Information Notice No. 88-13:Water Hammer and Possible Piping Damage Caused by Misapplication of Kerotest Packless Metal Diaphragm Globe Valves
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON D.C. 20555
April 18, 1988
Information Notice No. 88-13: WATER HAMMER AND POSSIBLE PIPING DAMAGE
CAUSED BY MISAPPLICATION OF KEROTEST
PACKLESS METAL DIAPHRAGM GLOBE VALVES
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is being provided to alert addressees to potential
problems resulting from the improper application of packless metal diaphragm
valves supplied by the Kerotest Manufacturing Corp. 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:
Kerotest Y-pattern packless metal diaphragm globe valves are used in a variety
of applications in nuclear power plant reactor systems. These valves are de-
signed to meet each owner's equipment specifications. However, incidents have
occurred involving flow throttling and reverse flow as a result of the misap-
plication of these valves.
On August 6, 1984, McGuire Unit 2 operators discovered a broken weld on the
letdown line of the residual heat removal system. The system was in use at the
time and contaminated water was spraying from the broken pipe and from the
stem of a valve. A subsequent inspection revealed a number of damaged
supports/restraints and a broken socket weld that had completely separated.
On April 5, 1985, seven socket welds with crack indications were discovered on
additional piping in this system, although no welds had failed as they had in
the August 1984 event. The root cause of these problems was attributed to
excessive piping vibration induced by "chugging" during reverse flow through
Kerotest Y-pattern packless metal diaphragm globe valves.
On May 12, 1987, while Trojan operators were transferring water from the "A"
accumulator via backflow through the fill line to the "D" accumulator, the
fill line ruptured at the "A" accumulator nozzle-to-pipe weld. On May 23,
1987, after the broken line had been repaired, operators again attempted to
transfer water, and the fill line ruptured at the same location. The cause of
the event was attributed to backflow through the Kerotest Y-pattern packless
metal diaphragm globe valve in the "A" accumulator fill line. This backflow
created a cyclic
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. IN 88-13
April 18, 1988
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vibration of the valve disk. This vibration induced high enough stresses in
the fill line to cause the pipe rupture.
On February 22, 1988, while Braidwood Unit 1 was draining the "D" accumulator,
the fill line ruptured at a location similar to the location of a break pre-
viously reported at Byron, which was not analyzed by the licensee. The break
location was also similar to that at Trojan. This line has a Kerotest
Y-pattern packless metal diaphragm globe valve installed. Analysis of the
break determined that it was caused by high cycle fatigue. The licensee has
not been able to rule out valve "chugging" as the cause of the high cycle
fatigue.
Discussion:
Reverse flow through Kerotest Y-pattern packless metal diaphragm globe valves
has caused broken piping welds at two nuclear plants and may be responsible
for other broken welds where the root cause has not been identified. Because
of the stem and disk design used in Kerotest Y-pattern packless metal
diaphragm globe valves, these valves are not intended for applications that
require flow throttling or that subject the valves to reverse flow. Reverse
flow in these valves can result in "chugging" that induces flow vibrations and
water hammer. It may not be clear to plant operating personnel that violating
these application criteria can result in serious consequences such as weld
cracks and pipe ruptures that breach the primary coolant pressure boundary.
The manufacturer's product literature did not clearly state that certain valve
types should not be subjected to reverse flow or used for flow throttling.
Older issues of Kerotest instruction and engineering manuals do not warn users
of the valves' unidirectional flow properties. More recent editions have
corrected this deficiency; however, licensees may not have the corrected
manual.
Purchase specifications may have been written without regard to flow direc-
tionality because the manufacturer's literature did not note its importance.
This may have caused the improper use of these valves in applications where
bi-directional flow is anticipated either in normal operation or in coping with
emergency situations that require other-than-normal plant lineups.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contact listed below or the Regional Administrator of the appropriate regional
office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact: Rudy O. Karsch, NRR
(301) 492-1178
Attachment: List of Recently Issued NRC Information Notices
. Attachment
IN 88-13
April 18, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
88-12 Overgreasing of Electric 4/12/88 All holders of OLs
Motor Bearings or CPs for nuclear
power reactors.
88-11 Potential Loss of Motor 4/7/88 All holders of OLs
Control Center and/or or CPs for nuclear
Switchboard Function Due power reactors.
to Faulty Tie Bolts
88-10 Materials Licensees: Lack 3/28/88 All NRC licensees
of Management Controls Over authorized to use
Licensed Programs byproduct
material.
87-44, Thimble Tube Thinning in 3/28/88 All holders of OLs
Supp. 1 Westinghouse Reactors or CPs for nuclear
power reactors
that employ a
Westinghouse NSSS.
88-09 Reduced Reliability of 3/18/88 All holders of OLs
Steam-Driven Auxiliary or CPs for nuclear
Feedwater Pumps Caused power reactors.
by Instability of Woodward
PG-PL Governors
88-08 Chemical Reactions with 3/14/88 All NRC licensees
Radioactive Waste generating or pro-
Solidification Agents cessing low level
radioactive waste.
88-07 Inadvertent Transfer of 3/7/88 All NRC broad
Licensed Material to licensees and
Uncontrolled Locations licensees
authorized to
possess byproduct
material as sealed
sources in
teletherapy
units or
"self-contained"
irradiators.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
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