Selection & Sizing

of
Valves
ROYKE R RORING ST.,MT
• Introduction
• Common types of valves
• Control Valve selection and sizing
Data collection
Selection parameters
Sizing Equations
Cavitation / choking
Noise calculations
Autovalv - a software for control valve selection & sizing
• Safety Relief Valve selection & sizing
Selection
Sizing Equations
Safevalv - a software for safety relief valve selection & sizing
• Hints
 Introduction
• Need for selection & sizing
– Varied choices of valves
– Selection & sizing - complementary
– Using available material
– Reducing the downtime
– Predicting the performance
 Common Valves types
Gate Valves
• Types : 1. Knife-edge Gate valve
2. Parallel/Conduit Gate valve
• Best Suited Control:
Quick Opening, Linear
• Recommended Uses:
1. Fully open/closed, non-throttling
2. Infrequent operation
3. Minimal fluid trapping in line
4. Throttling with V-shaped seat
• Applications: Oil, gas, air, slurries, heavy liquids, paper stock, pulp,steam,
noncondensing gases, and corrosive liquids
• Advantages: Disadvantages:
1. High capacity 1. Poor control in case of parallel gate valve.
2. Tight shutoff 2. Cavitate at low pressure drops
3. Low cost 3. Cannot be used for throttling
• 4. Little resistance to flow
Globe Valves
• Best Suited Control: Linear and Equal percentage
• Recommended Uses:
1. Throttling service/flow regulation
2. Frequent operation
• Applications: Liquids, vapors, gases, corrosive substances,
slurries
• Advantages: Disadvantages:
1. Efficient throttling 1. High pressure drop
2. Accurate flow control 2. More expensive than
other valves
3. Available in multiple ports
Ball Valves

• Types: 1. Floating ball 2. Trunnion mounted ball

3. Segmented ball
• Best Suited Control: Quick opening, linear
Recommended Uses:
1. Fully open/closed, limited-throttling
2. Higher temperature fluids
• Applications: Most liquids, high temperatures, slurries
• Advantages: Disadvantages:
1. Low cost 1. Poor throttling characteristics
2. High capacity 2. Prone to cavitation
3. Low leakage and maintenance
4. Tight sealing with low torque
 Butterfly Valves
• Types: 1. Symmetric disc (standard)
2. Eccentric disc(High performance)
• Best Suited Control: Linear, Equal percentage
• Recommended Uses:
1. Fully open/closed or throttling services
2. Frequent operation
3. Minimal fluid trapping in line
• Applications: Liquids, gases, slurries, liquids with suspended solids
• Advantages: Disadvantages:
1. Low cost and maintenance 1. High torque required for control
2. High capacity 2. Prone to cavitation at lower flows
3. Good flow control
4. Low pressure drop
 Diaphragm Valves
• Types 1. weir 2. Straight-through
• Recommended Uses:
1. Throttling services with low pressure, low temperature slurries
2. Minimal fluid trapping in line
• Applications: Liquids, gases, slurries, liquids with suspended solids
• Advantages: Disadvantages:
1. Low cost and maint. 1. Large sizes are difficult to manufacture
2. High capacity 2. Failure of diaphragm leads to leaking
3. Temperature and pressure limitations
 Pinch Valves / Iris Valves

• Recommended Uses:
for large size slurry applications
• Applications: Liquids, gases, slurries, liquids with suspended
solids, pastes
• Advantages: Disadvantages:
1. Tight shutoff 1. low maximum operating pressure
• 2. Easy maintenance 2. No draining possible and expensive
 Plug Valves

• Types : 1. Non-lubricated 2. Lubricated

• Recommended Uses:
1. On/Off duties
• Applications: Liquids, gases, slurries, liquids with suspended
solids, pastes
• Advantages: Disadvantages:
1. Fast response 1. Expensive
2. Lower pressure loss 2. Lubrication a must for lubricated plug valves
3. Tight shutoff
 Control Valve selection & sizing
Data Collection
• working details of the valve like fluid type,
max.flowrate, dp at max.flowrate, operating
temperature, pressure, flow characteristics,
leakage allowed, etc.
• details on valve choices available, ie., ANSI rating
of the valve, temperature range, leakage class,
purpose, flow characteristics, end connections,
valve size and valve flow coefficient for that size.
• details like pressure recovery factor, cavitation
index, sizing coefficient, discharge coefficient etc
are also to be collected.
Selection parameters
Operating temperature & Service
– affects material selection for body, trim and packing
-460° -400° -200° 0° 200° 400° 600° 800° 1000° 1200° 1600° 2000°

COMMON Stainless steel

BODY MATERIALS High nickel steel aluminium carbon steel chrome moly stainless Inconel
(use chrome moly for flashing service) (-20°F) steel(-450°F) (-400°F)
Nickel steel iron
ductile iron
Bronze thru bolting
ANSI studs limit for 750°F
BOILING3 nuts stainless steel alloy steel flangeless valve alloy steel stainless steel
A193 Gr B8 A193 Gr B7 A193 Gr B16 A193 Gr B8
A194 Gr 8 A194 Gr 2H A194 Gr 2H A194 Gr 8
PACKING

(Actual Packing TFE graphite-asbestos graphite

Temp.)
THERMAL Cryogenic Service Nominal Service Hot Service High Temperature Service
SERVICE
GLOBE extended bonnets std. bonnet extended bonnets req. with TFE Packing
above 450°F
use graphic packings above 850°F
TFE seats elastomer seats metal seats integral seat
Seal welded seat
rings
BUTTERFLY unlined elastomer unlined
lined (tight shut off)
piston disc seal metal and refractors lined
BALL TFE seats TFE and elastomer carbon graphite stellite
Seat seat seat
sealant injection
PLUG TFE lined
Metal to metal
(sealant injection)
DIAPHRAGM -30°F 350°F
elastomer
diaphragm
-460° -400° -200° 0° 200° 400° 600° 800° 1000° 1200° 1600° 2000°
Selection parameters
•ANSI class rating
–based on the material selected, this gives the maximum pressure
for the specified temperature that the material can withstand

A typical pressure-temperature rating for A217-WCl carbon Moly body material as per ANSI B16.5-1973
is given below.

Temperature Working Pressures in psi

Deg F 150 300 400 600 900 1500 2500

-20 to 100 265 695 925 1390 2085 3470 5785

200 260 680 905 1360 2035 3395 5655
300 250 650 870 1305 1955 3260 5435
400 245 640 855 1280 1920 3200 5330
500 230 620 830 1245 1865 3105 5175
600 210 605 805 1210 1815 3025 5040
650 205 595 795 1195 1790 2985 4970
700 205 585 780 1170 1755 2920 4870
750 195 555 740 1110 1665 2775 4630
800 160 535 715 1070 1605 2675 4455
850 105 495 660 985 1480 2470 4115
900 65 430 570 855 1285 2145 3570
950 40 290 390 585 875 1455 1430
1000 20 190 250 375 565 945 1570
Given an operating temperature of 200 deg F and pressure of 300 psi the ANSI rating would be 300 for
A217-WCl carbon Moly material as per the above table.
 Selection parameters
•Required flow characteristic
–relationship between flow through the valve and its travel
Quick Opening Characteristic. A valve with a quick opening throttle plug generates a curve that has a steep
slope for the first 25% of its lift and a gradual slope thereafter. Therefore, this type a valve provides a large
part of its flow capacity with relatively small lift as the valve opens. A steam "blast" coil is a typical
application for this type of valve because it requires a large flow quickly.
a. Used for frequent on-off service
b. Used for processes where "instantly" large flow is needed (ie. safety systems or cooling water systems)

Linear Characteristic. A valve with a linear throttling plug generates a characteristic curve with a constant
slope. The valve travel is directly proportional to the valve stoke. That is, a percent change in lift will produce
the same percentage in flow at any point of the curve.
a. Used in liquid level or flow loops
b. Used in systems where the pressure drop across the valve is expected to remain fairly constant (ie. steady
state systems)

Equal Percentage Characteristic. A valve with an equal percentage throttling plug generates a curve such
that a fixed step change in valve lift provides an equal percentage step change in flow over the previous step.
This type of curve provides small flow changes for the first half of the valve lift and large flow changes over
the last half of valve lift.
a. Used in processes where large changes in pressure drop are expected
b. Used in processes where a small percentage of the total pressure drop is permitted by the valve
c. Used in temperature and pressure control loops
Selection parameters
• Maximum leakage allowed
– the maximum leakage that can be allowed through the closed
valve at maximum pressure drop.
Leakage Class Allowable Leakage Rate Valve types Remarks
ISA RP 39.6 Air or Water

Class I Category II, III or IV but no Valve types listed in category II, III & IV Quality of mfg. Implies that
Test required by agreement between these valves do not exceed
user and supplier leakage classes II, III & IV,
stipulated
Class II 0.5% rated valve capacity, Globe, double seated, Globe, single
(maximum Cv) seated, balance with stepped metal piston
seat. Butterfly, metal lined.

Class III 0.1% of rated valve capacity High quality globe double seated. Globe,
single seated, balanced with continuous
metal piston seals.

Class IV 0.1% of rated valve capacity Globe, single seated. Globe, single seated,
balance with elastomer piston seals.
Rotary eccentric can type. Ball valves with
metal seat.
Class V 5 10-4 cc/mm. of water Globe valves in Class IV with heavy duty Few valves continue to
per inch of orifice diameter Actuators to increase seating force. remain this tight in service
per psi differential pressure. unless the seat plastically
deforms to maintain contact
with the plug.
Class VI Maximum permissible leakage Globe with resilient seat. Butterfly, elastomer sealed valves
associated with resilient seating elastomer lined. Rotary eccentric can with remain this tight for many
valves. Expressed as bubbles per elastomer seat. Ball with resilient seat. thousands of cycles until
min. as per RP 39.61 Solid ball type. Diaphragm, weir type, this seal is worn or cut
plug valves, elastomer seated or sealant
injection sealing system.
Selection parameters
• Purpose
– the intended use of the valve
Valve Function Typical valve types

Isolation Gate
Ball
Butterfly
Plug
Diaphragm/ Pinch
Globe
Flow diversion Plug
Ball
Globe

Prevention of flow reversal Swing Check

Lift Check
Diaphragm Check
Axial flow check
Selection parameters
• Valve end connections
– the type of end connections preferred, available, and the size of the
valve.
Type and Description Valve Types Used Sizes Usage
On
Screwed All 1/4 in. to 2 inches. General : Not suitable for hot thermal
Some low pressure cyclic service or high pressure gas.
3 & 4 inch Usua11y limited to 5000 psi ambient
connections liquids & 3000 psi gas.
Flanged All 1/2 in & larger General : Allows removal from piping
without a union required for screwed

Loose flange Primarily used on 1 in. to 4 inches 1) Allows use of low cost carbon
(Flange is retained to split body valves 150 lb. steel flanges with an alloy body
valve body pipe hub with (loose flange & 300 lb. 2) One body may be used with
split key ring) split body 600 lb. several flange ratings - 150,300 &
High pressure flanges applications limited (Same body - 6OO1b.
may be screwed to body by piping strains in different flanges) (Usually maximum due to pipe
piping hub ( usua11y some systems ) Non standard E to bending moments )
service above 15,000 psi) (Also on some E dimensions for 3) Ent to end dimension is the same
globe valves) 150 & 300 lb. for all ratings (usua11y the ISA or
optional ANSI standard for 600 lb. )
However this is optional

Flangeless Butterfly 2 to 24 inches 1 ) One body serves several pressure

(Through bolts from pipe Ball, solid type 2 to 16 inches ratings 150 lb, 250 lb, 300 lb, 400 lb
flanges surround and hold Ball, characterised 1 in. to 24 inches & 600 lb with the same end-t<>-end
body between pipe Rotary - Cam type 1 in. to 12 inches dimension
flanges) Globe 1 in. to 4 inches 2) Less metal in alloy bodies
Allow piping clearance 3) Ball and cam action valves are for long studs when
body smaller than line size to allow size is
Sma11er than line bolting to pass body size (Balls
are 800/0 line flow area )
4) Do not use with iron flanges as bolting strains will
break flange which overhangs valve body
5) Butterfly discs and solid ba11s may overhang
Valve end on short pattern valve bodies
Selection Example
Application
- Fluid : clean acid, liable to cause scaling
- Temperature : 150 deg C
- Pressure : 70 bar Rating
- Size : DN 150
- Flow resistance : low
- Seat tightness : Drop tight
From Table A1, consider the following
Flow resistance, Type of fluid, fluid condition, pressure,
temperature, size, leak tightness(Table A5). Check for desired
features (Table A3) and materials (Table A4)
 Sizing equations
Liquids
for turbulent liquid flow
Dp N1  1.0
qf  N1 FpCv
Gf
for laminar liquid flow
Dp N 52
qf  N10 (FsFpCv ) 3/ 2 10

for transitional liquid flow
Dp N1 10
q f  N1 FR FP Cv .
Gf

qf  U.S.gpm   centipoise p psia G  Specific gravity

Gases
equation for gases is
N 1360
x 7
q  N 7 FpCvp1Y
GT1Z or

x N  7320
9
q  N9 FpCvp1Y
MT1Z depending

on the known properties of the gas.

For dry saturated steam, x N1 10
w  N 1 FpCvp 1 (3  )( x ) .
x TP
Z Compressibility factor M Molecular weight T1 °R

wlb/hr q  scfh(14.73psia & 60°F) p psia G  Specific gravity

Cavitation/choking
if Dp / (p1 - pv) < Kc no cavitation occurs
Dp / (p1 - pv) >= Kc cavitation begins
Dp / (p1 - pv) >= (Kc + Fl2)/2 pitting occurs
Dp / (p1 - pv) >= 1 Flashing occurs
Cavitation occurs only in case of liquids.
A valve is said to be choked if
Dp/(p1 - 0.7 pv) >= Fl2
where Dp = valve inlet pressure - valve outlet pressure
Fl = Valve Pressure Recovery factor
p1 = valve inlet pressure in psia
pv = vapour pressure of liquid at inlet in psia
Noise Calculations
1. Hydrodynamic Noise Prediction
If Dp < Dp incipient
SL = 10 log Cv + 20 log Dp - 30 log (t) + 5 where
SL = A-weighted sound level,dBA , 3ft downstream from the pipe
Cv = Required Flow coefficient
Dp = pressure drop in psia
t = pipe wall thickness in inches
If Dp > Dp incipient < Dp critical
SL = 10logCv + 20log Dp +
5[(Dp/(p1 - pv) - Kc / (Fl2 - Kc)] log(p2 - pv) -30log(t)
+ 5 where
pv = fluid vapour pressure
2. Aerodynamic noise prediction
The noise prediction equation for valves is
Lp = 20log(40DpCv X ) + Lx + Lk
T

Lx = 20x0.45
Lk = 10log[4/p D/{(D - 2t2)(D + 72)}]
where D = pipe outer diameter in inches
t = pipe wall thickness in inches
x = Dp/p1
XT = Terminal value of x used to establish
expansion factor Y
 AUTOVALV

A software
for control valve
selection and sizing
 Safety Relief Valve selection & sizing
• Selection
– generally based on back pressure
In case back pressure is varying, a balanced bellows
safet relief valve is used, else a conventional safety
relief valve is used.
• Sizing
1. Gas or Vapour Relief
Required effective discharge area in inch2
W TZ
A
CKP1 Kb M or
 V TZM
A or
6.32CKP1 Kb

V TZG
A where
1175
. CKP1 Kb

T = absolute temperature of the inlet vapour, in °F + 460.

Z = compressibilty factor
Kb = capacity correction factor due to back pressure.(Fig 2 & 4)
K = effective coefficient of discharge = 0.975
V = required flow through valve,scfm (14.7 psia & 60° F)
P1 = upstream relieving pressure, in psia.
W = required flow through the valve, lb/hr.
C = coefficient obtained from table
G = specific gravity of gas referred to air = 1.00 at 60°F&14.7 psia.
2. Sizing for gas expansion due to external fire
F ' A3 where
A
P1
A = effective discharge area of the valve in sq.inches
F’ = an operating factor determined from Fig. 1
A3 = exposed surface area of the vessel in sq.feet.
P1 = upstream relieving pressure, in psia. This is the
set pressure plus the allowable over pressure plus the
atmospheric pressure in psia.
3. Sizing for Liquid relief
gpm G where
A
38KK P KW KV 1.25 p  pb
gpm = flowrate at selected percentage of overpressure in
U.S gpm
A = effective discharge area in sq.inches.
K = coefficient of discharge = 0.62
Kp =capacity correction factor due to overpressure Fig. 6
Kw = capacity correction factor due to back pressure. In
cases of atmospheric back pressure or conventional valves
Kw = 1. For balanced bellows valves Fig 5 is used.
Kv = capacity correction factor due to viscosity = 1 in
most cases for low viscosities.
p = set pressure at which relief valve is to begin opening,
in psig
pb = back pressure, in psig
G = specific gravity of the liquid at flowing temperature
referred to water = 1.00 at 70 deg F.
In case of viscous liquid service, using Kv = 1.00 a
preliminary discharge area is obtained. From
manufacturer’s standard orifice sizes, the next larger
orifice size should be used in determining the
Reynold’s number R.
 Reynold’s number
12700gpm
gpm(2800G ) R
R or
U A where
 A
gpm = flowrate at flowing temperature in U.S gpm
G = specific gravity of the liquid at flowing temperature
referred to water = 1.00 at 70 deg F.
 = absolute viscosity at flowing temperature, in centipoises
U = viscosity at flowing temperature, in Saybolt Universal
seconds.
After the value of R is determined, the factor Kv obtained
from Fig.3 is used to correct the preliminary required
discharge area. If the corrected area exceeds the chosen
standard orifice area, the above calculations should be
repeated using the next larger standard orifice size.
4. Sizing for Steam relief
W
A where
50P1 K SH

W = flowrate in pounds per hour

A = requires effective discharge area of the valve, in sq.inches
P1 = upstream relieving pressure, in psia. This is the set pressure
plus the allowable over pressure plus the atmospheric pressure in
psia.
KSH = correction factor due to the amount of superheat in the
steam.
for saturated steam, KSH = 1.00
for superheated steam use table.
 SAFEVALV
A software
for Safety relief valve
selection and sizing
Hints
The following data may also be of help in
getting a better performance from a valve.
The Line velocity may be in the range given
below
Liquid 5-10 ft/sec normally
40-50 ft/sec maximum
Gas 250 - 400 ft/sec typical
< Mach 0.3
Steam or Vapour 70-100 ft/sec 0-25 psig
100-170 ft/sec dry,
saturated > 25psig
<Mach 0.1
115-330 ft/sec superheated
> 200 psig <Mach 0.15
 U.S. Occupational Safety & health
Administration (OSHA) limits for noise level
exposure
Hours/day dBA Maximum
8 90
4 95
2 100
1 105
1/2 110
1/4 115(max)
THANKYOU