Improper return line connections can lead to premature seal failure and/or expensive motor damage. To maintain reliability and prolong the motor’s service life, Allied recommends the motor return line should always be routed directly back to tank, ahead of the carrier’s return filter as shown below in Figure 1.
Routing the return line though the carrier’s service valve should be avoided because both work ports open and close simultaneously. If the return port is closed while the Ho-Pac eccentric is rotating, the trapped oil can develop pressures capable of damaging the motor gear housing. If a direct route to tank is not feasible, Allied recommends installing a one-way check valve as shown below in Figure 2. The check valve will allow a path for the return oil to circulate while the eccentric coasts to a stop.
Select a one-way check valve with a cracking pressure of 10 – 30 psi and port sizes consistent with the flow requirement of the subject Ho-Pac model.
