United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9807060138


Namco Controls Corporation

5335 Avion Park Drive

Highland Heights, Ohio 44143

Tel. (440) 460-1360

Fax: (440) 460-3800

May 1, 1998

Document Control Desk

United States Nuclear Regulatory Commission

Washington, DC 20555

FAX 301-492-8187

Phone 301-951-0550

SUBJECT:  Notification of Product Anomaly

     Namco Controls EA180 Series Limit Switches

     Manufactured December 19, 1997 through March 27, 1998


     The purpose of this letter is to notify you of an anomaly with the

subject product line that was brought to my attention by the Namco

Controls' Evaluation Committee.

     During a review of our internal receipt inspection closed purchase

order file on April 1, 1998, it was discovered that the supplier who

impregnated the EA180 housings did not use the Namco Controls qualified


     Our investigation has determined that 112 EA180 Limit Switches were

shipped with this described condition.  We are notifying the affected

customers, see the attached list.

     At this time we are closing this issue and have generated a Technical

Bulletin TB9801 summarizing the conclusions and recommendations to the

affected customers by May 8, 1998. I have attached a copy of this Technical

Bulletin for your reference.

Thank you,

Best Regards,

Alex A. Joseph,



cc: Evaluation Committee file (D. Jackson III

TB9801                       NAMCO CONTROLS                 MAY 1998




The purpose of this Notice is to-inform the Nuclear Power Plant Operators

and others involved in the operation and maintenance of Namco Controls

Limit Switches of an impregnation sealant anomaly.


During a review of the receipt inspection closed purchase order, it was

discovered that the supplier who impregnated the EA180 housing did not use

the qualified sealant.  These limit switches were manufactured from

December 18, 1997 through March 27, 1998.  The list of affected customers

is attached.


A comprehensive review program by Engineering, Quality, and Marketing was

conducted.  It was determined that 112 improperly impregnated housings were

shipped to Nuclear customers, The Impregnation supplier used Imprex 95-

1000A which was not previously qualified by Namco Controls.


Namco Controls uses Imprex 95-500 impregnate sealer to fill microscopic

voids in the cost housing surface.  The sealer is not required for the

qualification of the Limit Switch, as long as the housing is look fight at

time of manufacture.  Based upon our experience, the majority of the cost

housings would require no impregnant to be leak fight, although all

housings are impregnated for ease of manufacturing.  Imprex 95-500 is a

mixture of Styrene and unsaturated polyester resin.  The material and

process was developed to meet the requirements of MIL-I-17563 and MIL-STD-


Due to environmental benefits, Imprex 95-500 is being discontinued and

replaced with 9&1000A.  Imprex 95-1000A is a mixture of Methacrylate and

unsaturated polyester resin.  The material and process was developed to

meet the requirements of MIL-I-17.563 and MIL-STD-276, Imprex recommends

95-1000A as direct commercial and Military replacement for Imprex 95-500.

The Namco Controls Engineering Report provides a comprehensive equivalency

comparison of the physical properties of the two sealants.  The comparison

addresses the capabilities of Imprex 95-1000A sealant to withstand the

Plant Service and Accident conditions.

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TB9801                       NAMCO CONTROLS            MAY 1998

                           TECHNICAL BULLETIN


The Engineering evaluation addresses all areas of qualification including

the critical areas of thermal aging/outgassing, gamma radiation, and LOCA.

To address thermal aging and outgassing, an accelerated thermal aging test

was performed.  At the conclusion of the test the Imprex 95-1000A sealant

passed the leak tightness requirement.  Also, there was no noticeable

discoloration of the housing.  The possibility of outgassing evaluated by

noting that the vapor pressure of 95-1000A is 1/5 of 95-500.  The lower the

vapor pressure the less outgassing would be present.  This would indicate

that 95-1000A would cause less contamination of the gaskets and contacts

than 95-500. Also, there were no stains on the housings after thermal aging

which indicates no out gassing of the impregnant.

Gamma radiation was evaluated by noting that the effect of radiation on the

plastic sealer would tend to swell the resin which would improve leak


Namco Controls Engineering evaluation determined that the pressure during

the LOCA test would not over stress either sealant.  The estimated stress

produced by the LOCA pressure was less than the tensile strength of the

sealants.  The published temperature capabilities of the sealants were

found to be equivalent and in accordance with the Mil STD rating.

All housings are required to pass a water pressure test after impregnation

and after final assembly.  The Imprex 95-1000A housings passed both of

these leak tests before shipment.

Namco Controls has conducted a thermal aging test to age the housing to an

equivalent of 3.0 years of service.  Based on this information, the EA180

Limit Switch with the Imprex 95-1000A Impregnant can be In service at 125

degrees F (51.7 degrees C) for 3.0 years with no effect on the integrity of

the impregnant sealer.  It is Namco Controls' Engineering opinion that

Imprex 95-1000A is equivalent to 95-500 foe the conditions identified



After a careful review and evaluation of the circumstances, it is our

opinion that the described condition is not a safety-related event.  In

fact, it's our intent, upon full qualification, to replace the Imprex.

95-500 with 95-1000A as our qualified impregnant.  Namco Controls is

establishing a full qualification test for Limit Switches impregnated with

Imprex 95-1000A.  Testing is expected to be completed within the next 18

months.  It is Namco Controls opinion, based on our Interim Engineering

Report, that Limit Switches built with Imprex 95-1000A are equivalent to

the originally qualified Limit Switches with 95-500.  Namco Controls

recommends the continued use of the Limit Switches, as stated above, while

Namco, Controls completes the final Qualification Tests and Reports.  Once

the qualification testing is complete the affected customers will be

notified of the results.

The affected customers are being notified.  The list of customers is


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TB9801                       NAMCO CONTROLS            MAY 1998

                           TECHNICAL BULLETIN


                              Customer List

                         Alabama Power

                         Arizona Public Service

                         Automatic Valve

                         Bettis Corp.

                         BW/IP International

                         Commonwealth Edison

                         Consumers Power

                         Duke Energy Company

                         Duquesne Light Co.

                         Florida Power and Light

                         Northeast Nuclear Energy

                         Northern States Power

                         Ontario Hydro

                         Vermont Yankee

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