Refined Globe Valve Thrust Prediction Model to Bound Midstroke ...

Refined Globe Valve Thrust Prediction
Model to Bound Midstroke Predictions of
AOV Margins
Zachary Leutwyler
Dr. M. S. Kalsi
Kalsi Engineering
Tenth NRC/ASME Symposium on
Valves, Pumps and IST
July 15, 2008
Slide #1 #

• Introduction
Objectives
Background
Two-point Two point thrust prediction model
KEI Bounding Thrust Zone (BTZ) Model
• KEI Flow Loop Testing
• KEI Flow Loop Test Results
• Comparison of BTZ prediction with Test Data
• Conclusion
Outline
Slide #2 #

Identify key limitations of Two-point Two point model
Objectives
Identify improvement gained through
implementing the Bounding Thrust Zone (BTZ)
Identify Key factors governing the “general general”
nature of globe valve thrust w.r.t. w.r.t.
position
Overview of BTZ model and model validation
Slide #3 #

Background
March March 2000 – NRC Issued RIS 2000-03 2000 03 “Resolution Resolution
of Generic Safety Issue 158: Performance of
Safety-Related
Safety Related POVs Under Design Basis
Conditions” Conditions
Prior Prior to RIS 2000-03 2000 03:
• NRC and INPO conducted surveys and identified
common cause failures with AOVs that can lead to
safety concerns, reactor scrams, reduced plant
efficiency
– NUREG/CR-6654 NUREG/CR 6654 & NUREG-1275 NUREG 1275 Vol. 13
– INPO SER 1-99 1 99
Slide #4 #

Background – Continued
• EPRI conducted an AOV AOV pilot pilot program program (1996-1999) (1996 1999) teaming with
four utilities to develop AOV evaluation methodologies
– EPRI AOV Evaluation Guide TR-107322 TR 107322, , issued May 1999
– Where applicable, EPRI MOV PPM validated methodologies
where used for AOVs
– Several Industry AOV issues identified, including three issues
related to globe valves
1) EPRI MOV PPM models were not applicable for flashing (two-
phase) or compressible flow. flow.
Valve factors as high as 1.6 - 2.35
were found during in-situ in situ plant tests for steam flow application
(INPO OE-11440) OE 11440)
2) No validated models exist for predicting globe valve disc side
loading/friction force
Mid-position position loads may be greater than fully seated loads under
dynamic conditions due to flow-induced flow induced forces
3) Mid
Slide #5 #

Background - Continued
EPRI refined and validated models to address issue 2) for balanced disc
globe valves only (NUREG/CP-0152, (NUREG/CP 0152, Vol. 3), July 2000
EDF/KEI addressed side-load side load and cavitating/flashing flow effects for an
unbalanced globe valve through experimentation and CFD (ASME PVP
conference July2008 , PVP2008-61238)
PVP2008 61238)
The methodology to address mid-position loads being greater or equal
than fully seated load developed and incorporated in AOV evaluation
software by KEI in 2000.
The methodology is addressed in this paper
Slide #6 #

The two-point two point model is the common
industry approach
- Suitable for MOVs, MOVs,
but not for AOVs
Limitations
Established by predicting the thrust at
the closed and open position.
Thrust at closed position is predicted
by imposing the peak thrust at the
closed position – peak thrust may be
as far away 30% from the seating
position
Two--point Two point model model may not bound all
thrust profiles and may result in non-- non
conservative conservative margin margin predictions predictions for
AOVs
Two-point Two point Model
Slide #7 #

BTZ - Enhanced Model
Peak thrust magnitude is predicted
the same as Two-point Two point model, but
“knee knee” position is defined by the
user to bound the thrust curve.
BTZ bounds F DP throughout the
stroke, thus eliminating non-
conservative margin predictions for
AOVs
Bounding Thrust Zone
Slide #8 #

Bounding Thrust Zone - Applicability
When is BTZ necessary?
Valve Parameters
• Flow Over the Disc
• Opening Stroke
Actuator Parameters
• Spring return (i. e., not
applicable to double acting
without spring actuators)
Notes:
Potential non-conservatism
non conservatism
can exist regardless of
actuator action (i. e., reverse
or direct).
• Actuator action only
determines if the air stroke
or spring stroke corresponds
to the opening stroke
Slide #9 #

Notes (Continued):
Bounding Thrust Zone - Applicability
Closing stroke generally not a
problem since actuator
capability decreases in the
closing direction – minimum
margin at seating position
Slide #10 # 10

Thrust Components
Disc DP Force, F DP
Stem Rejection Force, F P
Side-load Force, F US
Static Forces, F P
Packing
Bellows
Static Piston Seal
Friction
Sealing Load, F SL
Closing Stroke
Opening Stroke
Introduction
Thrust Components
FC = FDS + FP + FUS + FSR + FDF + FDP + FSL
FO = FDS + FP + FUS + FSR + FDF + FDP
Slide #11 # 11

Key Factors
Key Factors Influencing FDP DP vs. Position
Balanced/Unbalanced Trim affects
magnitude
Maximum Disc Head Diameter vs.
Seating Diameter
Disc Head-to Head to-Body/Cage Body/Cage Wall
Clearance
Trim Trim Flow Flow Characteristics
Characteristics
(focus (focus of of testing) testing)
Fluid Media
Operating Conditions (e.g. DP, Q,
T, & Cavitation/flashing)
Slide #12 # 12

Example of Geometric
Dependency
(e.g., Seat Based vs. Guide Based)
Unbalanced Unbalanced Disc
Clearance Clearance between Disc
Head and body/cage wall
is small ( (lower lower Figure) Figure)
Key Factors - Continued
Wide
Clearance
Narrow
Clearance
Slide #13 # 13

Key Factors - Continued
Area Based on D seat
Example of Geometric Dependency
(e.g., Seat Based vs. Guide Based)
Narrow clearance restricts flow and
causes high static pressure to act on the
disc face
Once disc opens, area on which pressure
acts increases from Dseat seat to Ddisc disc diam.
The increase in Area and preservation of
DP Close causes an increase in F DP
As such, F DP initially increases as the disc
moves from the seat untill ~ +25%
open, then decreases as DP drops below
DP
DPclose close
Area Based on D disc diam.
Slide #14 # 14

Test Specimen
4” Globe Valve
Unbalanced Trim
4 3/8 inch Port
Flow Under
Equal Percent or Quick Open Trim
(established by the Cage)
Quick Open Equal Percent
KEI Flow Loop Testing
Slide #15 # 15

Measurements/Instrumentation
Thrust (using a Crane ForceLink
and a traditional load cell)
Upstream and Downstream
Pressure
Upper Body Cavity Pressure
Flow Rate
Actuator Diaphragm Pressure
Key Parameters
Three DP/Flow rates
Equal Percent and quick open
trim flow characteristics
KEI Flow Loop Testing
Slide #16 # 16

KEI Flow Loop Testing
4-inch 150# unbalanced cage guided globe valve
Slide #17 # 17

Flow Coefficient, Cv
250
200
150
100
50
0
Quick Open - Test Data
Quick Open - Fisher Data
Equal Percent - Test Data
Equal Percent - Fisher Data
Test Results
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Disc Position, % Open
Comparison of Experimental versus Published C v Data
Slide #18 # 18

Disc Differential Pressure Force (F DP ), lbs
1600
1400
1200
1000
800
600
400
200
Test Results-Equal Results Equal Percent Trim
Equal Percent Trim
0
0
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Disc Position, % Open
Disc Head Force - Equal Percent
Valve Differential Pressure
Valve DP knee is a good indicator for the F DP knee for BTZ methodology
120
100
80
60
40
20
Valve Differential Pressure, psi
Slide #19 # 19

Test Results – Quick Open vs. Equal Percent
Disc Head Force Coefficient
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Equal Percent Trim
Quick Open Trim
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Disc Position, % Open
F DP coefficient is dependent on trim flow characteristics
Slide #20 # 20

Key Conclusions
Conclusion from Test Data
FDP DP (and consequently the resultant thrust) for Equal Percent
and Quick Open Trim are significantly different
FDP DP vs. position trend is dependent on Trim Type due to DP
and Disc DP force coefficient relationship with position
Valve and system resistance governs relationship of valve DP
w.r.t position
Knee location for Equal percent can be as far out as 55%
Open; Quick Open as little as 15%
Slide #21 # 21

Determining Knee Location without Testing
Valve Differential Pressure Ratio, ∆PR
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Quick Open
Equal Percent
Linear
0.0
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
∆P
ratio
∆P
=
∆P
v
sys
Disc Position, % Open
=
K
up
K
+ K
v
v(
x)
( x)
+ Kdown
Valve DP ratio can be analytically predicted and used to identify knee for BTZ
Slide #22 # 22

BTZ Prediction and Test Data Comparison
Disc Head Force, lbs
2000
1800
1600
1400
1200
1000
800
600
400
200
Equal Percent Trim
Running Average Closing Stroke Disk Head Force
Bounding Thrust Zone Prediction
0
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Disc Position, % Open
Predictions based on proper location of knee in BTZ
model bound test data
Slide #23 # 23

Conclusions
• BTZ provides bounding prediction of F DP and consequently
the resulting total thrust
• BTZ eliminates the potential for non-conservative non conservative margin
predictions in AOVs
• BTZ knee location can be analytically predicted using the
valve flow coefficients and system resistance
• Methodology validated by testing and incorporated in the
globe valve thrust prediction model in KVAP software (Kalsi
Valve and Actuator Prediction software)
Slide #24 # 24