Information Notice No. 90-72: Testing of Parallel Disc Gate Valves in Europe
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
November 28, 1990
Information Notice No. 90-72: TESTING OF PARALLEL DISC GATE VALVES
IN EUROPE
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is intended to alert addressees to the results of
tests of parallel disc gate valves by researchers from the United Kingdom
(UK) and the Federal Republic of Germany (FRG). 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.
Discussion:
On October 15 to 19, 1990, members of the U.S. Nuclear Regulatory Commission
(NRC) staff met with nuclear regulatory authorities and industry
representatives in the UK and the FRG to discuss the performance of
motor-operated valves (MOVs) at nuclear power plants. During these
discussions, researchers from both the UK and the FRG described tests of the
operation of parallel disc gate valves under high differential pressure and
flow conditions. According to the UK and FRG researchers, the tests
resulted in internal damage to the gate valves. This damage included
abrasion and galling of the disc and seat sliding surfaces. Because of this
damage, significantly more thrust was required to operate the valves than
was predicted by the commonly-used equation. In some instances, the
increased thrust requirements could have exceeded the setting of the MOV
torque switch or the capability of the motor operator.
During the meetings, the FRG representatives reported that an improved
design for parallel disc gate valves had been developed. This improved
design has additional sliding surface area to eliminate the excessive thrust
requirements for valve operation. The FRG representatives reported that, as
a result of their valve tests, the FRG valve vendors now typically assume a
valve friction factor of 0.4 (plus or minus 0.1) in the commonly-used
equation to estimate the thrust required to operate the improved valve
design. In the United States, a valve friction factor of 0.2 is typically
assumed for all parallel disc gate
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IN 90-72
November 28, 1990
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valves even though little research has been conducted regarding the
performance of these valves under conditions of high differential pressure
and flow.
A summary of the FRG parallel disc gate valve tests is provided in "Testing
of Safety-Related Valves of PWR and BWR Power Plants," by U. Simon, N.
Rauffmann, and H. Schafer, which is printed in The American Society of
Mechanical Engineers, PVP - Volume 180, Pipeline Dynamics and Valves (1989).
The parallel disc gate valve tests performed by the UK and FRG researchers
provided results similar to the results of the NRC-sponsored tests of
flexible-wedge gate valves performed by researchers at the Idaho National
Engineering Laboratory. As with the tests of parallel disc gate valves
performed by UK and FRG researchers, the NRC-sponsored tests revealed that
internal damage may occur to the flexible-wedge gate valves when operated
under conditions of high differential pressure and flow. Because of this
internal damage, the thrust required to operate the flexible-wedge gate
valves exceeded the thrust predicted from the commonly-used equation and
typical friction factors. The NRC-sponsored test results were discussed at
public meetings on February 1, 1989, and April 18, 1990, and are summarized
in NRC Information Notice 90-40, "Results of NRC-Sponsored Testing of
Motor-Operated Valves."
Licensees and construction permit holders may wish to consider the results
of the UK and FRG tests when evaluating the capability of
currently-installed parallel disc gate valves and when considering the
adequacy of replacement valves.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact: Thomas G. Scarbrough, NRR
(301) 492-0794
Attachment: List of Recently Issued NRC Information Notices
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