Sizing the surge-trol, Precise sizing for pump start-up, Precise sizing for pump shut-down – Amtrol SPT-28 User Manual
Page 3: Precise sizing example for pump shut-down based on
Description
Standard Construction
Shell
Steel
Bladder
Heavy Duty Butyl
NSF/ANSI 61
Bladder Thickness
.100 Minimum
System Connection Steel - ANSI Flange
Coating
Red Oxide Primer
Factory Precharge
25 PSIG (1.7 bar)
Use:
SG = Specific gravity of fluid:
Water 1
Ethylene glycol 1.1
Propylene glycol 1.1
Glycerin 1.3
Qs = Fire pump flow rate in gpm
Qss = Fire pump flow rate in feet per second
L
= Length of pipe in feet
a
= Speed of pressure wave
in feet per second:
Steel pipe 4500 ft/sec
Cast iron = 4500 ft/sec
Ductile iron 4500 ft/sec
PVC pipe = 1250 ft/sec
P
2
= Maximum allowable pressure
P
1
= Tank pre-charge pressure setting
n
= Gas constant (pre-charge gas) dry air 1.2
nitrogen 1.4
A = Area of Pipe - pipe size
V
= Velocity of water in feet per second
Precise Sizing For Pump Start-up:
Volume of Tank in Cubic Feet =
(
SG x 2 x Qs x L
) (
P
2
+ 14.7
)
1
/n
449a
P
1
+ 14.7
(
P
2
+ 14.7
)
1
/n
P
1
+ 14.7
-1
NOTE: Set pre-charge pressure 15% below static pressure.
NOTE: To convert cubic feet to gallons multiply by 7.481.
SIZING THE SURGE-TROL
™
Tank A
B
Sys.
C
D
E Ship
Vol. Height Diameter
Conn. Conn. Conn. Stand Wt.
Model
Inset CtrLine Dia
No.
Lit.
Gal
mm
ins.
mm
ins.
ins.
ins. ins.
ins.
kg
lbs.
SPT-7 200
53 1245 48
7
/
8
610
24
4
1
9
/
16
8
3
/
16
19 166 367
SPT-11 300
80 1600 62
7
/
8
610
24
4
1
9
/
16
8
3
/
16
19 208 459
SPT-14 400 106 1956 76
7
/
8
610
24
4
1
9
/
16
8
3
/
16
19 282 618
SPT-18 500 132 2311 90
7
/
8
610
24
4
1
9
/
16
8
3
/
16
19 333 731
SPT-21 600 158 1893 74
11
/
16
762
30
4
1
3
/
8
7
1
/
4
24 433 950
SPT-28 800 211 2365 93
1
/
8
762
30
4
1
3
/
8
7
1
/
4
24 513 1125
SPT-35 1000 264 2086 82
1
/
8
914
36
6
3
1
/
4
7
1
/
2
30 693 1520
SPT-42 1200 317 2465 94
1
/
2
914
36
6
3
1
/
4
7
1
/
2
30 784 1720
SPT-50 1400 370 2781 109
1
/
2
914
36
6
3
1
/
4
7
1
/
2
30 866 1900
SPT-56 1600 422 2178 85
3
/
4
1220 48
8
1
3
/
4
10
7
/
8
42 1049 2300
SPT-70 2000 528 2528 99
5
/
8
1220 48
8
1
3
/
4
10
7
/
8
42 1231 2700
Precise Sizing For Pump Shut-down:
Volume of Tank in Gallons = Vv
AF
AF - Acceptance Factor =
1 -
(
P
1
+ 14.7
)
1
/n
P
2
+ 14.7
Vv - Vacuum Volume = Qss x Tc x 7.481
Tc - Critical Time in seconds =
2L
a
NOTE: Set pre-charge pressure 50% below
static pressure.
Precise Sizing Example
For Pump Shut-down Based On:
Pump = 100 GPM
Pipe = 2” Steel Pipe; 1000 ft of pipe
Static Pressure = 100 psig
Max. Pressure = 150 psig
Pre-charge Gas = Dry Air
Tc =
2L = 2(1000) = 2000 = .444
a 4500 4500
Vv = Qss x Tc x 7.481 = 9.5 x .444 x 7.481 = 31.55
AF =
1 -
(
P
1
+ 14.7
)
1
/n =
1 -
(
64.7
)
1
/
1.2
= .54
P
2
+ 14.7
164.7
Volume of Tank in Gallons = Vv = 31.55 = 58.4
AF
.54
Recommendation = SPT-11