ML17207A637
| ML17207A637 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 12/04/1979 |
| From: | Herrell D, Mott J, Jay Robinson TECHNOLOGY FOR ENERGY CORP. |
| To: | |
| Shared Package | |
| ML17207A636 | List: |
| References | |
| R-9019, NUDOCS 7912110326 | |
| Download: ML17207A637 (20) | |
Text
Technology for Energy Corporation 10431 Lexington Drive
, Knoxville,Tennessee 37922 61 5 S66-5856 TEC REPORT NO ~ R-9019 TIME RESPONSE TESTING OF RTDs FROM ST LUCIE NUCLEAR POWER PLAhT by J. E. Mott DE C. Herrell J
Ci Robinson J
Ei Jones Technology for 'Energy Corporation 10 770 Dut ch tovn Road Knoxville, Tennessee, 37922 Septeraber 1979
TABLE OF CONTENTS Page 1.
XNTRODUCTXON.o.........o..o....o.e..
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l-l 2.
DATA ACQUISITION
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2-1 2. 1 Test Equipment
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2-1 2.2 Signal Conditioning and Control......................
2-2 2.3 Test Procedures.....;................................
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RESULTS e ~ ~ s ~ o ~
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3-1 3.1 Results
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/%AT C~
o CONCLUSIONS
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1.
INTRODUCTION The purpose of tnis report is to present the results of time constant measurements made at Technology for Energy Corporation's (TEC) laboratory in Knoxville, Tennessee.
These measurements were funded by Florida Power and Light Company as a part of their sensor time response measurement program.
Resistance thermometers (RTDs) furnished by Florida Power and Light Company from their St. Lucie site were tested using both plunge and LCSF techniques.
The purpose of these tests was to verify that LCSR tests and plunge tests gave the same time constant for these RTDs.
Industry standards for measuring RTD time constants are to plunge the sensor in a 170'F bath with a fluid velocity of three feet/second.
Since reactor con-ditions are considerably different (500-600'F, 40 ft/sec) from industry standards, most of the tests performed here were done in a 540'F bath of lead.
The velocity of the lead was set at one foot/second in order to obtain convective heat transfer coefficient similar to that obtained at reactor conditions Eight sensors were tested.
They are identified in Table 1.1.
All were tested in well 60 in lead, four were tested in well 66 in lead and in well 60 in water.
Three were tested without the well (bare) in the water.
In the balance of this report, we describe the experimental setup and test procedures and present the results of this testing progra
>Details of the LCSR testing method are described in TEC Report R-8007.
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1-2 TABLE 1.1 Sensor 5 7147 5 71'51 5 7161 57165 57170 A8994 B5630 B5642 T De 104vc 104vc 104VC 104VC 104VC 104vC 104-16 9 6-1 104-1696-1 Purchase Date October 1971 October 1971 Oc tober 1971 October 1971 October 1971 January 1976 I
April 1979 April 1979 Time in Peactor 33 months
'I 33 months 33 months 33 months not used not used not used not used
2.
DATA ACQUISITION INSTRUMENTATION AND MEASUREMENTS 2.1 Test Equipment All testing was performed using TEC's RTD Test Stand.
This stand consists of an insulated tub in which the fluid to be used in a test may be rotated at a given constant speed.
The temperature.of the fluid is I
contr'oiled by a p'roportional solid-state furnace controller, utilizing a thermocouple for rapid response to any slight temperature change in the fluid.
A sliding, vertical carriage is used to hold the RTD at a fixed radius perpendicular to the rotating fluid bath.
During plunge testing, an electrically actuated pneumatic cylinder 'serves to propel the carriage and mounted RTD approximately 3.75 inches.
This immerses approximately 3 inches of the RTD or RTD and well into the fluid.
Transit time for the assembly is approximately 0.1 seconds, from point of electrical actuation to fluid contact.
Two different fluids were utilized in this 'test sequence.
Mater
- was used as a base for comparison of tests performed at TEC and earlier tests performed by the RTD manufacturer.,
The ~ater batn was heated to a temperature of approximately 174 degrees F and rotated at the speed required to yield a 3.0 feet per second fluid velocity at tne RTD s ur face.
The lead-tin alloy bath was heated to approximately 540 degrees F
and ro"ated at the speed required to obtain a one foot/second fluid velocity at the RTD surface.
The heat transfer coefficient at this con-dition is 12,000 B/hr ft2-F which is the sam'e as that in a 40 ft/sec s tream of 540'F water.
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0 2-2 2.2 Si nal Conditionin and Contxol" Special instrumentation designed, fabricated, and tested by TEC was used in this measurement.
A block diagram of the test nstrumentation is presented in Fig. 2.1.
The rack mounted modular instrunentation system consisted of a TEC Model 1131 Constant Cuxrent Source, Model 1121 Control Module, and Model 1 101 LCSR Bridge.
Xn addition, three separate modular power sources were utilized to:
(1) provide a floating excitation voltage for the bridge (relative to the signal conditioning circuitry), (2) power the control and switching logic, and (3) provide the normal instrumentation power for signal conditioning.
The RTD under test was interfaced with the Model 1101 LCSR bridge via a special 3~ire test cable.+
During an LCSR test, a small standby current is furnished the RTD from the Model 1131 constant current I
source.
Upon initiation of the LCSR step (controlled from the model 1121 Control Unit),,
a controlled step in RTD current is-made and the l
output from the Model 1101 LCSR Bridge is sampled by the. computing system and saved on floppy disk.
During these tests, automatic control of the LCSR steps was pro-vided by the computing system.
During plunge'esting, the bridge was balanced with the RTD above the fl id bath.
Compute". sampling was initiated when the RTD and carriage began to move toward the fluid ba'th and continued during a time period specified by the operator.
Gains were determined by a single test performed during setup for each RTD.
-The RTD was connected to the bridge in a two wire configuration.
Nodule Power l3r idge power Su pp 1)
Model 1131 Constant Current Source Model 1101 LCSR Bridge Signal Conditioning 3-Wire Test Cable RTD Under Test LCSR Output Control Power Model 1121 Control Vnit Auto Ste Input Computing Sys tern Carria e
Home Pigure 2.1 LCSR Measurement Instrumentation.
2-4 During LCSR testing, the bridge was balanced with the RTD in the fluid bath.
Several sets of tests were initiated by the computing system on a timed basis.
Sufficient time was intr'oduced between tests to allow the RTD under test to return to equilibrium.
2.3 Test Procedures Eight RTDs and two wells were tested.
All eight RTDs were tested in well 60 in molten lead-tin alloy.
Pour representative RTDs were tested'in well 66 in molteri lead-tin alloy.
The same four RTDs were tested in well 60 in water.
Three bare RTDs were tested in water.
In all cases, the test procedure to be followed was simil'ar.
The RTD and well or the bare RTD was mounted securely in the TEC test equip-ment.
Measurement of the resistance of the connection to the LCSR bridge was made to verify correct connection of the device.
Phen the RTD reached thermal" equilibrium, the instrumentation was electrically balanced.
A preliminary plunge test was performed to allow possible modification of instrumentation gain to achieve maximum allowable signal magnitude.
The KTD was removed from-the fluid and allowed to return to a balanced condition.
A plunge test was then per-formed and the digitized results were saved on, floppy disk.
The bridge was balanced in the new environment and five LCSR measurements per formed.
Results of each test were saved on floppy disk, after computer d igiti..ation, for later o f&line reduction.
The RTD was removed from the fluid and allowed to regain thermal equilibrium.-
The six-test cycle was then repeated.
~ Once the 12 test cycle was completed, the next RTD was mounted and the test cycle repeated.
3.
RESULTS 3.1 Results The results of the tests described in Chapter 2 are presented in Tables 3.1, 3.2, and 3.3.
The plunge time constant error of 3% was determined in'arlier tests of repeatability of plunge tests.
The LCSR errors result from uncertainties in both geometry and eigenvalues.
The geometric uncertainties are platinum radius (+0.010") and sheath radius
( +0.010").
The uncertainty in first eigenvalue is +5X and +10X in the second eigenvalue.
The agreement of the plunge and LCSR tests was quite acceptable with an average difference of 0.3 seconds or 5X of the measured time H
constant.
Table 3.4 presents a comparison of plunge time constants of sensors in two wells and in both lead and water.
Three observations can be made from these results.
First, the time constant of a bare sensor has little effect on.its time constant in a well.
Bare sensor B5642 was 1.2
/
seconds slower than bare sensor A8994 yet their time constants in both wells in lead was virtually identical.
- Second, the time constant was not dependent on the well.
Sensor 57161 was faster in well 60 than in well 66 while the other three were faster in well 66.
Finally, surface transfer and bulk temperature had little direct effect on the time consta..t since there is no consistant difference in tne 540'F-lead resu' and the 170 F-water results, 3-1
3-2 TABLE 3.1
'LUNGE AND LCSR TINE CONSTANTS lN 540'P L"AD Pell Sensor Plunge c
LCSR r 60 60 60 60 60 60 60 60 66 66'6 66 57147 57151 57161 57165 57170.
A8994 B5630 B5 642 57161 57165 A8994 B5642
- 5. 9+0.2
- 6. 0+0.2
- 5. 0+0. 2
- 6. 9+0. 2 5.4+0. 2
- 6. 7+0.2 5.6+0.2 6 8+0.2 5.4+0.2 5.9+0.2
- 6. 2+0.2
- 5. 9+0. 2 6 ~ 0+0.4
- 6. 0+0.4 4 8+0 3 6.5+0 4 5.2+0 2
- 7. 0+0.4 5.8~0.4 6.9+0.4-6 0+0 2 5 3~0.5 7 0+0.5 5 7+0 3
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3-3 TABLE 3 '
PLUNGE AND LCSR TIME CONSTANTS IN 170'F WATER Well Sensor Plunge T
60 60 60 60 57161 57165 A8994
. B5642
- 5. 9+0. 2
- 5. 9+0.2
- 6. 8+0. 5
- 8. 3+0. 7
3-4 TABLE 3.3 PLUNGE TIME CONSTANTS OF BARE SENSORS Sensor Time Constant A8 994 B5 630 B5642
.2.3-+0. 1 2.2+-0.1 3.4+0.1
3-5 TABLE 3i4 COMPARISON OF PLUNGE TIME CONSTANTS Sensor Lead-Well 66 Lead-Well 60 Water Well 60 5 7161 5.4 5.0 5
9 5 7165 5.9 6 ~ 9 5
9 A8994 B5642 6.2 6.7 6.8 6.8 8.2'
3-6 The conclusion to be drawn from these results is that the contact resistance between sensor and well is an extremely important parameter that can contribute up to 50X of the time constant.
This resistance is a function of mechanical tolerances, differential thermal expansion and mounting procedures.
A sensor removed from a well and then rein-serted may experience a change in time constant of up to a second or two.
- Thus, a sensor and well may be 'tested in the laboratory and its time constant obtained; then its time constant can be significantly modified after disassembly,. welding into the piping and reassembly.
This change cannot be interpreted as a degradation in the sensor s'ince this will be the normal occurrence.
The last observation to be made from the results of these tests is
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that there is no consistant difference in the time constant of the sen-sors (57147-57165) that were removed from the reactor and the sensors (57170,
- A8994, B5630 and B5642) which had never been used.
There is no evidence that any degradation occurred during 33 months operation.
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4.
CONCLUSIONS The following conclusions can be drawn from the results of these tests:
1.
No measureable degradation in time constant could be attributed to three years of operation in the St. Lucie reactor 2.
No difference in time constants obtained from plunge tests and time constants obtained from LCSR tests and TEC's continuous
,model transformation were observed.
3.
Contact resistance between sensor and well was the determining factor in these measurements.
Thus, laboratory tests are of little use in predicting in-situ time constants.
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