thumb rules.xls for chemical engineer
TRANSCRIPT
Sn
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
THUMB RULESParticulars
PIPING PRESSURE DROP : For Raynold's no 2100 to 106
EQUIVALENT LENGHTS for Pressure drop in the system
MAXIMUM ALLOWABLE FLOW OF STEAM THROUGH PIPE 41, 12 & 2" only
ALLOWABLE VELOCITIES FOR PROCESS FLUIDS
SONIC VELOCITY CALCULATION
PERMANENT HEAD LOSS THROUGH ORIFICE
VENTURI Pressure Drop
FLOW RECTANGULAR WEIR
CONTROL VALVE SIZING
RELIEF VALVE SIZING FOR LIQUID EXPANSION
STORAGE VESSEL VOLUMES
NPSH
Pressure Drop in Pipeline
TUBESIDE PRESSURE DROP IN SHELL & TUBE HEAT EXCHANGER
MOTORS kVA
MOTORS AMPS ETIMATE
CENTRIFUGAL COMPRESSOR HP
CENTRIFUGAL COMPRESSOR HEAD
TEMPERATURE RISE IN COMPRESSION
PUMP EFFICIENCY
PUMP HORSE POWER
RELATION OF HP, IMPELLER DIA & SPEED
RELATION BETWEEN PUMP HEAD, IMPELLER DIA & SPEED
CHANGE IN PUMP CAPACITY WITH IMPELLER DIAMETER
TUBESIDE PRESSURE DROP IN AIR COOLED HEAT EXCHANGER
MOTOR HP OUTPUT
MOTOR TORQUE
GAS EXPANDERS : AVAILABLE ENERGY
POWER FACTOR
SELECTION OF TYPE OF VACUUM EQUIPMENT
FAN / BLOWER OR COMPRESSOR
SPRAY WATER FOR PRDS
MAXIMUM AVAILABLE ENERGY (EXERGY)
FUEL TO AIR RATIO
COOLING TOWERS : WINDAGE LOSSES
COOLING WATER CONCENTRATION RATIO
APPROXIMATE EFFICIENCIES OF COMPRESSORS
Physical Properties
PIPING PRESSURE DROP
viscosity m cp
Flow rate W lb/hr
Density rinternal pipe diameter d Inch
Frictional pressure loss, #DIV/0!
Home
For Raynold's no 2100 to 106 :
lb/ft3
DPF psi/100 equivalent ft of pipe
EQUIVALENT LENGHTS
Nom
inal p
ipe s
ize (
in)
Glo
be v
/v o
r ball
check
v/v
Angle
valv
e
Sw
ing c
hek
valv
e
Plu
g c
ock
Gate
or
ball
valv
e
Elb
ow
45
°
Short
rad
Long r
ad
Hard
T
Soft
T
90° miter bend Enlargement Contraction
2 m
iter
3 m
iter
4 m
iter
sudden std sudden
Equiv. Length in terms of small d
d/D
= 1
/4
d/D
= 1
/2
d/D
= 3
/4
d/D
= 1
/2
d/D
= 3
/4
d/D
= 1
/4
d/D
= 1
/2
d/D
= 3
/4
1.5 55 26 13 7 1 1 3 2 8 2 5 3 1 4 1 3 2 1
2 70 33 17 14 2 2 4 3 10 3 7 4 1 5 1 3 3 1
2.5 80 40 20 11 2 2 5 3 12 3 8 5 2 6 2 4 3 2
3 100 50 25 17 2 2 6 4 14 4 10 6 2 8 2 5 4 2
4 130 65 32 30 3 3 7 5 19 5 12 8 3 10 3 6 5 3
6 200 100 48 70 4 4 11 8 28 8 18 12 4 14 4 9 7 4
8 260 125 64 120 6 6 15 9 37 9 25 16 5 19 5 12 9 5
10 330 160 80 170 7 7 18 12 47 12 31 20 7 24 7 15 12 6
12 400 190 95 170 9 9 22 14 55 14 28 21 20 37 24 8 28 8 18 14 7
14 450 210 105 80 10 10 26 16 62 16 32 24 22 42 26 9 20 16 8
16 500 240 120 145 11 11 29 18 72 18 38 27 24 47 30 10 24 18 9
18 550 280 140 160 12 12 33 20 82 20 42 30 28 53 35 11 26 20 10
20 650 300 155 210 14 14 36 23 90 23 46 33 32 60 38 13 30 23 11
22 688 335 170 225 15 15 40 25 100 25 52 36 34 65 42 14 32 25 12
24 750 370 185 254 16 16 44 27 110 27 56 39 36 70 46 15 35 27 13
30 312 21 21 55 40 140 40 70 51 44
36 25 25 66 47 170 47 84 60 52
2 30 30 77 55 200 55 98 69 64
48 35 35 88 65 220 65 112 81 72
54 40 40 99 70 250 70 126 90 80
60 45 45 110 80 260 80 190 99 92
Home
Contraction
Std
Equiv. Length in terms of small d
d/D
= 1
/2
d/D
= 3
/4
1
1
2
2
3
4 1
5 2
6 2
7 2
MAXIMUM ALLOWABLE FLOW OF STEAM THROUGH PIPE :
In FPS : In SI :
600 175 30 41
Density (lb/ft3)0.88 0.41 0.10
Density (kg/m3)14.08
3 7.5 3.6 1.2 3 3.4
4 15 7.5 3.2 4 6.8
6 40 21 8.5 6 18.2
8 76 42 18 8 34.5
10 130 76 32 10 59.1
12 190 115 58 12 86.4
14 260 115 87 14 118.2
16 360 220 117 16 163.6
18 300 166 18
20 227 20
Home
Nominal pipe size (in)
Maximum lb/hr x 10-3 at Pressure (psig) Nominal pipe size (in)
Maximum T/hr at Pressure (barg)
12 2
6.49 1.62
1.6 0.5
3.4 1.5
9.5 3.9
19.1 8.2
34.5 14.5
52.3 26.4
52.3 39.5
100.0 53.2
136.4 75.5
227
Maximum T/hr at Pressure (barg)
ALLOWABLE VELOCITIES FOR PROCESS FLUIDS
Fluid ft/s m/s
Water 10 3.0
air 100 30.5
Dry gas 100 30.5
wet gas 60 18.3
high pressure steam 150 45.7
low pressure steam 100 30.5
Average liquid process 4 - 6.5 1.2 -2
Pump suction (non-boiling) 1 - 5 0.3 - 1.5
Pump suction (boiling) 0.5 - 3 0.2 - 0.9
BFW 4 - 8 1.2 - 2.4
Drain lines 1.5 - 4 0.5 - 1.2
Liquid to reboiler (no pump) 2 - 7 0.6 - 2.1
Vapor to condenser 15 - 80 4.6 - 24.4
Gravity separator flow 0.5 - 1.5 0.2 - 0.5
Vapours 326 99.4
Hot oil headers 1.5 psi/100 ft
Ref : "Rules of thumb for chemical engineers"
Home
SONIC VELOCITY
Sonic velocity Vs Ft/s 0
Absolute temperature T °R
ratio of sp. Heats (usually = 1.4) K 1.4
Accelearion by gravity g ft/s2 32.2
Universal gas constant R /mol wt 1544
Ref : "Rules of thumb for chemical engineers"
Home
PERMANENT HEAD LOSS THROUGH ORIFICE :
Do/Dp Permanent loss
0.2 95
0.4 82
0.6 63
0.8 40
For orifice :
Where
Uo = Velocity through orifice (ft/s)
Up = Velocity through pipe (ft/s)
Orifice pressure drop (ft of fluid)
D = Diameter
Co = Coefficient
(0.6 for typical applns)
Ref : "Rules of thumb for chemical engineers"
Home
Permanent loss = Dh (1-Co)
(Uo2 - Up2)1/2 = Co(2gDh)1/2
Dh =
Compiled by : Ms Gauri
VENTURI Pressure Drop
Venturi pressure drop (ft of fluid) #DIV/0!
Permanent Head loss (ft of fluid)* #DIV/0!
Velocity through orifice (ft/s) Uo
Velocity through pipe (ft/s) Up
Diameter D
Coefficient Co
(0.98 for typical applns)
Ref : "Rules of thumb for chemical engineers"
Home
(Uo2 - Up2)1/2 = Co(2gDh)1/2
Dh =
* Permanent head loss @ 3 - 4 % of Dh
Compiled by : Ms Gauri
RECTANGULAR WEIR
Flow over weir ft3/s Fv 0
Width of weir ft L
Height of liquid over weir ft H
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
CONTROL VALVE SIZING
For liquids :
Hence if control valve specs are known, Q can be calculated as :
Flow rate m3/hr Q 85
Body differential pressure psi 3.5
Specific gravity G 1
Liq. Sizing coeff Cv 2
Ref : "Rules of thumb for chemical engineers"
Home
Cv = Q (G/DP)1/2
DP
Compiled by : Ms Gauri
RELIEF VALVE SIZING FOR LIQUID EXPANSION
Required capacity (gpm) = #DIV/0! #DIV/0! m3/hr
Heat input (Btu/hr)
0.0008 3
Specific gravity
Specific heat (Btu/lb°F)
Ref : "Rules of thumb for chemical engineers"
Home
Coefficient of volumetric expansion per °F (Select fluid)
Compiled by : Ms Gauri
STORAGE VESSEL VOLUMES
For Horizontal Cylindrical vessel :
Choose Type of head : 4
Liquid hold up (m3) = #DIV/0!
Diameter (m)
Height of liquid in vessel (m)
Depth of head (m)
Length of straight portion (m)
* For spherical vessels same formula can be used with length of straight portion = 0
Ref. : Calc & shortcut deskbook, Chemical engg
Home
Compiled by : Ms Gauri
NPSH
Net Positive Suction Head = NPSH #DIV/0!
Where,
Suction head Feet
Vessel abs pressure Psia
Vapor pressure (pumping) Psia
specific gravity
Suction friction losses Ft of fluid
Ref. : Calc & shortcut deskbook, Chemical engg
Home
Compiled by : Ms Gauri
PRESSURE DROP IN PIPELINE
Pressure drop, Pa = #DIV/0!
Laminar flow :
f = Fanning friction factor = #DIV/0!
Enter :
Fluid viscosity, kg/m-s
D = Pipe diameter, m
L = Pipe length, m
e = Pipewall roughness, m
Q =
Ref. : Calc & shortcut deskbook, Chemical engg
Home
DP =
r = Fluid density, kg/m3
m =
Volumetric flowrate m3/s
Compiled by : Ms Gauri
TUBESIDE PRESSURE DROP IN SHELL & TUBE HEAT EXCHANGER
I. Straight tube loss :
viscosity m cp
Flow rate through one tube W lb/hr
Density rInternal tube diameter d Inch
Length of tube L ft
No. of tubes n
Velo.in pipe leading to & from HE ft/s
Number of tube passes N
Frictional pressure loss in tubes psi #DIV/0!psi 0psi #DIV/0!
psi#DIV/0!
Total tubeside pressure drop psi #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
lb/ft3
DP by Entering & exiting the HE
DP by Entering & exiting the tubes
DP by end losses in tubesidebonnets & channels
Compiled by : Ms Gauri
MOTORS kVA
Current Amps
Line to line voltage V
kVA kVA 0
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
MOTORS AMPS ETIMATE
Motor horse power HP 6900000
Line to line voltage V 11000
Motor efficiency fraction 0.8
Power factor fraction 0.86
Motor amps :
For three phase motor : 393.15218321
For single phase motor : 680.15327696
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
CENTRIFUGAL COMPRESSOR HP
Suction temperature T1 °R
Suction pressure P1 psia
Discharge pressure P2 psia
Flow W lb/min
Adiabatic efficiency Ea fraction
Avg compressibility factor Z 1
Universal gas constant R /mol wt 1544
Adiabatic component K Cp/Cv 1.4
Adiabatic Head Had (ft) = #DIV/0!
Horse power = #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
CENTRIFUGAL COMPRESSOR HEAD
Suction temperature T1 °R
Suction pressure P1 psia
Discharge pressure P2 psia
Polytropic efficiency Ep fraction 0.8
Avg compressibility factor Z 1
Universal gas constant R /mol wt 1544
Adiabatic component K Cp/Cv 1.4
polytropic component N =KEp/(KEp-K+1) 1.6
Polytropic Head Hpoly (ft)= #DIV/0!
Adiabatic Head Had (ft) = #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
TEMPERATURE RISE IN COMPRESSION
Suction temperature T1 °R
Suction pressure P1 psia
Discharge pressure P2 psia
Adiabatic component K Cp/Cv 1.4
Adiabatic : Disch Temp (°C)= #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
PUMP EFFICIENCY
SI units
Developed head m Applicable for :
Flow m3/hr Head = 15 - 92 m
Efficiency % 80 Flow = 23 - 227 m3/hr
fps units :
Developed head ft Applicable for :
Flow GPM Head = 50 - 300 ft
Efficiency % 80 Flow = 100 - 1000 GPM
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
PUMP HORSE POWER
SI units :
Flow rate m3/hr 1.5
Discharge pressure bar 7.5
Suction pressure bar 1
Pump efficiency % 80
Pump power HP 20.0211
FPS units :
Flow rate GPM
Discharge pressure psi
Suction pressure psi
Pump efficiency %
Pump power HP #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
RELATION OF HP, IMPELLER DIA & SPEED
Initial impeller diameter (m) =
Initial speed (rpm) =
Initial HP =
New impeller diameter (m) = #DIV/0!New speed (rpm) = #DIV/0!New HP = #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
U canCalculate any one by specifying other two parameters in column B
Compiled by : Ms Gauri
U canCalculate any one by specifying other two parameters in column B
Compiled by : Ms Gauri
RELATION BETWEEN PUMP HEAD, IMPELLER DIA & SPEED
Initial impeller diameter (m) =
Initial speed (rpm) =
Initial head (m) =
New impeller diameter (m) = #DIV/0!New speed (rpm) = #DIV/0!New head (m) = #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
U canCalculate any one by providing other two parameters in column B
Compiled by : Ms Gauri
U canCalculate any one by providing other two parameters in column B
Compiled by : Ms Gauri
CHANGE IN PUMP CAPACITY WITH IMPELLER DIAMETER
Initial diameter (m) =
Initial capacity (m3/hr) =
New diameter (m) =
New capacity (m3/hr) #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
TUBESIDE PRESSURE DROP IN AIR COOLED HEAT EXCHANGER
viscosity of fluid m cp
Flow rate through one tube W lb/hr
Density rInternal tube diameter d Inch
Length of tube L ft
No. of tubes n
Number of tube passes N
Frictional pressure loss in tubes psi #DIV/0!
All other losses psi #DIV/0!
Total tubeside pressure drop psi #DIV/0!
Total tubeside pressure drop bar #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
lb/ft3
Compiled by : Ms Gauri
MOTOR HP OUTPUT
Motor power input kW
Motor efficiency fraction
HP output = 0
OR :
Torque
speed rpm
HP output = 0
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
MOTOR TORQUE
Motor power HP
Speed rpm
Full load torque #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
GAS EXPANDERS : AVAILABLE ENERGY
SI units :Cp Btu/lb°C Cp kJ/kg°C
Inlet temperature °C Inlet temperature °C
Inlet pressure psia Inlet pressure barg
Outlet pressure psia Outlet pressure barg
K= Cp/ Cv K= Cp/ Cv
Actual available power Btu/lb #DIV/0! Actual available power kWh/kg
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
###
###
###
#DIV/0!
Compiled by : Ms Gauri
POWER FACTOR
kW input kW
kVA input kVA
Power factor #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
SELECTION OF TYPE OF VACUUM EQUIPMENT
Reciprocating piston pump down to 1 torr
Rotary piston pump down to 0.001 torr
Two-lobe rotary pump down to 0.0001 torr
Steam jet ejectors 1 stage down to 100 torr
Steam jet ejectors 3 stages down to 1 torr
Steam jet ejectors 5 stages down to 0.05 torr
Home
Compiled by : Ms Gauri
FAN / BLOWER OR COMPRESSOR ??
Fans For 3% rise in pressure
Blowers For differential of 40 psig
Compressors Higher than 40 psig
Home
Compiled by : Ms Gauri
SPRAY WATER FOR PRDS (Pressure Reduction Desuperheating Stations)
Enthalpy of high pressure steam kJ/kg
Enthalpy of lower pressure steam kJ/kg
Enthalpy of the spray water kJ/kg
Spray water required T/T #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
MAXIMUM AVAILABLE ENERGY (EXERGY)
Receiver temperature To °C
Enthalpy at receiver conditions Ho kJ/kg
Enthalpy at source conditions H kJ/kg
Entropy at receiver conditions So kJ/kg°C
Entropy at source conditions S kJ/kg°C
Maximum available energy Ex kJ/kg 0Ex kWh/kg 0
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
FUEL TO AIR RATIO
For fuel gas :
Density of fuel gas relative to air (i.e. MW/MWair) 0.78
Fuel gas / air ratio (mass/mass) 2145
For Fuel oil :
% Carbon
% hydrogen
Fuel oil / air ratio (mass/mass) #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
COOLING TOWERS : WINDAGE LOSSES
Type of cooling device
Spray pond 3
Atmospheric cooling tower 0.7
Mechanical draft cooling tower 0.2
Ref : "Rules of thumb for chemical engineers"
Home
Windage loss as per centage of system circulating rate
Compiled by : Ms Gauri
COOLING WATER CONCENTRATION RATIO
Chloride concentration in make-up water
Chloride concentration in blow down
Concentration ratio #DIV/0!
Ref : "Rules of thumb for chemical engineers"
Home
Compiled by : Ms Gauri
APPROXIMATE EFFICIENCIES OF COMPRESSORS
Efficiency Compression ratio
Reciprocating 65% 1.5
75% 2
80 - 85% 3.6
Large centrifugal 76 - 78%
Rotary compressor (except liquid liner type) 70%
Liquid liner type rotary 50%
Home
Compiled by : Ms Gauri
Physical Properties
Property Units Water Organic Liquids Steam Air
Heat Capacity KJ/kg °C 4.2 1.0-2.5 2 1
Btu/lb °F 1 0.239-0.598 0.479 0.239
Density kg/m3 1000 700-1500 1.29@STP
lb/ft3 62.29 43.6-94.4 0.08@STP
Latent Heat KJ/kg 1200-2100 200-1000
Btu/lb 516-903 86-430
Thermal Cond. W/m °C 0.55-0.70 0.10-0.20 0.025-0.070 0.025-0.05
Btu/h ft °F 0.32-0.40 0.057-0.116 0.0144-0.040 0.014-0.029
Viscosity cP 1.8 @ 0 °C varies with temp. 0.01-0.03 0.02-0.05
0.57 @ 50°C
Prandtl Number 1-15 10-1000 1 0.7
Home
0.28 @ 100°C
0.14 @ 200°C
Compiled by : Ms Gauri
2.0-4.0
0.479-0.958
0.02-0.06
0.116-0.35
0.01-0.03
0.7-0.8
Organic Vapors