Frank Beardsley examines how operational aid devices for crane operators are increasingly being customised to fit operators’ specific needs.
Nowadays with new technologies, it is simple to adapt a rated capacity indicator (RCI) software to ease the operators' work.
A couple of years ago, for example, an African crane company would have thought it impossible to ask for and receive changes to the arrangement and content of displayed information on a recently installed RCI display while the technician was calibrating the system on a job-site. With Rayco-Wylie Systems’ model i3000 Rated Capacity Indicator, this is now feasible.
Fig.1 shows one version of several available screens in a standard graphic display supplied to a customer, and below that is a new screen that was designed by the operator himself the way he wants to view the crane information.
In this example, the operator sketched this screen, faxed it to the factory where it was programmed, emailed back to the on-site technician who downloaded the program into the RCI. Even the size of the numerals in different places was customised to suit the operator. Additionally, the operator can still switch back and forth from his screen to the other standard screen whenever he wants. In this particular RCI, the flexibility available for customising the working screen is quite impressive.
Another feature showing the flexibility of the system is the hook height. You may have noticed that the display is showing hook height at the top right of the screen. In fact, it will read it in two modes; relative and absolute. In practice, the operator can ‘zero’ the hook height using the relative mode at water level on an offshore crane for example, and then view how many feet that his hook is lowered in the water.
The RCI is continuously monitoring ‘absolute’ hook height, which is the distance from the tip to the hook, but only displays the information selected by the operator. Hook height indication and tracking is accomplished using absolute encoders, and software to track the wraps of cable on each hoist drum along with the layers of rope on the hoist drum. Calculations for hook height take into account boom angle changes that will affect the hook height and rotation of each hoist drum plus the physical geometry of the crane. In this example, the customer’s crane there are five hooks, all with hook height indication.
In addition, the hook height monitoring system is accurate enough to be used for Anti-Two-Block approach warning on all five hooks. This feature eliminates any dangling hardware on the boom tip.
This particular crane is also equipped with two displays so the operator can view two of his hoists on one display and the other three hoists on the second display. An essential feature of the absolute encoder used to provide hoist drum rotation is that when power to the system is removed and reapplied, there is no loss of information. Another application of the same absolute encoder is to indicate the boom azimuth when the encoder is placed in a position to measure the rotation of the boom around its centre of rotation. This is a common addition to the i3000 on hydraulic cranes.
Frank Beardsley, Technical Director at Rayco-Wylie Systems, Alabama, USA. www.raycotech.com