| Giants from one source |
Demag crane handles big marine screw propellers
The Mecklenburger Metallguss GmbH (MMG) located in Waren (Müritz) uses a double-girder overhead travelling crane made by Demag Cranes & Components for handling heavy marine screw propellers. The crane has a load capacity of 150 tons. This investment allows the owner to use one single crane for handling very big propellers without the need for additional load bars.
MMG is a world-wide leading manufacturer of marine screw propellers. The company has more than 50 years experience in its product range and has collected considerable know-how over the years.
The new double-girder overhead travelling crane with a load capacity of 150 tons and a span of 26 metres is used in the building where MMG cuts, machines and grinds the surface and the contours of the marine screw propellers cast in one piece. Demag Cranes & Components installed the crane between two older cranes with a load capacity of 50 tons each without interrupting production. It is equipped with an open winch and a DR Pro rope hoist as auxiliary hoist having a load capacity of 10 tons.
The 150 ton crane is used for relocating and loading the propellers. Before it replaced one of the three older 50 ton cranes, MMG had to connect the cranes by means of load bars for handling loads with higher weights. This required considerable time and effort. Today the Mecklenburg company can pick up any propeller they have manufactured by means of the new crane. Furthermore they can reach any point in the building, which is not possible when using load bars. The decision to invest in the 150 ton crane was also influenced by an order MMG received for a marine screw propeller with a finished weight of some 134 tons and a diameter of 11 metres.
Since the new 150 ton crane must handle very heavy loads and additionally has a high deadweight, Demag has equipped it with four tandem travel units. The main hoist of the radio-controlled crane working with a load-dependent speed control provides for speeds from 0 up to 3 metres per minute. With a load weight of only 95 tons, lifting speeds of up to 5 metres per minute are possible. The speed range of the auxiliary hoist is from 0 to 9 metres per minute, for cross travelling it is up to 20 metres per minute and for crane travelling it is up to 40 metres per minute. The frequency inverter control used for crane travelling and lifting ensures that the load can be moved and positioned with virtually no sway and therefore quickly, gently, safely and precisely. The infinitely variable travelling speeds of the rope hoist crab also contribute towards this.
Another additional function of the double-girder overhead travelling crane is the digital load display which allows the crane operator to quickly and conveniently read the weight of the corresponding marine screw propeller. In addition, Demag Cranes & Components have equipped the new double-girder overhead travelling crane and the two older cranes travelling on the same runway in the propeller building with optical anti-collision devices, in order to keep the minimum safety distance.
As a prerequisite for the new 150 ton crane a new crane runway and new crane runway girders had to be fitted. Furthermore all building supports were statically reinforced by MMG. The existing cranes had to be adapted to the new crane runway. Examples for this work partially carried out by the Demag subsidiary Kranservice Rheinberg GmbH (KSR) are modifications on the wheels and drives as well as on the drive line.
There was a requirement for quiet running characteristics of the crane runway, because the natural plant grounds are in the direct vicinity of residential areas. Therefore after the crane runway had been measured precisely, all joints were surface-ground by means of a rail grinding machine. Smooth running characteristics are also required for inserting operations where utmost precision is needed. Thus MMG provides their customers with the service to fit the original shaft of the ship into the propeller hub during the acceptance.
Since the 150 tone crane is subjected to fine dust as soon as it enters the grinding area of the propeller building, Demag Cranes & Components has designed the control cabinets on the cranes in the IP 54 type of enclosure and provided additional protective measures for ventilating the control cabinets.
MMG uses two other double-girder overhead travelling cranes made by Demag Cranes & Components in the foundry where individual components such as blades, hubs and covers for controllable pitch propellers are cast. Both cranes have a load capacity of 50 tons and a span of 10.8 metres and are equipped with a 12.5 ton auxiliary hoist. The radio-controlled cranes are used in the entire process of manufacturing components. Due to the ambient conditions in the foundry characterised by radiant heat, flying sparks and dust, the cranes are of the IP 55 type of enclosure.
With the three new double-girder overhead travelling cranes of Demag Cranes & Components, Mecklenburger Metallguss GmbH have optimised their handling operations for casting and machining the marine screw propellers in a lasting way. While the owner benefits from efficient procedures in all processing stages of manufacturing components, the advantage in the propeller building is gentle and precise handling of the marine screw propellers saving a lot of time.
About Demag Cranes & Components
Demag Cranes & Components GmbH based in Wetter/ Ruhr, a subsidiary of Demag Cranes AG, offers industrial cranes and crane components for material flow, logistics and industrial drive applications. Other core elements of the range of services are spare parts, maintenance and refurbishment. With more than 650,000 cranes and hoists under the “Demag” brand name, the company has the broadest basis of installations world-wide and is represented with some 4,900 employees in 20 countries.
Contact:
Corporate Communications
Demag Cranes & Components
Mr Christoph Kreutzenbeck
Tel. +49 (0) 2335 / 92-7333
