Determining radar locations

Radar sensor locations

Radar sensors must be positioned in such a location that they have optimum 'line of sight' to the objects they are to detect. I-Series radar sensors scan in a horizontal beam. The Witness processing software is designed to generate an alarm signal, should an object appear within a detection zone. This zone is software configured to lie within the scan area. Other factors to consider when choosing a mounting location include how close the radar is to a power source on the machine. Also accessibility, both for installation and on-going maintenance.

Example 1 – Radar installed centrally on the underside of a boom

Below are two diagrams of a radar centrally mounted on the underside of a bulk loader boom. This mounting location is only suitable if there is no trolley, or loading chute that travels along the underside of the boom. In this case the installed radar would obstruct the free movement of the chute.
The reason for placing a radar in this location is to detect objects to the side of the boom, which could be struck if the bulk loader slewed or long travelled in that direction. A single radar offers protection on both sides of the boom

  
The primary use of the single radar scanning a horizontal plane is to protect slew and long travel. A secondary benefit though, is to stop the boom being lowered/luffed down on to an object that is raised above the deck level of a vessel. Although, this radar will not detect objects that are beneath the pane of the horizontal scan, as the boom luffs down these objects should be detected. Care should be taken to ensure the radar is mounted at a sufficient distance from the underside of the boom, so the luff motion can be stopped in time to prevent a collision.
By considering the rate of luff of the boom; the scan rate of the radar (typically 2Htz); and the number of required detections configured in the Witness processing software to generate a stop alarm; the ideal separation between radar and boom can be calculated.


A single radar sensor detects objects as the boom luffs

Calculating the installation distance of radar from boom to detect a raised spar whilst the boom Luffs 

Example 2 – Radar installed on each side of the underside of a boom

 
The example below shows how two sensors can be used to detect on either side of the boom. In this case it's not possible to use a single radar on the underside, this would impeded the free movement of the loading chute. See also example 4.

Example 3 – Radar installed on each side of the boom and scanning vertically

For extra protection of bulk loader boom, it is also possible to mount radar that scan through a vertical plane. These provide protection in the following cases:

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  • The distance between the underside of the boom, and the deck of a vessel it is handling will be continually measured. If the boom luffs towards the ship, the crane motion can be stopped. Although the horizontally scanning radar will protect a luff motion onto a vertical spar, it won't be adequate to stop luffing onto the deck or a hatch cover.

  • As well as during a luff movement, the distance between boom underside and loader may become too close as the boom long travels or slews along the vessel. This is particularly the case if the vessel bow is raised in relation to the stern, as the stern is loaded with heavy bulk first (or vice versa)

  • The distance between boom underside and vessel can reduce to an unsafe separation in the event that the tide changes, or the vessel is unloading and it raises on the waterline

 
This loader is shown with combined horizontal and vertical scanning radar




 
The scan planes of vertically scanning radar sensors

Example 4 – A single radar at the end of a boom structure

A single radar mounted on the underside of the boom, scanning a horizontal plane. This configuration is usually used on Ship to Shore container handling cranes. These cranes do not luff, or slew, but it is the long travel movement that needs protecting, since the crane may long travel into the ship structures in extreme conditions.
It is necessary to mount the radar at the end of the boom, to avoid obstructing the free movement of the trolley on the underside of the boom. However in this configuration, as the trolley approaches the end of the boom, the radar is obscured and then offers little protection. Many operators are of the opinion that the driver is well place in this location to have a good field of view of the vessel. As the trolley moves off the boom, the driver is further form the objects he needs good sight of, but the radar then has a completely clear view of the vessel, offering comprehensive detection. The alternative to having the trolley obscure the single radar at the boom tip, would be to use 2 radar as shown in Example 2.
  

 Single Radar on an STS, container handling crane

Orientation

The I-series scanning radar sensors, cover 360 degrees whilst rotating. The zero point or 0 degree point is set, at factory, to lie on the opposite side of the radar to the connectors. All I-Series radar rotate in a clockwise direction, whether upright or inverted.
It is always helpful when commissioning the radar if the encoder zero is aligned with the boom or structure it's to protect. For example, the zero point should be directed towards the end of the boom (with the connectors on the quay side of the radar). In this orientation, objects on the left of the boom will appear on the left hand side of the commissioning interface, and those physically on the right hand side of the boom will appear on the right of the interface. 
  
 

 Plan view of a radar, showing the encoder zero angle

Next: Mounting a radar sensor - I Series