SECTION 6 – ELECTRICAL
3120933 Rev. 0 USTC 6-1
GENERAL
The electrical system is an integral part of the ma-
chine and should not be tampered or modified in any
way.
WARNING: MODIFICATION OF MACHINE
WITHOUT CERTIFICATION BY A
RESPONSIBLE AUTHORITY THAT THE
MACHINE IS AT LEAST AS SAFE AS
ORIGINALLY MANUFACTURED IS A SAFETY
VIOLATION.
ANTI-TWO-BLOCK SYSTEM OPERATION
The anti-two-block system prevents the hook sheave
block from contacting the boom nose with consequent
structural and hoist cable damage. The electro-hy-
draulic system utilizes a single solenoid valve and
derives electrical power from the positive (+) termi-
nal of the power relay.
Power is cut to the telescope out and hoist up func-
tions in the event that the sheave block contacts the
anti-two-block counterweight suspended on the hoist
cable beneath the boom nose.
The normally open (NO) switch, mounted to the
boom nose, is held closed by the counterweight. This
switch opens when the hookblock comes into contact
with and raises the counterweight. The switch opens
the circuit to the solenoid valve, thus directing fluid
flow back to the tank.
A spring-loaded cable reel, mounted on the side of
the base section, permits extension and retraction of
the electrical cable. Roller guides prevent damage to
One and Three
Part Line. Hang weight
18 in. from boom nose.
Two, Four, Five and Six
Part Line. Hang weight
25 in. from boom nose.
A2B
Counterweight
A2B
Counterweight
A2B
Counterweight
Hoist
Cable
Counterweight
Assembly
Pins
Figure 6-1. Anti-Two-Block Positions
Courtesy of Crane.Market
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