DOE/EH-0113 --- Issue No. 89-05 --- 10/89

Undersized Valve Actuators

In November 1987, a commercial nuclear station had a problem with a steam generator feedwater bypass control valve. The valve was not responding as demanded, and the stroke time was slower than required for the control signal. The faulty valve was made by Fisher Controls International.

Investigators found that the actuator for the valve had been sized using a calculation that did not account for valve packing friction forces. This resulted in an undersized actuator that was incapable of seating, unseating, or properly operating the valve.

Reasons for Problem

Some valves are sized using a calculation that does not account for any valve packing friction forces. The following types of valves may be equipped with undersized actuators.

  1. Sliding stem valves--supplied by any manufacturer that were repacked using materials or procedures that increased the packing friction forces beyond those accounted for in sizing the actuators.

  2. Fisher Controls sliding stem valves--supplied by and shipped before 1/1/77 that were packed with graphite and other non-teflon materials. Packing friction forces were not taken into consideration when the valves were sized.

  3. Sliding stem valves--supplied by other manufacturers' actuators may also be undersized, depending on the actuator sizing methods used.

  4. Fisher Controls 9200 butterfly valves--ordered before March 1, 1982, may have undersized actuators because the torque needed to seat or unseat the butterfly disk may have been underestimated.

Recommendation

Review facilities' valve performance and if potentially undersized actuators are found, contact the manufacturer for additional information and take corrective action. For valves manufactured by Fisher, contact them at the following: 

                  Fisher Controls International
                  205 South Center
                  Marshalltown, IA 50158
                  Phone: 515-754-3011

DOE and DOE contractors should verify that replacement parts and maintenance activities (i.e., repacking of valve actuator stems) meet design and operating conditions. A well implemented Quality Assurance program would normally prevent situations as described from occurring. The Quality Assurance program should not only emphasize and control the design and procurement of the original hardware and equipment, but replacements should undergo the same degree of specification, checking, and control.

The procurement process should also consider these factors.

  1. Suppliers are required to provide no more than requested in the procurement documents.

  2. DOE and our prime contractors are responsible for verifying that activities affecting quality have been correctly performed. In the case of the valve actuators, for example, it would be appropriate to verify the manufacturer's performance test results on valve closure speed and leakage rates.

Additional Information

More data on undersized valve actuators may be obtained by reading NRC Information Notice 88-94 published on December 2, 1988.

This publication is one of several series of bulletins published so that DOE program managers and contractors can share information about potential occupational safety problems relevant to DOE operations. For more information or additional copies, contact Eleanor Crampton, Performance Evaluation Division, Office of Safety Compliance, Assistant Secretary for Environment, Safety & Health, U.S. Department of Energy, Washington, DC 20545; telephone (301)903-3732.

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