How Sprague Air Driven Hydraulic Pumps Work

The Sprague pump develops high output pressures by applying the principle of differential areas. The pump has a large area air piston, air driven at low pressures. This air piston drives a small area liquid piston that in turn pumps liquids at high pressures.

The liquid output pressure is determined by the ratio between the area of the air drive piston, the area of the liquid driven piston and the applied operating air pressure.

The area relationship of the air piston to the liquid piston is referred to as the pump ratio. This pump ratio is indicated in the dash number which follows the pump model basic number.

Example: S-216-J-10 pump has an approximate ratio of 10 to 1 or 10 psi liquid pressure for each 1 psi of operating air pressure.

In operation, an S-216-J-10 pump using 100 psi of input air pressure will produce a maximum liquid output pressure of 1000 psi; 80 psi air will produce an output pressure of 800 psi; 60 psi air . . . 600 psi output, and 40 psi air . . . 400 psi output.

By regulating the incoming air supply at the pressure regulator, the liquid output can be infinitely adjusted through the pump’s pressure range.

How pumps work
Pump Air Piston in UP Position

Wetted Section Materials

The materials used in the wetted section of the Sprague basic pump are compatible to most liquids to be serviced. Pump components and materials include:

Liquid Body
303 Stainless steel
Liquid (driven)
Piston 416 Stainless steel chrome plated
Piston O-ring
PistonBack-up Ring
Teflon® or equivalent compound
Check Valve Body
416 Stainless steel
Check Valve Poppet
17-4ph Stainless steel
Check Valve Spring
302 Stainless steel
Check Valve Seal

Teflon is a registered trademark of the DuPont Company

wetted section materials
Pump Air Piston in DOWN Position


For optimum efficiency, certain accessories are recommended for use with pump. Noise can be dampened by installing muffler at pump’s air exhaust port. For “J” type lubricated pumps, install an air control unit (filter, pressure regulator with air gauge and lubricator) in the supply line. For “JN” type non-lubricated pumps and boosters, install an air control unit (without lubricator) in the air supply line. These and other related accessory items are available from HiP.



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