U.S. patent application number 09/818534 was filed with the patent office on 2003-02-13 for seal arrangement for in-core instrument housing.
Invention is credited to Burger, Joseph M., Graeff, Kurt R., Martin, Kenneth A., Tursi, James G..
Application Number | 20030031287 09/818534 |
Document ID | / |
Family ID | 26889617 |
Filed Date | 2003-02-13 |
United States Patent
Application |
20030031287 |
Kind Code |
A1 |
Martin, Kenneth A. ; et
al. |
February 13, 2003 |
SEAL ARRANGEMENT FOR IN-CORE INSTRUMENT HOUSING
Abstract
A seal arrangement for providing a seal between a nuclear
reactor in-core instrument housing and an instrument contained
within the housing includes a lower seal assembly surrounding an
outer portion of the in-core instrument housing, an upper seal
assembly surrounding an outer portion of the in-core instrument, a
seal housing enclosing the lower and upper seal assemblies, and
lower and upper compression assemblies positioned on respective
ends of the seal housing. The compression assemblies each include a
drive nut and a compression collar. The compression collars engage
and apply an axial load on the seal assemblies to maintain a
reliable seal between the seal housing and the outer portion of the
in-core instrument housing, and between the seal housing and the
outer portion of the in-core instrument.
Inventors: |
Martin, Kenneth A.;
(Windsor, CT) ; Tursi, James G.; (Glastonbury,
CT) ; Burger, Joseph M.; (Windsor, CT) ;
Graeff, Kurt R.; (Windsor, CT) |
Correspondence
Address: |
WESTINGHOUSE ELECTRIC COMPANY, LLC
P.O. BOX 355
PITTSBURGH
PA
15230-0355
US
|
Family ID: |
26889617 |
Appl. No.: |
09/818534 |
Filed: |
March 28, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60194028 |
Apr 3, 2000 |
|
|
|
Current U.S.
Class: |
376/204 |
Current CPC
Class: |
Y10S 277/915 20130101;
G21C 17/10 20130101; Y10S 277/925 20130101; Y02E 30/30
20130101 |
Class at
Publication: |
376/204 |
International
Class: |
G21C 013/00 |
Claims
What is claimed is:
1. A seal arrangement for a nuclear reactor in-core instrument
housing, comprising: a first seal assembly surrounding an outer
portion of an in-core instrument housing; a second seal assembly
surrounding an outer portion of an in-core instrument inserted
within said in-core instrument housing; a seal housing having first
and second ends, said seal housing enclosing said first and second
seal assemblies; and first and second compression assemblies
positioned on and engaging said first and second ends of said seal
housing, respectively.
2. The seal arrangement as set forth in claim 1, wherein said first
and second compression assemblies are threadably engaged on the
respective first and second ends of said seal housing.
3. The seal arrangement as set forth in claim 1, wherein said first
and second compression assemblies compress said first and second
seal assemblies to form respective seals between said first end of
said seal housing and said outer portion of the in-core instrument
housing, and between said second end of said seal housing and said
outer portion of the in-core instrument.
4. The seal arrangement as set forth in claim 1, wherein said first
seal assembly comprises a first pair of graphite seal rings.
5. The seal arrangement as set forth in claim 4, wherein said
second seal assembly comprises a second pair of graphite seal
rings.
6. The seal arrangement as set forth in claim 1, wherein said first
compression assembly comprises a first threaded drive nut
threadably engaged to said first end of said seal housing, and a
first compression collar positioned between a flange of said first
drive nut and said first seal assembly.
7. The seal arrangement as set forth in claim 6, wherein said
second compression assembly comprises a second threaded drive nut
threadably engaged to said second end of said seal housing, and a
second compression collar positioned between a flange of said
second drive nut and said second seal assembly.
8. The seal arrangement as set forth in claim 7, further comprising
a first spacer ring positioned between said first compression
collar and said first seal assembly, and a second spacer ring
positioned between said second compression collar and said second
seal assembly.
9. The seal arrangement as set forth in claim 1, wherein said seal
housing comprises an integral retainer portion having external
threads threadably engaged with corresponding internal threads of
the in-core instrument housing to resist slipping when system
pressure is applied.
10. The seal arrangement as set forth in claim 9, wherein said seal
housing comprises an integral housing portion having external
threads engaged by corresponding internal threads of said first and
second compression assemblies.
11. The seal arrangement as set forth in claim 1, wherein said seal
housing is fabricated of a stainless steel alloy that resists
galling and seizing of threads.
12. The seal arrangement as set forth in claim 1, further
comprising a retainer nut having external threads threadably
engaged with corresponding internal threads of the in-core
instrument housing to resist slipping when system pressure is
applied, said retainer nut being separate from said seal
housing.
13. The seal arrangement as set forth in claim 1, wherein said
first and second compression assemblies comprise first and second
drive nuts and first and second compression collars, respectively,
said compression collars each having a first portion engageable by
one of said drive nuts and a second portion that protrudes axially
from said compression assemblies for engagement by an installation
tool.
14. The seal arrangement as set forth in claim 1, wherein said
first compression assembly comprises a first threaded drive nut
threadably engaged to said first end of said seal housing, and a
first compression collar positioned between a flange of said first
drive nut and said first seal assembly, said first compression
collar having an anti-rotation key received in a first mating
keyway of said seal housing.
15. The seal arrangement as set forth in claim 14, wherein said
second compression assembly comprises a second threaded drive nut
threadably engaged to said second end of said seal housing, and a
second compression collar positioned between a flange of said
second drive nut and said second seal assembly, said second
compression collar having an anti-rotation key received in a second
mating keyway of said seal housing.
16. The seal arrangement as set forth in claim 15, wherein said
first drive nut has a larger threaded diameter than said second
drive nut.
17. In combination, a nuclear reactor in-core instrument housing,
an in-core instrument inserted within said instrument housing, and
a seal arrangement for providing a seal between said instrument and
said instrument housing, the seal arrangement comprising: a first
seal assembly surrounding an outer portion of said in-core
instrument housing; a second seal assembly surrounding an outer
portion of said in-core instrument; a seal housing having first and
second ends, said seal housing enclosing said first and second seal
assemblies; and first and second compression assemblies positioned
on said first and second ends of said seal housing, respectively,
said first compression assembly engaging said first seal assembly
to maintain a seal between said first end of said seal housing and
said outer portion of said in-core instrument housing, and said
second compression assembly engaging said second seal assembly to
maintain a seal between said second end of said seal housing and
said outer portion of said in-core instrument.
18. The combination as set forth in claim 17, wherein said first
and second compression assemblies each comprise a threaded drive
nut threadably engaged to said seal housing, and a compression
collar positioned between a flange of said drive nut and a
respective one of said seal assemblies.
19. The combination as set forth in claim 18, wherein said
compression collars each have a first portion engageable by one of
said drive nuts and a second portion that protrudes axially from
said compression assemblies for engagement by an installation
tool.
20. A method of sealing a nuclear reactor in-core instrument
housing, comprising the steps of: positioning a first compression
assembly and first seal assembly around an outer portion of the
in-core instrument housing; positioning a seal housing over an end
of said in-core instrument housing; positioning a second seal
assembly and second compression assembly around an outer portion of
an in-core instrument contained within the in-core instrument
housing; and threading respective drive nuts of said first and
second compression assemblies onto said seal housing to maintain a
compressive sealing force against said first and second seal
assemblies.
21. The method of claim 20, further comprising the steps of:
applying a compressive axial preload to said first and second seal
assemblies using an installation tool; and threading said drive
nuts onto said seal housing while said seal assemblies are under
compression with said installation tool.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No, 60/194,028 filed on Apr. 3, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to nuclear power
reactors, and more particularly, to a seal arrangement and method
for sealing an in-core instrument housing ("ICI housing") after
reinsertion of an in-core instrument ("ICI") during a refueling
outage.
[0004] 2. Description of the Related Art
[0005] On typical pressurized water nuclear reactors, a plurality
of nozzles are located in an organized pattern across the head of a
reactor vessel. A majority of the nozzles are used to provide a
pressure boundary between neutron absorbing control rods and
respective drive mechanisms which provide controlling motion to the
control rods. A smaller number of the nozzles are used to provide
access into the vessel for ICIs, such as thermocouples and the
like.
[0006] At every refueling outage for typical nuclear reactors, the
ICIs must be partially withdrawn to allow for movement of the fuel.
In some cases, the process of withdrawing the ICIs has resulted in
damage to the O-ring sealing surfaces of the ICIs and/or the ICI
seal housing. In some cases, the sealing surfaces are damaged
beyond repair and, because the ICIs have to be reinserted with a
reliable seal prior to restarting, the damage must be repaired or
an alternate sealing method used.
[0007] One currently available option to repair the damaged seal is
to reinsert the ICIs without the O-rings, and perform a field seal
weld of the ICI to the housing. However, this requires costly and
time-consuming field welding. Also, at the next refueling outage,
the seal weld must be machined out so that the ICI can be
withdrawn, reinserted, and again seal welded. These operations are
very time consuming and costly and can only be performed a few
times before an alternate method must be used.
[0008] Another currently available option to repair the damaged
seal is to withdraw the ICI completely and replace the damaged
parts. However, because of high radiation contamination, there
currently are no methods available to remove the ICI without
cutting it up and disposing of the pieces underwater during the
withdrawal process. Thus, even a working, undamaged ICI must be
discarded and replaced, which is very costly. Moreover, replacement
of the seal housing requires field cutting and ASME Code welding,
which are very time consuming and costly.
[0009] Thus, there is a need for an improved seal arrangement and
method for sealing ICI housings after reinsertion of the ICIs
during a refueling outage.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a seal
arrangement and method for resealing an ICI housing during a
refueling outage that allows use of the existing components and
minimizes the need for costly field cutting and/or welding, and
which can be assembled and disassembled quickly and easily and
reused over the life of the plant.
[0011] It is a further object of the present invention to provide a
seal arrangement for sealing an ICI housing which is economical,
efficient and reliable in use, capable of a long operating life,
and particularly well adapted for the proposed use.
[0012] The present invention provides a seal arrangement for
establishing a seal between a nuclear reactor ICI housing and an
ICI contained within the ICI housing. The seal arrangement includes
a lower seal assembly surrounding an outer portion of the ICI
housing, an upper seal assembly surrounding an outer portion of the
ICI, a seal housing enclosing the lower and upper seal assemblies,
and lower and upper compression assemblies positioned on respective
ends of the seal housing. The compression assemblies each include a
drive nut and a compression collar. The compression collars engage
and apply an axial load on the seal assemblies to maintain a
reliable seal between the seal housing and the outer portion of the
ICI housing, and between the seal housing and the outer portion of
the ICI. Variations in the construction and methods for installing
the seal arrangements to the ICI housing and ICI are disclosed.
[0013] According to a broad aspect of the present invention, a seal
arrangement for a nuclear reactor ICI housing is provided,
comprising: a first seal assembly surrounding an outer portion of
an ICI housing; a second seal assembly surrounding an outer portion
of an ICI inserted within the ICI housing; a seal housing having
first and second ends, the seal housing enclosing the first and
second seal assemblies; and first and second compression assemblies
positioned on and engaging the first and second ends of the seal
housing, respectively.
[0014] According to another broad aspect of the present invention,
a seal arrangement is provided in combination with a nuclear
reactor ICI housing and an ICI inserted within the ICI housing. The
seal arrangement comprises: a first seal assembly surrounding an
outer portion of the ICI housing; a second seal assembly
surrounding an outer portion of the ICI; a seal housing having
first and second ends, the seal housing enclosing the first and
second seal assemblies; and first and second compression assemblies
positioned on the first and second ends of the seal housing,
respectively. The first compression assembly engages the first seal
assembly to maintain a seal between the first end of the seal
housing and the outer portion of the ICI housing. The second
compression assembly engages the second seal assembly to maintain a
seal between the second end of the seal housing and the outer
portion of the ICI.
[0015] According to another broad aspect of the present invention,
a method of sealing a nuclear reactor ICI housing is provided,
comprising the steps of: positioning a first compression assembly
and first seal assembly around an outer portion of the ICI housing;
positioning a seal housing over an end of the ICI housing;
positioning a second seal assembly and second compression assembly
around an outer portion of an ICI contained within the ICI housing;
and threading respective drive nuts of the first and second
compression assemblies onto the seal housing to maintain a
compressive sealing force against the first and second seal
assemblies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The present invention will become more clearly appreciated
as the disclosure of the invention is made with reference to the
accompanying drawings. In the drawings:
[0017] FIG. 1 is a schematic elevation view of the upper portion of
a nuclear reactor vessel, showing a conventional ICI housing
connected to a reactor vessel nozzle extending from the reactor
vessel head.
[0018] FIG. 2 shows a cross-sectional elevation view of a seal
arrangement for an ICI housing according to a first embodiment of
the present invention.
[0019] FIG. 3 shows a cross-sectional elevation view of the seal
arrangement of FIG. 2 with a compression tool for preloading the
seal arrangement during installation.
[0020] FIG. 4 shows an enlarged sect ion view of a sealing portion
of the seal arrangement of FIGS. 2 and 3.
[0021] FIG. 5 shows a cross-sectional elevation view of a seal
arrangement for an ICI housing according to a second embodiment of
the present invention.
[0022] FIG. 6 shows a cross-sectional elevation view of a seal
arrangement for an ICI housing according to a third embodiment of
the present invention.
[0023] FIG. 7 shows an enlarged section view of a sealing portion
of the seal arrangement of FIG. 6.
[0024] FIG. 8 is a plan view of a portion of a compression collar
having an anti-rotation key used in the seal arrangement of FIG.
6.
DETAILED DESCRIPTION OF THE INVENTION
[0025] A seal arrangement and method for sealing an ICI housing
according to the present invention will now be explained in detail
with reference to FIGS. 1 to 8 of the drawings.
[0026] FIG. 1 shows a portion of a nuclear reactor system 10 having
a reactor 12 including a substantially upright cylindrical vessel
14 and a substantially hemispherical head 16. The vessel has an
upper flange 18, and the head 16 has a lower flange 20. The flanges
18 and 20 are bolted together in a known manner for normal
operation of the reactor system 10. As is well known in the field
of nuclear engineering, the operating conditions within the reactor
12 can be monitored by ICIs, such as thermocouples and so forth.
This is typically accomplished by a plurality of ICIs 23 that pass
through respective nozzles 22 into the reactor 12. For the purpose
of simplifying the present description, only one of the reactor
vessel nozzles 22 on the head 16 is shown, but it should be
appreciated that normally there are several nozzles 22 positioned
in an organized array across the head 16. Each ICI 23 is housed in
an ICI housing 24 connected to a respective one of the nozzles 22.
The ICI 23, ICI housing 24, and other components shown in FIG. 1
are conventional.
[0027] As explained above, the ICIs 23 must be partially withdrawn
at every refueling outage to allow for movement of the fuel. The
process of withdrawing the ICIs 23 often results in damage to the
sealing surfaces of the O-rings installed in the grooves 25 (FIG.
2) of the ICIs 23 and/or to the ICI seal housing 24. The present
invention provides seal arrangements for resealing the interface
between the ICI 23 and the ICI housing 24 after the ICIs 23 are
reinserted following the refueling.
[0028] Three embodiments of seal arrangements according to the
present invention are described herein and shown in FIGS. 2 to 8 of
the drawings. All three embodiments utilize external seal rings,
preferably made of a graphite material, on the external surfaces of
the existing ICI 23 and ICI housing 24. To effect a seal against
full system design pressure of up to 2500 psi, the seal rings must
be compressed under very high loads to prevent leakage. The sealing
principle is the same in each of the three embodiments. The method
used to compress the seal rings differs.
[0029] As shown in FIGS. 2 to 4, a seal arrangement 30 according to
the first embodiment of the present invention includes a first
lower seal assembly 31 surrounding an outer portion 32 of the ICI
housing 24, and a second upper seal assembly 33 surrounding an
outer portion of an ICI 23 contained within the ICI housing 24. The
lower seal assembly 31 includes a first pair of seal rings 34, 35
positioned in abutting relationship with each other. The upper seal
assembly 33 includes a second pair of seal rings 36, 37 positioned
in abutting relationship with each other. The seal rings 34, 35 of
the lower seal assembly 31 have an inside diameter that fits
closely to the external surface of the ICI housing 24. The seal
rings 36, 37 of the upper seal assembly 33 have an inside diameter
that fits closely to the external surface of the ICI 23. The seal
rings 34-37 are preferably fabricated of a graphite material.
[0030] A seal housing 38 is provided which spans the interface
between the ICI 23 and the ICI housing 24. The seal housing 38 has
a first recess 39 formed in a first lower end 40 and a second
recess 41 formed in a second upper end 42. The lower seal assembly
31 is positioned in the first recess 39 so as to be enclosed by the
lower end 40 of the seal housing 38. The upper seal assembly 33 is
positioned in the second recess 41 so as to be enclosed by the
upper end 42 of the seal housing 38.
[0031] The seal housing 38 has a housing portion 43 and an integral
retainer portion 44. The retainer portion 44 has an inner diameter
45 that fits closely around the external surface of the ICI 23, and
an outer diameter having external male threads 46. The retainer
portion 44 is secured to the ICI housing 24 by threadably engaging
the external threads 46 of the retainer portion 44 to corresponding
internal threads 47 formed in the upper end of the ICI housing 24.
The retainer portion 44 has an abutment seat 48 at the top of the
external threads 46 that engages and seats against an upper end
surface 49 of the ICI housing 24. A lower end of the retainer
portion 44 has an abutment surface 50 against which the existing
spacers 51 surrounding the ICI 23 can be engaged. A lower end 52 of
the lowest spacer 53 is engaged by an annular shoulder 54 formed on
the ICI 23. Thus, the retainer portion 44 provides positive
retention against slipping of the ICI 23 and other parts relative
to the ICI housing 24 when system pressure is applied.
[0032] The housing portion 43 of the seal housing 38 is molded
together with the retainer portion 44 in a single, integral piece.
The housing portion 43 has external male threads 55 on each end,
which threads may extend along the entire length of the housing
portion 43, as shown in FIG. 2. The seal housing 38 is preferably
fabricated from a stainless steel alloy that resists galling and
seizing of threads, such as NITRONIC 60.TM. Stainless Steel.
[0033] A first lower compression assembly 56 and a second upper
compression assembly 57 are positioned on the lower and upper ends
40, 42 of the seal housing 38, respectively. The lower compression
assembly 56 includes a first lower drive nut 58 and a first lower
compression collar 59. The lower drive nut 58 has internal threads
60 threadably engaged on the external threads 55 of the housing
portion 43, and a flange 61 that extends inwardly at a lower end.
The lower compression collar 59 has a first annular portion 62
engageable by the flange 61 of the lower drive nut 58, a second
annular portion 63 which extends through the flange 61 and
protrudes from a lower end of the lower drive nut 58, and a third
annular portion 64 facing the lower seal assembly 31. A first lower
spacer ring 65 is positioned between the third annular portion 64
and the seal rings 34, 35 of the lower seal assembly 31. The lower
compression collar 59 is axially movable against the lower spacer
ring 65 using a compression tool, which will be described below, to
compress the lower seal assembly 31 to form a seal between the ICI
housing 24 and the seal housing 38. The lower drive nut 58 is
threaded onto the housing portion 43 of the seal housing 38 until
the flange 61 is engaged snugly against the first annular portion
62 of the lower compression collar 59 to maintain the compressed
seal between the ICI housing 24 and the seal housing 38.
[0034] The upper compression assembly 57 includes a second upper
drive nut 66 and a second upper compression collar 67. The upper
drive nut 66 has internal threads 68 threadably engaged on the
external threads 55 at the upper end of the housing portion 43, and
a flange 69 that extends inwardly at an upper end of the upper
drive nut 66. The upper compression collar 67 has a first annular
portion 70 engageable by the flange 69 of the upper drive nut 66, a
second annular portion 71 which extends through the flange 69 and
protrudes from an upper end of the upper drive nut 66, and a third
annular portion 72 facing the upper seal assembly 33. A second
upper spacer ring 73 is positioned between the third annular
portion 72 of the upper compression collar 67 and the seal rings
36, 37 of the upper seal assembly 33. The upper compression collar
67 is axially movable against the upper spacer ring 73 using a
compression tool, which will be described below, to compress the
upper seal assembly 33 to form a seal between the ICI 23 and the
seal housing 24. The upper drive nut 66 is threaded onto the
housing portion 43 of the seal housing 38 until the flange 69 is
engaged snugly against the first annular portion 70 of the upper
compression collar 67 to maintain the compressed seal between the
ICI 23 and the seal housing 38.
[0035] As shown in FIG. 2, the diameters of the threaded portions
60, 68 of the lower and upper drive nuts 58, 66 are the same. The
inner diameter of the flange 69 of the upper drive nut 66 and the
corresponding portions of the upper compression collar 67 are
smaller than the inner diameter of the flange 61 of the lower drive
nut 58 and the corresponding portions of the lower compression
collar 59.
[0036] An installation tool 74 for installing the seal arrangement
30 shown in FIG. 2 over the existing ICI 23 and ICI housing 24
during a refueling outage is shown in FIG. 3. The installation tool
74 includes a pair of leg assemblies 75, 76 each having a lower end
77 with a gripping portion 78 protruding inwardly toward the ICI
housing 24, and an upper end 79 supporting a hydraulic cylinder 80.
The gripping portions 78 at the lower end 77 of the leg assemblies
75, 76 engage the protruding second annular portion 63 of the lower
compression collar 59. The pair of leg assemblies 75, 76 can be
easily positioned over and removed from the seal arrangement 30
after the compression assemblies 56, 57 are installed with the
drive nuts 58, 66 threaded hand tight.
[0037] The installation tool 74 also includes an upper compression
plate 81 surrounding the ICI 23 above the upper compression collar
67. A lower surface 82 of the compression plate 81 engages the
protruding second annular portion 71 of the upper compression
collar 67. A piston 83 protrudes from each of the hydraulic
cylinders 80 into engagement with the upper compression plate 81.
When the tool 74 is placed over the seal arrangement 30, as shown
in FIG. 3, a predetermined pressure can be introduced into the
hydraulic cylinders 80 to force the respective pistons 83 against
the upper compression plate 81, which in turn pushes the upper
compression collar 67 against the upper seal assembly 33. At the
same time, a corresponding force is transmitted through the leg
assemblies 75, 76 to force the gripping portions 78 against the
lower compression collar 59 to compress the lower seal assembly 31.
The tool 74 is thus operable to provide a compression load to the
lower and upper seal assemblies 31, 33 simultaneously.
[0038] While the tool 74 is installed and a compression preload is
applied to the seal assemblies 31, 33, the lower and upper drive
nuts 58, 66 can be threaded further along the seal housing 38 until
the flanges 61, 69 of the drive nuts 58, 66 are engaged snugly
against the respective lower and upper compression collars 59, 67.
For example, the drive nuts 58, 66 can be seated hand tight while
the seal assemblies 31, 33 are under compression from the
installation tool 74. When the hydraulic pressure is released from
the tool 74, the drive nuts 58, 66 pick up the load and maintain
the compression preload on the seal assemblies 31, 33.
[0039] Having explained the construction of the seal arrangement 30
according to a first embodiment of the present invention, a method
of installing the seal arrangement 30 during a nuclear reactor
refueling outage will now be described.
[0040] After the seal welds have been cut (where applicable) and
the surfaces cleaned, the existing retainer nut (not shown) is
removed and discarded. The ICI 23 is partially withdrawn in
accordance with existing procedures. The existing ICI O-rings in
the grooves 25 can be discarded because they are not required with
the seal arrangement 30 of the present invention. The refueling is
then completed in accordance with existing procedures. The ICI 23
is then reinserted to the proper depth. The reinsertion can be done
by hand without using an insertion tool because the grooves 25 do
not have O-rings causing a friction drag during reinsertion.
Spacers 51 are added according to the existing procedure to a
defined height so that the seal housing 38 will seat properly.
[0041] The lower drive nut 58, lower compression collar 59, lower
spacer ring 65, and lower seal assembly 31 are lowered over the
outside of the ICI housing 24. The retainer portion 44 of the seal
housing 38 is threaded (e.g., hand tight) into the internal threads
47 of the ICI housing 24 until the seal housing 38 is seated on the
ICI housing 24. After the seal housing 38 is installed, the ICI 23
is pulled up slightly by hand to close any gaps with the spacers
51. The lower seal assembly 31, lower spacer ring 65, lower
compression collar 59 and lower drive nut 58 are then installed to
the lower end 40 of the seal housing 38 (e.g., hand tight), as
shown in FIG. 2. The upper seal assembly 33 and upper spacer ring
73 are installed in the upper end 42 of the seal housing 38. The
upper compression collar 67 and upper drive nut 66 are then
installed (e.g., hand tight), as shown in FIG. 2.
[0042] The installation tool 74 shown in FIG. 3 is used to seat the
lower and upper seal assemblies 31, 33, preload the seal
arrangement 30 during installation, and unload the seal arrangement
30 for removal. Because the tool 74 loads both seal assemblies 31,
33 simultaneously, the number of operations required to install or
remove the seal arrangement 30 is reduced, thereby saving
installation and removal time.
[0043] The upper and lower compression collars 59, 67 are axially
loaded simultaneously by the hydraulic tool 74 to compress the
lower and upper seal assemblies 31, 33 to the desired preload.
While under compression with the hydraulic tool 74, both drive nuts
58, 66 are seated (e.g., hand tight). When the hydraulic pressure
is released from the tool 74, the drive nuts 58, 66 pick up the
load and maintain the preload on the seal assemblies 31, 33. The
tool 74 can then be removed.
[0044] A seal arrangement 85 according to a second embodiment of
the invention will now be described with reference to FIG. 5.
[0045] The seal arrangement 85 shown in FIG. 5 is similar in most
respects to the seal arrangement 30 shown in FIGS. 2 to 4. The main
difference is that the seal arrangement 85 of FIG. 5 includes a
retainer nut 86 as a separate component from the seal housing 87.
The retainer nut 86 has external threads 88 which are threaded into
the internal threads 47 of the ICI housing 24 until the retainer
nut 86 is seated against the upper end of the ICI housing 24. The
seal housing 87 is installed over the retainer nut 86 after the
retainer nut 86 is seated in the ICI housing 24. An inwardly
directed flange 89 at the upper end of the seal housing 87 engages
an upper surface of the retainer nut 86 to maintain the vertical
positioning of the seal housing 87. The seal housing 87 and
retainer nut 86 are both preferably fabricated from a stainless
steel alloy that resists galling and seizing of threads, such as
NITRONIC.TM. 60 Stainless Steel. The installation tool 74 shown in
FIG. 3 is used for installing and removing the seal arrangement 85
of FIG. 5 in the same manner described above.
[0046] A seal arrangement 90 according to a third embodiment of the
invention will now be described with reference to FIGS. 6 to 8.
[0047] The seal arrangement 90 shown in FIGS. 6 to 8 is similar in
many respects to the seal arrangement 85 shown in FIG. 5. The main
difference is that the seal arrangement 90 of FIGS. 6 to 8 relies
upon the torque applied to the lower and upper drive nuts 91, 92 to
compress and load the lower and upper seal assemblies 93, 94 during
installation, rather than a hydraulic installation tool.
[0048] The seal arrangement 90 of FIGS. 6 to 8 includes a first
lower seal assembly 93 enclosed by a lower end of a seal housing
95, and a second upper seal assembly 94 enclosed by an upper end of
the seal housing 95. A first lower compression collar 96 and a
second upper compression collar 97 are installed against the
respective lower and upper seal assemblies 93, 94. The lower and
upper compression collars 96, 97 each have anti-rotation keys 98,
99 protruding radially outwardly, as shown in FIG. 8, for example.
The lower and upper ends of the seal housing 95 have mating keyways
100, 101 formed therein into which the anti-rotation keys 98, 99 of
the compression collars 96, 97 are received. The compression
collars 96, 97 act as a bearing surface for the applied thrust
loads and prevent rotational loads on the seal rings of the
respective seal assemblies 93, 94.
[0049] Thrust bearing rings 102, 103 are installed between each of
the drive nuts 104, 105 and the respective compression collars 96,
97. The thrust bearing rings 102, 103 reduce the rotational
frictional drag as the drive nuts 104, 105 are tightened. The
thrust bearing rings 102, 103 can be eliminated if the compression
collars 96, 97 are fabricated of a good bearing material.
[0050] The seal housing 95 has at least a pair of flat surfaces
106, 107 formed intermediate its ends on an external perimeter for
engagement by a wrench (not shown) to prevent rotation during
torquing of the upper and lower drive nuts 104, 105. For example,
the external perimeter of the seal housing 95 can be hexagonal
shaped. As shown in FIG. 6, the diameter of the threaded portion of
the lower drive nut 104 is larger than the diameter of the threaded
portion of the upper drive nut 105. The inner diameter of the
flange 108 of the lower drive nut 104 and the corresponding
portions of the lower compression collar 96 are also larger than
the inner diameter of the flange 109 of the upper drive nut 105 and
the corresponding portions of the upper compression collar 97.
[0051] A method of installing the seal arrangement 90 of FIGS. 6 to
8 will now be described.
[0052] As in the embodiments described above, the existing O-rings
in the grooves 25 on the ICI 23 can be removed and discarded
because they are not required with the seal arrangement 90 of the
present invention. After the refueling is completed, the ICI 23 is
reinserted to a proper depth. Spacers 51 are added according to the
existing procedure to a defined height. The retainer nut 86 is then
seated in the upper end of the ICI housing 24.
[0053] The lower drive nut 104, lower thrust bearing ring 102,
lower compression collar 96, and seal rings of the lower seal
assembly 93 are lowered over the outside of the ICI housing 24. The
seal housing 95 is then placed over the retainer nut 86 with its
upper flange 110 seated against the upper surface of the retainer
nut 86. The lower seal assembly 93, lower compression collar 96,
lower thrust bearing ring 102, and lower drive nut 104 are then
installed to the lower end of the seal housing 95. The lower drive
nut 104 is torqued using a wrench (not shown) until a sufficient
load is placed on the lower seal assembly 93 to prevent leakage
under full system pressure. A second wrench (not shown) is used to
engage the flat surfaces 106, 107 on the seal housing 95 to prevent
rotation of the seal housing 95 when the lower drive nut 104 is
being torqued.
[0054] The upper seal assembly 94, upper compression collar 97, and
upper thrust bearing ring 103 are then installed over the ICI 23
and seated into the upper end of the seal housing 95. While pulling
the ICI 23 up slightly by hand to close any gaps with the spacers
51, the upper drive nut 105 is threaded onto the upper end of the
seal housing 95 and torqued using a wrench until a sufficient load
is placed on the upper seal assembly 94 to prevent leakage under
full system pressure.
[0055] The seal arrangements 30, 85, 90 described above provide the
following advantages over the existing technology: (1) no field
cutting or welding are required; (2) the existing ICIs and ICI
housings can be reused, even with damaged O-ring sealing surfaces;
(3) the seal assemblies will seal the expected pressure without
machining or polishing the existing parts; (4) the seal
arrangements can be assembled quickly and easily by hand; (5) the
ICIs do not need to be withdrawn any further than normal to install
the seal arrangements; (6) the existing O-rings can be eliminated
making the ICI removal and insertion process easier; (7) the seal
arrangements can be fit and installed into smaller areas of access;
and (8) the seal arrangements can be reused throughout the life of
the plant.
[0056] While the invention has been specifically described in
connection with specific embodiments thereof, it is to be
understood that this is by way of illustration and not of
limitation, and the scope of the appended claims should be
construed as broadly as the prior art will permit.
* * * * *