United States Nuclear Regulatory Commission - Protecting People and the Environment

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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                                                            April 18, 1988 
                                                            Page 2 of 2 

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 
Page Last Reviewed/Updated Tuesday, November 12, 2013