Modernization of a spreader control

The conventional controller of an existing spreader was dismantled and replaced by a userfriendly PLC-based controller. Additionally, new spreaders were equipped with the same technology.

The PLC is located on the crane trolley and has been connected to the decentralised ASI bus modules on the spreader via an ASI bus system. The bus connection is direct using two unshielded wires in the spreader line. In these systems the connection to the crane controller is realized using binary inputs and outputs, which can also be achieved via a Profibus coupling. In the crane operator cabin a small display panel is provided for messages to operate the spreader and for receiving up-to-date operating states. It also displays maintenance intervals based on the operating hours.

This arrangement provides many advantages, of which the following stand out:

• The number of individual wires used in the spreader line has been greatly reduced because the connection signals to the crane are no longer necessary.
• The number of electro-technical components on the spreader has been considerably reduced and is limited mainly to the power contactors of the hydraulic pump, a few contactor relays and robust ASI bus modules, the electronics of which are potted.
• The crane operator has excellent diagnosis options for recognising errors immediately.
• For several spreaders a single PLC only is required, which carries out the automatic spreader recognition

By now this concept has been implemented on a number of cranes and different spreaders and is equally suitable for stacking ground cranes with small lifting heights as well as for the most recent generation of dockside container cranes.

Operation

The spreader is operated by the crane operator in the conventional manner.
In addition, the operator has an exact overview of the spreader status at all times which considerably reduces downtime.
Essential information available in the controller is registered, processed and archived to a certain extent. The archived data include the operating hours, the amount of goods transferred and error messages.

ASI-module for the sensors

The programmable logic controller deployed is a S7-300 by Siemens. It is equipped with an ASI bus and a Profibus interface connection. Communication with the crane controller is enabled using binary inputs and outputs. The operating display panel is connected to the controller via the Profibus coupling. The ASI bus modules on the spreader have been chosen according to their mechanical resilience to withstand extreme pulse loading and dynamic forces. Two years of experience have shown that, despite the high daily loads, no significant failures have been reported to date.

Why HIT?

HIT successfully completed this project. The crane operators have been provided with a user-friendly system and the maintenance personnel have a system that is easy to maintain. This technology was adopted swiftly in practice, and was soon appreciated. An increase in the crane productivity could also be detected.