Control Valves and Valve Flow Testing Webinar Tariq Boussouara Project Engineer Slide 1
Contents Slide 2
Control Valve Types and Characteristics Concepts and Definitions Control Valve Flow Testing Control Valve Wear CFD Modelling Slide 3
Control Valve Types and Characteristics Slide 4
Isolation Valves - Butterfly - Gate - Plug - Globe stop valve - Ball Non Return / Check Valves Process/Self activated - Flap Valve - Double flap (2x half moon) - Ball - Cone Slide 5
Pressure/Flow Control Valves Control Valves regulate or control the rate of flow of a fluid by varying the size of the flow passage Slide 6
Pressure/Flow Control Valves - Choke Valve - Cage-trim - Globe - Butterfly - Eccentric plug/disc - Ball - Needle Slide 7
FLOW CAPACITY Control Valve Characteristics VALVE TRAVEL Source: http://www.enggcyclopedia.com/2012/03/typical-control-valvedatasheet-pneumatic/ Slide 8
Control Valve Actuation Many shapes, sizes and types Manual operation, power actuated or process/self activated Can be a combination of all the above http://www.auma.com/cms/auma/en/documents /redcms-p/node-8350/order-desc/sortfriendly_name/1,111003,29635.html Slide 9
Control Valve Selection FLOW RANGE ACTUATION TEMPERATURE MATERIALS PRESSURE ACCESSIBILITY CONTROL VALVE SELECTION FLUID PROPERTIES PIPING DIFFERENTIAL PRESSURE NOISE LIMITATIONS ALLOWABLE LEAKAGE FIRE RESISTANCE Slide 10
Concepts and Definitions Slide 11
Flow Coefficient Expresses the performance capability of a control valve Independent of valve size or type Slide 12
Choked Flow Vapour formation so large that the flowrate cannot increase by further increasing the differential pressure across the valve or restriction Slide 13
Cavitation and Flashing Slide 14
Cavitation and Flashing Cavitation Noise emission Vibration of valve Erosion due to collapsing bubbles and shockwaves Flashing Noise emission Vibration of entire pipeline due to imbalance between liquid/vapour phases Erosion liquid droplet impact Slide 15
F L - Fluid Recovery Factor Capability of the valve to transform kinetic energy of fluid in vena contracta in to pressure energy Slide 16
Valve Type Globe 0.9 Eccentric Plug 0.75-0.85 Butterfly 0.5 0.8 Ball 0.35 0.6 F L Typical F L Values Slide 17
Cavitation Index σ = (P 1 P v ) (P 1 P 2 ) Slide 18
Acceleration or sound pressure level Increasing Cavitation Level Cavitation Index (σ) Choking Cavitation Damage σch (Equivalent to Flmax) Maximum Vibration Cavitation σmv Cavitation Regime IV Change of slope from III to IV Incipient Damage σid III Constant Cavitation σc Change of slope from II to III Incipient Cavitation σi II σ I Slide 19
σ 2 No cavitation 1.7 < σ <2.0 No cavitation control required 1.5 < σ < 1.7 Some cavitation control required 1.0 < σ < 1.5 Potential for severe cavitation σ 1 Flashing is occuring Typical globe valve example Slide 20
Valve Sizing Example Determine size of control valve (Cv) required to regulate water flow from a storage tank. 5-40m Max water level = 40m Min water level = 5m Water flow = 100 l/s Slide 21
Valve Sizing Example USGPM C v = Q 1 P 5-40m 100 l/s flow C v max = 1585 psi 1 10.3 5 14.5 = 597 Cv range?? C v min = 1585 1 10.3 40 14.5 = 211 Cv range 211-597 Slide 22
Valve Sizing Example Slide 23
Control Valve Flow Testing Slide 24
Why Flow Test Valves? Provides confidence Validates predicted performance data Highlights any issues with valve design Slide 25
Valve Flow Testing Standards (Cv and F L testing) ISA75.02, Control Valve Capacity Test Procedures IEC 60534-2-3:2015 Industrial-process control valves Part 2-3: Flow Capacity Test Procedures Slide 26
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Test Considerations Upstream/downstream pipework Pressure tapping dimensions Stem Calibration Differential pressure measurement Reference flowrate measurement Slide 28
Flow Coefficient Testing Cv recorded at three differential pressures Any large percentage deviation in Cv values from the average can indicate the presence of cavitation Slide 29
Valve Flow Coefficient- Cv (US) 16 14 12 10 8 6 4 2 0 0 20 40 60 80 100 120 140 160 180 200 220 Stem Position- Steps Slide 30
Valve Flow Coefficient Cv (Us) 90 80 70 60 50 40 30 20 10 0 0 20 40 60 80 100 120 Valve Travel Position % Slide 31
F L Testing Data point taken with high inlet pressure, and low differential pressure Data point taken with outlet pressure in facility reduced to a minimum Data points plotted in between both conditions Slide 32
Fl Value 1400 1.00 1200 Q2 Data Fl Data 0.90 0.80 0.70 F LA Flow 2 1000 800 600 0.60 0.50 0.40 0.30 0.20 0.10 400 0.00 1.5 2.0 2.5 3.0 3.5 4.0 Differential Pressure -(bar) Slide 33
F LA Limit Point at which cavitation is just starting to make itself evident hydrodynamically Lies between constant cavitation sigma level and choking cavitation condition Slide 34
Increasing Cavitation Level Cavitation Index (σ) Choking Cavitation Damage σch (Equivalent to Flmax) Maximum Vibration Cavitation σmv Cavitation Regime IV Change of slope from III to IV Incipient Damage σid III Constant Cavitation σc Change of slope from II to III Incipient Cavitation σi II σ I Slide 35
Control Valve Wear Slide 36
Control Valve Wear CORROSIVE WEAR CORRISION- EROSION ABRASIVE WEAR CONTROL VALVE WEAR JET IMPINGEMENT CAVITATION EROSION PARTICULATE WEAR Slide 37
Corrosive Wear Generally the most common cause of wear in valves Can increase surface roughness May reduce valve Cv Slide 38
Abrasive Wear Sand or particles get in between surfaces Gate valve sliding surfaces Ball valve rotating surfaces Slide 39
Abrasive Wear Slide 40
Particulate Wear Erosive wear due to solid particles Impinge surfaces at high velocity wear = f (velocity) 2.6 Slide 41
Particulate Wear Slide 42
Wear on a choke plug Choke Valve plug Slide 43
Cavitation Erosion Vapour formation in valve As pressure recovers, vapour bubbles implode Collapse of bubbles can remove material Slide 44
Reducing the effects of valve wear Velocity reduction Material selection Multi stage valve trim CFD and physical testing to predict and manage erosion Slide 45
CFD Testing Slide 46
CFD Testing FLOW Define Geometry Mesh Solution Slide 47
CFD Testing Slide 48
CFD Testing Gate Valve Slide 49
Combining CFD and Physical Erosion Testing Slide 50
Erosion in a choke valve cage Slide 51
Summary Key concepts and definitions Flow testing of control valves Control valve wear mechanisms CFD modelling Slide 52
Thanks for listening Questions? tariq.boussouara@tuv-sud.co.uk Slide 53