3. Design and Function
WIKA Operating Instruction, CPP4000-X
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3.3.1
Spindle pump
The spindle pump is bolted to the reservoir/high pressure cylinder block fastened to the base unit. A
sectioned view of the pump is shown. The rotating handwheel (C) which is operated by the spokes
(D) is attached to a threaded spindle (E). The spindle is supported in a sintered bearing (F). As the
spindle (E) is rotated, it drives a non-rotating ram (E and K) forward, the thrust being taken by a
needle thrust bearing (G). The large diameter of the ram (H) in the barrel of the pump (J) primes the
pressure system and provides the low pressure up to approximately 140 bar (2,000 lb/in²). The small
diameter of the ram (K) in the reservoir/high pressure cylinder block provides the higher test
pressures up to 4,000 bar (60,000 lb/in²).
3.3.2
Reservoir
A liquid reservoir is provided on the top of reservoir/high pressure cylinder block. The reservoir is
provided with a translucent cover to enable the reservoir level to be monitored. A plug in the middle
of the reservoir cover enables the reservoir to be filled or topped up (the plug is removed whilst the
test pump is in use). The reservoir contains enough liquid (approximately 150 cm³) to enable
normal operation of the test pump to be carried out.
Low pressure ram displacement = 60 cm³
High pressure ram displacement = 6 cm³
3.3.3
Control valves
Two control valves are provided on the top of reservoir/high pressure cylinder block. The valve
mechanisms are built into the reservoir/high pressure cylinder block and they control the flow of
liquid through internal drillings in the reservoir/high pressure cylinder block. The rear valve is
referred to as valve A and is used to control the output from the high-pressure ram of the spindle
pump. The front valve is referred to as valve B and is used to control the flow of liquid to and from
the reservoir.
3.3.4
Connection blocks
Pressure supply pipes from the spindle pump are terminated at two pressure blocks mounted on
the base unit. The pressure blocks are fitted with threaded bosses projecting up through the cover
plate of the base unit. These threaded bosses enable the delivered test connections to be directly
screwed on to them, and it is also possible, using threaded adapters, to connect the various sizes
of measuring instrument connections. Oil cups are fitted to the unit cover around the threaded
bosses of the connection blocks to catch any oil drips from the gauge stand during gauge fitting and
removal.
3.4
Function
Operation of the hydraulic comparison test pump is controlled by the two valves A and B on the top
of the reservoir/high pressure cylinder block. When initially priming the system valves A and B are
opened to fill the system with oil from the reservoir. Valve B is then closed with valve A left open and
the spindle pump operated to provide the lower test pressures. To provide the higher pressures
