Company profile: Konecranes

Would you find it fun to operate a crane with an electro-hydraulic grab (costing your annual salary if damaged beyond repair) that is hanging on a pendulum of 35 metres (about 100 feet) inside of a concrete bunker? Many operators do this eight hours a day for living, and now some of them even find it fun.

Regenerating electricity and heat from waste has become increasingly attractive solution even in sparsely populated Nordic countries, while it has for a long time been the most efficient method of waste processing in Central Europe. The main material handling tool in these plants is an overhead crane and its mechanically or electrically operated grab/bucket.

The waste is unloaded into the waste pit by trucks, and then distributed further into the whole pit area with the cranes. In some plants part of the waste is also fed first through a shredder, which breaks the waste into particles more suitable for burning process. Waste is typically handled 2-4 times by the crane before burning. Therefore special attention must be paid to the reliability of handling equipment.

Grab design and solutions

The mechanical grab is simple but hoisting machinery is difficult for maintenance and repairs, back-up equipment including the whole cranes. In particular the closing ropes are subject to extremely fast wearing. In addition, the mechanical grab doesn’t match well with the demands of full automation. In pit fires the mechanical grab could operate better in fire prevention.

The hydraulic grab is more effective with higher compaction factor. With a smaller grab the crane is easier to control, ending with more even material flow in the process. The savings are seen also in terms of building dimensions and structures, since loads are lower and space is saved. However the electro-hydraulic grab requires a vertical power feeding cable. In traditional solutions the power cable is reel-up through a motor driven cable reel up to the hoisting trolley. Konecranes has developed a tailored and patented system where the cable is reeled onto the rope drum, hence the hoisting machinery is utilised also to the lifting of power cables. Today’s sophisticated full automation requires also power down in the grab for sensors.

The steel structures and hydraulics of a waste handling grab are under very high strain. On the most critical points of jaws special wear resistant steel is used to reduce the abrasion. The hydraulics is dimensioned to operate 24 hours a day in different duties. The directional valve control with free circulation system has proved to be the most reliable in this environment.

Fast travelling speeds and dusty environment in WTE and bio fuel energy plants set high requirements also to the rail wheels. Into this application flame hardened chrome-molybdenum wheels have proved to be the most reliable. Konecranes provide the wheels also with special bearing housings to allow realignment of wheels afterwards.

In new advanced WTE-plants, the cranes are generally provided with unmanned fully automated controls and no particular crane operators are needed at all. The operation people from the central control room can set the new parameters to the touch screen whenever the process requires. The best layout is when the CCR and operator’s pulpit are integrated into the same room and the location is close to the end wall of the pit. Nevertheless, the ergonomic operator’s seat is recommended for this demanding environment for temporary operation purposes.

Due the very dusty and inconvenient service environment, the crane controls are mounted into the separate switchgear room in the building. Long wiring distances cause problems to the signal transmissions. In the modern layout the electric room has been located at the end of the pit area close to the power supply of cranes (festoon cables or power chain) to shorten the wiring distances to the bone.

The stepless frequency controllers in motor controls create a reliable and safe basis for the operation of cranes in the WTE environment. It is possible to shorten the cycle time in lowering motion with ESR (Extended Speed Range).

In the advanced crane control system, the braking resistors have been replaced by the regenerative network braking. Konecranes supplied DynAReg enables very efficient energy optimisation. DC-bus is applied between the motor controls and DynAReg – hence the field weakening of the motor can be increased. Consequently more power is achieved from the motors with reduced consumption.

The CMS Crane Management System, combined with a crane’s PLC, enables possibilities to collect extensive data from the cranes to utilise in many purposes. From the work station in the central control room or close to the pulpit, the operators and service people can study the active faults and events or the history data. In addition, for example, production statistics and reports, crane parameters, maintenance programs and instructions can be found from the system. With remote access the service people can study the crane history and utilise this data in their service tasks.

About 10 years ago hardly anyone believed that unmanned full automation could work in a WTE environment. However the new generation’s DynAC motor controls and DynAPilot load sway controls offered a completely new approach to this question. Today, most of the new cranes are equipped at least with full automation in feeding for the operation at nights and weekends.

More frequently, they are also requested to offer unmanned full automation for continuous operation. With the optimised building layout and functional interfaces to the hoppers and gates of tipping floor, high availability can be reached. The waste volume in the pit can also be followed directly from the screen. The set of working cycles (parameters) for the touch screen makes the system user-friendly.

Most new WTE cranes are operated with a help of modern automation systems. That helps maintenance personnel to monitor crane operation and find faults faster, often even without entering into the waste pit area. An even larger effect to the crane operation can be achieved when the automation system is used to aid the crane operator in optimising the crane driving and even the automation of the repeated crane tasks.

All Konecranes WTE cranes are equipped with DynAPilot load sway control system and AutOPilot features to prevent grab collisions with the pit walls. In a typical WTE crane the lifting heights can be over 30 metres, which results in a very slow pendulum motion of the payload. The result is that the grab follows the crane accelerations with a delay of 3-5 seconds. That, in combination with high speed travelling and traversing motions, makes the crane operator’s work demanding, and causes increased stress and fatigue.

Konecranes solution is to use its crane load control technologies to prevent unwanted collisions with the pit walls and other structures of the plant. While the traditional limit switch based solutions for this problem have caused unexpected load sway and operating time losses due to speed limitations, the new patented optimisation techniques allow for maintaining the full production capacity and virtually eliminate grab and crane damages caused by load collisions. The same principle of operation can be used in both manual, operator initiated operations and even unmanned, fully automated operations.

Konecranes WTE cranes can operate using the highest possible long and cross travel and hoisting speeds simultaneously, without the risks of collisions and without peak mechanical loadings caused by the crane accelerations and load swing dynamics. These technologies have been successfully tested in a number of new and modernised WTE cranes in Europe, Asia and the Americas. Payback time of less than one year for the system has been reportedly achieved in several places because of reduced grab repair costs only. Additional advantages are reduced maintenance costs of other crane components, improved crane cycle times and operator work conditions.

According to the crane operators, driving the new Konecranes WTE cranes is easy and operator stress and fatigue are greatly decreased. But, most importantly, crane driving is made fun again.

Find out more: www.konecranes.com

Konecranes WTE cranes can operate using the highest possible long and cross travel and hoisting speeds simultaneously.

All Konecranes WTE cranes are equipped with DynAPilot load sway control system and AutOPilot features.