The pump selection should consider the water margin

Determine flow and lift

1. If minimum, normal, maximum of flow is given in the production process of pump, the maximum flow should be considered. 

2. If only normal flow is given in the production process, the water pump should be considered for some residual amount.

For ns > 100 big flow pump, the flow take 5% margin, the ns < 50 small flow pump, the flow take 10% margin, the50≤ns≤100 flow pump , the flow take 5% margin, for poor quality and operating conditions, the flow margin should be 10%.

3.If the basic data only gives weight flow, it should be reduced to volume flow.

Reasonable selection of pipe diameter

1. Pipe diameter is big, under the same flow rate, liquid flow rate is small, small resistance loss, but the price is high. The pipe diameter is small, can lead to resistance losses increase sharply, increase the selected pump lift, installed with power increasing, the cost and operation cost are increased.Therefore, it should be considered in terms of technology and economics.

2. The discharge pipe and its pipe joints shall consider the maximum pressure that can be borne.

3. pipeline layout should decorate straight pipe as far as possible, try to reduce the attachment and try to narrow the pipe length, pipe must turn, elbow bend radius should be 3 ~ 5 times the diameter of the pipe, as much as possible Angle is greater than 90 ℃.

4. the discharge side of pump must be equipped with valve (ball valve or globe valve, etc.) and reverse stop valve.The valve is used to adjust the operating point of the pump. The reverse stop valve can prevent the pump reversal when the liquid is poured back, and the pump can avoid the blow of the water hammer.(when the liquid is poured out, a great reverse pressure is generated, causing the pump to damage)