5.5.1.1 General
Cranes with a rated capacity of 1 000 kg or above, or an overturning moment of 40 000 Nm or above due to the rated load shall be fitted with a rated capacity limiter complying with EN 12077-2 as amended by 5.5.1.2 and 5.5.1.3 of this standard.
5.5.1.2 Indirect acting limiter
Settings of rated capacity limiters shall be such that when lifting a load exceeding the hoist load multiplied by a triggering-factor, the limiter shall be triggered. In general, the triggering-factor shall be ≤ 1,1.
For cranes equipped with hoists in accordance with EN 14492-2 a load exceeding the rated capacity of the hoist multiplied by the triggering-factor shall trigger the limiter. The triggering-factor shall be less or equal to 1,25. A lifted load equal or greater than triggering factor times the hoist load, shall not be lifted from the ground higher than the maximum rated hoisting speed multiplied by 1 s.
In cases where in normal operation the factor ϕ2 is above the triggering factor, a delayed triggering system may be needed. If this is provided, it shall operate as described herein. In order to allow for higher values of ϕ2, the functioning of the rated capacity limiter may be delayed by a pre-set time value, after this time delay the limiter shall operate normally. In addition an instantaneous trigger shall be provided, this shall be set to trigger immediately in cases where the force in the hoist system rises 5 % above the level of ϕ2. The final, resulting force in the hoisting system shall be calculated according to 5.2.1.5.2. Operation of this two-stage triggering system is shown schematically in Figure 5. If the hoist media force encroaches into the hatched area, triggering takes place and hoisting will be stopped.
The force due to existence of ϕ2 shall be considered as a regular load in accordance with 5.2.1.3.2.
Key t time
F force in hoist media
mHg force in hoist media due to hoist load
the solid curve shows the time dependence of force level when lifting load equal to the hoist load.
the dotted line shows the force level in a stall load case, rising to level c
a triggering level of the rated capacity limiter with delay - force level a is exceeded at t = t1, however the triggering needs to be delayed at least until t = t3 to avoid spurious tripping due to normal hoist impacting. The vertical line limiting the hatched area indicates the trigger delay release.
b triggering level of an instantaneously acting limiter – triggering at t = t2 when in a stall load case c maximum force level occurring in stall load case
Figure 5 — !Force diagram for indirect acting lifting force limiter"
5.5.1.3 Direct acting limiter
Settings shall be such that a load equal to 1,1 times the rated capacity of the hoist can be lifted, in order to perform the dynamic overload test, see 6.3.2.3, without changing the setting of the rated capacity limiter. This setting shall not allow a load exceeding mRC multiplied by ϕ DAL to be lifted, which shall not exceed 1,6 times for frictional or pneumatic limiters and 1,4 times for hydraulic limiters, the rated capacity of the crane.
In applications where a risk assessment shows an increased severity of possible harm as listed in
!EN 13135", the rated capacity limiting facility shall not rely solely upon a friction torque limiter unless the brake is placed between the friction torque limiter and the load, or the torque of the limiter is increased to a working coefficient of at least 2 when the brake is engaged, or the same increased coefficient of safety is achieved by other means.
5.5.2 Indicators
5.5.2.1 Rated capacity indicator
Rated capacity indicators in accordance with EN 12077-2 shall be provided on bridge and gantry cranes where the rated capacity varies with the position of the load. Such indicators shall give a visual warning at 90 % of the rated capacity and a visual or audible warning at overload.
5.5.2.2 Wind speed indicator
!Cranes operating in areas where the in-service design wind speeds can be exceeded shall be fitted with wind speed indicators, unless other means are continuously available for the operator to receive the necessary information.
Where a wind speed indicator is fitted it shall activate an audible warning at the wind speed at which shut down shall be initiated.
Wind speed vst, defined as a 3 second gust speed, at which shut down should be initiated can be calculated as follows:
( ) 3 2 2300 vst = v − ⋅ t
where
v(3) is the design in-service wind speed expressed as the gust wind velocity averaged over a period of 3 seconds as defined in EN 13001-2, in metres per second;
t is the time needed to shut down the crane from any operating position, in minutes."
5.5.3 Motion limiters 5.5.3.1 General
Cranes shall be equipped with limiters at the end of each motion in accordance with
!EN 12077-2". Where electrical limiters are used, they shall actuate a category 0 or category 1 stop according to EN 60204-32, but allow movement in the opposite direction to a safe condition.
NOTE 1 Guidance regarding type and location of limiters are given in ISO 10245-5.
The horizontal motions of rail mounted cranes shall be provided with additional limiters, where there is need to limit operation of the crane, trolley or load in certain areas.
NOTE 2 In some applications it is maybe desirable to fit slow-down limiters in addition to limiters at the end of motions.
5.5.3.2 Use of back-up limiter for hoist motion
!A backup upper limiter of hoist motion independently activated from the first, complying with EN 12077-2 shall be used in high-risk applications as described in EN 13135. A backup upper limiter shall also be used on cranes where
— the failure of the first limiter results in the dropping of the load, that directly or indirectly causes an unacceptable high risk to persons and property: or
— the intended use of the crane is such that the upper limit is approached frequently.
The backup upper limiter should also be used to protect valuable properties, for example: power house cranes, shipyard cranes, harbour cranes, etc.
Following the operation of the backup limiter, a restart shall only be possible in the opposite direction after a reset action, e.g. by using a key-lockable hold-to-run control on the control stand or a manual reset button on the hoist. An indication of the failure of the first limiter, as called for by EN 12077-2 is not required. The rest action required by this clause is considered adequate indication of the failure of the first limiter.
Indication and reset action are not necessary, if the backup limiter is a friction torque limiter designed to accommodate the movement energy."
5.5.3.3 Collision of cranes or trolleys
Buffers between the cranes or trolleys are sufficient systems for risk reduction, if they are able to absorb the kinetic energy resulting from the moving masses in such a way as to prevent the following:
a) the strength of the components of the crane installation being exceeded;
b) the falling or tilting of the cranes or trolleys;
c) the dropping of the load;
d) the load swaying in a hazardous manner.
In other cases, anti-collision systems shall be provided.
Where an anti-collision system is evaluated as being required, all relevant crane or trolley motions shall be equipped with the system. The anti-collision system shall have some or all of the following features depending upon the assessment of the risks involved:
— the ability to reduce the speed of approach of the crane(s) or trolley(s) moving towards a collision;
— the ability to bring the moving crane(s) or trolley(s) to a stop before a collision occurs.
The forces resulting from kinetic energy of the collision shall also be taken into account with anti-collision system unless the system meets the requirements of 5.3.4.1.
The driver shall not be exposed to a deceleration exceeding 4 m/s2. NOTE Warning of approaching collisions can be required in some cases.
!Where buffer end stops for the crane or the trolley are fixed by a bolt tightening friction grip joint relying only on friction, to provide the possibility of adjustment of the travel range, there shall also be
• a positive locking provided behind the end stop as a back-up means or
• the end stop construction shall be designed with a risk coefficient γn = 1,6."
5.5.4 Performance limiters
Performance limiters (see !EN 12077-2") shall be provided where necessary, for example:
a) limiting the lifting capacity locally where there are limitations due to load bearing capacity of the crane supporting structures;
b) limiting of hoisting or travelling speed and/or acceleration/deceleration dependent upon the lifted load;
NOTE Limiting of deceleration can introduce additional hazards, and it can be necessary to limit the maximum speed.
c) limiting of (travelling) speed and/or acceleration/deceleration dependent upon wind conditions;
d) limiting of lifting capacity dependent upon the type of load, for example increasing safety factors for dangerous lifts.
The operation of the performance limiters shall not cause additional hazards.