Many hydraulic systems use fixed displacement pumps as the primary source of flow. The actual flow that a system attains is the specified pump displacement reduced by the pump's inefficiency. This inefficiency results in lost flow which returns to the tank through an external case drain line. By installing an inexpensive, direct reading flowmeter in the case drain line, the pump's efficiency can be evaluated. Any significant change in the case drain line flow rate acts as an early warning signal on the pump's continuing efficiency.
Tom Kuczenski, a Hedland consultant, says, "Based on experience, many engineers use declining efficiency as a factor to determine the need for a pump rebuild. A typical signal might be a 10-point loss in pump efficiency."
He cites the following example: a 50 cc/rev pump running at 1800 rpm would theoretically flow around 89/90 lpm at the specified rated pressure. At an efficiency of 92% actual flow to the system would be around 81 lpm with the remaining flow of 8 lpm flowing back to tank through the case drain line. However, if the pump's efficiency dropped to 82%, the flow to the system would reduce as case drain flow would increase close to 16 lpm - more than double the drain flow at an efficiency of 92%.
A suitable flowmeter would easily highlight the increased flow through the case drain line. The maintenance team or operator would be able to record flows and establish a trend of the rate of fluid flowing through this line at predetermined intervals. The Hedland EZ View requires no special piping or flow straighteners. It is easy to install, has a polysulfone plastic body, piston and cone and a T300-series stainless spring. The accuracy is within 5% of full scale. To minimise human involvement, an optional electric signal switch, called EZ View Flow Alert is available.
Hydrasales' Cheryl Johnson says that these meters can save owners expensive pump repairs and the resultant downtime by simply installing in the case drain line.
For more information contact Haroun Pochee, Hydrasales, +27 (0)11 392 3736, [email protected]
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