To Summarize, Determine ESP Volume, Average Capacity

Subtracting the feet of head required for lift (240′) we can convert this point to PSIG:

Maximum pump cut-out			= 420 feet
Less lift			= 240 feet

Maximum pressure			= 180 feet

To convert feet of head to PSIG, we divide by (2.31) (there is (2.31) feet of head for each PSI):

180 ÷ 2.31 = 77.9 or 78 PSIG.

Or pump cut-out pressure (P3) is 78 PSIG.

Even though the pump may be rated as a (85) GPM pump (as in our example) the actual capacity in GPM will vary as the pump operates throughout its pressure range from pump cut-in (30 PSIG) and pump cut-out (78 PSIG).

So, we’ll go back to our curve and determine what capacity in GPM the pump will deliver at its cut-in point, and what capacity in GPM it will deliver at its pump cut-out point. Then, we’ll average these two capacities by adding them together and dividing by two.

Reading the curve, we can find the point that indi- cates pump cut-in. We already know that this is:

700

600

500

30 PSIG x 2.31	= 70 Ft. of Head
Plus “Lift”	= 240 Ft. of Head

Point on Curve	= 310 Ft. of Head

TOTAL HEAD IN FEET

400

300

200

100

EFF.

20 40 60 80 CAPACITY IN GPM

80
60	%
	%
40	EFFICIENCY
40
20

100 120 140

TOTAL HEAD IN FEET

700

600

500

400

300

200

100

EFF.

80
60	%
	%
40	EFFICIENCY
40
20

To Summarize:

We have used actual pump performance as shown

20 40 60 80 CAPACITY IN GPM

100 120 140

on the pump curve for the pump selected, to complete step one in utilizing maximum capacity of the full acceptance Well-X-Trol®models, Series 420 and 450.

In this step we have determined:

System minimum pressure of 30 PSIG. To establish the Well-X-Trol®precharge pressure.

(P1) Pump cut-in pressure (P2) of 30 PSIG. Pump cut-out pressure (P3) of 78 PSIG.

Step Two – Determine, ESP volume required to control pump cycling. Determine average capacity in GPM:

With larger pumps, capacity, or flow of the pump will vary depending upon the pressure or feet of head at which it is operating.

Reading down to capacity we can determine that, at (310) feet of head, the pump will deliver (106) GPM.

We then read the curve to determine the capacity at pump cut-out:

78 PSIG x 2.31		= 180 Ft. of Head
Plus “Lift”		= 240 Ft. of Head

Point on Curve		= 420 Ft. of Head

Capacity at (420) Feet of Head = 90 GPM

Determine ESP Volume:

Being a large pump, we will want to have a mini- mum run time of at least (2) minutes on the pump:

Average Capacity			Average Capacity
at P2: 106			98 GPM x 2 = 196 ESP Volume
at P3: +90

196 ÷ 2 = 98

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