Allied 795 TSL, Operator And Parts Manual

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HSL General Note and Instructions - 795 Loader
HSL General Note and Instructions
1. The hydraulic self-leveling system (HSL) utilizes two metering cylinders which displace oil
into or out of the bucket cylinders as the loader is raised or lowered. The cylinder volumes and
geometry’s are carefully matched for each loader model to provide the correct amount of oil to
keep the bucket level after it is initially leveled.
2. The HSL system incorporates two relief valves which are only utilized if the bucket cylinders
are at either end of the stroke. If the loader is raised with the bucket fully dumped, oil will be
bypassed at high pressure into the lower side of the lift cylinder circuit. If the loader is lowered
with the bucket fully rolled back, oil will be bypassed at high pressure into the raised side of
the lift cylinder circuit. Note that these two conditions are likely to occur only intermittently,
and although the pump will be forced to supply oil at a higher pressure no damage to the
loader components will occur. It is, however, recommended to avoid the above situations and
keep the bucket somewhat level while raising or lowering the loader for smoother operation.
3. Note that the large volume (piston side) of the leveling cylinders is connected to the large
volume of the bucket cylinders, and the small volume (rod side) is connected between the two
sets of cylinders. The effect of this configuration is to create a breakout force “boost” if the
bucket cylinders are pressurized toward the rollback position during breakout.
4. The opposite effect of the above situation is that the loader will have poor lift capacity if lifting
with the bucket cylinders pressurized in the dumped position. This is, however, a very unlikely
occurrence (lifting a load with bucket fully dumped).
5. The cartridge style relief valves are factory set at 2,000 psi cracking pressure and are capable of
bypassing 15-20 GPM. If loader lock-up should occur due to a low tractor relief setting, higher
inlet flows or return line restrictions, the relief valve setting may be bucket off slightly until the
lock-up condition is overcome (as described in note 2 above).
6. Never utilize the leveling cylinders to raise the loader. This could occur if the lift cylinders are
placed in float while the bucket cylinders are held pressurized in the retracted position. If the
loader should rise, pressurize the lift cylinders to lower it; otherwise a rapid drop may occur
when the bucket cylinders are extended. Note that this situation is unlikely to occur during
normal loader operation and is possible only with a lightly loaded bucket.