Manitowoc 16000 Service And Maintenance Manual

Reference Only
HOISTS 16000 SERVICE/MAINTENANCE MANUAL
5-4
Published 05-09-17, Control # 014-28
BLOCK-UP LIMIT CONTROL
General
A block-up limit (also called anti two-block device) is a two-
blocking prevention device which 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 system consists of the following
components (see Figure 5-4
):
1. Normally closed limit switch assembly fastened at the
following locations:
a. Lower boom point
b. Upper boom point
2. Weight freely suspended by chain from each limit switch
actuating lever (weight encircles load line as shown).
3. Lift block fastened to load line or lift plates fastened to
load block.
Operation
See Figure 5-4 and Figure 5-5 for component identification.
For a complete wiring diagram of the system, see Boom
Wiring and Limits Drawing in Section 3.
Block-Up Limit Control Deactivated
During normal operation, the weight overcomes spring force
and rotates the actuating lever away from the limit switch
lever. This action allows the limit switch to close the load
drum UP and boom DOWN electric circuits. Therefore, the
load can be hoisted and the boom can be lowered.
Block-Up Limit Control Activated
When the weight is lifted by the lift block or the lift plates,
spring force rotates the actuating lever against the limit
switch lever. This action causes the corresponding limit
switch to open the load drum UP and boom DOWN electric
circuits.
The load drum and boom/mast hoist pumps stroke to off. At
the same time, load drum and boom parking brakes apply to
stop load drum from hoisting and boom from lowering.
WARNING
Two-Blocking Hazard!
Block-up limit 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 may not prevent two-blocking when load is
hoisted at maximum single line speed. Operator shall
determine fastest line speed that allows block-up limit to
function properly and, thereafter, not exceed that line
speed.

Manitowoc 16000 Specifications

General

Brand	Manitowoc
Model	16000
Category	Construction Equipment
Language	English