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SAFETY DEVICES

There are certain safety devices on the IC-20 that are designed to maintain control of a

load in case of power or hydraulic line failure. The operator should understand the

function and operation of these devices so that a continual check on their performance

can be made.

OUTRIGGER CYLINDER CHECK VALVE:

A double-acting check valve is flange-mounted on each of the outrigger cylinders. This

valve holds the outrigger in the extended position should power or hydraulic line failure

occur. This valve has no adjustment. If an outrigger creeps up while supporting a load,

there is an internal leak in the valve or in the outrigger cylinder piston seal. In either

case, maintenance is required.

BOOM ELEVATION CYLINDER HOLDING VALVE:

A single-acting holding valve is flange-mounted on the cylinder barrel. This valve holds

the boom in the elevated position should power or hydraulic pressure line failure occur.

This valve is adjustable to hold the desired load. If the boom creeps down with loads up

through maximum capacity, this valve should be adjusted. If adjustment fails to correct

the problem, there is an internal leak in the holding valve or the hydraulic cylinder. Refer

to the maintenance instructions.

BOOM EXTENSION CYLINDER HOLDING VALVE:

A single-acting holding valve is flange-mounted to the cylinder rod end. This valve holds

the cylinder in the extended position should power or hydraulic pressure line failure

occur. This valve is adjustable to hold the desired load. If the boom creeps in under

load, this valve should be adjusted. If adjustment fails to correct the problem, there is an

internal leak in the holding valve or the hydraulic cylinder. Refer to the maintenance

instructions.

ANTI-TWO-BLOCK SYSTEM:

This system prevents damage to the hoist rope and machine components from acci-

dentally pulling the load hook against the boom tip. A pivot arm-actuated electric switch

is connected, through a cable reel mounted on the boom, to a solenoid dump valve in

the hydraulic circuit. This valve will dump the HOIST RAISE, TELESCOPE EXTEND

and BOOM LOWER circuits. No other circuits are affected. These circuits are returned

to normal operation by operating the HOIST LOWER or TELESCOPE RETRACT

control. An emergency override switch is provided for the Anti-Two-Block System, on the

upper instrument panel, in case of system failure. Holding this switch will allow the

operator to override the system dump valve.

WARNING

We recommend the emergency override switch be used with discretion. Improper
or careless use of this switch can cause damage to the crane and endanger
people and property.

WARNING

Even though the crane is equipped with an anti-two-block device, we strongly
recommend that the operator always watch the downhaul weight and stop
movement before two-blocking occurs. Two-blocking can cause sudden stopping
of boom movement or can break the load hoist rope and let the load fall. This
could cause death or serious injury.