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b) Connecting drain port T
These motors have a 1/8” G drain hole in the centre of the cover. The motor is supplied with the
port closed by a metal plug (see gure below).
Two non-return valves are incorporated in the motor casing to maintain internal pressure at the
same level as the low pressure line A or B if the drain port is not connected to the tank.
1) If the drain port is connected up, pressure at the shaft seal is always equal to the pressure in
the drain line.
2) If the drain port is closed off, pressure at the shaft seal never exceeds pressure in the return
line.
The maximum values for pressure in the drain line (case 1) or return line (case 2) are given in the
following gure (for continuous and intermittent operating conditions).
Incorporated non-return
valves
The drain port must always be connected up when more motors are operated in series.