System calculation and selection (matching core components) in Irrigation

2025-10-09

1.Calculate the required pump flow rate (Q_pump)

Core formula:

Q_pump (m³/h) = Q_day (m³/day) ÷ [daily average peak sunshine hours (T, unit: hours) × irrigation efficiency (η)]

Parameter analysis：

-Daily peak sunshine hours (T): A standardized reference value, not the duration of sunshine. It can be understood as "effective power generation hours", usually 4-6 hours. You can check the specific value in your location through NASA database or weather software.

-Irrigation efficiency (η): must be considered! Different irrigation methods result in huge differences in water loss. This is an efficiency coefficient less than 1.

-Flood irrigation: η ≈ 0.5

-Furrow irrigation: η ≈ 0.6-0.7

-Sprinkler irrigation: η ≈ 0.7-0.8

-Drip irrigation (highly recommended): η ≈ 0.85-0.95

This formula means that the pump needs to draw out the water required for a full day (and consider losses) within T hours.

Example:

Take T=5 hours and use drip irrigation η=0.9.

Q_pump = 180 m³/ day ÷ (5 h/ day × 0.9) = 40 m³/h

Conclusion: You need to choose a pump with a flow rate of no less than 40 m³/h at a lift of 60 meters.

2.Pump selection

According to head and flow type:

-High head, small and medium flow (such as deep well): submersible pump (most common).

-Low head, large flow (such as water from rivers and ponds): surface centrifugal pump is selected (note that the suction head should not exceed 8 meters).

Selection Guidelines:

Based on the calculated H_total and Q_pump values, consult the performance curve (H-Q curve) provided by the pump manufacturer. The required operating point (H=60m, Q=40m³/h) should fall within the pump's high-efficiency zone rather than the edge. Confirming Pump Power: Locate the corresponding operating point on the performance curve to determine the required input power (kW).

Performance curve table case

Model	Motor Power		Rated Flow	Rated Head	The best use the flow head
Three phase	Motor Power		Rated Flow	Rated Head	L/min	0	333	500	666	750	833
380-415V- 50Hz	KW	HP	m³/h	m	m³/h	0	20	30	40	45	50
6SP40-18-2-3	3	4	40	18	Head（m）	26	25	21	18	16	13
6SP40-27-3-5.5	5.5	7.5	40	27		40	37	32	27	25	20
6SP40--36-4-7.5	7.5	10	40	36		53	50	43	36	32	26
6SP40-46-5-7.5	7.5	10	40	46		67	63	54	46	41	33
6SP40-55-6-9.2	9.2	12.5	40	55		80	75	65	55	49	40
6SP40-64-7-11	11	15	40	64		94	88	75	64	57	47
6SP40-74-8-13	13	17.5	40	74		107	101	86	74	65	54
6SP40-92-10-15	15	20	40	92		134	126	108	92	82	67
6SP40-110-12-18.5	18.5	25	40	110		161	151	130	110	98	80
6SP40-129-14-22	22	30	40	129		188	176	151	129	115	94
6SP40-156-17-26	26	35	40	156		228	214	184	156	139	114
6SP40-184-20-30	30	40	40	184		268	252	216	184	164	134
6SP40-221-24-37	37	45	40	221		322	302	259	221	196	161

Rough Calculation Formula:

Pump Power (kW) ≈ [Flow Rate (m³/h) × Head (m) × Water Density (kg/m³) × Acceleration Due to Gravity (9.8 m/s²)] / (360,000 × Pump Efficiency × Inverter Efficiency).

Typically, the pump efficiency and inverter efficiency are estimated at 0.5 and 0.95 respectively. This formula is relatively complex to calculate. We strongly recommend using parameters directly provided by the pump manufacturer.