United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #: 9608120083



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Limitorque Corporation

5114 Woodall Road o P. O. Box 11318 o Lynchburg, VA 24506-1318

Telephone (804) 528-4440 o FAX (804) 845-9736



LIMITORQUE TECHNICAL

UPDATE - 93-03



SUBJECT:       Reliance 3-Phase Limitorque Corporation Actuator Motors

               (Starting Torque @ Elevated Temperature)



REFERENCE:     Potential 10CFR21 Condition Dated May 13, 1993 (Attached)



                         Issued September, 1993



The purpose of this update is to provide guidance in addressing the

referenced document.



1.   550/575 Volt 3-Phase - The tabulated data presented in the

     referenced document is applicable to 550/575 volt, 3-Phase Reliance

     motors.



2.   Motor Applicability - The tabulated data presented in the referenced

     document is applicable to all Reliance 3-phase motors.  The motor

     start torque, no-load speed, and frame size must match that given in

     the tabulation, e.g.:

          Existing Reliance 230/460, 3-phase, 60 Hz, 100'#, 1800 RPM, 210

          Frame motor design curve unavailable.  From the tabulation,

          percent current loss is 17.8 percent, and percent torque loss

          is 13.1 percent when subjected to a 155 degrees C increase in

          temperature.



3.   Deration Start Temperature - The torque reduction is to be applied

     at temperatures >40 degrees C (104 degrees F).  The tabulation

     details percent loss over a 155 degrees C change in temperature

     (i.e., from 25 degrees C to 180 degrees C).  The percent torque loss

     per degrees C for a 10'#, 1800 RPM, 56 Frame motor is:



               27.7%   =      0.179% / degrees C

               -----

               155 degrees C



     The percent torque loss for this motor operating in 100 degrees C

     ambient is:

          (0.179%) (100 degrees C - 40 degrees C) = 10.7%



4.   Temperature Rise With Motor Energized - Reliance 3-phase motors are

     designed with thermal characteristics that result in </=75 degrees C

     temperature rise in:

     a)   15 minutes @ full load running torque.



                               Page 1 of 2







Limitorque Corporation                             Technical Update 93-03



     b)   10 seconds @ locked rotor.



     A typical valve stroke time of 30 seconds will increase the motor

     temperature as follows:



          Equation omitted.



     The above example is simplistic and is given only to show that the

     motor temperature rise associated with stroking the valve is

     insignificant.  However, applications that allow the motor to draw

     locked rotor current until the system or valve stabilizes must be

     addressed.  A 5 second duration at locked rotor current will result

     in a temperature increase of </= 37.5 degrees C.  It should be noted

     that continual diagnostic testing will increase motor temperature

     and decrease output torque and thrust.



5.   Motor Speed at Elevated Temperature - Elevated temperature will

     reduce the motor full load speed.  The speed reduction is minimal

     (nearly equal to 2% or 3%) from 25 degrees C to 180 degrees C.



6.   Limitorque Corporation Sizing Equation - The standard sizing

     equation required the use of a 0.9 application factor.  If the motor

     terminal voltage is less than 90 percent, this factor may be revised

     to 1.0.  As before, there is no reduced voltage factor down to 90%

     voltage but below 90% voltage the square of the percent voltage

     available to rated motor voltage must be applied.



7.   Misprint in Referenced Document - The 2'#, 1800 RPM, 56 Frame motor

     of the tabulation is a 48 frame motor.



8.  Additional Motor Data:

     Start/RPM/Frame     % Current Loss           % Torque Loss

     1'# / 900 / 48      30% / 155 degrees C      19% / 155 degrees C

     2'# / 900 / 48      30% / 155 degrees C      19% / 155 degrees C 

     175'# / 3600 / 256  16.7% / 155 degrees C    9.9% / 155 degrees C

     150'# / 1800 /256   15% / 155 degrees C      12% / 155 degrees C



P. McQuillan

Nuclear / Special Projects Manager



                             Page 2 of 2                    





Limitorque Corporation

5114 Woodall Road o P. O. Box 11318 o Lynchburg, VA 24506-1318

Telephone (804) 528-4440 o FAX (804) 845-9736



                                        May 13, 1993



U. S. Nuclear Regulatory Commission

Washington, D. C. 20555





Attention:  Document Control Desk



                                   Re:  Potential 10 CFR 21 Condition



                              Subject:  Reliance 3[symbol omitted]

                                        L. C. Actuator Motors

                              (Starting Torque at Elevated Temperature)



Limitorque Corporation has completed an evaluation of the subject motors. 

The results of this evaluation should be utilized to determine actuator

operability at motor temperatures of 25 degrees C through 180 degrees C. 

The motor starting torque decreases with increasing temperature thereby

decreasing actuator output torque.  This condition could potentially be

reportable depending on the operating practice of the license. 

Therefore, pursuant to the requirement of 10 CFR Part 21, herein provided

is notification of a potential defect in Limitorque Corporation supplied

motor actuators or motors supplied as spare parts.



Identification of Basic Component



The affected component is the Reliance 3[symbol omitted] A.C. motor that

provides input power to actuator types SMB/SB/SBD 000 through 5 and SMB

000 through 5/HBC 0 through 7 combinations.



Discovery Date



The discovery date of this potential defect was July 27, 1989.



Nature of the Defect



The electrical characteristics of the Reliance 3[symbol omitted] A.C. 

Limitorque Corporation valve actuator motor are temperature dependent and

locked rotor torque and locked rotor amperage will vary with motor

temperature.  Typically locked rotor torque and locked rotor amperage

decrease as motor temperature increases.  The attached tabulation details

both parameters percentage changes in the temperature range of 25 degrees

C to 180 degrees C.  The percentage change is linear with respect to

temperature for parameters with baseline data at 25 degrees C.





Page 2

May 13, 1993

Potential Part 21 Condition



The tabulation provides data that is relevant to standard Limitorque

Corporation motor designs.  The user must ensure that the motor

performance curve number shown on the tabulation (e.g. M2735A) is

applicable to the motor that is undergoing analysis.  If this data is not

available, the licensee may furnish the applicable motor identification

numbers to Limitorque Corporation in order to make this determination.



The following guidance is offered:



1.   Credit should be taken for the locked rotor amperage decrease which

     will result in a higher available motor terminal voltage.



2.   Motor temperature rise due to prior motor energization and motor run

     time (valve strike time) must be accounted for.



3.   The tabulated data is expected to also predict 550/575 V 3[symbol

     omitted] 15 minute duty motor performance.  The starting torque

     rating, no load speed and frame size of the 550/575V motor must

     match the attached data to allow this analysis.  The licensee is

     requested to provide the motor identification numbers to Limitorque

     Corporation to verify this assumption.



4.   The tabulated data is based on analysis by Reliance Electric. 

     Limitorque Corporation performed testing on two motor designs

     (quantity of 5 motors) which validated the analysis.



Equipment Affected



1.   Same as the basic component identification.

2.   Previously supplied technical data that may be used as the basis for

     operability justification.  Where applicable this data should be

     revised to account for the applicable elevated temperature effects.



Licensee Corrective Action



Ensure operability justification considers the effect of motor

performance at the applicable motor temperature.



Limitorque Corporation Corrective Action



Revise the selection procedure for safety related actuators, motors, and

technical data packages to account for motor performance at the

applicable motor temperature.





Page 3

May 13, 1993

Potential Part 21 Condition



A copy of this notification has been sent to the Nuclear Regulatory

Commission (NRC) under a separate cover letter.



Any questions or clarifications regarding the above notification may be

directed to P. McQuillan, Nuclear/Special Projects Manager at (804) 528-

440 Ext. 714.



Signed:



I. E. Wilkinson

Vice-President of Engineering



Attachment



cc:  T. Mignogna

     Part 21 Notification File





Table "Current/Torque Changes from 25 to 180 Centigrade" omitted.





ATTACHMENT

Part 21

May 13, 1993



                            LIST OF RECENTLY

                         REPORTED PART 21 ISSUED



10 CFR 21                                              NRC       

Evaluation                                             Report

Number              Topic                              Date



36             Torque Switch Groove Pin                04/03/91



37             Worm Gear Failures                      08/04/92



40             Declutch Lever Seismic Test Resonance   12/07/92



41             SBD 1 Bolt Thread Engagement            10/05/92



43             Failure to Comply - L/C failed to       05/10/93

               issue the required interim reports

               to the NRC open more than 60 days





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