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As a policy of continual improvement, STAUFF reserves the right to alter the specification without prior notice.
201.031
Date of Issue: 06 November 2018
2 Low Pressure, Off-Line Operation
Figure 6.9 LPM working pressure generated by hydraulic component
3 Very Low Flow Systems
Figure 6.10 Entire system flow rate is within the range of the LPM
6.1.3.1 Flow Rate
For the majority of systems, a differential pressure of a few Bar will generate an in-range flow for an LPM
connected using two 1.5 meter lengths of microbore pressure hose. The required differential pressure
can be obtained by taking advantage of an existing pressure drop within the system. Alternatively one
can be created by inserting a check valve. The LPM can then be connected across this differential
pressure source.
6.1.3.1.1 Detailed Calculations
In general the flow rate of fluid through the LPM needs to be kept within the range of the unit (see
hydraulic specification 3.2). The LPM measures the flow during operation, so this can be used to check
that the flow is correct.
A flow that is out of range will be indicated by a fault code (see section 7.2).
Note: Results taken with out-of-range flows are not logged.
The flow is entirely generated by the differential pressure between the ends of the pipes used to connect
the LPM. The pressure needed to generate an in-range flow can be estimated by assuming a target flow,
and determining the resulting pressure drop across the LPM and connection piping. Use Figure 6.10 on
page 24 to lookup the LPM
pressure drop, and manufacturers’ data to lookup the piping pressure drop at
the desired flow. The sum of these two pressures is the pressure needed.
The user connects the LPM between two points in the hydraulic circuit that have this pressure difference.
In order to use the graph:
Determine the working viscosity of the fluid, e.g. 30 cSt
Decide on a desired flow rate. 200ml/minute is normally used since this is in the middle of the
LPM flow range. But 100ml/minute is also suitable and uses less oil
Use the figure 6.11 to look up the pressure drop, across the LPM ports, at this flow rate and
viscosity. E.g. at 30cSt and 200ml/minute, this is 0.4 Bar. The maximum and minimum allowed
differential pressures can also be determined using the 400ml/min and 20ml/min lines,
respectively.