New Technology –
Particular regulations apply for transporting molten metals or similarly hazardous materials such as acids or lyes. German Industry Standard EN 14492-2 requires hoists to be designed in such a way that it is impossible for the load to fall even if a component in the power flux should fail.
This requirement can be met in two ways: either by the redundant design of the hoist, or by an emergency stop brake on the rope drum in conjunction with a redundant rope drive.
The new off-standard hoist with Twin Drive Concept (TDC) is STAHL CraneSystems’ answer to this tricky question. By equipping the wire rope hoists with two synchronously controlled motor-gear assemblies and continuous drive monitoring, it provides the maximum possible safety when transporting molten metals with a weight of 5 to 40 tons. The complete redundancy of motor and gear always guarantees at least double gear and brake safety, the safety-relevant electronics are in category 3.
The demands of the standard are even exceeded: it requires only a factor of 1.5. A practical advantage: when not transporting molten metals, the wire rope hoist can carry a 60 % higher load. As with all other STAHL CraneSystems hoists, the use of standard components for the TDC ensures good availability, simple erection and fast service.
Both motors of the TDC have brakes which are dimensioned so that each is able to brake or hold the load by itself in an emergency. As the two brakes are of the same type, no increased time or effort is necessary for the annual periodic test. The brakes are synchronously controlled and function both as operating and as holding brake. If a fault should occur (e.g. gear breakage), the load can be lowered with the two manual release brakes. “Retrieving the load” is thus no longer necessary. Providing extra safety, a special condition monitoring system from STAHL CraneSystems monitors the speeds of both drives. If an overload is detected, a separate load monitor automatically disconnects the motor. The robust system is fully enclosed and thus not susceptible to dust and damp.