HARBEN CENTURY, Service Manual

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Flowplant Century Pump Manual
1.2 PUMP DESCRIPTION
1.2.1 Functional
The following description of the Harben Century Type Pump applies equally to the 4 and 8
cylinder variants. Performance details of each type of pump are given later in this section.
The Century pump works on the radial piston design principle which uses one-way valves
in conjunction with tubular diaphragms, fitted with an internal support or mandrel. The
pumped fluid, which passes through this diaphragm, is enclosed by a cylindrical pressure
chamber or barrel, in the ends of which are fitted inlet and delivery valves.
The pump crankcase, which contains the only mechanical moving parts, is filled with
mineral hydraulic oil. This oil provides for the lubrication of all moving parts within the
crankcase, and as a means of pressure to compress the diaphragm.
As the pump shaft rotates, the piston advances and its ports pass the end of the cylinder,
sealing the chamber. Further advance of the piston causes the trapped oil to compress
the diaphragm around the mandrel, expelling the water in the diaphragm through the
delivery valve and into the delivery manifold.
When the piston retreats, the diaphragm reverts to its tubular form and draws water
through the inlet valve. Any oil slippage past the piston during the delivery stroke is made
up through the piston ports as they open to the crankcase oil.
All mechanical parts, with the exception of the inlet and delivery valves, run in the oil-
flooded crankcase and are therefore unaffected by contamination by the pump fluid, or by
running dry.
1.2.2 Filtration
Standard filtration for the pump is normally 50 microns. This filter is usually fitted to the
inlet of the supply tank or reservoir. This arrangement ensures that if the filter is neglected
to the point of blockage, the tank will empty and the pump will run dry, thus enabling the
dry-running qualities of the pump to be used as a filter maintenance indicator. Inlet
conditions required are flooded suction; pressure feeding is not necessary.
1.2.3 Fluid Flow
Arrangements are made on the pump for the incoming fluid to cool the crankcase oil.
The use of standard diaphragm/barrel assemblies provides a choice of flows, depending
upon the number of barrels fitted to a crankcase. The cylindrical form of these barrels is
well suited to containing high pressures. Three piston diameters are available to suit a
range of pressure up to 700 bar (10 000 psi).
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