Street Crane ZX6, Инструкции по установке, эксплуатации и обслуживанию

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© Street Crane Co Ltd
Ref: D3256 rev. B Page 15 of 103
2.2 LIMITING DEVICES
Each hoist is fitted with upper and lower limits and a rated capacity limiter (RCL). These are essential items for
the safe operation of the hoist. Additional limiting devices may be fitted if deemed necessary by the risk
assessment.
2.2.1 Hoisting and lowering limits
Hoisting and lowering limit switches are fitted to all hoists to prevent the hook from going too high and
damaging the hoist and from going too low so as to allow the ropes to go slack. These are safety devices and
should NOT be used as a normal method of stopping the hoist. Movement in the opposite direction, at the
speed selected by the operator (slow or fast) is still possible after the normal limit has been triggered.
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Certain crane configurations allow the upper hook position to be set at a higher level than the
underside of the bridge girders (double girder cranes). In such instances the operator must
take extreme care when lifting to ensure that adequate clearance is maintained between the
load or lifting attachment and the hoist or crane structure.
An optional second hoist upper limit or ultimate limit may also be fitted if deemed necessary by the user risk
assessment.
The ultimate limit is an emergency limit employed only if the normal upper limit fails. Once tripped, the limit
must be manually re ‐ set by service or maintenance personnel and will require the hook block to be lowered
manually and the limit re ‐ set. If the second hoist upper limit operates, the hoist should be taken out of service
until the reason for the normal upper limit switch failure has been investigated. The failure should be rectified
before putting the hoist back into service.
The second hoist upper limit, when tripped, will prevent movement from all hoist and traverse motions. The
travel motion (long travel) will remain fully operable.
A red warning light on the base of the control panel will illuminate to indicate when the second ultimate limit
has been activated.
2.2.2 Rated capacity limiter (RCL)
All hoist units are fitted with a rated capacity limiter (RCL) to prevent the lifting of loads beyond the capacity of
the hoist / crane. If the RCL is tripped the hoist motion will stop and it will then only be possible to move in the
lower direction.
2.2.3 Travel / Traverse limits (optional)
Limit switches at the extremes of long and cross travel are optional based on the user’s risk assessment. There
are three types: ‐
1. On reaching the limit the crane or hoist travel motion will stop altogether.
2. On reaching the limit the crane or hoist will change from fast to slow speed and proceed at slow
speed until the end stop is reached.
3. If a two stage limit is fitted, on reaching the first stage the motion will reduce to slow speed. On
reaching the second stage the motion will stop.
Operation of the limit does not have any effect on other crane motions. Movement in the opposite direction,
at the speed selected by the operator (slow or fast) is still possible after the limit has been triggered.