ML20195G933
| ML20195G933 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 12/01/1987 |
| From: | Deb A, Will Smith WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20151B787 | List: |
| References | |
| IEIN-87-035, IEIN-87-35, NSID-TB-87-11, NUDOCS 8801040586 | |
| Download: ML20195G933 (17) | |
Text
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Subset Westinghouse Circuit Breakers Type 05/OSL:
~
Welds on Breaker's Pole Shaf t Number System (s)
NSr0 TB-87-11 All Plant Systems Date Anected Plants December 1. 1987 All Plants with DS/DSL Circuit Breakers S.O.(s)
References 309. 386. BOP see selew Anects Safety Yes s Sheet 1 Of 17 Related tost 4nt No O
REFERENCES:
1.
Westinghouse generic project letter on the subject dated 9/87.
2.
USNRC Information Notice IN 87-35.
This bulletin applies to DS series breakers - 206. -416, and -420, and DSL series-206 and -416.
It provides additional information on the subject noted above, and guidance for follow up actions if required.
To consolidate the total contents on the subject in this document,' sections from the 9/87 letter have also been excerpted here and amplified / clarified as needed.
This bulletin also includes a procedure for replacement of the pole shaft if the present pole shaft needs to be replaced to meet the required criteria.
This technical bulletin supercedes and replacet the 9/87 letter, and it is to be regarded as the controlling document for inspection of the breaker's pole shaft and alignment, and corrective action if required.
Aaseensiintermaeon. r me.uired. mev te onehd om sw ct_4 ; Telenhene 412 374-3492 4
er anos 284-3492 h
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_ A. Deb. Sr. Engineer G
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W. J. Smith, Jr., Manager RCS Engineering Electrical Support Services cYU MSN7MTM'*wEWa"nTO%"O U7"E7" n
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N510-TB-87-11 Page 2 f 17 The contents here are organized as follows:
Section 1.0
Background
Section 2.0 Investigatien Results Section 3.0 Potential Safety Impact Section 4.0 Recommended Actions Section 5.0 General Notes for Inspection of Welds Section 6.0 Short Term Inspection Section 7.0 Long Term Inspection Section 8.0 Removal and Installation of Pole Shaft figures
1.0 BACKGROUND
On July 2, 1987, it was reported that a DS-416 reactor trip breaker did not open on dethand during rod drop testing following a refueling outage.
This malfunction was detected after plant personnel observed smoke in the vicinity of the reactor trip switchgear.
Since the breaker had not opened on demand the shunt coil current was not interrupted resulting in a burnt and damaged coil.
The breaker could not be tripped manually, but it tripped when the manual charging handle'was manipulated. During subsequent cycling on the test bench, the breaker jammed again.
An i
inspection was conducted at the site jointly by Wstinghouse, the Utility and the NRC, during which the breaker was cycled about 38 times.
It operated successfully each time. Visual inspection noted wear (nearly 3000 cycles of operation) and separation of the weld which attached the center pole lever to the pole shaft.
The NRC issued Information Notice 87-35 on July 30, 1987 reporting this event.
2.0 INVESTIGATION RESULTS The above breaker was subsequently shipped to Westinghouse for a detailed investigation following guidelines jointly developed by the Utility, the NRC and Westinghouse.
The breaker malfunctioned after some 130
s NS*D-TB-87-11 Pcge 3 of 17 additional cycles.
It was determined that the jaming could be repeated by manually forcing the close cam and main drive link into a unique constrained position.
The breaker did not assume this unique position on its own through about thirty subsequent operations.
The stated scenario can be explained as follows:
The roller attached to the main drive link normally rests on the outer close cam laminations.
The broken weld permitted lateral movement of the main drive link, which could allow the roller to move close to its tolerance limits.
In the jamed position, the roller had slipped inward off the outer laminate of the cam.
The force txerted by the breaker closing action induced a twisting motion which caused the roller to wedge oetween the close cam lamin; tion and the side frame. Although it was established that the stacking of part tolerances played a part in the jaming of the breaker, it was also concluded that the breaker would not jam unless a broken weld was present to permit the twisting action that allowed the roller to wedge.
Subsequent evaluation of this weld revealed that the weld had fused originally for only about 15% of its total length.
Complete separation of the weld was due to low cycle fatigue, striations indicating that the separation occurred after about 2,500 cycles. This is consistent with the Utility's estimate of operating cycles.
3.0 POTENTIAL SAFETY IMPACT Westinghouse considers this malfunction of the 05-416 Reactor Trip Breaker to be a random occurrence.05-416 breakers have operated through sany thousands of cycles without any malfunction similar to the one described above. Despite the quality of the weld in the said breaker, it performed for about 3,000 cycles confirming that the weld as designed is conservative.
It was also evident that while it is necessary to have a weld separation to initiate the occurrence it also requires other part tolerances to be near maximum, 1
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1 l
NSID-TB-B7-11 Page 4 cf 17 Although this event does not have any generic implications, Westinghouse considers it prudent, and recomends that the noted breakers be inspected to ensure that a similar condition does not exist in IE breaker applications.
The insps: tion should be performed in line with normal surveillance and maintenance practices.
4.0 RECOMMENDED ACTIONS The recomended actions are inspection of the welds on the pole shaf ts, and inspection of the alignment in the breaker closing mechanism.
The inspections are divided into two categories - short-term inspection, and long-term inspection.
This grouping is guided by the functional importance of the items to be inspected vis-a-vis the time required for performing the total inspection.
The short-term inspection is aimed at addressing the welds at the three main pole levers, since these receive the major forces during a breaker's opening or closing. Also, the alignment of the moving parts in the breaker's closing mechanism are maintained primarily by these three welds.
The long-term inspection eddresses the four remaining welds on the pole shaft.
It also includes a direct check of the alignment of the breaker closing mechanism.
5.0 GENERAL NOTES FOR INSPECTION OF WELDS 5.1 The inspection must be performed by a qualified welding inspector, certified per the station's requirements for welding inspection.
For the purposes of this bulletin, the welds are to be inspected for the following parameters - fusion at both legs, absence of cracks, weld size and length of weld.
The criteria for the inspection are detailed in Sections 6.0 and 7.0.
A visual inspection is recomended, with use of inspection tools as appropriate to aid good examination of the areas (exagle:
Inspection mirror, Light Source, Fiber Optics Instrument, etc.).
1
NSID-TB-E'-li Page 5 of 17 5.2 Fatigue tests performed on specimens of varying weld sizes and lengths provide the basis for the acceptance criteria given in this bulletin.
The given limits reflect a measure of conservatism, therefore, welds meeting these criteria are expected to sustain the performance limits given for them.
5.3 The welds can be inspected with the pole shaft within the breaker, per procedure in Section 5.4.
If the inspector chooses to perform the inspection with the pole shaft removed from the breaker, the pole shaft can be removed per Section 8.0 of this bulletin prior to the inspection.
Time limitations in the station's Technical Specifications should be considered in planning these procedures.
5.4 Procedure for inspecting the pole shaft within the breaker is as follows.
CAUTION:
THIS PROCEDURE MUST BE PERFORMED JOINTLY WITH PERSONS TRAINED IN HANDLING / SERVICING THIS TYPE OF BREAKER.
1.
Trip the breaker if energized and closed. Rack it out on cell rails fully extended, or transfer to bench.
2.
Remove front panel.
3.
Disconnect the leads for the spring charging motor, and the link for the auxiliary switches.
4.
Remove the bolts and screws securing the top cover at the front of the breaker. Lay it over on left, making sure that wires in the harness are not damaged.
5.
Remove the are chutes and the barrier plates surrounding them.
6.
Inspect the welds visually to the criteria given in Section 6.1, with tools appropriate for enhancing the inspection (Example -
N5I0-TB [
t Page 6 of 17 Inspection Mirror, Flashlight, Fiber Optics, etc.).
Rotate the pole shaft by~ manually pushing the moving contacis towards the j
closed position, so that the inside areas of the weld are exposed to view.
For safety of personnel, secure the contacts in this position with a locking ring or wire loop until the inspection is complete for this position 7.
Reinstall all items removed or disconnected before returning the breaker to service.
6.0 SHORT-TERM INSPECTION This inspection is to be applied to the breakers at the next available opportunity (maintenancs outage, e.g.), or during the next surveillance test for the breaker, whichever is earlier.
6.1 Acceptance Criteria This section lists the criteria to be applied to the welds for the three pole levers on the pole shaft.
See Figure 1, items 2, 3, and 6.
The remaining welds are discussed in Section 7.0.
6.1.1 A pole shaft, for which the 3 noted welds meet or exceed all of the criteria listed bel w, is to be considared acceptable for continued service up to the limit defined in Section 6.2.1.
a) weld cize - 3/16 inch fillet b) length - 180' continuous around the pole shaft c) fusion - fused to lever and shaft for the above length d) cracks no cracks are allowed 6.1.2 If the criteria listed in 6.1.1 are not satisfied, the pole shaft can still be retained in service, but for a limited time as defined in 6.2.2, provided it meets or exceeds the criteria given below,
- - - ~
d
7 l-N310-TB-87-M Page 7 of 17 a) weld size and length - 3/16 inch fillet for 90' continuously around the pole shaft, or 1/8 inch fillet for 120' continuously around the pole shaft b) fusion fused to lever and shaft for the above length c) cracks no
.as.re allowed 6.2 Time limits for the use of pole shafts, in consideration of their weld conditions, are defined here.
6.2.1 A pole shaft which meets the criteria in 6.1.1 is suitable for evntinued use until the time the total breaker is refurbished (due to wear, damage, age, service years, etc.).
At such time an assessment can he made for possible replacement of the pole shaf t.
Repeated inspection of the welds is not required, provided that the breakar is used and maintained properly in its service.
i 6.2.2 A pole shaft which does not meet criteria in 6.1.1, but meets those in 6.1.2 may be kept in service until the breaker reaches 4000 cyc hs of operation, but with the following restrict.ns and measures:
a) The weld (s) in question must be reias'>e:ted to this name criteria periodically after every 200 cycles of operation.
b) For a breaker applied in a system designed for high short-circuit current or interrupting duty, the wid(s) must be inspected after each time such hith cerrent may have res,ched the breaker.
T it inspection shall be to I
the same criteria (Section *:.1.2), and, is over and above the periodic reinspection noted in the preceding paragraph 6.2.2.a.
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N5!D-TB-87-11 Page 8 of 17 c) Specific attention is to be given during these inspections to ensure that no crack (s) or separation has desaloped in the welc(s) during the intervening period.
If any weld is found to have developed a crack or separation, the pole shaft must be replaced before returning the brecker to service.
if at any tinu during this 4000 cycle limit the pole shaft is replaced, the replacement unit shall meet the criteria in Section 6.1.1.
6.2.3
- pole shaf t which does not meet the criter's in 6.1.2 must L removed from servics immediately, and a replacement pole -
shaft installsd in the breaker before returning it to' service.
(See exception, Section 6.2.4.)
The replacement pole shaft shall meet the criteria in 6.1.1.
6.2.4 A pole shaft which does not meet the criteria in 6.1.2 may, as an exception, be used in the Bypass Breaker position in the Reactor Trip Switchgear, if approved by the welding inspector and station's engineering personnel, based on the weld condition. This exception is permitted in view of the following:
a) A bypas Breaker has very limited duty; b) There is another breaker in series with the Bypass Breaker; and c) The two breakers trip independently after receiving the trip signals.
i i
i It is strongly recommended, nevertheless, that steps be taken immediately by the station for replacement of this pole shatt, l
r NSD-75-57 ;
Page 9 ef 17 7.0 LONG-TERM INSPECTION This inspection is to be applied to the breaker at the latest during the next refueling outage. The general notes in Section 5.0 still apply.
Long-term inspection also includes checking the alignment of the breaker.
Section 7.2 provides the direction for this inspection.
7.1 Acceptance Criteria for Welds This section lists the criteria for acceptance of the 4 welds on the pole shaft, which were not addressed in short-term inspection described in Section 6.0.
See Figure 1, items 1, 4, 5 and 7.
a) size and length at least 3/16 inch fillet for a minimum of 90' continuously around the shaft, or at least 1/8 inch fillet for a minimum of 120' continuously around the shaft.
b) fusion -
good fusion along both legs of weld.
c) cracks -
no cracks are allowed.
If the above criteria are not met, replace the pole shaft prior to l
returning the breaker for service.
Exception - The lever for the Auxiliary Switch Drive Link spans about 90' around the shaft, and carries an extremely light l
load.
This lever should be checked for a well fused joint only.
7.2 Alignment of Breaker This section provides direction for checking that the alignment of the breaker mechanism is within allowable limits.
This procedure
h5D a Page 10 of 17 should be performed, at the latest, during the next refueling outage. Further, this check should be made on the bench with the closing springs disconnected from the cam shaft (common shaft gcing through the close cam), and the breaker electrically disconnected.
CAUTION:
THIS PROCEDURE MUST BE PERFORMED ONLY BY PERSONN IN HANDLING / SERVICING THIS TYPE OF BREAKER.
7.2.1 Procedure
- 1) Remove front panel of the breaker.
- 2) Disconnect the closing springs from the cam shaft. The other and may be left undisturbed.
- 3) De energize control power to the breaker, if wired to power supplies. Breaker should be open with springs discharged.
- 4) Restrain the UVTA with a wire loop so that the breaker is not in a trip-free mode.
- 5) Simulate manual charge of the closing springs to the charged position, to turn the close cam to the "Ready to Close" position.
- 6) Mith the roller as indicated in Figure 2, slowly turn the clasing can manually by the spring charging handle.
(Note:
To release the can to turn, depress the manual close button.) Continue to turn the can until the breaker contacts reach the closed position.
At this i tre, the manimum lateral play of the roller is in effect.
g NSID TB-57-;;
Page 11 c; 17 4
7)
Through the front of the breaker, sight the close cam, the roller and the side frames. Using a flashlight, verify -
a) Roller is on top of both of the two outer laminates of the close cam.
It is not required to be centrally placed with respect to the cam assembly. See Figure 2.
b) There is a visible gap between the side frame and the roller side at each end of the mechanism.
If either of the two checks are not satisfactory, contact Westinghouse with details of the observations.
- 8) Reinstall all components removed before returning the breaker for service.
8.0 REMOVAL AND INSTALLATION OF POLE SHAFT This section provides instructions for the ' removal and installation of the pole shaft. This procedure is to be performed on the bench with the breaker open, springs discharged, and circuits doenergized.
CAUTION: THIS PROCEDURE NUST BE PERFORMED ONLY BY PERS HANDLING / SERVICING THIS TYPE OF BREAKER.
It is recessended that personnel assigned to do this task review figure 3 before beginning the tasks.
It shows the components involved in this procedure.
8.1 Procedure
- 1) Remove the front cover, i
NSID TB-57-;;
Page 12 cf 17
- 2) Remove the three are chutes.
- 3) Remove the four barrier plates around the are chutes.
- 4) Disconnect the opening spring from the top end where it is connected to the pin on the right pole lever on the pole shaft.
Lay it down connected at the bott:a end.
- 5) Remove the auxiliary switch drive link by disengaging the retainers connecting the lever on the pole shaft to the switch drive link.
Remove the wire spring from the cycle counter if the breaker is so equipped.
Slide out the switch drive link (anti the wire spring if operations counter is present).
Steps 7 through 9 outline the procedure for disengaging the pole shaft from the 3 pole unit assemblies and the main drive link assembly.
Before proceeding to those steps, take the caution in step 6 to ensure that the contact settings for the poles are not altered.
- 6) CAUTION: Wark the top of the insulators to identify orientation.
Further, put a dowel pin through the three insulating links as soon as they are disengaged from the pole shaft.
This is to prevent inadvertent rotation of the insulator on the reassembly.
- 7) For each insulating link to be disangaged, only one "X" washer needs to be removed where it connects to the pole shaft via the 3 pole levers on the shaft. Remove the ones noted below, a) Either one of the two 'X" washers for the conter pole.
b) The "X" washer nearest to the breaker side sheets for the left and the right poles.
NSIC-T5-87-11 Pest 13 of 17 8)
Slide out the pins connecting the insulating links to the pole levers.
Insert the dowel pin as recommended in Step 6.
Secure the moving contacts in the forward (closed) position using wire or cord loops.
9)
Disengage the main drive link from the pole shaft at the center pole lever by removing the "X" washers and the flat washer.
Withdraw the pin and disconnect the drive link.
The drive link is still attached at the front of the breaker, carefully lay it down to rest on the bottom pan of the breaker.
The pole shaft is now free from its attachments, resting on the bearing plates mounted on the side sheets of the breaker.
- 10) Ramove bolt-nut-lockwasher set at the top of the bearing plates on each side of the breaker.
- 11) Remove the combination bolt-nut-lockwasher set and stop assembly at the bottom of the bearing plates on each side of the breaker.
Support the pole shaft by hand while doing this step to avoid having the shaft slip downwards.
Three plats: c:: each side will come out with the shaft.
- 12) Slowly lift the shaft and the bearing platas forward and upwards out of the breaker.
The following steps re-assemble the replacement pole shaft into the breaker.
- 13) Prior to installing the new pole shaft in the brosker, lubricate the shaft at both ends and at the conter where it rests against the two pir.ies in the closing mechanism fr ue.
The lubricaM should be a zine-oxide grease, like Lubriplate 130-A (Fiske Brothers Reft. Ting Co., Newark, N.J.), Westinghouse No. 53701HE.
NS10 TE-57 ;1
[
Page 14 ef 17
- 14) Place the new shaft in the breaker, seating it into the mechanism frama.
Install all hardaare removed in steps 10 and 11 to ancher the pole shaft in the breaker.
Use standard snug fit torque values.
The pole shaft should be checked for ability to rotate after the bearing plates are anchored to the breaker side sheets.
- 15) Reconnect the auxiliary switch drive link and the operations counter (if applicable) to the pole shaft lever using new "X" washers. Use two 1/4 inch flat washers on the pin.
- 16) Reconnect the main drive link to the pole shaft with twe "X" washers. Make sure that the mechanical indicator link and the 1/2 inch washer are installed.
- 17) Remove the restraint on the contacts.
(
- 18) Insure the setting of the insulating links by verifying the marirs put on in step 6.
Remove the dowel pin.
- 19) Reconnect the three insulating links to the pela shaft using the three inch link on either side and'the 1 1/8 inch link in the middle.
- 20) Reconnect the opening spring on the right pole pin.
- 21) Charge and close the breaker manually.
Verify that the contact settings are as specified in the published manuals.
- 22) Reinstall the are chutes and the barrier plates, and the top cover.
- 23) Remove all tools, accessories, etc.
Reinstall the front cover.
- 24) Test the breaker electrically for 5 times before returni.mg it to service.
r 4
NSID-75 57 ;;
Page 15 ef 17 4
flGURE 1
POLE SHAFT ASSEMBLY
- 3/16 Fillet Weld ~ 7 A
(all levers)
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SECTION A-A 1.
Pole shaft is shown as it would be placed in a breaker, viewed from the front.
2.
Diegram is schematic, and not to scale.
3.
Index:
1 - Stop Lever (Left) 2 - Left Pole Lever 5 - Lever for Auxiliary switch 3 - Center Pole Lever Drive Link 4 - Anti-bounce Lever 6 - Right Pole lever 7-StopLever(Right)
-2.
7 NSIC 75 57-11 Page 16 af 17 FIGURE 2
MICHANISM SIDE FAAME 1
I MIN DRIVE LINx
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CONSTRAIN!N3 LINK J,,
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[ 4AP MIN ROLLER
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i OUTER LAMINATES 2
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t NSID-TE-87-;!
Page 17 of 17 f!GURE 3
l PARTIAL VIEW OF BREAKER CONFONENTS rrei S
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1.
Diagram is schematic, not to scale, and is expanded laterally to show details pertinent to this bulletin.
'. 5-numbers reflect step numbe,' in procedure section 8.1.
2 3.
Index 1 - Shunt Trip Attachment 13 Right Pole Lever 2 - Trip Shaft 14 - Pole Shaft 3 - Mechanism Frame (left) 15 - Aux. Sw. Lever 4 - Close Cam 16 - Aux. Sw. Drive Link 5 - Mechanism Frame (right) 17 - Spring to Cycie Coanter 6 - Roller (in Cam) 18 - Pole Unit 7 - Main Roller 19 - Insulating Link 8 - Manual Charging Lever 20 - Center Pole Lever 9 - Cam Shaft 21 - Main Roller 10 - Closing Spring 22 - Link to Indicator 11 - Opening Spring 23 - Left Pole Lever 12 - Bearing Plates 24 - Bearing Plates
NRCB 88-01 February 5,1988 LIST OF RECENTLY ISSUCD NRC BULLETINS Bulletin Date of No.
Subject Issuance Issued to 87-02 Fastener Testing to 11/6/87 All holders of OLs Determine Conformance with Applicable Material or cps for nuclear Specifications power reactors.
87-01 Thinning of Pipe Walls in 7/9/87 All licensees for Nuclear Fower Plants nuclear power plants holding an OL or CP.
86-04 Defective Teletherapy Timer 10/29/86 All NRC licensees That May Not Terminate Dose authorized to use cobalt-60 teletherapy units.
86-03 Potential Failure of Multiple 10/8/86 All facilities ECCS Pumps Due to Single holding an OL or Failure of Air-Operated Yalve CP.
in Minimum Flow Recirculation Line 86-02 Static "0" Ring Differential 7/18/86 Ail power reactor Pressure Switches facilities holding dn OL or CP.
86-01 Minimum Flow Logic Problems 5/23/86 All GE BWR facilities That Could Disable RHR Pumps holding an OL or CP.
85-03 Motor-Operated Valve Common 11/15/85 All power reactor Mode Failures During Plant facilities holding Transients Due to Improper an OL or CP.
Switch Settings 85-02 Undervoltage Trip Attachments 11/5/85 All power reactor of Westinghouse 08-50 Type i
Reactor Trip Breakers facilities holding an OL or CP.
OL = Operating License CP = Construction Permit
3 UNITED STATES NUCLEAR CEGULATORY COMMISSION WASHINGTON. 0.C. 20555
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