ML20090G355

Forwards Summary of Test Procedures & Equipment for Electromatic Relief Valve RC-RC2.Early Meeting to Discuss Other Problems Requested

ML20090G355
Person / Time
Site:	Three Mile Island
Issue date:	03/29/1976
From:	Bolger F DRESSER INDUSTRIES, INC.
To:	Cotter W METROPOLITAN EDISON CO.
References
TASK-06, TASK-6, TASK-GB B&W-0447, B&W-447, NUDOCS 8307110713
Download: ML20090G355 (5)

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diSSER In0:.'STRIES i  :*g .t

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Industrial valve & Instre:nt Ofvisier.

l Q P.O. Box 1430 Alexandria, t.A [

g l March 29,1976 {g l 1 E 1 '

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i Hr. W. W. Cotter '

f Metropolitan Edisen Ccepany A..

Three M11e Island nuclear station -

' P.O. Box 480 E l , Hiddletown, PA 17057 E l

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Dear Mr. Cotter:

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After a pretty' frustrating week which en1mina-ted with the unsuccessful test -

of valve RC-RV2 (Electroracic) on Saturday evening (unsuccessful being a '

relative term, the 10 bubbles / minute achieved would be normally acceptabic),

Mr. Prevett, our servicer.2n, has returned to base at Alexandria. '

2 I have elected to rer.afn at the Unit in an atte=pt to improve our coordinatica ,.

and verk ficw and in particular to insure that the facilitics and equiceent g.

. required are available when Preuett returns with the new RC.RV1 disc.

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The attached r.emoranaa will hopefully assist in clarification of our problems k-

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. and requirements, and written additions will be :::ade to cover operation .

,,,. % . schedules when these can be formulated. .

7 I suggest that an early recting of all c ncerned be held to define other i ,

problems. .Those present should include ycurself. Jim Shetler, Bill Light and- f-I the supervisor assigned to *.he project by Crouse, Steve Loden.

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.. cs , Very truly yours. -

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.F. P. Bolger

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- . ..- l TESTI:G PROCEC"RES JJa Emt!PP.2:T i

i T RC-RV2 Electre=atic P. R. Yalve Type 2fs - 31573VX I g

There has apparently been confusion betueen this valve and the procedure *

(written by F. p. Solger dated 2/27/7o) for testing the Pressurizer Valves' z 1

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1 The 31533YX valve is completely different fror: the spring loaded types such #l as the 31739 (RC-RV1). The disc is held closed by steam pressure instead of '

' a heavy return spring. When pressure etters the valve the disc is forced *

,, y onto its seat, the higher the pressure the tightcr it seals. A pilot valve i

is used to open this valve. An electrical signal usually from a pressure .-- gt

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switch but also from manual control operates a large electro magnet. This causes a' plunger to strike a lever w,hich opens a small pilot disc and allows f, pressure to bleed from the main valve. The forco holding the main disc g' closed becomes unbalanced and the main valve opens. Therefore, it can be seen solenoid. that this valvit can be opened at any pressure simply by energizing the

There is no set pressure as such, except for whatever pressure the controls are set to. -

2. g 8ecause this valve relies on pressure to reseat ce close, it is difficult to test if there is insufficient volume of air or steam to maintain pressure after it has been opened.

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Consider the action:. [

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a. Pressure holding the valve closed is relieved by the pilot and the main .

-- disc drops and the valve is.open to atmosphere.  ; E

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b. The solenoid is de-energized and the pilot valve closes allowing pressure g to build up behind. the dise. - g ..-

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This pressure lifts the main disc giving it velocity..as it moves it

' creates a larger vol'ume behind it with a consequential reduction in pressure. ,

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d. However,-although the forcing pressure is reduced the momentian of the . t 's disc keeps it moving until it strikes the seat. 1

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t e. The system elasticity causes rebound unless the pressure force has .

increased sufficiently to dampen it. tv:

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J This rebound may, and usually does,. damage the seat. The ide'al situation ..

is for the design staan inlet Ifmitation preventsto be this.

the same size as the disc diameter but valve

~ k it *- It is, however, extrecely desirable b, that the pipe supplying pressure should at least be as large as the valve

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inlet andproximity.

it should be connected to a tann or reservoir c f some volume -- E at close ' 1.

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,- 3.0. RC-RY1 A and 3 Pressurizer Safety Valve; Tyve B 31739  ; , ... . , ,

f similar test stand is required for quit., different reasons when tNtinT '

the spring loaded typt. valves 31/M an.] 2h (g rer.suri.:ce and ccin stea=). .. 1

@ Here the disc is rcturned to the '.c.it t.ndar the action of a heavy spring. t

, In normal service, the closinc a:cion is geep..ratively slow, virtually [.,

s following the steam pressure du p. .

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If the volt.;=e of stern or hir IP! Plied t.s n1ve vhen it is npen is less than '

f-sufficient to maintain pre *.'.ure Ln balance the spring force then the valve C closes. The quicker this pressure deteriorate t.* c faster thi. closing action. t The natural frequency of the return s. wing systesa is in the region of 30 c.p.s.  ?

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and so it can be seen that if the valve is allowed to close without restrictico b extremely high ic: pact velocities are attained. I believe that a very large

• i-percentage of the scat and disc damge found on thiese types of valves can be"- -

attributed to use of faulty test st.mds where air flow is too srall. [cf ,

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Another reason for a large air finw tn the valve is to cause sufficient lift -

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to allow the valve components to .cif align and produce a good reseating action.

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y 4.0 The existing test stand does not set.isfy any of these criteria and was designed, [.

I believe, to use water to obtain pressure control. Since our new precedure '

E for the R*ll valves requires the valve to be heated, it would be detricantal  ?.

to inject cold water into the test system. Only dry N2 or air should be used. b. . ,

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The system as assembled has a 8" schedule 160 cylinder about four feet long Mi connected to the test ilange by 3/8" diaceter stainless steel tube about seven '.-

. feet long. A pressure gauge is connected to tne cylinder. A 6000 psig N2 bottle  ;.

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supplies gas to the cylinder. It is certain that the pressure reading in the v. .

j @ cylinder icrediately the valve opens, will not be the pressure under the valve ~ $ ',

! disc, since flow velocity will be very high, probably sonic. This situation 1.

is a potential source of valve chatter and consequential seat damage.  ;

5.0 I strongly suggest that a.new test vig be designed and made before we attempt 5'

1 . further testing. The existing could be modified by welding in a 2" schedule 1

160 p-ipe nipple and connecting this to a similar nipple on the test flange. -

i The cylinder would 1sy under the test stand. A sketch is attached. The R.

available test gauge is marked " Water Caly". We need an air gauge, procerly  %.

calibrated, and having our 2500 psig test pressure in the middle third of the dial range. %p -

6.0 Electro =atic Test Procedure

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6.T Before connecting fl2 system to test flange, blow out to expel all imp'urities. . L "-

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Ut:nost care is necessary during fabrication and assembly of test stand to D

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prevent accumulation 'of dirt. .

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6.2 Check operation ci electrical systcz. Clean contacts of holding coil switch. h

These contacts get burned and spark eroded. The purpose of the switch is to F-3: ' 1 short out the bottone solenoid coil until the solenoid plunger has overcon:e . .'?

' ;* the pilot valve resistsnce. When the plunger reaches the end of its travel,  : [p ji it opens this switch, which allows current, to' pass through the bottom coil and

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. increases the electrical resistance of the solenoid so reducinJ current required. holding th If this switch does not work, the coil =sy overheat and fail.

Do not light confuse this switch with the "Unir ax" micro-switch unich is for warning operation.

@ prevent arcing. There may be a capacitor across the holding call switch to

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?ste, the existing test flange does not properly match the inlet flange of be electromatic valve. A special gasket has bosn :.ade to se.1 the joint but this should be regarded as nukest.ift and the fian7e should be altered for future j testing. The test flange is squcre and is not a cede flance and so no attempt e to torque the stud nuts to the norm:1 valves shculd be made. l.cakage is not<.

being way. checked at this .foint as it does not reiste to valve tightness in any .

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apply to Excess pipework leakage leaks. must be avoided to reduce t:2 loss. These rc= arks a k o * -

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. 6.4 With the !!2 suppi$p connected, raise system pressure to 2200 psig.

valve by energi:ing the solenoid. flote, car protection is required Pop and test the engineer should warn all adjacent personnel before the pop. This operation should seat the valve and test cocplete system.

6.5 Pour test bubbles. fluid (water) into outlet of valve to cover seat area. !!atch for fio bubbles visible for five minutes is required leak tightness level.

6.6 ifThisthetest- for leak required leveltightness is not isachieved.

severe and disc may have to be removed and relapped Difficulty in obtaining this degree of tightness should be recorded and the final test which is repeated in the reactor building should reflect and take into consideration these difficulties.

6@7 After satisfactory testing in the reactor building, the valve should be -

freediately counted on the 7900 gate valve in the pressurizer system. This -

valve should be closed and not opened until steam pressure is approximately  :

1000 psig. The RV2 valve will then close quickly, otherwise steam residue may damage the seat if it hangs partly open. It is good practice to pop this -

i valve once about 1500 psig to insure good seating.

7.0 The availability of tools and equipment together with improvised operating -

.' instructions. have impeded our work flow considerably during the past week. j.

O I offer the following as an attempti to more clearly define the test requirements

. and as a basis of discussion between B&W, Met-Ed. and Crouse.

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Test stand. This is complicated and needs discussion. I have stready outilined% -

soce suggestion. Presumably hydraulic testing will be required. It must be  ;

.] portable to allcw revement between work shop and reactor building and back probably. r q'

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.r- 7.2 Heating Faciif ties. 1  ?

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' temperature measurecant and control.These consist of heating The rate of terparature increase has been-. coils, insulation, power sup

'4 found to be extremely critical and a valve recently tested for Duke Power j/

4.i required seven hcurs to stabilize. I think we can reach say 100-1200F fairly T quickly and then go very slowly to 2000F. Holding the temperature constant may be difficult and the slightest variation will cause bubbles which may not ,

f be Teakage. This needs discussion.  ;

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7.3 IJ!fting and Handling Equip =ent. The spring !oa.'et! safety valva RC-PY1 weighs

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about 850 lbs. and the electronic about 2Fs lbs. Total lifting cleaance to get the valve on the test stand is about 10 rest (chec:.). [.'

• ightening and adjusting the cer.cros: ion seres to achieve the set pressure is I di f ficul t. An air operated impact wrench is desirabic but the wrench must bdg ~ b' long enough to clear the sris. die. If a wrench exteinfed by a piccc of pipe is , t u ed, the test stand rr.y fall r..*er or a r.ar. eay slip. R.tdiation hazard. &

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7.4 Small tools and caasuring equipcent. These are the areas which have wasted time.

I intend to discuss these and list them in detail. .  ! F

" . .4 8.0 Schedule r

. . f- i I think the governing facter is the test stand.. Until this is discussed and 1 agreed, no schedule can be for=ulate,d. M Ti The infor=ation we have puts tM RC-i'V1 dise here en Friday, April 2,1976. [

So, I would tentatively aim at having our facility operaticnal. by say Panday if:.

April 5,1976. E

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