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101 renewable - lift and head flow for solar pumps

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Last Updated
13th of October, 2018

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Pump manufacturers are documenting the performance of their pumps in several ways: LIFT & HEAD are used to rate the ability to move water vertically while FLOW reflects the quantity of liquid that can be moved in a given amount of time.

Liquid Pumps Terminology:~

Discharge Head:~

This is the vertical distance that you are able to pump the liquid. Say your pump is rated for a maximum head of 100 feet, this does not mean that you are restricted to100 feet of pipe, you could use 300 feet, so long as the final discharge point is not higher than 100 feet above the liquid being pumped.

Suction Lift:~

This is the vertical distance that the pump can be above the liquid source. Typically, atmospheric pressure limits vertical suction lift of pumps to 25 feet at sea level(see below) This does not mean that you are limited to 25 feet of pipe, you could use upwards of 200 feet of suction pipe, so long as the liquid source is not lower than 25 feet below the pump centerline.

Total Head:~

The sum of discharge head, suction lift, and friction loss.

Friction Head:~

Pressure expressed in Lbs. that is required to overcome the resistance to the flow in the pipe system.(see section below)

In a general conversation about the performance abilities of a pump, the term head usually refers to the maximum vertical distance from the water source to discharge point that water can be pumped. Please note that at this limit, the pump can push the water no higher. This is a rating assigned by the manufacturers based on design technologies and benchmark testing. An individual pump may perform slightly above or below that mark. This rating should be used to compare pumps and help evaluate the pump's suitability for the application.

Various Units for HEAD:~

Different pump manufacturers express their head ratings in different units. One might state that the maximum head for a specific pump is 200 feet while a competitive pump is rated at 90 PSI. A third pump may give the head at 6 bar. Although sounding quite different, they are actually comparable. The chart below shows the relationship of the various units.

Head Conversion Factors:

1 psi = 2.31 feet head, || 1 foot head = 0.433 psi,

Head Reference Chart:-

Feet PSI Meters Bar KPA
0 0 0 0.0 0
20 9 6 0.6 60
40 17 12 1.2 120
60 26 18 1.8 179
80 35 24 2.4 239
100 43 30 3.0 299
120 52 37 3.6 359
140 61 43 4.2 418
160 69 49 4.8 478
180 78 55 5.4 538
200 87 61 6.0 598
220 95 67 6.6 658
240 104 73 7.2 717
260 113 79 7.8 777
280 121 85 8.4 837
300 130 91 9.0 897
320 139 98 9.6 956
340 147 104 10.2 1016
360 156 110 10.8 1076
380 165 116 11.3 1136
400 173 122 11.9 1196
420 182 128 12.5 1255
440 191 134 13.1 1315

 

Feet PSI Meters Bar KPA
460 199 140 13.7 1375
480 208 146 14.3 1435
500 217 152 14.9 1494
520 225 158 15.5 1554
540 234 165 16.1 1614
560 243 171 16.7 1674
580 251 177 17.3 1734
600 260 183 17.9 1793
620 269 189 18.5 1853
640 277 195 19.1 1913
660 286 201 19.7 1973
680 295 207 20.3 2033
700 303 213 20.9 2092
720 312 219 21.5 2152
740 321 226 22.1 2212
760 329 232 22.7 2272
780 338 238 23.3 2331
800 347 244 23.9 2391
820 355 250 24.5 2451
840 364 256 25.1 2511
860 373 262 25.7 2571
880 381 268 26.3 2630
900 390 274 26.9 2690

Suction Lift:~

The vertical distance that a pump may be placed above the water level (and be able to draw water) is determined by pump design and limits dictated by altitude. The chart below shows the absolute limits. The closer the pump is to the water level, the easier and quicker it will be to prime.

Suction Lift at Various Elevations:~

Altitude: Suction Lift In Feet
Sea Level 25.0
2,000 ft. 22.0
4,000 ft. 19.5
6,000 ft. 17.3
8,000 ft. 15.5
10,000 ft. 14.3

Friction Head (Loss):~

As water is pumped through hose or pipe, pressure is consumed (or lost) due to the friction of the water against the inner surface of the waterway. The amount of loss depends on many factors including nature of waterway surface, the rate of water flow, the diameter of hose, pressure, temperature as well as the straightness of the water path. Sounds complicated ??? Well, it is.

Friction Head - Our 1˝" Forestry Hose:~ 

Gallons/Minute Loss in PSI/100' 60 7 70 9 80 12 90 15 100 19

The 1˝" hose available on our website experience a pressure loss of about 0.07 psi/ft. based on a flow rate of 60 GPM. Very few products can boast a lower loss rate. Competitive hoses are rated at 0.09, 0.14 & 0.16 psi/ft. Older hoses, hose in disrepair or trash /junk hose may have ratings in the 0.20 - 0.30 psi/ft. range or higher -- based upon the same flow rate.

Gallons/Minute Loss in PSI/100'
10 0
20 2
30 2
40 4
50 6

For general planning purposes, consider pressure loss to be 7 psi per 100 ft. the length of hose @ 60 GPM. In theory, with a pump producing 100 psi, 1000 ft. of the hose will leave you with 30 psi -- excluding elevation and other sources of head loss. If you restrict flow to 30 gallons per minute by using a different nozzle, then pressure loss becomes 2 psi per 100'. In this case, 1000 ft. of hose would leave you with 80 psi -- quite adequate for fire protection. In reality, the only way to get a true feeling of the effects of the various head loss factors is to actually perform tests in your setting.


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