ML12300A224
| ML12300A224 | |
| Person / Time | |
|---|---|
| Site: | Monticello, Boiling Water Reactor Owners Group  |
| Issue date: | 08/31/2012 |
| From: | Kalra A Sulzer Pumps (US), BWR Owners Group |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML123000308 | List: |
| References | |
| BWROG-12051 BWROG-TP-12-014, Rev 0 | |
| Download: ML12300A224 (15) | |
Text
Containment Accident Pressure Committee Task 6 - NPSHR Test Instrument Inaccuracy Effect on Published Results (CVDS Pump)
Author:
Ankur Kalra (Sulzer Pump)
Project Manager:
Kenneth Welch (GEH)
Committee Chairman:
John Freeman (Exelon)
BWROG-TP-12-014 Revision 0 August 2012
BWROG-TP-12-014 REV 0 INFORMATION NOTICE Recipients of this document have no authority or rights to release these products to anyone or organization outside their utility. The recipient shall not publish or otherwise disclose this document or the information therein to others without the prior written consent of the BWROG, and shall return the document at the request of BWROG. These products can, however, be shared with contractors performing related work directly for the participating utility, conditional upon appropriate proprietary agreements being in place with the contractor protecting these BWROG products.
With regard to any unauthorized use, the BWROG participating Utility Members make no warranty, either express or implied, as to the accuracy, completeness, or usefulness of this guideline or the information, and assumes no liability with respect to its use.
BWROG Utility Members CENG - Nine Mile Point Chubu Electric Power Company DTE - Fermi Chugoku Electric Power Company Energy Northwest - Columbia Comisión Federal de Electricidad Entergy - FitzPatrick Hokuriku Electric Power Company Entergy - Pilgrim Iberdrola Generacion, S.A.
Entergy - River Bend/Grand Gulf Japan Atomic Power Company Entergy - Vermont Yankee J-Power (Electric Power Development Co.)
Exelon (Clinton)
Kernkraftwerk Leibstadt Exelon (D/QC/L)
South Texas Project Exelon (Oyster Creek)
Taiwan Power Company Exelon (PB/Limerick)
Tohoku Electric Power Company FirstEnergy - Perry Tokyo Electric Power Company NPPD - Cooper NextEra - Duane Arnold PPL - Susquehanna PSEG - Hope Creek Progress Energy - Brunswick SNC - Hatch TVA - Browns Ferry Xcel - Monticello
BWROG-TP-12-014 REV 0 2
Executive Summary This BWROG Technical Product provides an evaluation of the potential effects of the inaccuracies of vendor test instruments on the results of factory NPSHR testing. The evaluation is based on the Sulzer CVDS model pump used at the Monticello station and at other BWR stations.
Implementation Recommendations This product is intended for use to address (in part) issues raised in the NRC Guidance Document for the Use of Containment Accident Pressure in Reactor Safety Analysis (ADAMS Accession No. ML102110167). Implementation will be part of the BWROG guidelines on the use of Containment Accident Pressure credit for ECCS pump NPSH analyses.
Benefits to Site This product provides a technical response to the NRC questions about the potential uncertainty in published NPSHR test results that originate from the inaccuracies of test instruments used during factory testing.
QUALITY LEVEL SULZER PUMPS (US) INC. DOCUMENT ASME CODE SECTION Direct DOC. NO: E12.5.1914 Indirect ORDER NO: 100072780 CLASS NO.
CODE EDITION (YEAR)
TITLE:
Task 6 - NPSHr Test Instrument Accuracy Affect on the Published Results Sulzer Pumps (US) Inc.
SEASON YEAR Monticello - 12x14x14.5 CVDS RHR Pump CUSTOMER GE-HITACHI Nuclear Energy Americas LLC PROJECT Monticello Nuclear Power Station, Monticello, MN CUSTOMER P.O. NO. 437054820 CONTRACT NUMBER SPECIFICATION NO.
ITEM / TAG NUMBER CUSTOMER APPROVAL NUMBER:
CUSTOMER APPROVAL REQUIREMENT Yes No
- Information Only SPACE FOR CUSTOMER APPROVAL STAMP CERTIFIED AS A VALID SULZER PUMPS (US) INC. DOCUMENT (when applicable/available)
For Outside Vendor
_For Manufacture at Sulzer Pumps (US) Inc.
Risk Release Inspection Report # ________________
Other (specify)
APPROVALS (SIGNATURE)
Date Engineering 03/12/12 Quality Assurance CERTIFICATION (when applicable)
Originating Advance Engineering This Document is certified to be in compliance Dept:
with THE APPLICABLE PURCHASE ORDER, By:
SPECIFICATIONS, PROCEDURES, AND ADDITIONAL REQUIREMENTS LISTED IN Ankur Kalra THE APPENDICES.
Title:
Hydraulic Design Engineer Date:
11/7/2011 Professional Engineer APPLICABLE S.O. NUMBERS:
0 State Registration No.
Date _______________
E12.5.1914 0
Rev.
DOCUMENT IDENTIFICATION
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 1/11 TABLE OF CONTENTS 1.0 PURPOSE................................................................................................................................................................. 2
2.0 BACKGROUND
...................................................................................................................................................... 2 3.0 SCOPE...................................................................................................................................................................... 3 4.0 ANALYSIS................................................................................................................................................................ 5 5.0 RESULTS AND CONCLUSION.......................................................................................................................... 10 6.0 BIBLIOGRAPHY.................................................................................................................................................. 11
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 2/11 1.0 PURPOSE To evaluate the impact of test instrument accuracy and test variables on the NPSHr curves published for the Monticello RHR pumps. During a LOCA event, RHR pumps of the Emergency Core Cooling System (ECCS) work under a reduced NPSH. This minimum required NPSH (or NPSHr) is a characteristic of a pump and it is determined by testing the pump under reduced suction head. Instruments used for testing pumps and obtaining NPSHr have an inherent measurement uncertainty. This report analyzes the impact of all these test instrument uncertainties and variables on the published NPSHr values.
2.0 BACKGROUND
NPSHr for a pump is defined in the industry as the suction head at which cavitation impacts the head performance leading to a three percent loss in head at a given flow and pump speed.
A general test loop setup is shown in Figure 1 below.
Figure 1: General Test Loop
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 3/11 During an NPSHr test, the pump is run at a constant flow and speed with the suction head reduced gradually to the point where cavitation and head loss are observed. Figure 2 below, from Hydraulic Institute's Centrifugal Pump Test Standards, shows sample NPSHr test curve results for different flow rates. These curves show the 3% head loss determination method.
These curves are also known as NPSH knees.
Figure 2: NPSHr Test Results, Hydraulic Institute Standards Copyright © 1997-2009 3.0 SCOPE Monticello 12x14x14.5 CVDS RHR pumps were tested in 1969 and the test curves were generated in compliance with the industry standards that existed at that time. Measurement techniques and instruments used for developing the original Monticello NPSHr curves are no longer used in the industry. However, the basic equations for calculating suction head and plotting the curves remain the same. The following factors will be considered for evaluating the overall impact of instrument uncertainties on the NPSHr curves.
a) Instrumentation Uncertainty - Measurement uncertainty of all the test equipment used during NPSHr testing is evaluated. Test instruments include -
x Barometer - For atmospheric pressure.
x Pressure gauges (with dead weight calibrator) - Suction and discharge pressures.
x Thermocouple - Suction inlet temperature for vapor pressure.
x Venturi tubes - Flow rate.
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 4/11 x
Stroboscope - Shaft speed.
x Micrometer - Suction inlet pipe ID and pressure instrument elevation from the fixed datum.
b) Uncertainty in NPSH (suction head) calculation using the test uncertainty calculation method outlined in ASME PTC 19.1-2005.
---> Eq 1.
- Where, Hatm = Head due to atmosphere at a given location.
Hsuction = Head observed in the suction line gauge.
Hvelocity = Head due to the velocity of the pumpage.
Hvapor = Head due to the vapor pressure of the pumpage at the given temperature.
Helevation = Head due to elevation of the measurement gauges from the datum point.
In the above equation, g
V Hvelocity 2
/
2
, where V is the flow velocity obtained from the flow rate and the suction inlet cross sectional area.
c) Other test factors not included in the equation above -
x Pump speed x
Discharge head measurement elevation vapor velocity suction atm H
H H
H H
NPSH r
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 5/11 4.0 ANALYSIS Much of the test instrumentation used for testing the Monticello RHR pumps is no longer the industry standard, e.g., stroboscopes have been replaced by digital tachometers, Venturi tubes by MagFlow meters, pressure gauges by transducers and thermocouples by high precision RTDs. Measurement uncertainties for these old instruments were obtained from ASME centrifugal pump test data and calibration documents. Following is a list of the instruments and their expected uncertainties at the measured value.
Table 1: Instrument Uncertainty Suction head is the total head that the pump impeller experiences at its inlet, which is the available NPSH. An NPSHr test curve is a discharge head versus suction head curve (see Figure 2). Uncertainties in measuring the suction head will lead to inaccuracies in the NPSHr curves.
The test instrumentation uncertainty provided in Table 1 is used for predicting overall NPSH (suction head) uncertainty for the Monticello RHR pump at the flow rate of (( )), and
(( )) as shown below.
Instrument Measure Units Accuracy (+/-)
Barometer Hatm mmHG
((
Suction Pressure Gauge Hsuction psi Discharge Pressure Gauge Hdischarge psi Thermocouple (Type J)
Hvapor
°C Venturi Tubes Hvelocity gpm Stroboscope Speed rpm Micrometer Helevation& Hvelocity in
))
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 6/11 Where, x Velocity head (Hvelocity) of (( )) is calculated at a flow rate of (( ))
and a suction piping internal diameter of (( )) using
- equation, g
V H velocity 2
/
2 (see Table 2).
x Hvapor of (( )) at (( )) water is obtained from the vapor pressure charts.
x Helevation of (( )) is estimated for the purpose of this calculation.
x Standard Hatm of (( )) is used.
x Hsuction of (( ] ]is assumed.
4.1 Uncertainty in NPSH using ASME PTC 19.1-2005 Test Uncertainty Method ASME PTC 19.1-2005 [1] outlines a method for determining uncertainties in results obtained using centrifugal pump test data. According to ASME PTC 19.1-2005, uncertainty in test results is a combination of systematic errors and random errors.
Systematic errors are errors due to imperfect calibration corrections, measurement methods, data reduction techniques, etc, which combine to equal instrument inaccuracy provided in Table 1. Random errors are due to uncontrolled test conditions, and non repeatability in the measurement system, measurement methods, etc. An accepted practice for this method of uncertainty determination uses 95% confidence levels in the analysis. Equations and methods used below for NPSH uncertainty determination are referenced in ASME PTC 19.1-2005.
The NPSH equation above consists of several parameters. Each parameter impacts the NPSH measurement with varying amounts; this is known as parameter sensitivity.
Sensitivity is also defined as the instantaneous rate of change in NPSH to a change in parameter. Sensitivity coefficient of each parameter is calculated and documented in Table 2 below.
elevation vapor velocity suction atm H
H H
H H
NPSH r
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 7/11 Table 2: NPSH Sensitivity Analysis Independent Parameter ()
Parameter Nominal value ()
Units Sensitivity Coefficient
( = Npsh/)
Hatm
((
mmHg
((
Hsuction psi Temperature
°C Suction Pipe ID in Flow gpm Helevation
))
ft
))
Table 2 shows that the sensitivity of suction pressure measurement of (( )) is high compared to the rest of the parameters. In other words, suction pressure uncertainty can impact the NPSH results considerably.
As mentioned earlier, NPSH uncertainty is a combination of systematic and random uncertainties. Overall uncertainty, UADD, for a 95% confidence is calculated using the following equation.
5 0
2 95 2
)
(
)
(
npsh npsh ADD xS t
B U
Equation 2
- where, Bnpsh = Systematic uncertainty of NPSH - also called bias Snpsh = Random uncertainty of NPSH - also called precision t95 = t distribution based on number of samples, assumed 4.303 for 3 samples.
Systematic uncertainty is calculated as follows:
2
/
1 2
2
)
(
)
(
suction suction atm atm npsh B
B B
u
)
u
)
Equation 3 Systematic uncertainty for each parameter is calculated and listed in Table 3. Bias is calculated using the instrument inaccuracy values provided earlier in Table 1 and the nominal parameter values listed below.
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 8/11 Table 3: Systematic Uncertainty Independent Parameter Parameter Nominal value Bias (+/-)
Systematic Uncertainty =
( x Bias)2 Hatm
((
Hsuction Temperature Suction Pipe ID Flow Helevation Bnpsh
))
Random uncertainty for each parameter is generally obtained by taking several measurements at the same point and studying the scatter in the results. Since for this analysis only one measurement per parameter is available, a random uncertainty equal to systematic uncertainty has been assumed. In other terms, bias used in systematic uncertainty is equal to the precision value in the random uncertainty analysis below.
Random uncertainty is calculated and listed in Table 4 below.
2
/
1 2
2
)
(
)
(
suction suction atm atm npsh S
S S
u
)
u
)
Equation 4 Table 4:Random Uncertainty Independent Parameter Parameter Nominal value Precision (+/-)
Random Uncertainty
= ( x Precision)2 Hatm
((
Hsuction Temperature Suction Pipe ID Flow Helevation Snpsh
))
If we input the above values in the 95% confidence level equation; 5.0 2
2
)
3.4
(
)
(
npsh npsh ADD xS B
U
, we obtain ((
)). Therefore, the uncertainty in NPSH obtained is ((
)) at ((
)).
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 9/11 4.2 Other Test Factors Since NPSHr curves are generated by using the drop (3%) in the discharge head, it is important to analyze the uncertainties in the discharge head measurement as well. Just like the suction pressure, discharge head is measured using the dead weight calibrated pressure gauges. The overall accuracy of these gauges is approximated to be
(( )). Therefore, discharge pressure measurement variations at (( )) (head at (( )) and (( ))) would be approximately (( )).
Another factor that could lead to uncertainty in NSPHr curves is the pump speed measured using a stroboscope. NPSHr characteristics of a pump change with speed, therefore, for the purpose of consistency it is important that the pump performance (head, flow and NPSHr) be corrected to a common speed. Stroboscopes with an accuracy of (( )) at (( )) would provide a speed ranging between
(( )).
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 10/11 5.0 RESULTS AND CONCLUSION Determination of the test uncertainty shows that the total amount of variation of the suction head and discharge head measurement is approximately (( )). Based on the analysis performed herein, the uncertainty in NPSH obtained due to instrument inaccuracy is (( )) ((
)). Pump speed measurement uncertainty using a stroboscope is a negligible
(( )). Measurement uncertainty due to instrumentation (systematic error) is small compared to the random uncertainty as observed in Equation 2. Figure 3 below shows the original NPSHr3% curve along with the instrument uncertainty over the flow range.
It is important to note that the Sulzer Pumps uses industry standards described in this report for performing NPSH and performance tests on a large number of the newly manufactured pumps. There is a sizable collection of test data acquired over the years that verifies and validates the test instrument accuracy, and data collection and analysis techniques provided in this report.
((
))
Figure 3: NPSHr Uncertainty Range
Task 6 - NPSHr Test Instrument Accuracy E12.5.1914 12x14x14.5 CVDS 11/11 6.0 BIBLIOGRAPHY
[1]: ASME PTC 19.1-2005 Test Uncertainty.
[2]: ANSI/HI 1.6, 1994, American National Standard for Centrifugal Pump Tests.
[3]: Centrifugal Pumps, Johann Gulich, 2nd Edition.
[4]: Centrifugal Pumps Book, Stepanoff.
[5]: Water vapor pressure charts, http://intro.chem.okstate.edu/1515sp01/database/vpwater.html