Information Notice No. 94-67: Problem with Henry Pratt Motor-Operated Butterfly Valves
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
September 26, 1994
NRC INFORMATION NOTICE 94-67: PROBLEM WITH HENRY PRATT MOTOR-OPERATED
All holders of operating licenses or construction permits for nuclear power
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to a problem with Henry Pratt motor-operated
butterfly valves that can lead to the decoupling of the valve operator from
the valve stem. 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 are not NRC requirements; therefore, no specific action or written
response is required.
Description of Circumstances
On October 17, 1993, the Duquesne Light Company conducted a full flow
surveillance test on a recirculation spray pump at Beaver Valley Power
Station, Unit 2. The pump did not establish adequate flow or discharge
pressure during the test. The licensee found that the pump suction valve was
shut, though the annunciator in the control room indicated it fully open. As
the result of the investigation, the licensee found that the valve operator
had decoupled from the valve stem, allowing the operator to move independently
of the valve. Two of the three other recirculation pump suction valves were
starting to decouple because the valve spline adapters separated from the
operator drive sleeves.
On December 10, 1993, the licensee reported to NRC in accordance with the
requirements of 10 CFR Part 21, "Reporting of Defects and Noncompliance," that
the recirculation pump suction valve disc could disengage from the motor-
operator which could cause the recirculation spray system to operate in an
The recirculation spray pump suction valves at Beaver Valley Unit 2 are
12 inch nominal size Henry Pratt 1400 series butterfly valves with Limitorque
HBC-1 operators. The drive sleeve on a Limitorque HBC valve operator rotates
a spline adapter. The spline adapter is keyed to the valve stem, but the key
does not prevent the adapter from moving down the valve stem toward the valve.
9409200069. IN 94-67
September 26, 1994
Page 2 of 2
If the spline adapter slips down the valve stem, it will disconnect from the
drive sleeve. On a Henry Pratt valve, the spline adapter is held in position
by an adapter plate, which is designed to permit passage of the valve stem,
but not the spline adapter. Additionally, the valve bonnet plate, which is
located below the adapter plate, is designed the same way. The adapter plates
and bonnet plates were designed and manufactured by Henry Pratt.
Duquesne Light Company found that the center holes in the valve bonnet plates
and adapter plates were about 1.3 cm [0.5 inches] larger (in diameter) than
the corresponding design dimensions. This was sufficient to allow the spline
adapters to slip down the valve stem during operation of the valve. This is
shown in Figure 1.
The licensee checked all 54 Henry Pratt butterfly valves at the Beaver Valley
Nuclear Power Station for proper adapter plate and bonnet plate dimensions.
No problems were noted beyond the recirculation pump suction valves. The
licensee placed temporary spline adapter retaining clamps on the recirculation
spray pump suction valves pending permanent modification.
Related Generic Communications
The NRC discussed a separate root cause of decoupling of a valve from its
motor-operator in NRC Office of Inspection and Enforcement (I&E) Circular
80-12, "Valve-Shaft-to-Actuator Key May Fall Out of Place When Mounted Below
Horizontal Axis," dated May 14, 1980, and I&E Information Notice 85-67,
"Valve-Shaft-to-Actuator Key may fall out of Place When Mounted Below
Horizontal Axis," dated August 8, 1985.
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 Office of
Nuclear Reactor Regulation (NRR) project manager.
/s/'d by CIGrimes/for
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Scot A. Greenlee, RI
Thomas G. Scarbrough, NRR
Attachments: (see file IN94067.WP1 for Figure 1)
1. Figure 1 - Henry Pratt Butterfly Valves With Limitorque Motor Operator
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