The vacuum producer on all Nash Jennings Vacuum Heating Pumps is what is generically called a Liquid Ring Vacuum Pump.
Liquid Ring vacuum pumps are a positive displacement type that use a spinning ring of liquid, usually water, like a piston, to pump a gas, usually air.
The non-compressable liquid is thrown out from the blades of the pump’s rotor by centrifugal force, and follows the eccentric contour of the pump housing. This eccentric location causes the liquid ring to recede from, and then be compressed back into the space between the blades of the rotor.
The reciprocating motion of the liquid ring between the blades of the rotor is what causes the air pumping action. The internal air inlet port is located where the liquid is being thrown out from between the blades of the rotor. The internal air discharge port is located where the liquid is being forced back into the space between the blades of the rotor.
A graphic illustration of the liquid ring pumping principle is shown below:
The illustration shown is a Circular Lobe type liquid ring vacuum pump. Earlier designs of Nash Jennings Vacuum Heating Pumps used a Double Lobe type liquid ring vacuum pump where the pump’s housing internal contour is elliptical in shape, and 2 pumping cycles occur with each rotation of the pump’s rotor.
The sealing liquid for the liquid ring vacuum pump is a small amount of condensate that recirculates within the unit.
The condensate pumping function is always handled by a separate single suction centrifugal impeller.
Most early designs of Nash Jennings Vacuum Heating Pumps have the vacuum rotor and condensate impeller mounted on a common shaft and they rotate together in tandem, powered by single motors. These included the Piped Up Manifold Types, Unit Types, and Type CSI pumps.
Later designs, including Type CSM, CSC, Combination Boiler Feed and Air Removal Units, and our current Type CLS designs have vacuum rotor and condensate impeller powered separately, each by it’s own motor as individual pump and motor assemblies.