Abstrakt

Starting hydraulic pumps in low ambient temperatures may cause: decreased hydraulic-mechanical efficiency, larger vibration of hydraulic installation, faster wear and more frequent damage to the elements of pumps, change of material properties of elements, increase of pressure drop. As a result of pressure drop in the suction pipe, large underpressure may be experienced, causing incomplete filling of pump working chambers with oil and reducing volumetric efficiency. Starting of cooled hydraulic pump in low temperatures may occur when pump is supplied either with oil of the same ambient temperature or with the oil warmed to higher temperature. During start-up of a hydraulic pump in thermal shock conditions, parts warm up in a nonuniform way, due to varying material and shape properties. This causes change of clearances between the co-operating elements and may lead to faulty operation of hydraulic pump or to its break-down. Experimental tests of pumps during start-up in low ambient temperatures, were performed in the Hydraulics Laboratory of the Faculty of Mechanical Engineering of the Gdańsk University of Technology. The Laboratory is equipped with multipump supply devices with oil temperature stabilization, devices for testing hydraulic components as well as a system for measuring and recording mechanical, hydraulic and thermal quantities. In low temperature chamber it was possible to cool down hydraulic components to –25 °C. The supply oil temperature was kept in the range from 20 to 60 °C (usually at 50 °C) by means of oil temperature stabilizing system.

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