OVERVIEW
This is a brief write up describing the basic functions of Zone Control & Anti-Collision.
Rapicon West is not responsible for the accuracy of this information.
Use all information provided below at your own risk.
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Multi-Crane work sites MUST have controls in place to prevent a collision.
Zoning is used to limit the area in which a hook block can pass- for example, the site boundary with a road or railway. It works by limiting the slewing and trolleying the luffing motions with the crane.
Anti-Collision is used to prevent 2 or more cranes from colliding with each other
(either the structures themselves or the ropes).
In both cases, a trained technician sets up the system. The technician will measure the slow down distance from full speed slewing, at full radius with a full load. This is used to establish when the system intervenes (and crane speeds are cut).
Cranes cannot stop instantly- they have a slow down distance. A crane that stops too quickly will put too much stress on the cranes mechanisms, structure and base, and introduce a swing into the load.
HOW ZONE CONTROL WORKS
When active, the system constantly monitors the position of the crane with relation to fixed obstacles or boundaries (zoning) or other cranes (anti-collision).
So, for zoning, when the crane approaches the zone, the system compares the
current speed to the slow down angle, and will intervene by cutting gears until the crane is in 1st speed (to ensure it can stop before the boundary).
It will then allow the crane to slew in first speed, until the buffer distance reaches the zone. The driver can then only operate in “safe” motions that take the crane AWAY from the boundary. The position of the crane to a zone will limit it’s efficiency- careful placing of loading bays is critical.
HOW ANTI-COLLISION WORKS
When you use anti-collision, the cranes communicate with each other via radio link.
So, when a crane approaches another crane on site, the system wheel is constantly checking the speed of the cranes against the slow down angles. It will intervene and start slowing down BOTH cranes when the approach zone is entered.
Eventually, they will both be restricted to 1 st speed, and then STOP when the buffer zone is reached. Just like with zoning, only safe motions will be permitted; they can now only slew, luff and trolley away from each other.
Other considerations:
-The system does NOT know the size of the load.
-The system does NOT know the deflection of the crane.
-The system does NOT know the height of the load.
-The system will assume the load is infinitely long, so it cannot pass over any
zones or other cranes as it may impact them.
-Placing cranes too close to each other will significantly impact crane performance, as they will often be speed limited.
-If the buffer zone is too small there is a potential for clash.
-On small/tight sites, there may be no option but to have the system in
passive mode (i.e. audible and visual warnings only).
-This must be carefully managed with a crane supervisor in permanent attendance.
-When using anti-collision, if the system looses communication with another
crane, either because it is switched off or faulty, it estimates where the crane
could move to whilst communication is lost and expands the zone until the
full radius of the crane is protected.
