This would be a nice little interesting project to work on
Just for reference I have done more than a few projects like this
The fact that you haven’t ordered the hoist yet works in you favor. First when you order the hoist you want to use a “No Load Brake Hoist” to get the control you want. Please don’t confuse the load brake with the motor brake they are different.
Next I would not use any of the tank position switches they are expensive to install and a high maintence item that can give you nothing but headaches
I would use a laser measurement system for position feedback. That way when you are setting up the positions you just need to plug a number into the processor and you can adjust it on the fly when necessary.
As for the crane vfd’s I would use Magnetek crane drives. In this case I would use Flux vector drives on both the hoist and the trolley ( Noload brake hoist drive) these at designed for crane duty not just a label put on a standard drive, they do require an encoder on the motor but they will allow you to control the motor speed down to 0 including suspend the load on the motor and yes I have done this many times. Also don’t forget to order the correct braking resister for each drive to give you the needed braking to control the load.
Because the primary control of this system is from the plc I would swap out the pendent controls with a small radio control for those times when the operator or maintence needs to control the crane. That way the operator can have full control and still remain in a safe location. Each station would have a preset position you just need to tell the control what station to go to.
Sa for the hoist position hear again the hook position will be from the encoder feedback on the hoist motor. As not here with cable hoist’s the cable will stretch a little as time and load effect it so I have found I can correct for this by using the first hoist travel limit switch to reset the hoist position every time it is activated the cable drum on the hoist will give you a constant travel distance. You should also use the hoist travel limit to ensure that the hoist id fully raised before the trolley can move.
If this system were setup correctly I can see it running for many years with very little operator interaction
There other things to consider when doing a system like this you need to go over you requirements carefully
A lot of things here I hadn't even considered. Laser measurement systems instead of limit switches? I was concerned about maintaining those switches up on the I-beam, and not looking forward to it. My spiderman days are behind me. Do you have any supplier recommendations?
Using radio control to keep the operators out of harm's way sounds like a must, now that I think about it.
A lot here to consider. And thanks to everyone who commented about safety. I will do a thorough safety assessment.