Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02510364 2005-06-21
1 "APPARATUS AND SYSTEM FOR ONLINE HIGH PRESSURE,
2 HIGH TEMPERATURE LEAK SEALING"
3
4 FIELD OF THE INVENTION
Embodiments of the invention relate to apparatus and methods for
6 sealing flanges and the like in apparatus under high pressure and
temperature
7 without the need to take the apparatus offline and more particularly for
sealing
8 pipe flanges in a high pressure heat exchanger.
9
BACKGROUND OF THE INVENTION
11 Apparatus which operate at high pressure, such as heat
12 exchangers, and which often also operate at high temperature differentials,
are
13 subject to pressure and thermal conditions which place seals, such as
gaskets
14 between the flanges of a shell end and an end cap of the heat exchanger,
under
stress which can result in leakage during operation. One such heat exchanger
is
16 an effluent waste heat boiler used in an ammonia plant which operates at
17 pressures of about 125 kg/cm2 and at a temperature of about 330°C.
18 Fasteners, such as nuts and studs, hold an end cap to the heat
19 exchanger shell and sandwich a gasket therebetween. Conventionally, in an
attempt to stop leaking at the gaskets or seals, the fasteners are often
merely
21 retightened or further tightened. If, however, the tightening does not stop
the
22 leak, the heat exchanger must be shut down and the flange face inspected
and
23 repaired, and if necessary the gasket replaced. Shutdown, loss of
production and
24 startup adds significantly to plant operation costs.
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CA 02510364 2005-06-21
1 Clamps, such as C-clamps, are known for attachment across mated
2 flanges to apply additional and axial mechanical force, flange-to-flange, in
an
3 attempt to improve compression and sealing at the interface between the
flanges.
4 As with tightening however, if the clamp is not successful, the heat
exchanger
must be taken offline for repair.
6 What is required is a means by which leakage can be stopped
7 without necessitating shutdown of the heat exchanger and thus realize
significant
8 savings in operational costs which would otherwise be lost using
conventional
9 means.
2
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CA 02510364 2005-06-21
1 SUMMARY OF THE INVENTION
2 Apparatus, system and method of use are taught for sealing leaks
3 between flanges of an apparatus, such as a heat exchanger, which is in
4 operation and particularly, for apparatus that is being operated at high
pressures
and temperatures, without need for taking the apparatus off line or
disassembly
6 thereof. A circular clamp, having a plurality of injection ports formed
radially
7 therethrough, is positioned about the flanges for sealingly engaging the
flanges at
8 a clearance between the flanges. A sealant which is capable of diffusing
into the
9 clearance and thereafter curing in the clearance at the operating conditions
is
injected though the injection ports. Injection of the sealant is at pressures
greater
11 than the pressure at which the apparatus is being operated.
12 Preferably, the clamp has a flange which extends substantially
13 parallel to the periphery of the mated flanges for sealing against the
flanges.
14 More preferably, the clamp is formed in two half circle sections
which are bolted together about the flanges. An insertion member extends from
16 an inner surface of the clamp and is inserted into the clearance to
positioned the
17 injection ports, which extend therethrough, into the clearance.
18 A valve is used between the injection ports and an injection means,
19 such as an injection gun, to ensure that sealant which has been injected
into the
ports cannot be forced back out of the injection ports.
21 In one broad aspect, embodiments of apparatus of the invention
22 comprise a clamp for the application of sealant into a clearance between
mated
23 flanges comprising: a circular clamp body adapted to straddle the clearance
and
24 seal around a periphery of the mated flanges for sealing the clearance; and
a
3
CA 02510364 2005-06-21
1 plurality of injection ports formed through the clamp body and in fluid
2 communication with the clearance for injection of a sealant therethrough
into the
3 clearance so as to seal leaks therefrom.
4 In another broad aspect, embodiments of the invention comprise a
system for sealing a leak from a clearance between mated flanges in an
6 apparatus at operating conditions and without disassembly comprising: a
clamp
7 for sealing engaging about a periphery of the mated flanges, the clamp
having a
8 plurality of injection ports formed therethrough; and a sealant capable of
diffusing
9 into the clearance upon injection and thereafter curing at operational
pressures
and temperatures, wherein the injection ports are fluidly connected to the
11 clearance when the clamp is sealing engaged about the periphery of the
mated
12 flanges and the sealant is injected through the injection ports formed in
the clamp
13 and into the clearance for forming a seal therein.
14 In another broad aspect, embodiments of the invention comprise a
method for sealing a leak between mated flanges in an apparatus at operating
16 conditions and without disassembly comprising: providing a clamp for
sealing
17 about a periphery of the mated flanges, the clamp having a plurality of
injection
18 ports formed therethrough; injecting a sealant into the injection ports and
into the
19 clearance; and permitting the sealant to cure in the clearance for sealing
leaking
therein.
21
4
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CA 02510364 2005-06-21
1 BRIEF DESCRIPTION OF THE DRAWINGS
2 Figure 1a is a front view of a heat exchanger illustrating an
3 embodiment of a prior art sealing method between a shell tube sheet and an
end
4 cap;
Figure 1 b is a cross-sectional view according to Fig. 1 a, along lines
6 A-A;
7 Figure 2 is a cross-sectional view of a clamp according to an
8 embodiment of the invention in use in a system for sealing leaks in a high
9 pressure, high temperature environment;
Figure 3 is a schematic illustrating regions about a cross-section of
11 a heat exchanger according to Fig. 1 b and having a leak in region F, the
regions
12 corresponding to temperatures illustrated in Table A found in the
specification;
13 Figure 4 is a plan view of one half of a clamp according to Fig. 2,
14 illustrating some of a plurality of injection ports formed through the
clamp;
Figure 5 is a cross-sectional view of the clamp half according to Fig.
16 4, at an injection port;
17 Figure 6 is a cross-sectional view of the clamp half according to Fig.
18 4 between injection ports;
19 Figure 7 is a plan view of a half of a clamp according to Figs. 2 and
4-6 illustrating end plates for connection to a second, corresponding clamp
half;
21 Figure 8 is a front view of an end plate according to Fig. 7
22 illustrating holes for fasteners for fastening corresponding end plates of
clamp
23 halves together for forming a circular clamp;
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1 Figure 9 is a perspective view of a join between two clamp halves
2 according to Fig. 2, the end plates being fastened together for forming a
circular
3 clamp;
4 Figure 10a is a front view of one embodiment of a clamp formed
about a fastener for sealing leaks therefrom; and
6 Figure 10b is a sectional view of the embodiment of the clamp of
7 Fig. 10a, illustrating a plurality of radial ports formed therethrough, at
least two of
8 which are used for injection of a sealant.
9
6
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1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
2 As shown in Figs. 1 a-b and 2, the embodiments herein are
3 described in the context of an apparatus and sealing system for sealing
leaks in a
4 heat exchanger 10, such as an effluent waste heat boiler for an ammonia
plant,
having mating flanges 11,12 for sealing between structural components such as
6 a shell tube sheet 13 and an end cap 14 of the heat exchanger 10. One
skilled in
7 the art would understand that the embodiments of the invention are
applicable for
8 sealing flanges in other high pressure, high temperature apparatus.
9 A gasket (not shown) is positioned in a clearance 16 between the
mating flanges 11,12. The flanges 11,12 are fastened together face-to-face
using
11 fasteners 15 such as nuts 15n and studs 15s which compress the gasket
12 sealingly therebetween. Regardless how tight the fasteners 15 may be
tightened,
13 the clearance 16 may not fully seal or remain sealed, particularly when
subjected
14 over time to high pressure or high temperature, resulting in a leak
therebetween.
Having reference to Figs. 2 and 3 and to Table A, leakage between
16 the flanges 11,12 at location F, results in a loss of temperature in the
flanges
17 11,12 of both the tube sheet 13 (T1) and the end cap 14 (T2), which
significantly
18 affects the performance of the heat exchanger 10.
19
Table A
A B C D E F G H I
T1 C 105.5127 135 115 104 73 85 91 85
T2 C 101 116 105 103 85 67 78 71 76
21
7
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1 Having reference to Figs. 2, 4 - 9 and in a preferred embodiment of
2 the invention, apparatus and system for using said apparatus is provided for
3 sealing between the flanges 11,12.
4 As shown in Fig. 2, a clamp 20 is provided for installation
circumferentially about a radial periphery 21 of the joined flanges 11,12 and
for
6 straddling the clearance 16. The clamp 20 is compressed radially inwards
onto
7 the periphery 21.
8 Preferably, as best seen in Figs. 4 and 9, the clamp 20 is formed of
9 at least two clamp portions 22,23 configured as circular sections adapted to
fit the
periphery 21 of the flanges 11,12. Two sections would be configured as two
11 semi- circular clamp portions 22,23. Each clamp portion 22,23 has first and
12 second distal ends 24,25. The first distal end 24 of one clamp portion 22
is
13 fastened to the second distal end 25 of an adjacent clamp portion 23. An
inside
14 diameter (ID) of the clamp 20, when assembled, is typically substantially
equivalent to the outside diameter (OD) of the flange periphery 21. Tightening
of
16 the adjacent distal ends 24,25 reduces a diametral radial extent of the
clamp 20
17 for compressing the clamp onto the flanges 11,12. Preferably the distal
ends
18 24,25a and 24a, 25 seal therebetween when fastened together. The first and
19 second distal ends 24, 25 are fastened after positioning each of the clamp
halves
22,23 over the clearance 16 between the flanges 11,12.
21 Having reference to Figs. 2, 5 and 6, the clamp 20 may further
22 comprise protuberances 33 extending radially inward which can be inserted
into
23 the clearance 16 for assisting in aligning the clamp 20 over the clearance
16
24 between the flanges 11,12.
8
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CA 02510364 2005-06-21
1 For connecting the distal ends 24,25a;24a,25, and as shown in
2 Figs. 7-9, each clamp portion 22,23 has clamp connectors such as end plates
27
3 at each distal end 24,25, 24a, 25a and which are formed having holes 28 for
4 insertion of fasteners 26 therethrough. The fasteners 26, when tightened,
draw
the end plates 27, and thus the ends 24,25a,24a,25 toward one another, thus
6 retaining the adjacent clamp portions 22,23 together for forming the
circular
7 clamp 20.
8 A plurality of sealant injection ports 40 are formed through the
9 clamp 20, at intervals around the clamp 20. The injection ports 40 extend
from an
exterior surface 41 of the body 30 through the body 30 of the clamp 20 to an
11 inner surface 42 of the clamp 20 to fluidly connect with the clearance 16.
The
12 number of injection ports 40 formed in the clamp 20 is dependant upon the
size
13 of the clamp 20, and upon the pressure and temperature of the apparatus to
14 which it is to be attached.
Having reference again to Figs. 2, 5, 6 and 9, and in an
16 embodiment of the invention, the clamp 20 is formed having a body 30 with a
17 radially inward sealing face 31 and a radially outward face 32. The body 30
can
18 have a wedge-shape, wherein the inward sealing face 31 is narrow and the
19 outward face 32 is wider. Preferably, once installed, the clamp 20 may be
cold-
welded to the flanges 11, 12.
21 At the inward sealing face 31, clamp flanges 34 extend axially and
22 substantially perpendicularly from opposing sides 35,36 of the body 30 and
act to
23 extend the inward sealing face 31 for sealing against the mated flange's
24 periphery 21. Preferably, the inward narrow face 31 of the body 30 extends
9
CA 02510364 2005-06-21
1 radially inward beyond the clamp flange 34 terminating in a substantially
2 rectangular protuberance or insertion member 33 along the inner surface 42
of
3 the clamp body 30. In such cases, the injection ports 40 extend through the
4 insertion member 33. The insertion member 33 is sized to fit within the
clearance
16 between the shell 13 and the end cap 14 which, when inserted therein, aids
in
6 positioning the injection ports 40 at the clearance 16.
7 In use, to seal a leak and without taking the apparatus 10 off-line or
8 dismantling the apparatus 10, the clamp portions 22,23 are positioned about
the
9 periphery 21 of the flanges 11,12. In cases implementing an insertion member
33, the insertion member 33 is positioned in the clearance 16 between the
11 flanges 11, 12. Corresponding end plates 27 are fastened together using
12 fasteners 26, typically nuts 15n and studs 15s, to secure the clamp 20
about the
13 apparatus 10.
14 An injection means (not shown), such as an injection gun, is
connected to one or more injection ports 40 adjacent the region where the leak
is
16 occurring and a sealant, such as a polymeric compound is injected into the
17 injection ports 40 for sealing the leak. The clamp flanges 34, which seal
against
18 the mated flanges 11, 12 aid in preventing injected sealant from leaving
the
19 clearance 16 during and following injection.
The sealant or polymeric compound is selected so as to diffuse into
21 the region of the leak when injected and to cure therein, sealing the leak.
Proper
22 selection of the polymeric compound to match the operating conditions,
23 particularly the temperature ensures proper curing and sealing. One such
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CA 02510364 2005-06-21
1 polymeric compound is disclosed in Iranian patent 25547. and is operable for
2 sealing at temperatures of about -45° to about 700°C.
3 In order to ensure injection of the polymeric compound into the
4 injection ports 40, and should pressure in the clearance 16 equalize to
apparatus
pressure, the injection pressure is preferably greater that the pressure in
the
6 apparatus 10. A valve 50 is positioned between the injection means (not
shown)
7 and the injection port 40 to ensure the polymer remains in the injection
port 40
8 following injection.
9 Additionally, as shown in Fig. 2 and Figs. 10a and 10b, and in
another embodiment, should leakage of injected polymer occur from around the
11 fasteners 15 used to fasten the flanges 11, 12 together, a clamp 60 is fit
about
12 the fasteners 15. In the example shown in Fig. 2, the clamp 60 is
sandwiched
13 between the nut 15n and a second nut 62 is secured to the stud 15s. The nut
62
14 retains the clamp 60 against outer surface 61 of the nut 15n while polymer
is
injected into injection ports 63 formed in the clamp 60. The polymer diffuses
and
16 cures therein sealing any leaking from around the fasteners 15. The clamp
60
17 can have the form of a hollow cylinder or washer having a plurality of
radial ports
18 63 formed about the circumference thereof and directed radially inward
about the
19 stud 15s for distribution of sealant about the stud 15s through the nut
15n.
Preferably, due to the small circumference of the nut 15n, stud 15s and clamp
60,
21 only two of the radial ports 63 are typically provided for injection of
sealant.
11
