Pump Ratios

The ratio is the area of the air piston compared to the area of the fluid piston in an air-powered pump. The pump ratio determines the multiplication factor between the air-input pressure of the air motor and the fluid-output pressure of the pump.

For example, if the air-input pressure is 100 psi, a pump ratio of 1:1 will yield a fluid-output pressure of 100 psi. For a pump ratio of 3:1, the same input pressure of 100 psi will yield a fluid-output pressure of 300 psi. For a pump ratio of 5:1, the same input pressure of 100 psi will yield a fluid-output pressure of 500 psi.

 
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  • 1:1 Ratio Pumps: Ideal for pumping low viscosity fluids over short distances, typically less than 30m.

  • 3:1 Ratio Pumps: Ideal for pumping low and medium viscosity fluids over distances of approximately 45m.

  • 5:1 Ratio Pumps: Ideal for pumping medium and heavier viscosities over distances of 60m or more.


Capacity 

The capacity of a reciprocating pump indicates the quantity of fluid it delivers. The capacity of a pump is read in two ways: relative capacity and real capacity.

The “relative” capacity or “approximate” capacity is obtained via laboratory testing under the following conditions: 

  • pump operated at 87 psi (6 bar)

  • using SAE 30 oil

  • at room temperature (20°C)

  • with free outlet, i.e. without any connection, delivery hose or gun connected to the pump.

The ”real” capacity, i.e. the “real delivery quantity” in certain applications and combinations, varies according to:

  • type of compression ratio

  • single or double-acting pump

  • viscosity and temperature of the fluid

  • pressure of air feeding the pump

  • transfer with one delivery hose only

  • delivery hose and gun for dispensing near the drum

  • centralised systems with one or more delivery points

  • size of dispensing tube

  • height and length of system in suction and delivery

  • type of connections and accessories for completing the system.

 

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