ML20136J598

Forwards Transmittal of Supplementary Pressure Locking Data from Flexible Wedge Gate Valve Tests

ML20136J598
Person / Time
Issue date:	03/19/1997
From:	Mayfield M NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To:	Wessman R NRC (Affiliation Not Assigned)
References
NUDOCS 9703200149
Download: ML20136J598 (4)

Text

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. , s, March 19, 1997 MEMORANDUM T0: Richard H. Wessman, Chief Mechanical Engineering Branch Division of Engineering. NRR FROM: Michael E. Mayfield. Chief original /s/ by Electrical. Materials, and Mechanical Engineering Branch Division of Engineering Technology, RES

SUBJECT:

TRANSMITTAL OF SUPPLEMENTARY PRESSURE LOCKING DATA FROM FLEXIBLE WEDGE GATE VALVE TESTS j The subject data in the attachment is being transmitted as requested in discussions with Mr. Weidenhamer of my staff. The attachment also includes dimensional information for the Walworth flexible wedge gate valve and on the steps used by the Idaho National Engineering Laboratory for performing the tests.

The data is supplementary since it was obtained early in the test program during the friction surface preconditioning process. For these early tests the disk-to-seat friction factors ranged from 0.10 to 0.16 and are lower than the friction factors

. for the fully conditioned surfaces reached later in the test program. The data that was obtained after the friction surfaces were fully conditioned was forwarded to you

, in my memorandum, dated June 25, 1996, and a copy was also sent to the Public .

Document Room at that time. The disk-to-seat friction factors corresponding to the later data ranged from 0.46 to 0.64. The phenomenon of surface conditioning has been shown to be dependent on operational and thermal exposure and has been observed

' in previous INEL and EPRI MOV tests.

4 The results from these early tests are being provided to give pressure locking data over a full range of friction factors. The data will be useful for evaluating l analytical methods for predicting opening thrusts for valves that may experience pressure locking conditions.

! A copy of this memorandum and the attachment is being sent to the Public Document Room to be made available to others outside the NRC as requested in the discussions with Mr. Weidenhamer.

If you have any questions on the attachment, please call Gerald Weidenhamer on 415- l 6015. I

Attachment:

As stated Distribution:

4 Signature File (LCS) f[SYrb ejg 9703200149 970319  ;

S.G.Tingen PDR ORG NREB i E.J. Brown .

Document Control Desk ,

Public Document Room 200005 DOCUMENT NAME: G:WVEIDENHA\SUPPDATA To receive a copy of this document,ind6cese in the box: 'C" - Copy without attachment / enclosure "E* = Copy with attachment / enclosure g<

1

'N' = No copy a'l , ,

OFFICE EMMEM l G" SC\EMME9McG l C\EMMEB g @l M l l NAME_ % G.Weidenhamer J Vora V M.MayfieWM '

DATE7(lt 318 Y 197 3 / IT /97 T/lI/97 OFFICIAL RECORD COPY flGS Fue Code: 19  %

• ATTACHMENT i

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Supplementary Pressure Locking Test Results,6-inch Walworth Valve ne U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research, funded research at the Idaho National Engineering Laboratory (INEL) to provide technical information to support NRC's evaluations of industry responses to Generic Letter 95-07, " Pressure Locking and Hermal Binding of Safety-Related Power-Operated Gate Valves." Pressure locking and thermal binding are potential operational phenomena that may prevent a closed gate valve from opening. Pressure locking can occur when operating sequences or temperature changes cause the pressure of the fluid in the bonnet (and, in most valves, between the discs) to be higher than the pressure on the upstream and downstream sides of the disc assembly. This high fluid pressure forces the discs against both seats, making the disc assembly harder to unseat than anticipated by the typical design calculations, which generally consider frictional effects at only one of the two disc /sgat interfaces.

The objectives of the INEL gate valve pressure locking research include the following:

1. Determine the relationship between the pressure in the benet and the opening thrust with the valve cold, and again with the valve hot

2. Evaluate the impact of temperature changes in the bonnet region on the rate of bonnet pressurization and on the associated thrust requirement to overcome thermally-induced pressure locking. .

3. Evaluate the effect of valve leakage for mitigating or eliminating pressure locking 3

4. Evaluate the effect of entrapped air for mitigating or eliminating pressure locking, and the ]

extent to which air will remain entrapped in the valve bonnet during operation.

The test program consisted of testing two gate valves at various pressure locking conditions. l The first valve tested was a 6-in.,600-lb-class Walworth flexible wedge gate valve equipped with a Limitorque SMB-0-25 motor actuator. Preliminary results from the Walworth valve tests were reported earlier (available in the NRC Public Document Room, Accession Number 9606270097). 4 he second valve tested was a 6-inch,900-lb-class Anchor / Darling double disc gate valve equipped with a Limitorque SMB-t-60 motor actuator. Preliminary results from the Anchor / Darling valve tests were reported earlier (available in the NRC Public Document Room, Accession Number 9701240039).

The results contained in the attached table were obtained from tests at the beginning of the program when the disc-to-seat friction factors were low. This data is being documented at this time to supplement the information identified in the previous paragraph for the Walworth valve. l 1

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a TEST SETUP The first valve tested was a Walworth 6-inch,600-lb-class flexible-wedge gate valve with a Limitorque SMB-0-25 motor operator. The important valve specific information is listed below. 1 Disc thickness (one disc) 0.520 in, i Mean seat diameter 5.515 in. 1 Stem diameter 1.250 in. ]

Hub diameter 2.580 in. .

i Hub length 0.928 in. l

. Wedge angle 5*0' to 4*56' Poison's ratio (disc material) 0.3 Modulus of Elasticity (disc material) 29,700 ksi (A217WC6) 5 Because the valve had been used in previous testing, the valve sealing surfaces were reconditioned in preparation for the pressure locking tests. Following this reconditioning, the valve

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seat leakage was well below accepted limits.  !

t LOW TEMPERATURE PRESSURE LOCKING TESTS i

The low temperature pressure locking tests evaluated the relationship between the fluid pressures ,

in the valve and the valve opening thrust. The test matrix consisted of various upstream, I downstream, and bonnet pressures distributed across a range of possible conditions. . Periodic baseline

! valve strokes were also performed throughout the testing to evaluate the wedging versus unwedging

, relationship, obtain upstream and downstream seat friction values, and determine the load due to i

packing friction. He baseline strokea included a static valve closing and opening cycle and two j

! differential pressure opening stokes: one with the downstream side and the bonnet pressurized, and

one with the upstream side and the bonnet pressurized.

Two different methods were used to simulate pressure locking conditions. The first method began with the valve open and the test volume pressurized to 1200 psig. The valve was then closed and the pressures in the upstream leg, downstream leg, and bonnet were reduced to the desired test values. He valve was then opened and the stem force required to extract the valve disc was -

measured.'.He second method began with the valve open and depressurized. The valve was then closed and the pressures in the upstream leg, downstream leg, and bonnet were increased to the desired test values. The valve was then opened and the stem force required to extract the valve dise I was measured. He results of the cold pressure locking tests are summarized in Table 1. Tests 201 4 through 218 used the first pressurization method and tests 219 through 225 used the second method.

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Preliminary Table 1. Summary of Supplementary Pressure Locking Test Results Test Pressure (psig) Temp (*F) Stem Packing Valve Thrust Drag

' Disc Friction (Ibd (Ibd Number Type Up Bonnet Down Bonnet Factor Factor

. 201 HD 1092 1093 -2 72 1693 0.101 0.100 J 203 HU 0 1107 1103 72 16 % 0 100 0.100 204 S 0 0 0 72 1988 408 205 PL -1 222 -1 72 3045 206 PL -1 497 -1 72 4217 207 PL -2 778 -2 73 5360 208 PL -1 1097 0 73 6801 209 PL -1 1081 301 72 6293 210 PL -1 1077 587 72 5052

! 211 PL -1 1160 912 72 4764 212 HU -1 1130 1125 72 2423 0127 0.123 213 PL 314 1116 -2 72 7268

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214 PL 621 1132 -l 73 6479 215 PL 899 1122 -2 72 5535

'216 HD 1136 1137 -1 72 1948 0.108 0.108 217 PL 614 1126 297 72 5848 218 PL 319 1082 316 73 6659 j 219 HD 1092 1092 -1 73 2091 0 116 0.116 221 HU -1 1092 1086 72 3151 0 158 0 157 222 PL -1 255 -l 72 4083 223 PL -1 547 -l 73 5816 224 PL -2 829 -2 73 7258

??5 Pt. -1 1106 -1 7? RRRR I

Test Type:

S = Static opening test HU = Hydro opening test across upstream seat HD = Hydro opening test across downstream seat PL = Pressure lock opening test 3