ML20148E801

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Part 21 Rept Re Worm Gear Component of Type H3BC Valve Actuators.Initially Reported on 880317.All safety-related Worm Gear Components Will Be Subj to Documented Insp Verifying Absence of Casting Porosity
ML20148E801
Person / Time
Site: Comanche Peak  Luminant icon.png
Issue date: 03/18/1988
From: Mcquillan P
LIMITORQUE CORP.
To:
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
References
REF-PT21-88-018-000 PT21-88-018-000, PT21-88-18, NUDOCS 8803250320
Download: ML20148E801 (6)
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Text

.

g Limitorque Corporation

Automoted Volve Actuotors and Jacks for IndAfry-5114 Woodoll Road P.O. Box 11318 Lynchburg, VA 245061318 rp l Telephone-804 528 4400
  • Telex-82 9448 4m y . .

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e ss,, March 18, 1988 l

d Director, Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, DC Gentlemen:

Subject:

10 CFR Part 21 Report Refe.ence: H3BC Worm Gears Limitorque Corporation is notifying the commission of a potencial defect in the worm gear component of type H3BC valve actuators. Reportability was determined by Limitorque Corporation on March 17, 1988.

Background:

Stone and Webster, acting on behalf of Tu Electric, advised Fisher Controls of a defect in the worm gears of two H3BC actuators furnished by Fisher Controls to the Comanche Peak Steam Electric Station. The actuators were supplied by Limitorque Corporation on S/0 No. 3A6274-A and 3A6274-B in 1978.

Fisher Controls advised Limitorque Corporation on January 29, 1988, of Stone and Webster's findings. Limitorque Corporation visited the Comanche Peak site on February 4, 1988. Two cracked H3BC worm gears were observed. These gears were sectioned in halves and a section of each gear was returned to Limitorque Corporation for failure analysis.

Analysis:

The Limitorque Corporation Engineering Department has concluded that the presence of porosity in the cast worm gear is the root cause of failure.

Further, it was cor.cluded that failure cf a worm gear component with similar deficiencies would be instantaneous upo. gear loading and would be evident at the time of installation. There is no indication of a previous failure associated with the presence of casting porosity.

l Corrective Action:

Limitorque has advised Fisher Controls that actuators supplied on S/0 No.

3A6274-A (quantity 4) and S/O No. 3A6274-B (quantity 16) be inspected for l

l similar deficiencies.

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8803250320 880318 i PDR ADOCK 05000445 S DCD

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LIMITORQUE CORPORATION Sheet NB. 2 Action to Prevent Recurrence:

All H3BC worm gear castings presently in stock have been visually inspected for evidence of casting porosity. No porosity has been observed.

Additionally, a sampling of components has been sectioned or X-rayed with no j porosity or defects observed.

i Further, all safety related worm gear components will be subject to a documented inspection verifying the absence of casting porosity. This inspection will be implemented on March 21, 1988.

Conclusion:

The root cause of failure (casting porosity) is the result of the casting process. Limitorque Corporation has not been previously advised of a failure associated with the presence of worm gear casting porosity. It is judged that a casting "lot" or a portion of that casting "lot" may be defective. Effocts to obtain "lot" traceability have been inconclusive due to the fact that the probable casting supplier discontinued operations in 1983.

Limitorque Corporation recommendations are as follows:

1. Inspect worm gear components of H3BC actuators that have not yet been placed in service.
2. H3BC actuators that have been previously operated under load should have the worm gear component inspected at the utilities' discretion.
3. The required inspection procedures are attached.

Limitorque Corporation is requesting the commission's recommanded mailing list to transmit this information to the industry.

Very truly yours, LIMITORQyECORPORATIO,N ff bL faddbd P. G. McQuillan Q. A. Administrator jh pc: T. Mignogna F. Denham

1. Wilkinson W. Miluszusky

ENGINEERING INSTRUCTION PROCEDURE Section B.4.5.1 SUB-ASSEMBLY INSTALLATIONS Sheet 1 of 2 H3BC DRIVE SLEEVE 900 WORM GEAR Prepared By DJM j ASSEMBLY DWG. 01-440-0354-4 IssueDate3/17/88Appvdjf3p4)/j/}yr.s9' IDENTIFICATION /PART NO. EIP-0051 Rev. Date Appvd The following is a step-by-step description for removing the drive sleeve Assembly Items 24, 25, 29, and 30. These instructions are intended to be used in conjunction with the assembly drawing listed above.

Before proceeding, the actuator must be disassembled from its mounting and free of all mechanical loads.

DISASSEMBLY;

1. Caution: This actuator is filled with grease. Prepare to recover any grease that flows from the actuator during disassembly. All grease that flows f rom the actuator must be replaced during reassembly.
2. Set the actuator in a clean area and prepare to disassemble the unit.
3. With the unit in an upright position, worm shaf t , Item 31, horizontal and pointer, Item 16 on top, remove stem nut, Item 28. Remove fasteners, Items 19 and 20 that secure housing cover, Item 14 to housing, Item 1. Remove fasteners, Items 21 and 23 that secure pointer cap, Item 15, to drive sleeve, Item 25.
4. Remove assembly of pointer cap, Item 15, and potnter, Item 16. Remove housing cover, Item 14, bearing, Item 7 (Item 7 is press fit to Item 14), and o-ring, Item 8. Remove gasket set, Item 5.
5. Remove fasteners, Items 11 and 12, that secure cover-limit stop, Item 3, to housing-limit stop, Item 2. Rotate nuts, Items 27, to the center position (away from housing, Item 2) to enable worm shaf t, Item 31, to be rotated. Rota te vorm sha f t , Item 31, until worm gear, Item 24, is disengaged f rom worm shaf t, Item 31 (rotate nuts, Item 27, as required to achieve disengagement).

! 6. Remove drive sleeve assembly that consists of Items 24, 25, 29, and 30.

Lift this assembly out of housing and set aside.

7. If further disassembly of the drive sleeve assembly is required, remove nuts, Item 30, from bolts, Item 29. Remove bolts, Item 30.

i Remove dowel pins, Item 26. Remove wo rm gea r, Item 24, fron drive sleeve, item 25.

l l

l ASSEMBLY:

l During assembly, spread a thin coat of grease on all o-rings and quad rings.

i Use Step 8 if worm gear, Item 24, is being reinstalled (was not replaced with a new part). Use Step 9 if the worn gear, Item 24, is being replaced by a new l worm gear. Then proceed to Step 10.

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ENGINEERING INSTRUCTION PROCEDURE Section B.4.5.1 SUB-ASSEMBLY INSTALLATIONS Sheet 2 of 2 H3BC DRIVE SLEEVE 900 WORM GEAR Prepared By DJM ASSEMBLY DWG. 01-440-0354-4 IssueDate3/17/88Appvd)h#47" /87'. //

IDENTIFICATION /PART NO. EIP-0051 Rev. Date Appvd

8. Install worm gear, Item 24, on drive sleeve, Item 25. Install two dowel pins, Item 26. Secure worm gear to drive sleeve with bolts, Item 29, and nuts, Item 30.
9. Secure worm gear to Item 24 to drive sleeve, Item 25, with fasteners, Items 29 and 30. Ream the two 23/64 inch diameter holes in Items 24 and 25 to a diameter of .3745/.3750 inches. Install two dowel pins, Item 26, to secure Items 24 and 25 to each other.
10. Verify o-ring, Item 8, is installed in housing, Item 1. Install drive sleeve assembly of Items 24, 25, 29, and 30 into housing, Item 1.
11. Rotate vorm shaf t, Item 31, and the drive sleeve assembly in a manner to engage these two gears. Engage to a position as shown on the assembly drawing (rotate nuts, Item 27 as required to achieve engagement).
12. Replace all grease back into the actuator. Clean the gasket surfaces of housing, Item 1, and housing cover, Item 14, to insure gasket, Item 5, will seal properly. Install gasket, Item 5.
13. Install o-ring, Item 8, in housing cover, Item 14. Install housing cover, Item 14, and bearing, Item 7, secure cover, Item 14, to housing, Item 1, with fasteners, Items 19 and 20.

t 14. Install and secure pointer cap assembly to drive sleeve, Item 25, with l fasteners, Items 21 and 23.

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15. Install actuator. Set stop nuts, Item 27, to restrict travel. After setting, rotate nuts so a flat on each nut will face cover, Item 3, l after assembly.
16. Clean the gasket surfaces of housing, Item 2, and cover, Item 3, to insure gasket, Item 6, will seal properly. Install gasket, Item 6 L

and cover, Item 3. Secure Items 3 and 6 to housing, Item 2 with fasteners, Items 11 and 12.

17. The actuator is ready for service.

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ENGINEERING INSTRUCTION PROCEDURE Section B.8.1.1.1 INSPECTION Sheet I of 1 POROSITY Prepared By DJM WORM GEAR HBC 900 WORM GEAR Issue Date 3/17/88 IDENTIFICATION /PART NO. EIP-0052 Rev. Date Appvd M A /,,/.

The following is a detailed standard intended to establish the inspection procedure / criteria for acceptance / rejection of the H3BC 900 worm gear based on a visual inspection of all external surfaces.

1. Thoroughly clean all surfaces of the worm gear. Remove all grease and foreign matter.
2. Visually examine all surfaces for porosity (blow holes, pin holes, etc.)
3. If any porosity is present, the worm gear must be replaced.

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