All Hydraulic dredging pumps are submersible pump. They need to be operated underwater because submersible pump is design in the way that it needs to be in underwater to keep it cool. That is always one of the reason to cause submersible pump spoiled because operates on the surface of water (Dragflow cooler jacket, the solution for surface pumping without overheat the pump, read more on The Required Condition For Submersible Pump Applications?). All pumps are impossible to work at zero head because hydraulic dredging pump require head to pump even it is to pump from underwater to water surface. I will further explain to you with following example,
Brand X Pump Specifications Table
The table and curve above show the specifications and performance curve for Brand X. Refer to the specifications for Model A at 50 Hz, we can see that this model can produce maximum capacity of 1.65m³ per minute and maximum head is 14.8m. However, when we refer to the curve, this pump can produce 1.65m³ per minute but at nearly zero meter head which is impossible. This is a submersible pump and need to operate underwater because it needs water to keep it cool. Operate underwater require head for the pumping action. Yes, this pump maximum head is 14.8m but at 0 capacities which are useless. Same goes to model B and C.
Dragflow HY24 Dredge Pump Specifications Table
The curve above is one of our product Dragflow HY24 dredge pump. From the pump performance curve, you can know that our product specifications is on working capacity because our dredge pump capacity is up to 105m3/h at 24 m head but not in zero meter head. Based on pump performance curve, our dredge pump head can up to 34m but only stated 28m in table. This is because we know that it is unrealistic the maximum head to be at 34m and capacity is at 0m3/h.
As the comparison above, you have learnt working capacity is the maximum capacity of a submersible pump with the workable pump head at particular dredging depth. It is useless to have zero or near to zero meter head, even you have very high pump capacity over a period of time. Before you looking at the maximum capacity, must check with the meter of head at that so called “maximum capacity”, because it might be the capacity u wouldn’t be able to reached because most of the time it is a non-working capacity. At dragflow, we practice our salesperson to quote the pump capacity with the pump head to show customer a workable pump capacity instead of “unreachable” pump capacity (Read more on The Wrong Or Half-True Information For Pump Dredging).