Test rig for large sized components and closed circuit pumps

  Circuit diagram of the efficiency test rig for closed circuit hydraulic pumps Copyright: © ifas

The efficiency test rig for closed-loop hydraulic pumps at ifas permits the recording of efficiencies in accordance with ISO 4409.


Efficiency Measurement

Efficiency measurements are primarily used as a benchmark for different product series and between competing products. Furthermore, efficiency measurements are suitable as a customer argument with regard to the fuel efficiency of the hydraulic drive. Efficiencies are divided into volumetric and hydro mechanical efficiency. Volumetric efficiency is the sum of internal leakage (from the high-pressure to the low-pressure section) and external leakage (from the machine to the tank). All losses that reduce the torque, such as solid-state and fluid friction in the hydraulics and friction in seals and bearings, are referred to as hydro mechanical losses. The definition of the efficiencies depends on the operating mode of the engine. The standard ISO 4409 includes regulations on the design of the hydraulic circuit, in particular on the placement of the sensors, as well as on the conduct of the test.


Test rig for measurements in closed circuit

The test rig consists of an asynchronous motor with an output of 200 kW, which can be operated with speed regulation via a frequency converter. Both the speed and the torque delivered via the shaft are measured by sensors. The maximum possible torque is 4000 Nm, the maximum speed 1600 min-1.

The flow rate is measured in the high-pressure section by means of a gearwheel sensor. The maximum flow rate (HLP 46, 40°C) is specified as 2100 l/min. The load pressure can be adjusted between 10 and 300 bar by means of an electrically controlled pressure relief valve. Furthermore, the test bench is equipped with a circuit cooler. This enables the hydraulic circuit to be operated under temperature control. The hydraulic circuit is fed from a 3000l tank via the central hydraulic power supply adjustable pressure between 10 and 30 bar. A separate control oil pump is available. The temperatures as well as the volume flows of all supply and feed flows can be recorded.