ML18289A457
| ML18289A457 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 10/08/2018 |
| From: | Franchuk T Curtiss-Wright Nuclear Division |
| To: | Division of Inspection and Regional Support |
| References | |
| Download: ML18289A457 (8) | |
Text
CURl1SS .. Nuclear Division 4800 East Tech Dr.
- Clndnnall, OH 45245 Phone: 513.628.7900
- Fu:-513.528.9292 WRIGHT www.CWNuctaar..com
- October 8, 2018 U.S. Nuclear Regulatory Commission
- Attn: Document Control Desk Washington, D.C. 20555-0001
Subject:
Interim Notification Report for Potential Part 21.
Dear Sir or Madam:
Curtiss-Wright was notified on August 7'11, 2018 by Exelon's Dresden Plant that a Curtiss-Wright Supplied*Namco Limit Switch, PIN: EA700-90964 had failed during a planned m.ainterumce test.
. The switch contacts were found to be sluggish in returning to the normal shelf state after actuation, or would not return at a)J. The switch was identified as Curtiss-Wright Tag*# STI4603 and was provided as a safety related component to Exelon in September 2005. :According to Exelon the item was stored .for 8 years then failme occurred approximately 5 years into service.
The part has a manufacturer date coded as August 2005.
- The switch was subsequently sent to Exelon Powerlabs where a detailed failure evaluation was performed_ (See Attached). Exelon Powerlabs confirmed the failure mode* and determined that there was insufficient lubrication in place to support normal switch function. The switch was then sent to N~co for further evaluation and Namco confirmed the lack of lubricant was the likely cause of the failure.
Curtiss-Wright is currently investigating this issue and will provide a follow up report .by November 15th, 2018. * *
- Sincerely:
-nrl~
Tim Franchuk Director, Quality Assurance Curtiss-Wright Nuclear Division, Cincinnati Operations 513-201-2176 TFranchuk@CurtissWright.com
~
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- Exelon Generation Exelon Powerlabs To: Danny Srisawasdi, Quad Cities Station, 309-227-3847 From: Devan Wachter, 815-458-7599 devan.wachter@exeloncorp.com Project: QDC-07067
Subject:
Failure Analysis of a NAMCO Limit Switch from Quad Cities Station Manufacturer: NAMCO Controls Corp Component ID: 1-5699-MSVl '." ASSY -
Ul TURB MSV #1 AR/CR/WO: 04145668 .
PO.: FAILURE ANALYSIS Model: Snap-Lock 700-90964 Quantity Received: 1 Date: 08/08/2018 DESCRIPTION During performance ofQOS 5600-02 (Turbine Stop Valve Closure Scram Instrumentation Functional Test) in June 2018, the Unit 1 main stop valve #1 testing did not produce the appropriate alarms or relay actuations for 10% RPS closure function. The failed limit switch was replaced and sent to PowerLabs west for failure analysis. The site reported the switch was installed during the Q2R22 refuel outage (roughly four and a half years prior to failure).
CONCLUSIONS The failure analysis functionality testing verified the limit switch malfunction by replicating the issue identified on the Quad Cities work request. The limit switch did not operate smoothly and seized up when returning to shelf state. Based on the internal component inspections, the binding was due to insufficient (i.e., dried out) lubrication on the moving components. Manufacturer confirmed lubrication was not present in the Limit Switch and was the primary cause for component failure. In addition, the shaft 0-ring was severely hardened from aging, which would have contributed to binding. Rye Lubrication 181 is applied during the manufacturing process.
COMMENTS AND RECOMMENDATIONS The site should review/evaluate the limit switch replacement frequency for this application. The site may also want to look into limit switches with higher temperature ratings, or evaluating insulation to reduce the exposure temperature.*
REQUIREMENTS Determine the failure mechanism that prevented the limit switch from performing its intended function.
The Exelon PowerLabs Quality System meets 10CFR50 Appendix B, NQA-1 (1994), ANSIN45.2, ANSI/NCSL 2540.3-2006, ISO 9001:2008, ISO 17025:2005, and 10CFR21/10CFR50.55 (e).
36400 S. Essex Road Wilmington, IL Page 1 of7
TEST PLAN
- 1. Document nameplate, photograph sample, and inspect for defects.
- 2. Perform functionality testing on limit switch. *
- 3. Examine internal components for causes of failure and take photographs if needed.
- 4. Manufacturer's Findings STATEMENT OF QUALITY Testing was performed with standard equipment that have accuracies traceable to nationally recognized standards, or to physical constants, by qualified personnel, and in accordance with the Exelon PowerLabs Quality Assurance Program.
Technician(s): Devan Wachter, 815-458-7599 devan.wachter@exeloncorp.com Peter Graffy, (815)458-7603, peter.graffy@ExelonCorp.com Prepared by: Devan Wachter 6/27/2018 ANSI Level ill/ Sr Engineer Date Reviewed by: Peter Graffy 6/27/2018.
ANSI Level ill / Sr. Engineer Date Approved by: Jim Chynoweth 7/3/2018 ANSI Level ill/ Sr. Engineer Date Project review and approval are electronically authenticated in the Exelon PowerLabs project record.
cc: PowerLabs FIA Fleet Distribution Exelon Po:werLabs, LLC - TECH SERVICES WEST Project Number: QDC-07067 36400 S. Essex Road Wilmington, IL Page 2 of7
OBSERVATIONS AND DATA
- 1. Document nameplate, photograph sample, and inspect for defects.
Manufacturer: Namco Controls Corp.
Shaft I Torque Model: EA 700-90964 Measurements Typ e: Limit Switch Rating: 20A - 125VAC / 5A - 125VDC 15A - 250VAC / 1.5A - 250VDC 10A-480VAC
~ RE RATING 5A-600VAC VOLTS AC DC 125 20 5 250 15 1.5 Defects?: Limit switch appeared to have no visible defects. 410 8()0 10 5
- 2. Perform functionality testing on limit switch.
Table 1: Contact Resistance (0 )
Contact 1st Reading 2°d Reading A-B 0.01277 0.01095 C-D 0.06123 0.05865 E-F 0.00732 0.00459 G-H 0.06814 0.07258 J-K 0.04105 0.03680 L-M 0.01629 0.01685 Table 1: Contact resistance measurements show acceptable contact between pads. Acceptable resistance is below 0.1n.
Image 2 Image I : Namco Controls H Limit Switch Nameplate.
Image 2: Contacts G-H show signs of arcing between pads. From the data in table 1, contacts do not show signs of increased resistance.
Exelon PowerLabs, LLC - TECH SERVICES WEST Project Number: QDC-07067 36400 S. Essex Road Wilmington, IL Page 3 of 7
Table 2: Torque Measurements Table 2: The contacts inside the limit switch are actuated by Clockwise 17 inch-lbs rotating a shaft at the top (Image 1) clockwise or counter Counter Clockwise 26 inch-lbs clockwise. By using a torque meter at the center of rotation, it was discovered that more torque is required to rotate the lever in the counter clockwise direction.
When releasing tension on the limit switch, the latch assembly would intermittently bind preventing the contacts from smoothly returning to shelf state.
- 3. Examine internal components for causes of failure and take photographs if needed.
The manufacturer uses Nye Lubricant 181 (Technical Data Sheet: Image 7). During examination, dry lubricant residue was found in all of the internal components (Images 3 and 4). The residue is suspected to be dried from the environmental temperatures or insufficient quantity of lubricant.
Image 3 Image 4 Image 3: With internals removed from limit Image 4: Latch assembly shows signs of dried switch casing, we can see signs of dried lubricant causing binding during operation.
lubricant.
Exelon PowerLabs, LLC - TECH SERVICES WEST Project Number: QDC-07067 36400 S. Essex Road Wilmington, IL Page 4 of 7
When the shaft (Image 1 & 5) is rotated to actuate the limit switch, it pushes the roller (Image 6) located on the latch assembly (Image 4) inward. The latch assembly then moves the contacts (Image
- 2) together or apart, making or breaking connections.
Image 5 0-Ring Locatio Shaft 0-Ring Pivot Point Image 5: The shaft 0-Ring was found intact, but fractured into pieces during removal. The 0-ring material was severely hardened and embrittled from environment aging. Using fourier-transform infrared spectroscopy (FRIT) techniques, the 0-ring was found to be of Buna-N material (Image 8).
The combination of dried lubrication and a hardened 0-ring would have contributed to binding forces.
Image 6: Dried lubrication at multiple moving components contributed to the limit switch failure. The dried lubricant at the 0-ring would increase the amount of torque required to rotate the shaft. If lubrication was present, the shaft would rotate and the roller on the latch assembly would properly operate to actuate the contacts.
When torque on the shaft is released, a spring in the latch assembly pushes the contacts back to shelf state (opening the contacts).
Exelon PowerLabs, LLC - TECH SERVICES WEST Project Number: QDC-07067 36400 S. Essex Road Wilmington, IL Page 5 of 7
Image 7: Technical Data Sheet for Rye Lubricant 181
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Image 8: FTIR showing the unknown hardened 0-ring material to be consistent with Buna-N.
Exelon PowerLabs, LLC - TECH SERVICES WEST Project Number: QDC-07067 36400 S. Essex Road Wilmington, IL Page 6 of 7
- 4. Manufacturer' s Findings Namco limit switch is 8 years or older due to the base plate being black paint (now manufactured as plated), gasket material is of earlier alternate, and the part number was stamped instead of engraved.
Namco re-assembled the switch with a new 0-ring and passed all tests. 0-ring is confirmed to be made of Buna-N material. Lubrication is manually applied by manufacturer during assembly.
Manufacturer confirmed lubrication was not present in the Limit Switch and was the primary cause for component failure. Contacts were worn from use.
Note: There are double pole nuclear grade switches available. In our current application, two of these nuclear grade switches would be required for the one triple pole. Namco will discard the unit.
Exelon PowerLabs, LLC - TECH SERVICES WEST Project Number: QDC-07067 36400 S. Essex Road Wilmington, IL Page 7 of 7