An overhead crane in a production hall often runs for thirty or forty years. Runway, girders and travel gear can take it. Contactors, slip-ring motors and resistor stages usually cannot. At some point spare parts run out, or the crane is supposed to position more precisely, start more smoothly or be operated by radio. Then a modernisation is due, and with it a question that decides the whole conversion. Will the crane still be inspection-ready afterwards?
The crane is inspected, and so are its documents
In Germany cranes are among the work equipment that is inspected at regular intervals, based on the Industrial Safety Regulation (BetrSichV) and DGUV regulation 52. Inspectors look not only at the mechanics but also at what the documents say. For the electrical equipment of hoisting machines, EN 60204-32 is a dedicated part of the well-known standard on the electrical equipment of machines.
After a conversion, the circuit diagram, terminal diagrams and the description of the safety functions must match the actual state. A change made only on the crane and not in the drawings will show up at the next inspection at the latest. Or worse, at the next fault, when someone searches for it at night with the wrong documents.
Survey first, then plan
As with any existing plant, the work starts with a survey that compares the available drawings with the crane. Why that is the real core of every modernisation is described in In a retrofit, the as-is survey decides. Cranes add their own typical findings. Retrofitted limit switches, contacts bridged during a repair and never restored, conductor rails wired differently than the drawing says.
From slip-ring motors to frequency inverters
The most common core of a modernisation is the drive. Where slip-ring motors with resistor stages used to run, frequency inverters now control travel and hoist motions continuously. That is gentler on mechanics and load and makes starting smoother. It does require careful sizing.
Hoists need a braking concept that holds the load safely in every state, including a power failure. The energy released while lowering has to go somewhere, via brake resistors or regenerative feedback. And the mechanical brake has to work with the inverter, not against it. For a first estimate of motor currents, our motor current calculator helps.
Long runways, long cables
A crane takes its power via conductor rails, festoon systems or cable reels, often along the entire length of the runway. Voltage drop grows with length. A new drive can become a problem on an old supply that was just enough for the old crane. That can be calculated beforehand, for example with the voltage drop calculator. Why voltage drop is often the real limit on long cables is explained in Why cable sizing rarely fails on current.
Safety circuits first
Emergency stop, hoist and travel limit switches, overload cut-off and, with several cranes on one runway, collision protection. We plan these functions first and everything else around them. Radio remote control adds further questions, such as what happens when the link drops or two transmitters address the same crane.
What matters is that every safety function is described unambiguously in the drawings. An inspector has to be able to find it in the installation without calling the designer.
Conversion in short windows
A workshop crane is rarely out of service without production suffering. So we split the modernisation into steps that fit a weekend or a maintenance window. Control cabinets that are fully built and tested in advance shorten the time on the crane considerably. The documentation is not updated afterwards. It is finished before the conversion and confirmed with every step.
How we approach existing plants in general is described under Modernisation of existing plants.