United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 90-03: Malfunction of Borg-Warner Bolted Bonnet Check Valves Caused by Failure of the Swing Arm

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C.  20555

                              January 23, 1990


Information Notice No. 90-03:  MALFUNCTION OF BORG-WARNER BOLTED BONNET 
                                   CHECK VALVES CAUSED BY FAILURE OF THE 
                                   SWING ARM


Addressees: 

All holders of operating licenses or construction permits for nuclear power 
reactors. 

Purpose: 

This information notice is being provided to alert addressees to the 
potential malfunctioning of Borg-Warner bolted bonnet check valves caused by 
failure of the swing arm.  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 May 31, 1989, a 4-inch 150 lb Borg-Warner bolted bonnet swing check valve
installed in the service water system at the Comanche Peak Steam Electric 
Station (CPSES), Unit 1, exhibited excessive backleakage.  This resulted 
from separation of the disk from the swing arm which connects the disc and 
stud assembly to the clevis.  The swing arm's collar, which surrounds the 
disc stud, fractured radially in two places.  Indications of surface flaws 
were also found in two other swing arms.  The swing arms in question were 
produced from a 17-4PH alloy in accordance with Aerospace Materials 
Specification 5398A and were required to be heat treated to an H1100 
condition per Military Specification MIL-H-6875. 

Discussion: 

The licensee for CPSES, Texas Utilities Electric Company (TU Electric), and 
consultants performed evaluations of six swing arms removed from service; 
these evaluations included visual examination and fractography, chemical 
analysis, metallography, the effects of heat treatment, and non-destructive 
examination.  It was concluded that the failure of the swing arm was caused 
by surface defects formed during the fabrication process.  Other 
deficiencies identified as contributing factors of the failure were 
inadequate heat treatment, weld repairs, high residual stresses, and the 
high chloride environment of the service water system.  


9001170021
.

                                                            IN 90-03 
                                                            January 23, 1990
                                                            Page 2 of 3 


The failure mechanism was defined as preexisting surface and subsurface 
casting defects which propagated under the influence of raw water and 
residual stresses during normal operating conditions.  TU Electric's 
consultants concluded that the swing arm castings were of poor quality; they 
exhibited hot cracks, porosity, weld repair, and inadequate heat treatment.  
When some of these swing arms were solution annealed and aged to produce the 
H1100 condition, the swing arms exhibited lower hardness.  If the swing arms 
had been properly heat treated, little or no change in hardness would have 
been expected.  As a result of these problems, TU Electric is purchasing 
replacement swing arms produced from investment castings, rather than sand 
castings.  The consultants also recommended that additional examinations be 
performed on the remaining swing arms, including a 10X visual examination, 
dimensional inspection, liquid penetrant test, and replication.  Using these 
inspection and testing methods, 17 of 91 swing arms examined by TU Electric 
were rejected.

An NRC inspection of BW/IP International, Incorporated, Vernon, California, 
(formerly Borg-Warner Nuclear Valve Division of Van Nuys, California) was 
performed from September 11-14, 1989.  During the inspection, BW/IP could 
not produce documentation to support the placing of companies on the list of 
qualified suppliers for manufacture of the swing arms used in safety-related 
check valves.  Records reviewed indicated that the swing arm that failed in 
service was manufactured by the Industrial Pattern and Casting Company and 
was subsequently heat treated by the Valley Heat Treating Company.  During 
the inspection, it was determined that Valley Heat Treating Company was not 
on the list of approved suppliers.  In addition, the inspectors could not 
determine from the records whether the failed swing arms were properly 
solution annealed or heat treated, nor were the swing arms serialized for 
traceability.

The inspectors also reviewed the replacement swing arms ordered by TU 
Electric. TU Electric had imposed Appendix B of 10 CFR Part 50 and 10 CFR 
Part 21 in the purchase order for the replacement swing arms and required a 
certificate of conformance.  During the inspection, it was determined that 
eight swing arms sold as replacements to TU Electric had been transferred in 
1986 from the Van Nuys plant to the Vernon plant.  During this transfer the 
records associated with the swing arms were apparently lost.  Because BW/IP 
did not have documentation to support this inventory as meeting 
safety-related requirements, BW/IP decided to dedicate the swing arms for 
use by performing a material identity check, and a visual and dimensional 
verification.  However, the NRC inspectors determined that BW/IP's 
dedication was inadequate because the swing arms' primary critical 
characteristics (mechanical and chemical properties) were not verified by 
BW/IP.  The method used by BW/IP was only capable of sorting generic alloy 
groups such as austenitic and martensitic stainless steels, but could not 
distinguish between the four typical martensitic specifications used by 
BW/IP.  In addition, the results of the visual inspection performed on the 
arms were not documented.

The NRC concluded that Borg-Warner and BW/IP classified non-pressure 
boundary valve internals as exempt under requirements of Section III of the 
American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel 
Code, failed 
.

                                                            IN 90-03 
                                                            January 23, 1990
                                                            Page 3 of 3 


to recognize that Appendix B to 10 CFR Part 50 was imposed and applicable to 
the valve internals, and as a result did not impose nuclear quality 
assurance requirements on the manufacturer of these parts.  The swing arm 
failure at the CPSES raises concerns about the quality of non-pressure 
boundary items supplied by BW/IP for use in safety-related applications.

Documentation reviewed during the BW/IP inspection identified additional 
weaknesses such as the placement of vendors on the approved vendors list 
without an adequate basis and the use of ASME Quality System Certificate 
holders without any evaluation of the suppliers' or manufacturers' quality 
assurance program by BW/IP.  This practice was contrary to BW/IP's 
procedures.  In one example, there was no documented basis to support 
qualification of ACME Castings, Incorporated, which is currently furnishing 
cast swing arms to BW/IP.

The subject of qualification and oversight of vendors and procurement of 
non-pressure boundary parts has been discussed in NRC Information Notice (IN) 
88-95, "Inadequate Procurement Requirements Imposed By Licensees On 
Vendors," and IN 86-21, "Recognition of ASME Accreditation Program For N 
Stamp Holders."

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:  R. L. Pettis, NRR
                     (301) 492-3214

                     M. R. Snodderly, NRR
                     (301) 492-0978

Attachment:  List of Recently Issued NRC Information Notices

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