Page 60 - Commercial Catalogue 2011

This is a SEO version of Commercial Catalogue 2011. Click here to view full version

« Previous Page Table of Contents Next Page »
2. Calculate the total expected head using the following simple equation:-
Total Head =VH + PH + FH
WhereVH =
the Vertical Head, or the total height in metres that the water needs to be “lifted”.
and PH =
the Pipe Pressure Head generated from the pipework.This figure will need to be
determined by referring to Table 1 below (please note that the tables below are in feet, and values will
need to be converted into metres by multiplying the end result by 0.3048). For example, a flow rate of
60 US gpm through a 2” pipe will generate 6.6ft of head per 100ft of pipe. If only 50ft of pipe were
used, the total Pipe Pressure Head will be 3.3ft x 0.3048 = 1.00m head.
and FH =
the Fittings Pressure Head generated by the fittings used in the installation.This can be
determined by utilising Table 2 below (please note that the tables below are in feet, and values will
need to be converted into metres by multiplying the end result by 0.3048).For example, if 10 x 2” 90º
Elbows were utilised for a flow rate of 60 US gpm, the resultant expected friction loss would be
equivalent to 10 x 5.7 = 57ft of 2” pipe. From Table 1, 57ft of 2” pipe at this flow rate would be
equivalent to 6.6/100 x 57 = 3.76ft of head loss. 3.76 x 0.3048 = 1.15m of head loss.
3. Utilise the total expected head value to read off the performance curves for the pumps to correlate with the
desired flow rate. Do not work outside of the optimum
performance range indicated on the curves. A pump
that is run outside of its optimum range can end up
working too hard, will draw too many amps and will
overheat and this will eventually result in permanent
damage. In the Example Pump Performance Curve
(on the right) this pump is required to run at between
12 and 6 metres head pressure, at which it will generate
approximately 9.3m
3
/hr and 17.2m
3
/hr respectively.
1 gal (US)/min = 3.7853 l/min = 0.2271 m3/h = 0.8327 Imperial gal (UK)/min. 1 ft (foot) = 0.3048 m
For thermoplastic pipes velocites above 5 ft/sec should be avoided.
Example Pump Performance Curve
Table 2: Friction Loss Equivalent Length - feet of Straight Pipe (ft)
Nominal Pipe Size (inches)
Fitting
1 / 2
3 / 4
1
1
1 / 2
2
2
1 / 2
3
4
6
90
o
Elbow
1.5
2.0
2.5
4.0
5.7
6.9
7.9
12
18
45
o
Elbow
0.8
1.1
1.4
2.1
2.6
3.1
4.0
5.1
8.0
Tee - Branch
4.0
5.0
6.0
8.0
12
15
16
22
32.7
Table 1: Pressure Friction Head Loss (ft/100ft)
Volume Flow
US Gallons Cubic Metre
Per Minute Per Hour
Nominal Pipe Size (inches)
(GPM)
(m
3
/hr)
1 / 2
3 / 4
1
1
1 / 2
2
2
1 / 2
3
4
6
1
0.23
1.4
0.4
0.1
2
0.45
4.8
1.2
0.4
4
0.91
17.1
4.2
1.3
0.2
5
1.14
25.8
6.3
1.9
0.2
6
1.36
36.3
8.8
2.7
0.3
0.1
8
1.82
63.7
15.2
4.6
0.6
0.2
10
2.27
97.5
26.0
6.9
0.8
0.3
0.1
20
4.54
86.9
25.1
2.9
0.9
0.4
0.1
30
6.81
48.1
6.3
1.8
0.8
0.3
40
9.08
82.0
10.7
3.1
1.3
0.4
0.1
50
11.36
16.5
4.7
1.9
0.7
0.2
60
13.63
23.5
6.6
2.7
0.9
0.3
70
15.90
28.7
8.8
3.7
1.2
0.3
80
18.17
36.8
11.4
4.7
1.6
0.4
90
20.44
14.3
5.8
2.0
0.5
100
22.71
16.5
7.1
2.4
0.6
0.1
125
28.39
25.9
10.8
3.8
1.0
0.1
150
34.07
35.0
14.7
5.2
1.3
0.2
55 Commercial Catalogue
Tel: +44 (0) 1923 284151 www.tropicalmarinecentre.co.uk