Information Notice 1990-37, Sheared Pinion Gear-To-Shaft Keys in Limitorque Motor Actuators

Sheared Pinion Gear-To-Shaft Keys in Limitorque Motor Actuators
	ML031140125
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	05/24/1990
From:	Rossi C; Office of Nuclear Reactor Regulation
To:	;
References
	IN-90-037, NUDOCS 9005180095
	Download: ML031140125 (5)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 May 24, 1990

NRC INFORMATION NOTICE NO. 90-37: SHEARED PINION GEAR-TO-SHAFT KEYS IN

LIMITORQUE MOTOR ACTUATORS

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice alerts addressees to potential problems related to

sheared pinion gear-to-shaft keys in Limitorque motor actuators. It is ex- pected 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 April 27, 1990, the Public Service Electric & Gas Company (PSE&G) submitted

a 10 CFR Part 21 report to the NRC regarding a materials misapplication in valve

motor actuators supplied by the Limitorque Corporation at its Salem Nuclear Power

Generating Station, Units 1 and 2. PSE&G reported that it had discovered that

the pinion gear-to-shaft keys in the motor actuators of six service water valves

(three per unit) were sheared or severely deformed. These keys had failed under

conditions of normal operation, and one of them showed significant deformation

after only 15 valve cycles. The valve units use high-speed (3600 rpm) Limitorque

SMB-O actuators with 25 ft-lb of torque that operate 30-inch Jamesbury butterfly

valves. At Salem this type of valve is only used for the fast isolation (closing

within 10 secondsl of non-safety thermal loads in the turbine building from the

safety-related service water system load during accident conditions. These keys

failed after the licensee had replaced the original valves with the subject

Jamesbury valves in a recent upgrade program during the last fuel cycle. The

original valves manufactured by the Henry Pratt Company had Limitorque SMB-1 actuators.

The failure identified by PSE&G indicated that the failed keys had wedged

between the motor shafts and the pinion gears at the key-slots. These wedged

keys had allowed the valves to operate under low-flow conditions. However, during normal flow conditions, the failure of these keys could prevent the

valve units from operating reliably. PSE&G realized the magnitude of the

49t'180095

IN 90-37 May 24, 1990 problem after performing a thorough inspection following a second valve failure

during service water valve testing. The licensee did not initially realize the

magnitude of the problem because even during normal flow conditions, the valve

appeared to operate adequately, masking the potential for valve failure.

Discussion:

In the past, the NRC issued Information Notices 88-84, Defective Motor Shaft

Keys in Limitorque Motor Actuators;" 85-67, "Valve-Shaft-to-Actuator Key May

Fall Out of Place When Mounted Below Horizontal Axis;" and 81-08, "Repetitive

Failures of Limitorque Operator SMB-4 Motor-to-Shaft Key," regarding the failure

of keys in the actuators of motor-operated valves. These earlier failures

resulted either from use of improper materials or incorrect installations, whereas, the failure reported by PSE&G resulted from an apparent misappli- cation of material.

Although the licensee is continuing its investigation, the preliminary results

indicate that the failures resulted from the impact loading on the soft keyway

assemblies during fast valve closures. The licensee performed a hardness check

of a failed key and of 38 other keys in stock supplied by Limitorque. The

inspection confirmed that the material was within the ASTM-1018 range for

material hardness that was specified by Limitorque. The licensee also in- spected all 14 actuators supplied by Limitorque under the same purchase order

and found the remaining 8 actuators had no similar problems.-These-& actuators

are used for valves that are not required to close within 10 seconds and are

not subject to the same impact loading experienced in the failed service water

system valves.

PSE&G decided to replace the failed keys in the 6 valve actuators with keys

made from a harder material, such as ASTM-4140 stainless steel. The licensee

tested one valve with a key made from this new material with a hardness of 290

(Brinell) and found no apparent wear after it was operated for 60 valve cycles.

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. ossD rector

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Peter C. Wen, NRR

(301) 492-1172 Paul D. Swetland, RI

(215) 337-5114 Attachment: List of Recently Issued NRC Information Notices

Attachment

IN 90-37 May 24, 1990 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

.. . .. . ..... .... ...... .. ............. ..... ........... ........

Information Date of

Notice No. - Subject__ ---- -- -Issuance . --Issued-to.- . -.-

90-36 Apparent Falsification of 5/24/90 All holders of OLs

State of Connecticut or CPs for nuclear

Weight Certificates power reactors, and

10 CFR 70 licensees.

90-35 Transportation of Type A 5/24/90 All U.S. NRC licensees.

Quantities of Non-Fissile

Radioactive Materials

90-34 Response to False Siren 5/10/90 All holders of OLs

Activations or CPs for nuclear

power reactors.

90-33 Sources of Unexpected 5/9/90 All holders of OLs

Occupational Radiation or CPs for nuclear

Exposures at Spent Fuel power reactors.

Pools

.. .. I .; .. .... .

~~. ~ ~ :. . :- .

90-32 Surface Crack and Subsurface 5/3/90 All holders of OLs

Indications in the Weld of or CPs for nuclear

A Reactor Vessel Head power reactors.

90-31 Update on Waste Form and 5/4/90 All holders of OLs

High Integrity Container or CPs for nuclear

Topical Report Review power reactors, fuel

Status, Identification cycle licenses, and

of Problems with Cement certain by-product

Solidification, and materials licenses.

Reporting of Waste Mishaps

90-30 Ultrasonic Inspection 5/1/90 All holders of OLs

Techniques for Dissimilar or CPs for nuclear

Metal Welds power reactors.

90-29 Cracking of Cladding and 4/30/90 All holders of OLs

Its Heat-Affected Zone in or CPs for nuclear

the Base Metal of a Reactor power reactors.

Vessel Head

-__ ___

OL = Operating License

CP = Construction Permit