Information Notice 1989-62, Malfunction of Borg-Warner Pressure Seal Bonnet Check Valves Caused by Vertical Misalignment of Disk
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
August 31, 1989
NRC INFORMATION NOTICE NO. 89-62:
MALFUNCTION OF BORG-WARNER PRESSURE SEAL
BONNET CHECK VALVES CAUSED BY VERTICAL
MISALIGNMENT OF DISK
Addressees
All holders of operating licenses or construction permits for
reactors.
nuclear power
Purpose
This information notice is intended to alert addressees of the potential mal- functioning of Borg-Warner pressure seal bonnet check valves caused by the
misalignment of the valve disk.
It is expected that recipients will review
the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. 'However, suggestions contained
in this information notice do not constitute NRC requirements; therefore, no specific action or written response is required.
Description of Circumstances
On April 23 and May 5, 1989, during hot functional testing at Comanche Peak
Unit 1, a combination of procedural errors and malfunctioning check valves
resulted in the backflow of high temperature water from the steam generators
through the auxiliary feedwater system to the condensate storage tank. This -
flow caused abnormally high temperatures, thermal stresses in excess of the
code allowable stresses, and damage to piping supports.
The procedural errors that occurred during testing on both dates involved simul- taneously opening both an auxiliary feedwater pump discharge valve connecting
the pump to the steam generators and an isolation valve in a test line leading
back to the condensate storage tank. During the time period covering both dates, each of the eight 4-inch Borg-Warner check valves in the auxiliary feedwater
supply lines leading to the steam generators :was Jammed partially open as a
result of improper assembly. This combination of circumstances allowed water
from the steam generators to flow back through the check valves, a pump dis- charge valve, and a test line isolation valve to the condensate storage tank.
In a separate incident on April 19, 1989, a 3-inch Borg-Warner check valve
located in the motor-driven auxiliary feedwater pump miniflow recirculation
-
line was found to be inoperable.
On examination, the two remaining 3-inch
miniflow recirculation valves in the auxiliary feedwater system also were
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IN 89-62 August 31, 1989 Investigation revealed that the valve disks of these three 3-inch valves, as
well as the eight inoperable 4-inch valves, were all positioned too low in the
valve body relative to the valve seats.
As a result, when the valve disk moved
toward the seat, the outside upper edge of the disk was caught under the inside
upper edge of the seat causing the disk to be jammed open with the plane of the
disk at a large angle relative to the plane of the seat (Figure 1).
All eleven
of the inoperable valves were of the 900 psi pressure seal bonnet type.
Discussion:
During the two steam generator water backflow events, the operators made almost
identical errors, although two different sets of valves were involved. On
April 23 an auxiliary operator intended to realign valves associated with the
turbine-driven auxiliary feedwater pump to permit recirculation flow to the
condensate storage tank.
The procedure required closing the normally open
turbine pump discharge valve (1AF-041) before opening the turbine pump recircu- lation test line isolation valve (1AF-042). However, the valves were operated
simultaneously and the recirculation valve which could be opened rapidly, was
fully open while the discharge valve which took a half hour to close, was still
open.
In about 10 minutes the levels in steam generators 1, 2, and 4 were
noticed to be decreasing rapidly.
At about 20 minutes into the event, paint
on the pipes in the turbine pump room was reported to be "bubbling and peeling"
and the recirculation valve was closed, terminating the backflow.
On May 5 the operators were conducting an auxiliary feedwater system operabil- ity test. The motor-driven auxiliary feedwater pump recirculation test line
isolation valve (1FA-055) was opened while the motor-driven pump discharge valve
(lFA-054) was still open. Again, this was contrary to the procedure in use, which required closing the discharge valve prior to opening the test line
isolation valve.
During this event, only water from steam generator 1 is
believed to have reached the auxiliary feedwater piping.
The backflow was
initially stopped when the discharge valve (-054) was fully closed.
However, when the operators attempted to restore the valves to the original position
to resume pumping to the steam generators, the test line isolation valve (-055)
was inadvertently left partially open, reestablishing the backflow to the con- densate storage tank. This backflow persisted for- the next hour and a half, being interrupted intermittently by the operation of the two auxiliary feed- water motor-driven pumps. The operators observing inconsistencies in the flow
to the steam generators finally realized that the test line isolation valve
was open and closed it, terminating the backflow.
The reason that the disk assemblies of the malfunctioning check valves were
positioned too low in the valve bodies was that an essential step was missing
from the vendor's reassembly procedure. The disk assembly, as well as the
valve bonnet and seal, is suspended from and positioned vertically by a threaded
ring that is screwed into the top of the valve neck, called the retainer ring
(Figure 1). The prescribed assembly procedure for the 3- and 4-inch valves
(Borg-Warner Operation and Maintenance Manual, OMM 1003) was to install and
bottom out the retainer ring.
This had the effect of locating the disk assembly
too low in the valve.
The original factory assembly process included the backing
IN 89-62 August 31, 1989 out of the retainer ring while observing the disk through the valve ports until
the disk had been raised to the correct height.
However, the necessary step of
backing out the retainer ring to its original factory assembly height was not
included in the reassembly procedure provided with the 3- and 4-inch valves.
All of the auxiliary feedwater check valves had been disassembled and inspected
in 1983 because of a concern about the adequacy of the disk stud fillet welds.
During the following reassembly using the incorrect procedure, all of the 3- and
4-inch valve disks were positioned lower than the original factory adjusted
position. Larger Borg-Warner check valves (6, 8 and 10-inch) could also be
affected by this error.
The April 23 backflow of high temperature water caused a significant amount of
blistering and flaking of the paint on the auxiliary feedwater supply lines as
well as some unusual stressing of the auxiliary feedwater piping.
However, the
May 5 backflow is believed to have caused the most damage.
Several areas in the
piping are known to have experienced thermal stresses that exceeded the code
allowable stresses. In addition, one of the piping supports failed and had
to be replaced. As a result, an extensive analysis of the piping, the piping
supports, and the penetrations had to be made to ensure the continued reliabil- ity of the auxiliary feedwater system.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact one
of the technical contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: H. H. Livermore, NRR
(817) 897-1500
M. F. Runyan, NRR
(817) 897-1500
Attachments:
1. Figure 1, Check Valve Shown with
Disk Jammed in Open Position
2. List of Recently Issued NRC Information Notices
Attachment 1
IN 89-62 August 31, 1989 RETAINER RING-
ADJUSTS HEIGHT OF
DISK ASSEMBLY
VALVE NECK
Figure 1. CHECK VALVE SHOWN WITH DISK
JAMMED IN OPEN POSITION
U4 v
Attachment 2
August 31,1989 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
89-61
88-48, Supp. 2 Failure of Borg-Warner Gate
Valves to Close Against
Differential Pressure
Licensee Report of Defective
Refurbished Valves
Maintenance of Teletherapy
Units
Suppliers of Potentially
Misrepresented Fasteners
8/30/89
8/22/89
8/18/89
8/16/89
89-60
89-59
89-58 Disablement of Turbine-Driven 8/3/89
Auxiliary Feedwater Pump Due
to Closure of One of the
Parallel Steam Supply Valves
89-57
89-56
89-45, Supp. 1
89-55
89-54
Unqualified Electrical
Splices in Vendor-Supplied
Environmentally Qualified
Equipment
Questionable Certification
of Material Supplied to the
Defense Department by Nuclear
Suppliers
Metalclad, Low-Voltage
Power Circuit Breakers
Refurbished With Substandard
Parts
Degradation of Containment
Isolation Capability by a
High-Energy Line Break
Potential Overpressurization
of the Component Cooling
Water System
7/26/89
7/20/89
7/6/89
6/30/89
6/23/89
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All NRC Medical
Teletherapy Licensees.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
OL = Operating License
CP = Construction Permit
4 ,
IN 89-62 August 31, 1989 out of the retainer ring while observing the disk through the valve ports until
the disk had been raised to the correct height.
However, the necessary step of
backing out the retainer ring to its original factory assembly height was not
included in the reassembly procedure provided with the 3- and 4-inch valves.
All of the auxiliary feedwater check valves had been disassembled and inspected
in 1983 because of a concern about the adequacy of the disk stud fillet welds.
During the following reassembly using the incorrect procedure, all of the 3- and
4-inch valve disks were positioned lower than the original factory adjusted
position. Larger Borg-Warner check valves (6, 8 and 10-inch) could also be
affected by this error.
The April 23 backflow of high temperature water caused a significant amount of
blistering and flaking of the paint on the auxiliary feedwater supply lines as
well as some unusual stressing of the auxiliary feedwater piping.
However, the
May 5 backflow is believed to have caused the most damage. Several areas in the
piping are known to have experienced thermal stresses that exceeded the code
allowable stresses. In addition, one of the piping supports failed and had
to be replaced. As a result, an extensive analysis of the piping, the piping
supports, and the penetrations had to be made to ensure the continued reliabil- ity of the auxiliary feedwater system.
This information notice requires no specific action or written response.
If
you have any questions about the information in this notice, please contact one
of the technical contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: H. H. Livermore, NRR
(817) 897-1500
M. F. Runyan, NRR
(817) 897-1500
Attachments:
1. Figure 1, Check Valve Shown with
Disk Jammed in Open Position
2. List of Recently Issued NRC Information Notices
- See previous concurrence
08LZ"w9 OGCB:DOEA:NRR*
- NRR
- NRR
RPB:ARM*
- C/O-CB:DOEA:NRR
DCKirkpatrick
HHLivermore
MRRunyan TechEd
CHBerlinger
08/14/89
08/21/89
08/21/89 08/18/89
08/23/89
o-,
.
4 .
IN 89-XX
August xx, 1989 out of the retainer ring while observing the disk through the valve ports until
the disk had been raised to the correct height.
However, the necessary step of
backing out the retainer ring to its original factory assembly height was not
included in the reassembly procedure provided with the 3- and 4-inch valves.
All of the auxiliary feedwater check valves had been disassembled and inspected
in 1983 because of a concern about the adequacy of the disk stud fillet welds.
During the following reassembly using the incorrect procedure, all of the 3- and
4-inch valves disks were positioned lower than the original factory adjusted
position. Larger Borg-Warner check valves (6, 8 and 10-inch) may also have been
affected by this error.
The April 23 backflow of high temperature water caused a significant amount of
blistering and flaking of the paint on the auxiliary feedwater supply lines as
well as some unusual stressing of the auxiliary feedwater piping.
However, the
May 5 backflow is believed to have caused the most damage.
Several areas in the
piping are known to have experienced thermal stresses that exceeded the code
allowable stresses.
In addition, one of the piping supports failed and had to
be replaced. As a result, an extensive analysis of the piping, the piping
supports, and the penetrations had to be made to ensure the continued reliabil- ity of the auxiliary feedwater system.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact one
of the technical contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: H. H. Livermore, NRR
(817) 897-1500
M. F. Runyan, NRR
(817) 897-1500
Attachment:
List of Recently Issued NRC Information Notices
D/DOEA:NRR
- See previous concurrence
CERossi
08/ /89 OGCB:DOEA:NRR*
RPB:ARM*
C/OGCB:DOEA:NR
DCKirkpatg;ick
HHLivermore
MRRunyan
TechEd
CHBerlingef: M red
08/14/89k&.rC)'
08/at/89
08/,<J/89
08/18/89
08PVV89 t A: R
se.
IN 89-XX
August xx, 1989
'%..
i factory assembly process included the backing out of the retainer ring while
observing the disk through the valve ports until the disk had been raised to
the correct height.
However, the necessary step of backing out the retainer
ring to its original factory assembly height was not included in the reassembly
procedure provided with the 3- and 4-inch valves. All of the auxiliary feed- water check valves had been disassembled and inspected in 1983 because of a
concern about the adequacy of the disk stud fillet welds. During the following
reassembly using the incorrect procedure, all of the 3- and 4-inch valves disks
were positioned too low in the valve body.
Larger Borg-Warner check valves were not affected by this error. The manual
instructions for the Borg-Warner 6-inch valves correctly identified the need
to set the bonnet elevation (and consequently the disk elevation) by adjusting
the retainer ring to the proper height.
The lack of an adequate procedure apparently also resulted in maintenance per- sonnel being unaware of the need to establish the correct retainer ring height
during the disassembly of the valves so that they could reassemble the valves
correctly. As a consequence, the Comanche Peak personnel found it necessary to
go through a complex dimensional analysis process in order to establish the
correct positions of the retainer rings.
The April 23 backfilow of high temperature water caused a significant amount of
blistering and flaking of the paint on the auxiliary feedwater supply lines as
well as some unusual stressing of the feedwater piping.
However, the May 5
backflow is believed to have caused the most damage.
Several areas in the
piping are known to have experienced thermal stresses that exceeded the code
allowable stresses. In addition, one of the piping supports failed and had to
be replaced. As a result, an extensive analysis of the piping, the piping
supports, and the penetrations had to be made to ensure the continued reliabil- ity of the auxiliary feedwater system. The 3-inch valve leakage discovered on
April 19 was initially attributed to excessive axial play in the disk assembly
rather than the retaining ring maladjustment. A more detailed investigation
into the root cause of the problem at that time might have precluded the
subsequent events and saved much of the resulting effort.
This information notice requires no specific action or written response. If
you have any questions about the Information in this notice, please contact one
of the technical contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: H. H. Livermore, NRR
(817) 897-1500
M. R. Runyan, NRR
(817) 897-1500
Attachment: List of Recently Issued NRC Information Notices
D/DOEA:NRR
- See previous concurrence
CERossi
08/ /89 OGCB:DOEA:NRR*
RPB:ARM
C/OGCB:DOEA:NRR
DCKirkpatrick
HHLivermore
MRRunyan TechEd '
CHBerlinger
08/14/89
08/ /89
08/ /89 08//9/89
08/ /89