FIELD OF THE INVENTION
The present invention relates to a connecting device for joining two pipes
requiring electrical isolation and no leak at very high pressure up to 400 bar and
temperature up to 700°C conditions of the working medium which is flowing
through the pipes. More particularly, the invention relates to a device for
producing a leak tight electrically isolative joint between two connecting metal
pipes carrying fluids at very high pressure and temperature conditions present in
operating boilers.
BACKGROUND OF THE INVENTION
In a test device to conduct experimentation on heat transfer, simulating boiler
conditions require electrical heating of the tube carrying a working medium
which inter alia simulate the heat flux of the boiler. The tube of the test device
has to carry the fluids at very high pressures up to 400 bar and temperatures up
to 700°C which are the operating conditions of the future boilers. In order to
isolate the other associated pipes in the loop from the electrically heated test
section, a joint capable of providing electrical isolation is needed. The joint
should also provide leak-free condition at the rated parameter conditions at 400
bar and 700°C.

US 6505866B1 discloses a device comprising a main body and a connector made
from resin to connect two pipes and to provide a highly reliable leak proof pipe
joint which is superior in workability, inexpensive and light, resistive against
chlorine and oxygen contained in hot water or vapour, good mechanical strength
and impart resistance and capable of withstanding deformation due to water
pressure or water hammer phenomenon. But this type of pipe joint cannot be
used for high pressure high temperature application as resins have low melting
point.
WO 2011155082A1 teaches about a device to connect two pipes with sealing
material where pressing rings are fitted over the pipes to be joined. This method
of pipe joint uses a pipe joint body, tightening elements and sealing material to
provide a leak proof joint between two connecting pipes. The leak tightness is
ensured by pressing the sealing material between pressing rings and pipe joint
body which are moved by the operation of tightening elements. However, the
electrical insulation between the connecting pipes is silent in this cited patent
and hence it deviates the present invention.
UK Patent GB 773159A discloses a method for jointing two pipes consists of two
flanges connected to the pipes to be joined and a packing member composed of
alloy steel having high temperature creep properties coated with Nickel. The
packing member is placed inside the groove between the two flanges and both
the flanges were tightened by operating the flange studs to provide a leak proof
joint at very high temperature. This method requires direct contact between
metal to metal surfaces of flange and the packing member. Hence, electrical
isolation between the two connecting pipes cannot be ensured in this method.

German Patent DE 10234245A1 discloses a method for joining two pipes
consisting two opposite lying, interconnected flange connectors which in identical
form each have a slot to accommodate a sealing ring, and a separate seal carrier
with two sealing rings for locating in the slot in the contact faces is fitted
between the flange connectors. The seal carrier is an encompassing annular
component with axially protruding ribs which reach into the slots in the contact
faces and serve as a holder for the sealing rings on both sides. The leak
tightness can be ensured by operating the tightening elements. However, this
method of pipe joint does not provide electrical insulation between the two
connecting pipes and also the maximum operating temperature is limited
depending on the properties of the sealing rings.
US 5938246A describes a method of maximizing system operating pressure
capability of a selected flange joint in a fluid carrying pipeline system consisting
two mating flanges, a set of self energizing seals and gasket element. The
gasket element is interposed in a surrounding relation to the seal assembly at an
outer radial locating proximate to the outer flange surface margin. The flanges
are connected with the bolts to form the flange joint while supporting the self-
energizing seal assembly and the gasket element at the inner and outer radial
locations, respectively, thereby to compress the self-energizing seal from the seal
thickness to the gasket thickness. However, the maximum pressure withstand
capability of this method is only 1000 psi and also this method of flange joint
does not ensure electrical isolation between the two connecting pipes.

UK Patent GB 2038972B teaches a method of providing a leak tight all-metal
joint where a metal gasket is disposed between mating flanges which can readily
be removed when the joint is disassembled. Opposing faces of the mating
flanges are configured to provide a recess between the flanges in which a soft
metal gasket of annular configuration can be placed when the flanges are
coupled together. Symmetrically disposed ridges on the opposing flange faces
penetrate into a peripheral region of the gasket, thereby causing a portion of the
gasket material to flow into an annular groove that forms the periphery of the
recess between the opposing flange faces. This compressed gasket material in
the annular groove provides a gas-tight seal between the mating flanges. But
this method does not talk about electrical isolation between the two mating
surfaces of the flanges.
In the above prior patents, method or device for providing an electrical isolation
between two connecting pipes for very high pressure and temperature are not
taught or suggested. Thus, the prior art only envisages knowledge of leak proof
joints for low temperature use without providing electricai isolation.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a device for
producing a leak tight electrically isolative joint between two connecting metal
pipes carrying fluids at very high pressure and temperature conditions present in
operating boilers.

SUMMARY OF THE INVENTION
Accordingly, there is provided a device for producing a leak tight electrically
isolative joint between two connecting metal pipes carrying fluids at very high
pressure and temperature conditions present in operating boilers, the device
comprising identical flanges having grooves on mating surface welded with the
pipes to be connected, a gasket assembly consisting of one stainless steel disc
with or without ceramic coating and two stainless steel ring joint gaskets placed
in the grooves, two copper rings placed inside the grooves, mica sheet gaskets
of corresponding thickness placed at the contact surfaces (top and bottom) of
the ring joint gaskets and stainless steel disc, the flanges being tightened by
using stainless steel studs and nuts including washers, the studs and the
washers coated with ceramic to ensure electrical isolation between the two
connecting pipes.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows a connecting device for joining two different pipes according to
the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in figure - 1, a connecting device for joining two different pipes as per
the present invention, consists of two identical metal flanges (10 and 13) having
grooves made on the mating surface and welded to the pipes (1 and 7) required
(Remarks: Sentence continuity shall be maintained without break)

to be connected together, a stainless steel disc (12) with or without ceramic
coating which is placed between two stainless steel ring joint gaskets (+4 and 5)
fitted in the grooves. To prevent leakage through the grooves, machined copper
rings (11 and 6) are placed at the bottom of the grooves as shown in figure 1.
To ensure the leak tightness through this joint, both the flanges (10 and 13) are
tightened by using stainless steel studs (8) and nuts (3). Stainless steel washers
(9) are provided on the studs (8) to ensure tightness. To ensure electrical
isolation between the two connecting pipes (1 and 7) all the studs (8) and
washers (9) are coated with ceramic, and mica sheet gaskets (2 and 14) of
appropriate thickness are placed at the contact surfaces of the ring joint gaskets
(4 and 5) and the stainless steel disc (12) with or without ceramic coating as
shown in figure 1. To ensure leak free joint, a pre calculated torque is applied in
a sequential and stepped manner such that the tightening force is uniform all
around the joining faces.
The connecting device of this present invention having following advantages
features:
a. Ensures electrical isolation between the two connecting metal pipes.
b. Can withstand very high pressure and temperature up to 400 Bar and
700°C of the working medium flowing through the pipes.
c. Provides leak tight joint meeting simultaneously the three functional
requirements of pressure, temperature and electrical isolation.

WE CLAIM :
1. A device for producing a leak tight electrically isolative joint between two
connecting metal pipes carrying fluids at very high pressure and temperature
conditions present in operating boilers, the device comprising identical
flanges (10 and 13) having grooves on mating surface welded with the pipes
to be connected, a gasket assembly consisting of one stainless steel disc (12)
with or without ceramic coating and two stainless steel ring joint gaskets (4
and 5) placed in the grooves, two copper rings (6 and 11) placed inside the
grooves, mica sheet gaskets (2 and 14) of appropriate thickness placed at
the contact surfaces (top and bottom) of the ring joint gaskets (4, 5) and
stainless steel disc (12), the flanges being tightened by using stainless steel
studs (8) and nuts(3) including washers (9), the studs (8) and the washers
(9) coated with ceramic to ensure electrical isolation between the two
connecting pipes (1, 7).
2. The device as claimed in claim 1, wherein a pre calculated torque in a
sequential and stepped manner is applied such that the tightening force is
uniform all around the joining faces.

3. The device as claimed in claim 1, wherein the high pressure and
high temperature fluid for example up to 400 bar and 700°C respectively
passes through the connecting pipe.

ABSTRACT

The invention relates to a device for producing a leak tight electrically isolative
joint between two connecting metal pipes carrying fluids at very high pressure
and temperature conditions present in operating boilers, the device comprising
identical flanges (10 and 13) having grooves on mating surface welded with the
pipes to be connected, a gasket assembly consisting of one stainless steel disc
(12) with or without ceramic coating and two stainless steel ring joint gaskets (4
and 5) placed in the grooves, two copper rings (6 and 11) placed inside the
grooves, mica sheet gaskets (2 and 14) of appropriate thickness placed at the
contact surfaces (top and bottom) of the ring joint gaskets (4, 5) and stainless
steel disc (12), the flanges being tightened by using stainless steel studs (8) and
nuts(3) including washers (9), the studs (8) and the washers (9) coated with
ceramic to ensure electrical isolation between the two connecting pipes (1, 7).