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It is the standard that makes the difference

25.01.2021 von Achim Altmann

For 25 years ALTMANN has manufactured crane solutions and hoists that have to meet very special requirements in most cases, such as a crane manufactured completely from stainless steel 20 years ago. With this crane, the company from the Upper Bavarian Albaching laid the cornerstone for its very successful clean room cranes. Among them the world's biggest synchronised clean room cranes, with a lifting capacity of total 60 tons (30 tons each) and a span of 30 metres.

But what exactly is the difference between ALTMANN clean room cranes and others on the market?

At first sight, the continuously smooth surfaces stand out, making the crane very easy to clean. All components are discreetly integrated. This means that cables, geared assemblies, screw connections, electrical components, sensors etc. as well as the hoist with electric belt hoist are all hidden in the housing. Due to the housing, the otherwise complex cleaning of undercuts is not required, particularly in the drives. To improve clean room conditions for maintenance works, the housing cover is equipped with a quick-release fastener. It can not only be opened quickly but unlike a screw, it does not produce any wear.

Benefits of powder coating

To avoid wear is the most important criterion in surface treatment and the choice of material combinations. Powder coating is suited to protect the components made of steel against corrosion, such as for example the supporting structure. Only with this method such smooth surfaces can be created, so that no wear will be produced when isopropyl alcohol wipes are used for cleaning. Severe shortcomings of varnished surfaces (also water-based coatings) are outgassing, poor wear resistance and the total lack of cleaning resistance. An increased air exchange in the clean room is necessary until the contamination caused by the evaporated solvent has settled. This means additional costs for the company and can be avoided from the start by using powder coating.
A further advantage of powder coating compared to varnish is its scratch resistance. A running wheel that moves on a varnished surface, removes the varnish gradually, pushes it forward, thus loses grip and starts to spin after a certain time. This problem can be easily avoided by dispensing with varnish on the running surfaces. However, it is inevitable that rust will appear on the uncoated steel surface, which is mostly invisible because it is abraded by the running wheel. This is a contamination which cannot be eliminated by using wheels made of stainless steel, as they would also start to corrode someday (galvanic corrosion). To avoid wear of the considerably more scratch resistant powder-coating on the running surfaces, ALTMANN uses running wheels made of synthetic material specifically suited for this application. These wheels have even proved effective in the world's largest clean room crane. This is why a completely sealed surface and the plastic running wheels are part of the clean room standard defined by ALTMANN.

Maintenance-free and inherently stable load belt

When it comes to improved clean room compatibility through clever use of material, it is above all the ALTMANN load belt that scores. On the one hand, it is completely maintenance-free, which means that unlike chain or rope it does not need any lubrication which would again contaminate the clean room. On the other hand, it hardly expands due to its particular material combination. Conventional textile belts first expand in length, before the load is actually lifted. As a consequence, the compulsory emergency stop button for the highest hook position closes too early under load and the maximum lifting height cannot be achieved. However, in clean rooms in particular, this slight effect may become a big problem as these rooms are dimensioned as small as possible for cost reasons. With the inherently stable duplex belt by ALTMANN, the cut-off point remains consistent.
Due to its low-wear material combination, the load belt is subject to very low wear. Its long service life is in addition due to the complex belt guide – also in the hook block –, due to which the load belt is only exposed to rolling friction. The belt guide prevents the belt from striking against the guidance elements, even with vibrations caused by the load. Finally, a high-precision positioning of the load is possible due to its low inherent vibration. To avoid wear on the rotating load hook, it is either made of stainless steel or hard nickel-plated, in compliance with DIN 15400.

 

Technology also considers details

As far as clean room cranes are concerned, ALTMANN attaches importance to optimum clean room compatibility not only in design and material. The technology in particular takes into account the special conditions in the clean room and above all its enormous operating costs. Each detail that may contribute to cost reduction is standardised. For example, the drives do not have fan impellers. These impellers would emit particles which are sucked off to the bottom by the clean room ventilation and finally get stuck in the ceiling filters. The design of the drives thus has a positive effect on the exchange cycle of the expensive filter pads.
Often the goods to be moved are also expensive. This is why it is for example possible to move sensitive loads with a speed of 5 mm/min in order to reduce shocks of the load as best as possible. As a standard, the speed relation between slow and fast in the inverter controls of trolley and hoist axis is conceived with 1:100 and can be adapted continuously. As an option, a spread (ratio slow versus fast speed) of 1:1000 for the hoist axis and positioning with millimetre accuracy are available.

PLC for more safety and functionality

The PLC included as standard in the ALTMANN crane control is a very good platform for extensions. It has got a load master with blackbox function and provides the option to evaluate and display the electronically measured load, without much extra effort. Either on the wireless remote control which is part of the standard equipment or on a digital display that can be easily retrofitted. The special thing is: The accuracy of the digital load display is 2 % instead of the otherwise usual 5 % of the nominal load. As this specification refers to the maximum lifting capacity and not to the current load, this may possibly have fatal consequences in operation.
It is easily possible to extend the PLC with monitoring functions such as cumulative load monitoring of several cranes on the same or a neighbouring crane runway. It is precisely because such borderline cases rarely occur, this monitoring should be left to the PLC which is programmed to stop one of the cranes in such a case. Due to the electronic load measurement, the overload protection mandatory for a load capacity of 1,000 kg or more is of course more precise than a load measurement by means of spring or friction clutch. Here the cut-off is also checked again via the PLC.
With the PLC as standard component, different extension levels are subsequently possible without much additional expenditure. For example, a touchless and millimetre-precise position sensor system can be upgraded fast and easily, without contaminating the clean room. As the sensor only needs to be connected to the PLC, no further hardware extension is required. Retrofitting a pendulum damping (no hook movement when starting or braking the crane) is also possible at any time. ALTMANN is even capable of equipping cranes with positioning with integrated pendulum damping - a novelty in the world of cranes!

Options and features

The position sensor system is part of the extension kit that ALTMANN offers for its PLC. Furthermore, the retrofitting with partially and/or fully automatic solutions is possible. In addition, the following solutions are available: electronic load monitor for recording operating data, tandem operation function for simultaneous control of two or more crane systems, synchronisation of several crane axes with millimetre accuracy, wireless communication for data exchange with neighbouring clean room cranes or higher-level process control systems, distance monitoring of neighbouring clean room cranes as well as avoidance controls for permanently installed obstacles in the clean room crane area.
Generally, the clean room cranes with lifting capacities between 500 and 15,000 kg are available in various designs: Under flange push or motor carriage, double girder trolley with optimised construction height, two-rail crab with optimised lifting height and special models such as internal rotors or versions complying with explosion protection. Different qualities can also be chosen for the model that is completely made of stainless steel.

 
 

Technical contribution - Cleanroom online - 27.11.2020: https://www.reinraum.de/news.html?id=6712&lang=en