National Crane Published 08/16/19 Control # 112-05 3-1
500E2 SERVICE MANUAL ELECTRIC SYSTEM
SECTION 3
ELECTRIC SYSTEM
SECTION CONTENTS
Anti-two Block System Description . . . . . . . . . . . 3-1
Anti-two Block Operation . . . . . . . . . . . . . . . . . . . 3-1
Anti-two Block Internal Wire Repair . . . . . . . . . . . 3-2
Three Section Boom ATB Wire Repair . . . . . . . . . 3-2
Alternative #1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Alternative #2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Hydraulic Capacity Alert System . . . . . . . . . . . . . 3-4
HCA Maintenance & Repair . . . . . . . . . . . . . . . . . 3-4
HCA System Adjustment . . . . . . . . . . . . . . . . . . . 3-4
Jib Load Limiting Device . . . . . . . . . . . . . . . . . . . . 3-5
Single Character Display . . . . . . . . . . . . . . . . . . . 3-5
Jib Load Limiting Device Troubleshooting . . . . . . 3-6
Outrigger Monitoring System (OMS) (Optional—
Standard in North America) . . . . . . . . . . . . . . . . . . 3-6
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Remote Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
Danger Remote Start Hazard . . . . . . . . . . . . . . . . 3-9
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
Hydraulic System Description . . . . . . . . . . . . . . . 3-10
Service and Maintenance . . . . . . . . . . . . . . . . . . 3-10
Troubleshooting, Repair and Replacement . . . . . 3-10
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
Radio Remote Controls. . . . . . . . . . . . . . . . . . . . . 3-11
Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
Service and Maintenance . . . . . . . . . . . . . . . . . . 3-11
Quick Test for Receiver Antenna and Cable . . . . 3-12
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
ANTI-TWO BLOCK SYSTEM DESCRIPTION
The anti-two-block system provided on your National Crane
can help prevent cable damage by sensing the position of
the hoist cable end attachments with respect to the sheave
case and disabling the functions that can cause a two block
condition.
The anti-two-block system consists of normally open, work
port unloader valves in the main and hoist control valves.
When the cartridge solenoid is energized, the crane
functions normally, when de-energized, the oil to the boom
extend, boom down, and hoist up crane functions are
diverted to tank. These solenoids are controlled by a limit
switch, which is attached to the boom or jib sheave case.
This switch is held in the closed position by a chain
suspended weight. The weight, which is looped around the
hoist cable, causes the contacts to remain closed until the
hoist cable end attachments contact the weight and release
the tension on the switch. At this point the contacts in the
switch open, breaking electrical continuity through the circuit
provided by the internal anti-two-block cord routed through
the boom. When this continuity is broken, the unloader
cartridges de-energize and divert the function oil to tank. An
indicator light is provided on the control console to alert the
operator when a two-block condition is detected.
On machines equipped with an optional Rated Capacity
Limiter (RCL) System, the anti-two-block system is integral
with the RCL wiring and display. An audible, visual warning
of the two block condition is provided in the display console.
See RCL Operators Handbook for additional information.
Normal functioning is restored by hoisting down (or retracting
boom) until the weight is once again suspended freely.
Occasionally if the hoist up and boom extend functions are
operated at maximum speed in the dump mode, the back
pressure induced in the circuit will cause the hoist up or
boom extend functions to creep slightly (with no load on the
hook). Such a condition is not cause for alarm, as the back
pressure is not of sufficient magnitude to damage the cable
or end connections.
Anti-two Block Operation
The internal anti-two-block wire is routed from the control
console to the hoist mount end of the boom, following the
path of the extend cables to the rear of the 3
rd
section boom.
This is the length of the wire that proportions in and out with
the boom length, similar to the route of the extend cables. At
this point at the rear of the 3
rd
section, the wire loops around
and anchors at the anti-two-block cable clamp on the extend
cable anchor. The anti-two-block wire, now attached at the
rear of the 3
rd
, runs the length of the section and attaches to
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