Two post hydraulic lift HAPP 95
© 2013 HAPP Australia Pty Ltd
Version 9
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and fittings / oil pump suction lines must be firm to ensure no air leakage when not in use.
As mentioned previously, because of its hydraulic synchronization design, typically carriages lift within
0-‐20mm once oil lines are equalized and the hoist is bedded in. If oil lines are not equalized the hoist
may lift unevenly from 0-‐40mm.
In general, if an oil line has 8mm of oil more in one side than the other then the hoist will lift unevenly
by 10mm.
Some hydraulic attributes that are in effect are:
•
Oil is a non compressible fluid.
•
Air will typically bleed past the seals in cylinder even though it will not let oil through
•
Bleeding air from a HAPP 90/95 hoist whilst useful is only part of the setup process, air will often
push through the system and past seals during initial operation or possibly when left idle. The
issue this causes is an imbalance in oil volumes left after the air is expelled which causes more
uneven lifting.
The oil line setup can be performed in a number of ways including the following steps.
8.3 Bleeding air from lines
Can be performed by raising the columns and lowering to the lowest position, then loosening the fitting
to the hose at the base of the column allowing air to be expelled and / or decoupling the line from the
quick connector and releasing fluid into a container as shown below, you can see the air bubbles come
out using this approach. A clear graduated plastic container is recommended such as the disposable
units used for measuring paint. This approach is recommended as it does not create mess and allows
the oil lines to be calibrated. for even lifting.
Picture 3: Oil line bleeding and balancing with plastic measure.
8.4 Equalizing oil line volumes
The columns should be running freely (lubricated with WD 40, dry lube) and an initial bleed of air from
the system has been performed. If the system has been sitting for a while there may be air in the line
which will bleed out of each cylinder quickly (air passes seals where oil does not), which is fine, but as
the air is thinner than oil it can pass through the control block in an uncontrolled manner, causing the oil
lines to be out of balance. The air can come from new installation, on standing due to loose fittings or
low oil level in the reservoir. Or in some rare cases leaky fitting in the suction pipe from pump.
