ML20255A199
| ML20255A199 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 06/11/2020 |
| From: | Hobbs M, Sizemore A, Strong M Flowserve US |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 54584 | |
| Download: ML20255A199 (9) | |
Text
Flow Control Division Anchor/Darling Valves BW/IP Valves Edward Valves Valtek Control Products Worcester Valves June 11, 2020 US Nuclear Regulatory Commission Document Control Desk 11545 Rockville Pike Rockville, MD 20852-2746
Subject:
Bench Test Failure of Model 38878-x, 3-Way, 2-Position Solenoid Valves at Seabrook Station for use on FWIV Actuator This is to notify the US Nuclear Regulatory Commission that, in accordance with the provisions of 10CFR Part 21, Flowserve has completed the investigation into the bench test failure of the two 38878-x, 3-way, 2-position solenoid valves at Seabrook Station for use on the FWIV actuator.
Description:
On January 14, 2020, Flowserve was informed that a Model 38878-8, 3-way, 2-position solenoid supplied to Seabrook Station for use on the feed water isolation valve actuator failed bench test at the customer site on January 13, 2020. A second solenoid valve, Model 38878-1, failed bench test at the site on January 14, 2020. The failed solenoid valves were returned to Flowserve for evaluation.
Evaluation:
The first solenoid valve that failed, model 38878-8, serial number BX933 was manufactured in December 2019 and was tested in the as received condition. This solenoid valve BX933 did not shift when energized but technicians reported hearing it try to move. This solenoid appeared to be stuck in a nearly shifted position. The coil cap (5) is attracted by the energized coil assembly (10) to provide the required force to shift the spool (27).
The coil cap (5) is not rigidly attached in the solenoid valve and will typically rattle during handling. This solenoid valve did not rattle during test setup.
The end cap (6) was removed. The coil cap (5) was very difficult to remove. Once the coil cap (5) was successfully removed, it was re-inserted into the coil housing and the solenoid valve was tested again, and it passed test.
The solenoid valve was then disassembled for inspection and root cause analysis. The solenoid valve was built in accordance with the 38878-8 configuration. All o-rings, back-up rings, quad seals and seats were inspected, and no damage was found. The resistance of the solenoid coil assembly (10) was checked and found to be within tolerance, 298.8 ohms. Since the coil cap (5) was so difficult to remove, close examination of the coil assembly (10), the coil cap (5), the set screw (16) and the hex nut (18) was made. The inside diameter of the coil assembly (10) showed signs of damage due to foreign material. In the following figures, the 12 oclock position is the location of the electrical wires.
Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com
Figure 4: Inner Diameter of Coil Assembly Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com Page 2 of 9
Figure 5: Inner Diameter of Coil Assembly Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com Page 3 of 9
Figure 6: Inner Diameter of Coil Assembly There was also evidence that the set screw (16) had become wedged in the inside diameter of the coil assembly (10) binding up and not allowing the coil cap (5) to move.
Please note the indentions in the figure below.
Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com Page 4 of 9
Figure 7: Inner Diameter of Coil Assembly During assembly and test of this solenoid valve, it is cycled over 100 times. As the pictures above show, the foreign material that was in the coil assembly inner diameter could not have been present during assembly and test. Somehow, foreign material was introduced into the coil assembly inner diameter after final assembly and test.
Unfortunately, none of the foreign material was captured or identified, therefore identification of the foreign material and its source is impossible.
The second solenoid valve that failed, model 38878-1, serial number CMS368-4 was manufactured in May 2012 and was tested in the as received condition. This solenoid valve did not shift when energized and appeared to be stuck in the energized position.
The coil cap (5) is attracted by the energized coil assembly (10) to provide the required force to shift the spool (27). The coil cap (5) is not rigidly attached in the solenoid valve and will typically rattle during handling. This solenoid valve did not rattle during test setup.
Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com Page 5 of 9
The solenoid valve was disassembled for inspection and root cause analysis. The solenoid valve was built in accordance with the 38878-1 configuration. The spool in the solenoid valve appeared to be stuck and would not move. Solenoid coil resistance was measured and found to be within tolerance, 296.1 ohms. There was no evidence of damage to coil cap, end cap, set screws or spring. The internals of the solenoid valve were removed.
Figure 1: Coil Side Seat O-ring and Back-up Ring Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com Page 6 of 9
The o-ring (14) and back-up ring (15) for the coil side seat were damaged and in multiple pieces. One small piece of the back-up ring (15) was found between the coil side seat (25) and the seat spacer (24). One piece of the back-up ring (15) and two pieces of the o-ring (14) were found in the gap between the seat spacer (24) and the seat retainer end (23). One piece of the back-up ring (15) and one piece of the o-ring (14) were found in a body cavity at the solenoid valve ports. If the piece of the back-up ring (15) between the coil side seat (25) and the seat spacer (24) protruded across the seat (25) face, this would contact the spool and prevent it from shifting. Note that the solenoid valve would not have passed Flowserves test in this condition, therefore this had to have happened after passing functional testing. There were slivers of seat material that were also found.
Figure 2: Seat Material Slivers Examination of the seats (25 and 26) showed some areas that could indicate where this seat material may have originated. These slivers of seat material would not have caused the described failure of this solenoid valve.
Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com Page 7 of 9
Figure 3: Spring Side Seat (Left) and Coil Side Seat (Right)
All these points indicate that the internals of this solenoid valve were at least partially disassembled and re-assembled after functional testing.
Based on the investigations detailed above, Flowserve has concluded that the failures of these two solenoid valves do not constitute reportable events in accordance with 10CFR21.
Extent of Condition:
Flowserves investigation has concluded that these two failures are isolated incidents. There was no evidence found that indicated either of these two solenoids had these defects or deviations prior to being shipped to the customer. Flowserve believes that any 38878-x solenoid valve that has successfully passed test at the customer site and is in service do not have either of the conditions associated with these two solenoid valves.
Corrective Actions:
None required.
Summation:
In summary, one Model 38878-8 and one Model 38878-1, 3-Way, 2-position solenoid valves failed bench test at Seabrook Station prior to assembly on the FWIV Actuator. The solenoid valves were returned to Flowserve and failed as received tests. The model 38878-8 solenoid valve had evidence of foreign material in the solenoid coil assembly inner diameter that caused the actuation components to bind up and wedge in place, preventing the solenoid valve from functioning. This condition would have made it impossible for the solenoid valve to pass assembly and test at Flowserve. The model 38878-1 solenoid valve had evidence that the internal had been partially disassembled after Flowserve completed the assembly and test.
Upon reassembly of this solenoid valve the coil side seat o-ring and back-up ring were damaged allowing a piece of the back-up ring to become trapped between the spool and the coil side seat. This caused the solenoid valve to be stuck in the shifted position and not functioning.
This condition would also have prevented the solenoid from passing assembly and test at Flowserve. Flowserve has concluded that these two solenoid valve failures are not defects or deviations that occurred at Flowserve that would be associated with substantial safety hazards.
Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com Page 8 of 9
Respectfully Submitted, Sincerely, Sincerely, Sincerely, Megan Strong Andy Sizemore, PE Matt Hobbs, PE Quality Manager Engineering Specialist Engineering Manager mstrong@flowserve.com ASizemore@flowserve.com MHobbs@flowserve.com Flowserve U S Inc Raleigh Operations Toll Free: 1-800-225-6989 Flow Control Division PO Box 1961 Phone: 1-919-832-0525 1900 South Saunders Street Facsimile: 1-919-831-3369 Raleigh, NC 27603 www.flowserve.com Page 9 of 9