System Pressure; Case Pressure; External Shaft Seal Pressure - Danfoss H1 Series Technical Information

Technical Information
H1 Bent Axis Variable Displacement Motors, Size 060/080/110/160/210/250
Operating parameters

System pressure

Case pressure

External shaft seal pressure

26 | © Danfoss | December 2016
System pressure is the differential pressure between high pressure system ports. It is the dominant
operating variable affecting hydraulic unit life. High system pressure, which results from high load,
reduces expected life. Hydraulic unit life depends on the speed and normal operating, or weighted
average, pressure that can only be determined from a duty cycle analysis.
Application pressure is the high pressure relief or pressure limiter setting normally defined within the
order code of the pump. This is the applied system pressure at which the driveline generates the
maximum calculated pull or torque in the application.
Maximum working pressure is the highest recommended application pressure. Maximum working
pressure is not intended to be a continuous pressure. Propel systems with application pressures at, or
below, this pressure should yield satisfactory unit life given proper component sizing.
Maximum pressure is the highest allowable application pressure under any circumstance. For
applications which are above the maximum working pressure, please contact Danfoss
Minimum pressure must be maintained under all operating conditions to avoid cavitation.
All pressure limits are differential pressures referenced to low loop (charge) pressure. Subtract the low
loop gauge pressure from the high loop gauge pressure readings to compute the differential.
Summing pressure is the sum of both the low and high loop pressures. Summing pressure above 30 bar
[435 psi] guarantees reliable use within the rated speed.
Servo pressure is the pressure in the servo system and is supplied from the high side of the loop to keep
the motor at the required displacement.
Under normal operating conditions, the rated case pressure must not be exceeded. During cold start,
case pressure must be kept below maximum intermittent case pressure. Size drain plumbing accordingly.
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Caution
Possible component damage or leakage.
Operation with case pressure in excess of stated limits may damage seals, gaskets, and/or housings,
causing external leakage. Performance may also be affected since charge and system pressures are
referenced to case pressure.
In certain applications, the output shaft seal may be exposed to external pressures. The shaft seal is
designed to withstand an external pressure up to 0.25 bar [3.6 psi] above the case pressure. The case
pressure limits must also be followed to ensure the shaft seal is not damaged.
11037153 | BC00000043en-US1103