These units comprising the MFE Group are designed to supply the lubricant used in intermittently operated, single-line centralized lubrication systems.The basic setup includes a gear pump unit with motor, a 3 or 6 liter lubricant reservoir – optionally of metal or plastic – or a 15 liter metal reservoir and float switch to monitor the minimum permissible level of lubricant. Explanation of hydraulic functionBoth types have the same hydraulic function.Oil is sucked in at S and flows under pressure through the duct in the direction P. The oil pressure closes valve V and opens valve E3, at the same time closing valve E1 against spring tension. If air is entrained (due to low oil level in the reservoir), valve V remains open and diverts the air or, respectively, the air-oil mixture into the return duct (see bubble (o) marking in direction R1). Valve C allows oil under overpressure to flow out into the return duct (see cross (+) marking).When the unit stops (interval time), spring-loaded valve E1 opens and valve E3 simultaneously closes. The system pressure at P can now be released through valve E1 – with the exception of asmall amount of residual pressure determined by valve E2. This pressure release is required for the piston distributors to function correctly.The pressure relief process is shown in fig. 4.Explanation of the structural differencesIn the case of model ME5, the long screw plug D1 blocks flangedport R2 of the return duct. The oil returning from valves V, C and E1 flows via port R1 through a tube to the separately mounted oil reservoir (see fig. 1 and 2).In the case of model MFE5, the short screw plug D2 – unlike D1 with model ME5 – leaves flanged port R2 open. A plug closes off external port R1. – Flanged port R2 of the return duct drains directly into the reservoir without any connection threads