally-spaced in front of the circular ring for positioning along the up and
down motion; wherein the sliding plate assembly having plates on either end and
the carrier plate is placed in between a plurality of guide plates and tightened
equally on both sides by the carrier plate locking nut, wherein the pipe is
preheated to ensure heating of the circular pipe to a length equal to the carrier
plate, and wherein the tack welding is carried out when the said pipe and carrier
plate attain the required temperature .