ML18017A144

Final Deficiency Rept Re Cutler Hammer E-30 Pushbutton Sticking Problem & Dislodgement of Switch Ch E-30AB from Contact Block.Sticking Pushbutton Corrected by Scraping Edge.Locking Devices for Ch E-30 Switches Retightened

ML18017A144
Person / Time
Site:	Susquehanna
Issue date:	04/18/1980
From:	PENNSYLVANIA POWER & LIGHT CO.
To:
Shared Package
ML18017A143	List: ML18017A142 ML18017A144
References
PLA-472, NUDOCS 8004290399
Download: ML18017A144 (4)

Text

~Sut ect Cutler F~r E-30 Pushbuttons Descry>tion ae Cutler-Hamner pushbutton switches installed in PGCC/ACR benchboards, are sticking; of 189 switches inspected, ten switches do not retract when manual depression is relieved. Ihese switches bear GE P/N 851E341P2GXGXXX and are purchased from Cutler-F~er under P/N CH E-30AC. 'Ihese nonconfor-mances are documented on NCR 4313.

b. A second condition, as described on Sheet 20 of NCR 3403, involves switch

{HV-1112D) CH E-30AB, which became dislodged due to failure of the mechanical locking device between the pushbutton operating module and contact block.

While this particular switch and the second switch of the same type which have failed were installed in non-safety related equipnent, the concern is for similar switches used in safety related equipment.

Cause

a. Ihe stickirg of the pushbuttons occurs on 2-button modules. Men one is depressed, a latch device is actuated that prevents depres- 'ushbutton sing the other pushbutton. Curing the manufactur~>> process the lower edge of.the plastic pushbutton cap will have a sharp edge formed. 'Ihis can beccme wedged agent the latch preventirg the button fraa resetting when it is released.

b. 'Ihe dislodgement of the pushbutton operating module frcm the contact block is apparently caused by the mechanical lockir~ ring not be>>~g tightly locked.

Anal sis of Safet Imnlications

a. CH E-30 pushbuttons are used in Class 1E safety related circuiw. 'Ihe stiddng of the pushbuttons could result in the &operation, misoperation, or improper line-up of electro-mechanical or st>>d state logic when push-but~ operation is attempted.

sti~ I~ineering Pro5ect has deterndrad t+at the reported is reportable def>>ciency urger a 10CRP50.55 CH E-30 pushbutton (e).

Attachment 1 Page 1 of 3

b. The dislodgement of the CH E-30 lo~ device pernd.tted the contact blocks to disengage from the pushbutton operator sufficientiy to prevent the con-tacts fran d~'g state upon depression of the pushbutton. 'lee identi-fied deficiency, had it gone uncorrected, could have prevented a safety system fran perform~ its intended function.

Prospect EhgLneering has determined that the reported CH E-30 dislodged mechanical locking device is a reportable deficiency under 10CPR50.55(e) ~

Corrective Actions ao GK requested that Cutler-Haamer investigate the pushbutton sticking problem for the PGCC/ACR at the site. After the investigation Cutler-Hamner reported .

that the problem was'n pushbutton switches manufactured before November 1978.

In a report attached to a letter dated Pebruary 29, 1980 (IXN 116060), Cutler-F~rnot stated that the sticking problem was first noted in June 1976. 'Ihey consider it to be a critical problem because if the button stuck did on the first attempt to depress, it could always be depressed with further attanpts. Fracturing changes were made in September 1977 and November 1978. Cutler-F~r feels tlat, with these &arges, i.t is reasonable to assune that devices made after November 1978 wi13. not exhibit this problem.

2m date stamp is located under the button on top of the button plate and show the month and year the device was manufactured. 'eal In the letter Cutler-Hanzner states that a sticking pushbutton can be corrected by scraping or buffing a slight radius to the sharp lower edge of the button where it contacts the latching device, or by operating the pushbutton several times. 5hey state that the operation of the pushbuttons should improve with use due to anoothing of the sharp edge of the button against the interm~ck surface.

For tlat PGCC/ACR berxhboards General ELectric has ag~ to replace all Cutler-F~r E-30AC operator pushbutton audules manufactured prior to November 1978.

The contact modules wiil not be replaced. NCR 4313 si~ be revised to re-flect the corrective action taken.

b We construction of the Cutler-Hanxrar ~~ E-30 pushbutton switches is such that the contact blocks are held to the operating module by a locking ring mounted on the operating module and actuated by a quarter-turn locking screw.

Dhe dislodgement of the contact modules fran the operating modules was in-vestigated and no manufacturir~ defect was apparent.

Knee these same devices successfully passed an integrated system factory test at the manufacturers it facility, is assed the locking devices worked loose during transit. We locating devices for CH E-30 switches wiil be retightened to assure proper installation for both Units 1 and 2. QC inspection will verify that the locking devices are tight.

pace 2 of 3

Prospect Engineering is investigating the usage of c.

pushbuttons M essential applications in the the conclusion of the investigation any reer Cutler-Hanzner deficiencies will type of the plant.

E-30 be docunented At on NM's and the field advised of any future corrective actions to be .

taken.

Conclusions a4 'Ihe replacanent of pushbutton operation modules tIwt are, or are suspected of not operating properly should resolve the problem of the E-30 AC pushbuttons on the PIC/ACR benchboards. NCR 4313 will track the replacement of the pushbutton modules on the PGCC/ACR benchboards.

Pro)ect Engineer~ instructions and field verification should insure no further dislodgenent of the contact modules frcm the operating module.

c. Further investigations to date have failed to locate any Cutler-Haaxner type E-30 pushbutton switches being used in the remainder of the plant.

Page 3 of 3

Amphenol fanale connectors DESCRIPTICN The arxznalies sumnarized below have be~ noted during routine Quality Control surveillance and/or inspections of PGCC/BZR Panels.

Ampheml female connector pins are not seating properly in the dielectric.

The relative position of the pins often vary after mating and umating of the connectors. It has been observed that sane pins partially retract as the re-sult of turning the connector. This is especially the case after pins have been removed and reinserted into the connector dielectric.

While perfomung force of the pin crimps to the wires, the connector fenale pins mme fram &a dielectric, in many instances, before ~ ~a~

pull tests on the individual conductors to check the holding recpured pull test force was achieved.

One of th mettzds for performing the pull testing of conductor pin crimps was to use a hemostat pull testing device. The device was utilized for pull testing to avoid ccmplete rarxnr~Q. of all pins fran connectoxs. The hemostat pull test method tended to amplify or Gu~w aggravate the Amphe~l connector problem.

General Electric conducted a auality study on t~~ condition identified with these Ampherol connectors. T6e results were attached to their letter GB-79-283 datad Decanber 10, 1979 and forwaxded to the HRC in our PLA-438. GE concluded that the probable cause of pin serg nonconformances was not due to connector design hut rather to damaged mating connectors, errors during assembly or remark at the plant sim.

ANALYSIS OF SAFETY 3MPLICATICNS The identification of pins which had backed out frcm the die~~ic raised a coraern relative to the connectors ability to maintain continuity. F~ver, regardless of hm well the pin seats in the dielectric, as long as the male and female pins are mated together; the cixcuit continuity can be maintained thxough tta pins. In no inatarce was it xeported that the pins failed to mate together.

Project Engine ~i'as determined ttat the identified Azaherol conractor pins, that did ?et seat properly in the dielectric, do mt constitute a report&le def iciency urdar 10CFR50. 55 (e) .

Attachnent 2