HOISTS 2250 SERVICE/MAINTENANCE MANUAL
5-4
Published 11-06-15, Control # 040-13
BLOCK-UP LIMIT CONTROL ADJUSTMENT
General
The block-up limit control (also called anti two-block device)
is a two-blocking prevention device that automatically
stops the load drum from hoisting and the boom from
lowering when a load is hoisted a predetermined distance.
DEFINITION: Two-blocking is the unsafe condition in
which the load block or the weight ball contacts the sheave
assembly from which either is suspended.
Two-blocking can result in failure of sheaves and wire rope,
possibly causing load to fall.
The block-up limit controls must be installed according to
Boom Wiring, Limits and Load Indicator Electrical Assembly
drawing in your Operator Manual.
FIGURE 5-2
A1050
#44 Boom Shown;
#44 Boom with Luffing
Jib is Similar
Item Description
1 Upper Boom Point
2 Limit Switch Assembly
3 Lower Boom Point
4 Junction Box
5Chain
6Weight
7Lift Block
8Weight Ball
9Lift Plate
10 Load Block
11 Electric Cord to Reel on Boom Butt
12 Block Angle Transmitter (optional)
13 Angle Sensor
14 Batteries
15 Push to Install Button
1
2
3
4
5
6
9
7
8
10
11
5
6
12
13
14
15
With European
Standard Only
WARNING
Two-Blocking Hazard!
Block-up limit control is a protective device designed only
to assist operator in preventing a two-blocking condition.
Any other use is neither intended nor approved.
Block-up limit control may not prevent two-blocking when
load is hoisted at maximum single line speed. Operator
shall determine fastest line speed that will allow block-up
limit control to function properly and, thereafter, not
exceed that line speed.
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