ML20101H471
| ML20101H471 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 06/08/1992 |
| From: | POWER AUTHORITY OF THE STATE OF NEW YORK (NEW YORK |
| To: | |
| Shared Package | |
| ML20101H453 | List: |
| References | |
| [[::JAF-RPT-MISC|JAF-RPT-MISC]], JAF-RPT-MISC-00, NUDOCS 9206290365 | |
| Download: ML20101H471 (13) | |
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4 ATTACHMENT Ill to JPN 92-030 ATTS TRANSMITTER RESPONSE TIME TESTING METHODOLOGY (JPTS 92 010) i
. T New York Power Authority JAMES A. FITZPATRICK NUCLEAR POWER PLANT Dccket No. 50-333 hk ADO O g3
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ATTS TRANSMITTER RESPONSE TIME TESTING METHODOLOGY JAF-RPT-MISC-00543 PREPARED BY NV ibm *S DATE 6 [B/9 Z.
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ATTS TRANShITTER RESPONSE TIME TESTING M2THCDOLOGY The Response Time Testing (RTT) methodology proposed here applies to transmitters whose dynamic response exhibits linear first order characteristics. Rosemount transmitter models 1153 and 1154 are linear first order instruments, therefore this methodology applies. The proposed methodology for performing sensor (Rosemount transmitter) Response Time Testing (RTT) will consist of verifying the transmitter time constant as defined by NEDO-21617-A, Section 3.3.2 which states:
"The transmitter response time is measured in terms of the ' time constant', which ls defined as the time taken -
for the output to reach 63% of the final value following a step input."
The time constant of a transmitter is virtually independent of the direction of the step change, ie, increasing or decreasing process variable. In order to provide the most rapid pressure step change input to the transmitter, the transmitters will be pressurized to an equivalent increased signal level and then rapidly depressurized to atmosphere to most closely approximate a step change; hence the step change will be in the decreasing direction. Figure I shows an actual recorder trace of the step change as monitored by a fast (1 ms) pressure transducer and the response of a typical Rosemount transmitter. The actual step change input is an expcnential function which approximates a step change. In order to ensure conservatism in the methodology, the initiation point of the step (time t q ) will be considered to be the step change. The time constant is the measured delay from t o until the transmitter response trace reaches 63% of the step _
magnitude. Since the input pressure change is not a perfect -
step change, the transmitter response reflects this added test method-induced delay, thus ensuring inherent conservatism in the measurement of the transmitter time constant.
The proposed methodology will optimize cost / benefit aspects because the test is easy to setup and collect data, it uses minimal test equipment and is simple to conduct, requires minimal time in the plant per transmitter (based on trial experiences during testing to support the ATTS Enforcement Conference) thus improving ALARA and optimizing I&C department resources.
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Figure 1 Step Change Input and Transmitter Response Note that the response time of a linear first order system can also empirically be determined by monitoring the system's response to a linear ramp input. This methodology is presented in EPRI NP-267 and is presented below. Also note that both methodologies are analytically valid.
The dynamic response of a linear first order system to both step and ramp inputs is well understood and is fundamental to all linear first order systems Page 2 of 10 t
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ATTS TRANSMITTER
- RESPONSE TIME TESTING METHODOLOGY The relationship between the transmitter time constant and actual time delay associated with "respense time" is as follows:
- 1. Response time is defined in fairly consistent terms in the BWR standard technical specifications and ISA S67.06:
The time interval from the time when the monitored variable exceeds its trip setpoint until the time when a protective action is initiated.
This definition is consistent witt. the definition of sensor (transmitter) response time from EPRI NP-267 which is shown graphically in Figure 2.
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o I N TM A g gg Figure 2 Ramp Rate Delay Time Measurement Thus, the EPk- methodology specified a linear ramp input to the transmittet such that the process ramp begins above the trip setpoint and proceeds through and below the setpoint (or vice-versa).
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ATTS TRANSMITTER RESPONSE TIME TESTING METHODOLOGY
- 2. The Rosemount transmitter r.odels 1153 and 1154 are first-order, linear instruments. Therefore. the transmitter output response signal will be an exponential function with a steady state output which has the same slope as the input (same as is shown in Figure 2). The time lag between transmitter input and output in this case at the trip setpoint is also defined as the transmitter time constant as shown in Figure 3 from Appendix E of EPRI NP-267, " Analysis of the Suitability of Step and Ramp Hydraulic Signals":
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"r (Time Constant) can also be determined directly from the visicorder traces, as the elapsed time between w.2en the reference and process sensors reach some fixed pressure (e.g., the process sensor setpoint) " .
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-ATTS TRANSMITTER RESPONSE TIME TESTING METHODOLOGY By definition in EPRI NP-267 Section 1.0: I "It should be noted that the meaning usod in this study for the phrase ' sensor response
.. . time' is actumlly the elapsed time delay for the sensor to produce a tripped output st ate from the time that the process variable reached the trip setpoint value at the ssnsor input."
Tnus, sensor response time as reasured by the linear ramp method of EPRI NP-267 is also the steady state time lag shown in Fig. 3 and is therefore an alternate method of measuring the tf~r constant for a first order linear instrument.
- 3. EPRI NP-267, Appendix E states that the disadvantage of the step input methodology is that it requires exact determination of the step initiation point t o. The JAF step input methodology eliminates this disadvantage by conservatively assuming to to begin the instant that the test solenoid valve is energized (or deenergized).
Additionally, as agreed on by General Electric (Ref. 1):
"The individual sensor response time may be measured by the alternative method of applying a step change of the particular parameter as proposed by JAFNPP. This method provides a conservative value for the sensor response time, an6 confirms that the instrument has retained its specified electro-mechanical characteristics."
Furthermore,.as stated in Ref. 4, page 3-2, when referring to the step test mothed:
"This is usually a conservative estimate of the asympototic ramp time delay. The step test is used in a few nuclear power plants using equipment that is setup by utility personnel."
Therefore, measurement reselts of the Time Constant using
. the proposed step change _ test nathodology are a conservative representation of the ' sensor response time' specified by EPRI NP-267.
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ATTS TRANSMITTER
. RESPONSE TIME TESTING METHODOLOGY The specific details for implementing this RTT methodology are
-separated-into two distinct categories: Gauge Pressure Transmitters and DP'(level / flow) Transmitters. The best exponential response of a Rosenount transmitter occurs when it's calibration is zero-based and a full scale st(p input pressure is obtained. Most transmitter applications are <such that their calibrations are not zero-based. Elevation and suppression of-the transmitter zero will result in an output signal response which is not a true exponential. However, although the following procedures for inputting a full scale step change to the transmitters may nct result in a perfect exponential response, the assumption of an exponential response is still valid in determining the transmitter time constant (attachment 1).
Gauce Pressure-Transmitters 02-3 PT-5 5 ( A-D) 0 2-3 PT-13 4 ( A-D)-
Referring to-Figur'e 4, the following actions are performed to conduct the transmitter RTT:
Pressurize transmitter to approximately its upper calibrated range.
Close 1/4 turn ball valve on test rig.
Turn on recorder-(set up for SV full scale and 200 mm/sec).
Start. recorder and initiate transmitter response by toggling test switch that otaens solenoid valve.
After signal response output stabilizes, stop recorder.
This_ method allows the input pressure step initiation point (t ) o -
to be_" marked" by the SOV energizing (voltage step change on
. recorder), and the transmitter output signal response is measured at the trip unit and recorded on a high-speed strip chart recorder. The transmitter time constant is determined by measuring the time t, -t a- signal delay at 63% of the total step change on the recorder trace.
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. EJdPONSE TIME TESTING METHODQLOGY I
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Figure 4 Gauge Transmitter RTT Equipment Setup Level / Flow transmitters 02-3LT-101(A-D) 02-3LT-57A,B 02-3LT-58A,B O2DPT-116, 117, 118, 119 ( A, B , C, D) _
Referring to Figure 5, the following actions are performed to conduct the transmitter RTT by applv!'.ig a. decreasing step change to both the low side of the transm;er (increasing DP) and the high side of the transmitter (de.. -'. sing DP) . The main steam line flow transmitters contain c.echan: cal pin-type snubbers on the process sensing lines and filtor capacitors on the signal input to the master trip units. Tnis method will allow the time delay contribution from both of tnese devices to be included in the transmitter output signal reaponse, such that all applicable delays are accounted for in the rime constant measurement.
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ATTS TRANSMITTER RESPONSE TIME TESTING METHODOLOGY
'Decreasina DP Steo
- Pressurize the Hi-side of the transmitter via the water pots to approximately its upper calibrated range.
Close pressure source isolation valve.
Turn on recorder (set up for SV full scale and 200 mm/sec).
- Start recorder and initiate transmitter response by toggling test switch which will open the solenoid valve.
After signal response output stabilizes, stop recorder.
Jncreasinc DP Sten Pressurize the Hi and Lo side of the transmitter to approximately its upper calibrated range.
-- Close the pressure source isolation valve, and Hi side air isolation valve.
Start the recor' der and open the solenoid valve by toggling the test switch to initiate the pressure step change.
After signal response, output stabilizes, stop recorder.
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Figure 5 Level / Flow Transmitter RTT Equipment Setup Page 8 of 10 n
i - ATTS TRANSMITTER
, RESPONSE TIME TESTIPG METHODOLOGY In a manner similar to the gauge pressure transmitters, the time constant is determined by measuring the time t, (step initiation)
-to- signal delay at 63% of the total step change on the recorder trace.
This method of mer;uring the transmitter time constant is a technically valid, repeatable, resource-effective, and ALARA-consistent means of verifying proper transmitter response time.
These test results are a subcomponent of the total channel response time, which can be trende1 over time to provide a predictive, diagnorcic too' for fucure assessment of equipment _
performance.
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, s. ATTS TRANSMITTER
.- . RESPONSE TIME TESTING METHODOLOGY References
- 1. .NEDO-21617-A,' December 1978, Analog Transmitter / Trip Inputs, -)
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- 2. Basis for sensor-Response Time Testing (RTT) at the JAFNPP, General Electric, April 28, 1992, [[::JAF-RPT-MISC|JAF-RPT-MISC]] '0542
- 3. Instrument-Society of America (ISA) standard-S67.06,
-Response Time Testing of Nuclear Safety-Related Instrument.
Channels in Nuclear Power Plants
- 4. EPRI NP-7243, May-1991 - Investigation-of Response-Time Testing Requirements-Attachments
- 1. Rosemount lettar dated 5/29/92, Rosemount Pressure Transmitter Response Time Testing, to J. .Lazorus from Timothy J. Layer.
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May 29,1992 Mr. John Lazarus New York Power Authority J. A. Fitzptrick Plant P.O. Box 41 Lycoming, NY 13093 Subj: Rosemount Pressure Transmitter Response Time Testing -
Dear Mr. Lazarus,
Rosemount has received your transmittal, dated May 20,1992, regarding response time testing procedures for Rosemount pressura transmiaers installed i at the J. A. Fitzpatrick Station and have the following comments:
. The overall methodology, procedure and accompanying descriptions follow the same descriptions and methodology RosemouM would utilize to determine response times of pressure transmitters.
. Page 1 of 7: The second paragraph starting with "The time constant of a transmitter is indeoendent of the direction of the step change . " This should be stated as " Virtually Independent" since some rare calibrations could result in different time constant measurements for increasing and decreasing step changes. Another example is if a transmitter is under a sensor oilloss condition, here again the time constant measurement may differ for -
increasing or decreasing step changes depending upon which side of tha sensor was effected by the oil loss condition.
. Page 4 and 5 of 7: Our comments here a merely a clarification regarding a transmitters calibrated range and the response to a step change. The best exponential response of Rosemount pressure transmitters occurs when the unit calibration is zero based and a full scale step input pressure is obtained.
Most all transmitter applications will not include transmitters with zero based calibrations. Elevation and suppression of the transmitter zero will result in a response which is not a true exponential. Therefore, the pocadure to include a step pressure change equal to the full scale calibration of the transmitter may not result in a perfect exponential response. However, the assumption of an exponential response is valid in determining Time Constants for most all calibrated ranges.
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NYPA 05/29/92 Page 2 L-In summary, the methodology and procedures outlined in your transmittal are concluded as valid and correct in determining the time constants of Rosemount pressure transmitters. The above comments are offered to aid in clarification of possible results from these test procedures.
If there are any questions, please do not hesitate to contact me at (612) 828-3540.
Sincerely, ,
Timothv.J. Layer 7
Marketing Engineer Rosemount Nuclear Products TJL/
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