Control systems and crane mechanisms electric drive to a variable frequency drive modernization
Are the crane modernization or reconstruction really so expensive that it is necessary to abandon them?
The problem of reconstruction and modernization of handling equipment for some organizations seems to be an unsettled and unacceptable task in view of the large capital investments required for their implementation. But the acquisition of new equipment is much more expensive, so organizations are at a dead end. After all, in the conditions of competition, there are opportunities for more flexible schemes for the introduction of new equipment, which help to increase the willingness to solve the problems of technical equipment in this way, and not to purchase new equipment that is not yet available to our enterprises.
In the process of transporting goods, the cranes occupy a central position. Their breakdowns lead to a break in the technological chain of transportation. Of course, it is possible to replace them by using other transport vehicles: cars, mobile cranes, etc. But this replacement is still an inadequate and unsatisfactory alternative for transport and reloading organizations, rather the replacement of cranes for idle time with other equipment indicates the miscalculations of the company's management or those people who are responsible for the working conditions of the cranes and their operation. As it was already mentioned above, replacing the crane with other equipment greatly reduces the volume of loading and unloading operations, which in turn leads to large economic losses, not to mention the breakdown of contractual terms and the distrust of potential customers emerging. Customers that are unsure of the reliability of the technical base of the contractor refuse to deal with such organizations and are forced to look for partners with a higher level of technical support. Considering the current difficult situation in our country, this task is not an easy thing to do. The overwhelming majority of organizations was turned out to be at about the same level of technical support. This led to a long economic crisis, the development suspension of the machine-building industry, the termination of the design and activities of research institutes and design organizations that have been engaged in the development of industry and contributed to the competitiveness of domestic technology with foreign counterparts. Therefore, almost all organizations contain on their balance cranes of the late 70's - early 80's release. Since then, the technology has not been updated, and it still functions, despite its long-established regulatory deadlines.
It's good that the structures in the former Soviet Union had hing strength and durability, which makes it possible to extend their operation today. But even this technique has its limit, it breaks down, leads to a large expense in maintenance and repair, which forces the company's management to look for other ways to restore the technical base. Large enterprises such as ports are trying to update their base with new foreign and domestic cranes, which, as you know, is not a cheap deal. The pace of renovation is small due to the limited funding. Therefore, this variant of solving the problem is not always acceptable even with large organizations, not to mention small enterprises.
One of the ways out of this situation is the modernization of the operating machinery. In general, modernization is needed for crane drives and electric drive controll systems as far as the metal structure, which has a large margin of safety, allows further operation. The modernization of the control systems of the crane mechanism electric drive consists of replacing the existing relay-contactor rheostatic control systems with a frequency control system that provides contactless smooth speed control in a wide range with a high level of energy saving, obtaining small (running) speeds that ensure the required accuracy of installation, cargo safety, increase of productivity, reducing the number of technical services and repair the electric and mechanical parts of the crane, reducing the flow of spare parts and therefore equipment downtime.
The cranes' modernization effect is quite high:
- reduction of the starting currents almost in two times and as a result of shock loads due to the possibility of smooth engine starting/stopping. It leads to an increase in the service life of the mechanical units (reducers, shafts, gears, couplings, etc.) as well as the metal structure itself.
- reduction of power consumption of the drive due to exclusion of resistance cabinets with speed regulation and power factor increase (cosφ - 0,98 ÷ 1) of the mechanisms drives.
- the accuracy of positioning increased speeds (they were obtained as a result of small (finishing). It became possible with the use of frequency converters, which led to an increase in productivity due to a reduction in positioning time).
A relatively large economic effect is provided by the use of programmable logic controllers (PLC) and remote control systems for cargo lifting mechanisms.
The PLC's replacement of relay control circuit gives a significant reduction in weight and dimensions, as well as an increase in reliability and time of trouble-free operation.
The use of remote control allows to exclude the harmful effect of production factors on a person and reduce the likelihood of injury and other negative consequences in the case of an emergency at the production site. It also allows the more rational use of human resources by combining the work of the crane operator and slinger (as an example).
The customer either solves the issue of servicing new equipment by himself, or by the forces of the organization that made the installation and served the upgraded drives and control systems.
All the above-described moments about the frequency drive, PLC-based systems and remote control are applicable both to new cranes and the ones which are currently in the design stage. Production, installation, adjustment of such control systems and drives do not require more time than relay-contactor systems.
Questionnaire for calculating the cost of a crane reconstruction to a frequency drive