Lowering A Load; Hydraulic Lines; Hydraulic Oil; Clean - Yale 524150797 Maintenance Manual

Operation

LOWERING A LOAD

A load is lowered by depressing the lower button.
When the lower button is depressed, electric current
is sent to the normally closed solenoid lowering valve,
which causes it to change position and open a path
for the trapped hydraulic oil to flow from the cylinder
back to the reservoir.

HYDRAULIC LINES

1. All hydraulic lines must be thoroughly cleaned be-
fore installation.
2. When making repairs, use the least number of fit-
tings and connections to minimize flow resistance
and the possibility of leakage.

HYDRAULIC OIL

The hydraulic oil in the system performs the dual
function of the power transmission and lubrication.
Using the correct fluid is essential to proper system
operation. Refer to Capacities and Specifications
8000YRM1511 - Hydraulic Oils, for the recommended
hydraulic oil to be used.
Check the reservoir level when troubleshooting lifting
problems. Low oil levels will make it appear that a
problem exists with the battery or hydraulic system.

CLEAN

Adhere to the following precautionary steps to ensure
that the hydraulic system remains clean.
4
1. Flush the entire system when a failure is encoun-
tered to make sure all paint, metal chips, welding
shot, and debris are removed.
2. Filter each change of oil to prevent the introduc-
tion of contaminants into the system.
3. Provide continuous protection from airborne con-
tamination by keeping the breather clean and
serviceable.

SOUND LEVEL

Hydraulic system noise is caused by both improperly
selected oil and loose or damaged system compo-
nents.
• Hydraulic oil with high or moderately high vis-
cosities - At startup, temperatures can cause
pump noises due to cavitation and also im-
pedes the release of trapped air. Air does not
have sufficient time to purge itself from the fluid
while in the reservoir before recycling through
the system.
• Aerated Hydraulic Oil - Results in system noise
that is similar to cavitation. Aerated oil is
caused by the ingestion of air through the pipe
joints of the inlet lines and high velocity dis-
charge lines, as well as cylinder rod packing.
Aeration can also be caused by oil discharging
above the fluid level.
1900 YRM 1506