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ISTOG Winter 2010 – Ed Cavey Fermi 2

ISTOG Winter 2010 – Ed Cavey Fermi 2. ISTOG Issues - Code Inquiries / Proposed Code Cases. ISTOG Issues from 2010 January meeting and subsequent telecons Accuracy requirements of ISTB-3500 Digital vs Analog Suction pressure accuracy relative to DP accuracy

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ISTOG Winter 2010 – Ed Cavey Fermi 2

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  1. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases • ISTOG Issues from 2010 January meeting and subsequent telecons • Accuracy requirements of ISTB-3500 Digital vs Analog • Suction pressure accuracy relative to DP accuracy • Smooth-running pump vibration criteria ISTOG submitted inquiries to ASME ISTB Committee related to the first two items above – this presentation will discuss the responses to those inquiries and follow-up activities. Also, recent experiences with NRR on Relief Requests on the second and third items above will be discussed, with recommendation to ASME ISTB for possible action

  2. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases • Accuracy requirements of ISTB-3500 Digital vs. Analog • This item generated a very animated discussion during the January ISTOG meeting. The problem lies with the following wording in ISTB-3510(a). • For individual analog instruments, the required accuracy is percent of full-scale. For digital instruments, the required accuracy is over the calibrated range. • Consider the following from NUREG-1482 Section 5.5: • For Group A and Group B pumps, OM Subsection ISTB 3510 requires an accuracy of +/- 2% of full scale for analog instruments, +/- 2% of total loop accuracy for a combination of instruments, or +/- 2% of reading over the calibrated range for digital instruments.

  3. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Accuracy requirements of ISTB-3500 Digital vs. Analog (cont’d) ISTOG submitted the following inquiry in 2010 Inquiry Code Edition: ASME OM Code 1998 and later Editions and Addenda Question 1: Is it the intent of ISTB-3510(a) that the required accuracy of digital gauges be expressed as "percent of reading"? Answer: No Question 2: Is it the intent of ISTB-3510(a) that the required accuracy of digital gauges be expressed as "percent of maximum calibrated value"? Answer: Yes.

  4. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Based on the ISTOG Inquiry the following proposed Code change was drafted

  5. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Accuracy requirements of ISTB-3500 Digital vs. Analog (cont’d) Of particular significance was the following statement in the response – It was never the intent of the Code Committees to require higher calibration accuracy for digital instrumentation than for analog instrumentation. The question now is how current IST engineers can deal with this issue. What can be cited as a reference? It will be many years before this Code change can become useful. Would a guidance standard from ISTOG that describes the decision of the ISTB Committee be an adequate citation source in the interim?

  6. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Suction pressure accuracy relative to DP accuracy This issue covers all the scenarios where either direct or indirect measurement of pump suction pressure is done using instruments which can meet Group A/B +/- 2% accuracy but not the CPT ½% accuracy. The fundamental concept is that IF the resulting value of DP is accurate to within +/- ½% it should not matter what the accuracy of the suction pressure measurement was. Inquiry Code Edition: ASME OM Code 1998 and later Editions and Addenda Question: Is it within the intent of ISTB-3510(a) and Table ISTB-3500-1 that a combination of gauge accuracies may be used as long as the resultant DP value is accurate to within the requirements of ISTB-3500-1. Reply: Yes

  7. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Suction pressure accuracy relative to DP accuracy (contd) Alternative Inquiry / Response as Code Case Code Edition: ASME OM Code 1998 and later Editions and Addenda Question: What alternative to the instrument accuracy requirements in ISTB-3510(a) may be used when measuring differential pressure of a pump with separate suction and discharge pressure instruments? Reply: The individual suction and discharge pressure instrument accuracies in Table ISTB-3500-1 need not be met as long as the resultant DP measurement meets the accuracy requirement of Table ISTB-3500-1. The accuracy of the derived DP value shall be calculated as the square root sum of the squares of the individual suction and discharge pressure accuracies expressed as +/- psi.

  8. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Suction pressure accuracy relative to DP accuracy (contd) ISTB RESPONSE - INTENT PORTION Question: Is it the intent of ISTB-3510(a) General, that an individual instrument used for suction pressure that does not meet the requirements of Table ISTB-3510-1 can be used provided the resultant DP determination meets the accuracy requirement of Table ISTB-3510-1 (Required Instrument Accuracy). Reply: Yes Question: Is it the intent of ISTB-3520(b) Differential Pressure, that one of the individual instruments used to determine differential pressure by taking the difference in pressure between the pressure at a point in the inlet (e.g., suction pressure) and a point in the discharge pipe not meet the requirements of Table ISTB-3510-1 provided the resultant DP determination meets the accuracy requirement of Table ISTB-3510-1 (Required Instrument Accuracy). Reply: Yes

  9. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Suction pressure accuracy relative to DP accuracy (contd) The responses from ISTB show that, as far as the intent, it is the DP value which is the critical measurement. Use of a highly accurate discharge pressure gauge can offset a lower accuracy suction pressure – as long as the resultant DP value meets the ½% requirement. This Code change would eliminate the need for relief which several plants now have to submit. It would also allow for the use of existing plant analog gauges where the use of a temporary digital gauge installation is exceedingly difficult. Again – need to consider how this can be made useful to ISTOG members in the short term. A Code Case may be desirable but still involves a separate wait for a Reg Guide 1.192 update. An ISTOG guidance standard may not be appropriate for this issue since it is tied to such specific wording in the Code. Thoughts????

  10. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Smooth-running pump vibration criteria There have been many relief requests submitted and approved over the last few decades on this issue. The technical concern is that pumps/motors with exceptionally low baseline vibration data will have correspondingly low Alert criteria. Here is an example from Fermi: R3001C008 Diesel Generator 14 Service Water Pump EC1 baseline vibration (> pump/motor replacement) => 0.009 ips Alert criteria = 0.009 * 2.5 = .022 ips Our vibration acquisition equipment is accurate to app. +/- .019 ips. You can see that we could have a measurement which is at or near Alert criteria due solely to instrument and/or test flow variation, with no corresponding pump/motor degradation.

  11. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Smooth-running pump vibration criteria (cont’d) The typical relief request approved by the NRC provides for establishing a bottom threshold of 0.05 ips for a baseline reading. The acceptance criteria for all points with a baseline < 0.05 ips would be 0.125 (2.5x) and 0.300 (6x). Fermi recently received approval for relief on this subject, however we proposed a 0.04 ips minimum baseline. That was based on evaluation of all low baseline pumps/motors, with the majority well under 0.04 and only a few between 0.04 and 0.05. Obtaining this relief typically requires commitment to provide coverage of these components under effective PM/PdM programs. The use of 0.04, with minimum Alert / RA limits of 0.100 and 0.240, as the Fermi standard versus the traditional 0.05 provided additional conservatism that seemed to offset NRC concerns about potential lack of early degradation.

  12. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases Smooth-running pump vibration criteria (cont’d) ISTOG and ASME ISTB should work together to provide for a Code change or Code Case which addresses this issue and eliminates the need for such redundant relief requests. Any ideas on how best to proceed on this topic?

  13. ISTOG Winter 2010 – Ed Cavey Fermi 2 ISTOG Issues - Code Inquiries / Proposed Code Cases • In summary, ISTOG will continue to: • Gather innovative testing ideas from around the industry • Identify common areas of Code implementation difficulty • Then • Draw upon the collective knowledge and experience of our membership to study these issues and develop technically sound guidance standards and/or recommendations and inquiries to ASME QUESTIONS?????

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