
Reference
Only
HOISTS
18000 SERIVCE/MAINTENANCE MANUAL
5-8
Published 12-05-17, Control # 035-23
BLOCK-UP LIMIT ADJUSTMENT
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
):
1.
Normally closed limit switch assembly fastened at any or
all of the following locations:
a.
Lower boom point
b.
Upper boom point
c.
Lower luffing jib point
d.
Upper luffing jib point
e.
Fixed jib point
2.
Weight freely suspended by chain from each limit switch
actuating lever (weight encircles load line as shown in
3.
Lift block fastened to load line or lift plates fastened to
load block (see
).
Operation
See the wiring diagram in the Boom Wiring and Limits
Electrical Control Assembly drawing in this manual.
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 hoist pumps stroke to off. At the
same time, the load drum and boom parking brakes apply to
stop load drum from hoisting and boom from lowering.
Installation
for installation of the weights.
The block-up limit controls must be installed according to the
Boom Wiring and Limits Electrical Control Assembly drawing
in this manual.
Load Block Level Transmitter
The optional load block level transmitter is only used with
tandem drum operation. See load block level screen topic in
Section 3 of this manual. The wireless screen on digital
display indicates load block level battery status.
1.
The load block level transmitter is mounted on block as
shown in
, Item 14. Locate on block where
there are no obstructions between transmitter and
receiver on boom top.
2.
When reeved, load block level transmitter must be on
left side of load block when viewed from operator’s cab.
3.
Use a smart level to check level sensor zero and
compare to block angle on Level screen. If a zero
adjustment is required, follow adjustment procedure.
4.
Past Production adjustment procedure.
a.
Open enclosure
b.
If European Standard transmitter is used,
press to
install button
must be pressed to enable.
c.
Loosen screw on each side of sensor (
,
Item 15) and turn sensor slightly either way until
sensor is zeroed.
d.
Tighten screws on each side of sensor when
adjustment is complete.
e.
Close enclosure
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.
Содержание 18000
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