Curvetech Technical Manual - Ref : ENG-MAN-1012.HT230BA.03
Issue 3 Confidential and copyright property of Soil Machine Dynamics Limited. All rights reserved.
C. Case Drain Connection
The case drain returns oil which has leaked through the motor
assembly to the motor case. This oil must be returned to tank (LP
reservoir) to ensure the case drain pressure remains below the
motor return line pressure.
A d inch hydraulic hose should be used and connected to a low
position d inch BSPP case drain port on the motor. This hose
should be a minimum of 0.5m long to match the main hoses and
should be similarly routed to minimise water flow restriction through
the thruster.
The standard motor shaft seal can accommodate up to 2.0 bar (29
psi) pressure from the case drain oil to the bearing housing oil and 0
bar pressure from the bearing housing oil to the case drain oil.
Please contact SMD Hydrovision if alternative pressure rating is
required.
The following considerations should be noted.
1. The drain line must be connected in a way, which ensures all
air can be bled from the motor and hose.
2. For installations where the motor shaft is vertically mounted,
the thruster should be bled to remove all air before mounting
the thruster as it is very difficult to remove all air after the
thruster is mounted.
3. There are special considerations associated with the case
drain in multiple motor installations and the following should
be addressed.
The case drains should not be commoned together unless the pipe
is increased in size to take into account the extra flow from the
additional case drains. Negligible back, pressure at the case drain
must be maintained.
Failure to comply introduces the possibility of pressurising a motor
case to a level higher than return port pressure, which may result in
damage of the motor. This could occur, for example, if the motor is
unloaded whilst other motors in the system are functioning normally.
