ML20005B743

Advises That Util Response to IE Bulletin 79-15, Deep Draft Pump Deficiencies, Is Inadequate to Demonstrate & Assure long-term Operability of Pumps.More Detailed Info Should Be Provided within 60 Days.Guidelines Encl

ML20005B743
Person / Time
Site:	Shoreham File:Long Island Lighting Company icon.png
Issue date:	08/13/1981
From:	Tedesco R Office of Nuclear Reactor Regulation
To:	Pollock M LONG ISLAND LIGHTING CO.
References
IEB-79-15, NUDOCS 8109020067
Download: ML20005B743 (18)

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Docket ho. 50-322 Qs 4

fir. 11. S. Pollock

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XJ 175 East Old Country Road V>#- T v /.O-Hicksville, New York (1801 c.

Subject:

Long Tem Operability of Deep Draf t Pumps IE Bulletin 79-15, dated July 11, 1979, was issued to all licensees and holders of construction pemits as a result of deep draf t pump deficiencies that were identified at facilities both operating and under construction.

In your response to the bulletin you identified deep draf t pumps as being utilized at your f acility. However, your response to the bulletin did not include enough infomation to demonstrate and assure the long tem operability of these pumps.

Enclosed is a document entitled, " Guidelines for Denonstration of Operability of Deep Draf t Punts." Within 60 days from the issuance cate of this leter, you should provida infomation on all the deep draf t pumps identified in your bulletin response and describe the extent to which your deep draf t pump long tem operability assurance program conforos to the various portions of these Guidelines. Enphasis snould be placed on (1) the establishment of installation procedures tnat are followed each tir.e these pumps are disassembled and reinstalled, and (2) the testing requirements and bearing wear criteria. The instrunentation called for in the Guidelines should not be considered a requirement.

These Guidelines establish an acceptable method of assuring long tem operability of deep draf t pumps. They do not necessarily constitute the only metnod for demonstrating long tem operability. The staff will review the information you subiait to detemine whether your long tern operability assurance progran for deep draf t pumps is in sufficient conformance with these Guidelines to assure long term operability.

If not, the staff will determine wnether you have established and utilized other netnod.' and procedures, preferably with the assistance of the pump manufacturar, that also demonstrate va assure that these pumps will perfom their intended function for the lengtn of time required.

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2-If you have any questions regarding this matter, please contact the Licensing Project llanager.

Sincerely, Robert L. Tedesco, Assistant Director i

for Licensing Division of Licensing Office of Nuclear Reactor Regulation

Enclosure:

Guidelines for Demonstration of Operability of Deep Draft Pumps cc w/ enclosure:

See next page nistribution Docket File NRC PDR Local PD9 l

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' " " '980- 329 624

Mr. M. S. Pollock Vice President - Nuclear Long Island Lighting Company 175 East Old Country Road Hicksville, New York 11801 ccs:

Howard L. Blau, Esq.

David Gilmartin, Esq.

Blau and Cohn, P. C.

Suffolk County Attorney 217 Newbridge Road County Executive / Legislative Building Hicksy'ille, New York 11801 Veteran's Memorial Highway Hauppauge, New York 11788 Jettrey cohen, Esq.

Deputy Commissioner and Counsel MHB Technical Associates New York State Energy Office 1723 Hamilton Avenue - Suite K Agency Building 2 San Jose, California 95125 Empire State Plaza Albany, New York 12223 Stephen Latham, Esq.

Twomey, Latham & Schmitt Energy Research Group, Inc.

P. O. Bo.v. 398 400-1 Totten Pond Road 33 West Second Street Waltham, Massachusetts 02154 Riverhead, New York 11901 B. R.

McCoffrey Joel Blau, Esquire 4

Shoreham Nuclear Power Station New York Public Service Conmission P. O. Box 618 The Governor Nelson A. Rockefeller Bldg.

Wading River, New York 11792 Empire State Plaza Albany, New York 12223 W. Taylor Reveley, III, Esq.

Hunton & Williams Ezra 1. Bialik P. O. Box 1535 Assistant Attorney General Richmond, Virginia 23212 Environmental Protection Bureau New York State Department of Law Ralph Shapiro, Esq.

2 World Trade Center Cammer & Shapiro New York,"New' York 10047 i

9 East 40th Street l

New York, New York 10016 Jeffrey Futter Long Island Lighting Company 250 Old Country Road Mineola, New York 11501 Resident Inspector /Shoreham NPS c/o U.S. Nuclear Regulatroy Commission P. O. Box B Rocky, Point, New York 11778 l

l Honorable Peter Cohalan Suffolk County Executive County Executive /Lagislative Building i

Veteran's Memorial liighway Hauppauge, New York 11788 l

1

r GUIDELINES FOR DEMONSTRATION OF OPERABILITY OF DEEP DRAFT PUMP 5 DISCUSSION I.E.Bulletin 79-15 dated July 1979, identified problems associated with deep-draft pumps found at operating facilities and near term operating licensee facilities.

Deep draf t pumps,which are also called " vertical turbine pumps" are usually 30 to 60 feet in length with impe11ers located in casing bowls at the lowest elevation of

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the pump. The motor (driver) is located at the highest pump elevstion with the discharge nozzle just below the motor.

Bulletin 79-15 was initiated because several nuclear power plant facilities could not demonstrate operability of their pumps. The

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pumps were experiencing excessive vibration and bearing wear. Thei~

rapid bearing wear suggested that these pumps could not perform their required functions during or following an accident. As a

- s result of the staff's lnitial review of the responses to IEB 79-15,.

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several plants were identified as having potential problems with their deep draft pumps. These guidelines are provided for these '

plants so that the licensee or applicant involved may have a method acceptable to the staff.for demonstrating the operability of deep-draft pumps.

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DEEP DRAFT PUMP OPERATING CHARACTERISTICS In order to better understand the operating characteristics of 1

these pumps, a rotor dynamics analyses was performed to ascertain the response of the pump rotor under ste,ady state operation.

The analyses considered journal bearing to shaft dynamic response at various eccentricities and fluid viscosities. The model for the analysis depicted a typical deep draft pump utilized by the nuclear industry. The analysis resulted in recommendation,s for improving the stability of the pump rotor from externally applied inputs and by self-generated inputs.

The conclusions which were derived from the analysis and staff evaluations of North Anna, Beaver Valley and Surry facilities with similar pumps include:

1.)

Pumps with this type of configuration are prone to bearing whirl vibration problems due to the flexibility of the rotor and casing structure.

This phenomenon is accentuated as journal bearing clearance becomes large.

This phenomenon leads to bearing wear (Journal bearings).

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" Low Head Safety Injection Pucp Rotor Dynamic Analyses", by Franklin Research Center, Report FC4982, dated May 1980.

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2.) There may be natural frequencies associated with the pump assembly which occur near the operating speed of the pump.

Pump operation will drive these frequencies and can cause bearing wear. The severity of this condition is dependent on bearing diametral clearance, rotor unbalance conditions and housing flexibility. As an example, if the wear in column journal bearings becomes sufficiently large

( twice the original diametral cl earance)~so that t

these bearings are no longer active and the undamped critical frequency near the operating speed of the pump is allowed to expand, the additional uncontrolled bearing wear will occur. This wear can continue until the shaft rubs against the support structure of the bearing and can potentially sever the shaft.

3.) One acceptable method for correcting instabilities in the l

pump shaft is to utilize a journal bearing design which exhibits stable characteristics.

One such design is the

• Taper land bearing". This design is more stable than the plain journal bearing, is less susceptible to wear because

_i of the taper and will cause the bearing to form a hydro-dynamic film quickly during startup.

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4.) Stiffening uf the column sections of the pump is advantageous if there is ? column frequency near the operating speed of the pump.

The shif ting of the column frequency to a higher level will eliminate any coupling between the pump operating speed and the column frequency.

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5.) Flow in'let conditions to the pumps and su p designs can be important to' pump operability.

Certain installations have demonstrated flow characteristics which produced vortexing at the be11 mouth of the pump. This vortexing is due to sump design or sump supply line entrance con-

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ditions. This condition can contribute to additional pump vibration and wear.

Flow straightener devices, reduction of be11 mouth diameters, and bottom clearance reductions have proven to be effective in eliminating this problem.

6.) This type of pump has exhibited operational problems due to design and installation deficiencies. The high flexibility of the shaft and column make this design rather forgiving when it comes to installation deficien-cies such as misalignment between the shaf t and column,

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-S-low-precision coupling assemblies, and non-perpendicular mounting flanges. This fact however, can lead to excessive bearing wear without significant noticeable change in pump operating characteristics. To ensure proper pump operation, proper alignment should be estaolished between all mating surfaces and measures should be emphasized which prev'ent column and shaft eccentricities. These measures can include optical alignment of the column segments, use of high precision r

couplings and use of. accurate techniques to establish that the sump plumb line is perpendicular to the pump mounting fl ange.

The above findings and conclusions have centributed significantly to the development of these guidelines. The guidelines listed below are divided into installation and test areas. The subjects to be addressed in these areas are considered to be of prime importance when establishing a pump operability assurance program.

The extent to which each of the two are~as are implemented at a specific facility is dependent on specific symptoms which have

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been identified with these pumps while in operation and'during service periods.

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Implementing the measures outlined below, at North Anna 18 2 in i

total, has been shown to provide reasonable assurance that the pumps will be operable when required for their safety function. These guidelines are not intended to replace the requirements of Standard Review Plan 3.9.3, Regulatory Guide 1.68 or any other requirements presently enforced by the staff.

Rather, the l

guidelines are to be used as supplemeritary material for establishing l

deep-draft pump operability.

GUIDELINES FOR OPERABILITY INSTALLATION 1.0 INSTALLATION PROCEDURES l

Experience has shown that these pumps are prone to having operability problems as a result of poor installation procedures. The guidelines emphasize those areas of the installation procedure,which if implemented, "

could significantly improve the itkelihood of an operable pump. The procedures utilized should be :;ubmitted to the staff for review.

1.1 PUMP INSTALLATION Detennine by measurement that all shaft segments are straight a.

within tolerances specified by the manufactur'er.

b.

Determine by measurement or provide certification that all couplings (for shaft segments & ' pump to motor coupling) are.

"i of high precision as specified by tne manufacturer.

c.

Determine by measurement that all pump segment flanges are perpendicular to the centerline of the segment, that the segments are straight and that any mating surfaces are concentric to an established datum. k'here journal

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, bearing guides (SPIDERS) are used, establish con-centricity between this assembly and its mating surface.

d.

Align full pump casing assembly optically to assure i

maximum straightness and concentricity of the asse:bly.

Any equivalent rethod is acceptable, as long as the procedure stresse' colue.n straightness and concentricity.

s Assure pump to motor flange perpendicularity and that

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proper coupling installation is perforned.

f.

Assure that all mating surf 6ce bolting is properly attached and that manufacturer torquing sequences are adhered to.

1.2 SUMP INSTALLATION Assure (where used) that sump / pump mating flange a.

is perpendicular to the sump pump line.

b.

Assure that sump design prevents fluid anomalies such as vortexing or turbulence near the intake to the pump bellmouth and that incoming piping is not so designed as to allow fluid conditions favorable to these anonalies (i.e., sharp bends in piping prior to entrance. into sunp).

c.

Assure that interference does 'not exist between the surp and any pump appendage such as a seismic restraint.

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2.0, Testing Requirements The installation procedures are essential in establishing punp operability.

In addition to careful installation, testing rey be required which will verify proper operation of these pumps.

Af ter cocpletion of the installation checks, licensees or appli-cants should evaluate the need for furthcr testing and report the.results of this evaluation together with the details of any test plans in the staff.

Should tests be required, an accep' table test procedure should include the items listed.below.

The staff recognizes that the instrumentation and procedures outlined below may be difficult to implenent at all facilities and, therefore, the staff is emphasizing good installation practices which lead to operable corponents.

If tests demonstrating operability cannot encocpass all the iterrs listed below, then alternative procedures should be proposed for evaluation by the staff.

The tests should erphasize reasurement of pump dynamic characteristics and wear data I

at different stages of testing, culminating with an extrapolation of the data to the desired life goal for the pump.

2.1 Test Instrumentation The following instrumentation should be incorporated into the test procedure aside from normal flow measu'rement, pressure and vibration instrumen'.ation:

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a.)

X, Y proximity probes at three axial locations on the pump column, for measuring and recording radial positions of shaft with respect to the column.

b.)

X, Y, accelerometers (at proximity probe locations) for measuring and recording radial accelerations of the column.

c.) Dynamic pressure transducers for measuring fluid pressure at the following locations:

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1.

Bottom of Column (suction)

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2.

Mid-Column 3.

Top of Column.

d.) Shaf t Rotational speed and dynamic variation instrument.

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2.2 PRE-TEST DATA With the pump disassembled, measure all journal bearing 0.D.'s, bearing I.D.'s and calculate bearing diametral clearances.

In addition with pumps fully assembled and using the proximity probes, obtain the." clearance circle" at each of the three axial stations by i

rolling the shaft section within the clearance volume of'its bearings and in this way, establish propar operation of the p, robes.

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3.1 PNASE 1 Testing (6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> plus start-stop)

This phase of testing should be co= prised of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of testing (Break-in) followed by start-stop testing. Test conditions should simulate as nearly as possible normal and accident conditions. Parameters to be considered are flow, temperature, debris, and chemical composition of fluid being pumped.

Static torque tests should be performed before'and after the test (i.e. measure amount of l

torque required to turn shaft by hand).

Data should be taken during the six hour test at 1/2 hour intervals.

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A total of 12 start-stop tests will be performed con-sisting of a start up from zero speed up [o full-speed,

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10-minute dwell at full-speed and a shutdown from full speed to zero speed, with recording of all instrumentation during full cycle of start-stop.

Upon completion of Phase 1 testing,the following data should be obtained and recorded:

1.) Obtain the " clearance circles" using the three sets of proximity probes.

I 2Tests at North Anna 1 & 2 and Manufacturers input indicates that 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> is an adequate time interval for bearing " break in" period.

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s 2.) Measure and record the following dimensions for each bearing:

a.) Journal 0.D.

b. ) Bearing 1.D.

c.) Bearing to Journal diametral clearance d.) Establish Phase 1 test bearing wear.

THE ACCEPTANCE CRITERIA IS AS FOLLOWS:

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3-1.)

If wear is?' S mils for any bearing, wear is unacceptable and test -should be terminated. ' ~ '

3 2.) If wear is( 5 mils fcr all bearings

a. ) Reassemble the pump

b. ) Obtain " clearance circles"

c. ) Reinstall pump in test loop. '-

2.4 Phase 2 Testing (48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />)

Phase 2 testing is to be performed at full system pressure.

and temperature and fluid conditions simulating those expected during accident and nornal operation.

Before start and at conpletion of Phase 2 test.obtain neasurement of static torque.

Data should be recorded continuously during the start-up period, 3This acceptable wear value nay be modified based on manufceturers reconrendation.

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and during the shutdown period. Data should also be recorded at 1-hour time intervals during the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> test.

The following measurerents should be made at the coupletion of Phase 2 of the test:

1.) Obtain the "c1*.arance circles" using the three sets of proximity probes.

2.) deasure and record the following dibEnsions for ~each bearing:

a.) Journal 0.D.

b.) Bearing 1.D.

c. ) Bearing to Journal diametral clearance.

d.) Establish accuculated bearing wear.

THE ACCEPTANCE CRITERIA IS AS FOLLOWS:

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1.)

If accumulated bearing wear on any bearing is

)P7 mils, wea; is unacceptable and test should be termi nated.

2.)

If accumulated wear on all bearings is47 mils E

for all bearings.

f a.)

Reassemble pump

b. )

Obtain " clearance circles"

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c.)

Reinstall pump in test loop.

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5.) Phase 3 Testing (96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br />)

Phase 3 testing is to be performed at full system pressure and temperature and fluid conditions simulating those expected s

.uring accident and normal operation.

The same procedures should be follo'wed as in Phase 2 testing except that data

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may be taken with less frequency.

The same measurements should be taken at the completion of this phase as with the other phases with the following acceptance criteria:

1.) If accumulated bearing wear is) 8 : alls for any bearing 3 wear is unacceptable and test should be teminated.

2.) If accumulated wear is ( 8 mils for all bearings,3, decision needs to be made to establish:

a.)

the need for additional testing or h.)

whether or not the bearing wear will be acceptably low.

The recommended decision process is outlined below..

Plot the values of accumulated wear versus time (H) for each bearing aftt:r Phase 2 and Phase 3 tests, namely.

Wear at H2 = 54 hour6.25e-4 days <br />0.015 hours <br />8.928571e-5 weeks <br />2.0547e-5 months <br /> Wear at H3 = 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> k

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Straight lines are then drawn through the plotted values of wear and extended to the right (See example Figure 11.

If the extension intercepts the maximum acceptable value of wear (8 mils) at a value H less than the life goal for this pump, additional testing should be performed.

If the intercept of the line with wear of 8 mils exceeds the life goal for this pump, no additional testing is required and bearing wear is acceptable.

If addition.al testing

_.s is deemed necessary it should be done in a similar manner to that performed during Phase 3 with similar acceptance criteria and decision process.

It is expected that such additional testing will either show a stable pump operation with no increate in bearing wear or increased bearing wear with t.. acceptable results.

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2.6 Evaluation of Pump Acceptability

-If bearing wear (after all testing phases) is acceptably lov (as per decision process) and if vibration levels over the frequency spectrum of 3 cps to 5000 cps are acceptably low and shew no unfavorable trend of increasing magnitude during the testing, the pump may be judged acceptable for its intended use.

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