NOTIFICATION OF POTENTIALLY CORRODED TERMINAL SCREWS VALCOR SOLENOID OPERATED VALVES WITH/WITHOUT POSITION INDICATION SWITCHES

Bracket Terminal Block Assembly

This is to notify our customers that terminal screws on certain Valcor solenoid operated valves may be subject to stress corrosion cracking, and may then be subject to failure while being tightened or loosened. There have been two reported instances, one in 1988 and the other this year.

Valcor solenoid valves with position indication switches use either P/N S1140-14-6 or P/N S1140-14-7 terminal blocks. Valves without position indicating limit switches use Valcor P/N S1140-14-1 terminal blocks. All of these terminal blocks are manufactured from a phenolic material and use metallic terminal screws and mounting plates made from yellow brass.

Valcor has had reports from Wolf Creek (1988) and from Seabrook (1999) that terminal screws were found to crack and break with minimal force. Following the 1988 report, an investigation revealed that the apparent cause of the failures was stress corrosion cracking due to an outgassing of ammonia from the phenolic material of the terminal block.

A second, more recent report from Seabrook appears to result from the same root cause. We have not had reports of other failures.

Valves subject to the problem are those in which the operating temperatures inside the solenoid switch housing rise above 300° F; a level generally created when fluid operating temperatures exceed 550° F and the coil is energized. The presence of a conduit seal may contribute to the problem by containing any such outgas within the switch housing.

Valcor does not have sufficient evidence that this is a 10CFR Part 21 reportable item. Therefore, Valcor is notifying all customers of this possible condition. The customer should determine if this is a potential problem with their specific application and to determine the safety significance should the problem be present. Field inspection of the terminal block and terminal screws should immediately reveal the presence of the problem. Loosening and tightening of the terminal screws may be appropriate.

It is noted that the corrosion, peeling of plating, and cracking occurred in valves sealed with a Conax type connector. If the solenoid has a "vented" connection or if the solenoid cover has been removed, then the corrosion, peeling, and cracking should not be a problem. If an inspection of the component does not reveal any evidence of corrosion, peeling, or cracking then the component should not require replacing.

Replacement terminal blocks that have been baked at out factory to drive off any ammonia gas are available from Valcor . Please contact Ms. Clarissa Del Pomo at (973) 467-8480 x328 or by fax at (973) 467-3365 or e-mail Valcor at nuclear@valcor.com for ordering information.

Reference pictures of corroded terminal screws accompany this notice.

With very best regards,

VALCOR ENGINEERING CORPORATION  

Jimmy Shieh

Director of Quality Assurance