OT positioning devices

Have had a problem dropped in our lap in regard to positioning of overhead gantry cranes. Is a new 200M long building with 2 adjacent bays with 5 cranes each. Basic issue is if cranes in adjacent bays are hoisting in same zone, building will fall down... Customer wants a system to track positions relative (to building and each other) and interlock hoist functions if necessary..

Knee jerk "how to achieve" seems most practical on each crane adding a encoder to the long travel, input to a PLC sitting on a wireless network. Also thought about lazer distance between, but not sure if alignment will be a problem...

Looking for any brilliant suggestions, which cost not a lot ??

For example, if one crane is supporting a load but is turned off, the other cranes in the same zone need to know this so they are not allowed to support more load.

My First Knee Jerk Reaction is To Run Away Dude. Run Fast and Run Far.

But, I think you need to consider a Monitor for Load And Control For Hoist And Travel.

1. If a Crane is not hoisting but contains a load in a section then you will not allow a lift in same area or Travel Thru the same Area With Load.

2. Not Allow But One Crane in any given section. This Could be done with Logic and something as simple as Photo-eyes and simple Traffic control.

3. Tell Workers if you lift 2 loads in the same area you are going to DIE! This is The Cheapest Method.

4. Add Additional Support To Allow For Multiple Lifts. To me This is The Correct method.

cwal61 said:

My First Knee Jerk Reaction is To Run Away Dude. Run Fast and Run Far.

But, I think you need to consider a Monitor for Load And Control For Hoist And Travel.

1. If a Crane is not hoisting but contains a load in a section then you will not allow a lift in same area or Travel Thru the same Area With Load.

2. Not Allow But One Crane in any given section. This Could be done with Logic and something as simple as Photo-eyes and simple Traffic control.

3. Tell Workers if you lift 2 loads in the same area you are going to DIE! This is The Cheapest Method.

4. Add Additional Support To Allow For Multiple Lifts. To me This is The Correct method.

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Agree with every point, especially the run away bit..

Lemming said:

Knee jerk "how to achieve" seems most practical on each crane adding a encoder to the long travel, input to a PLC sitting on a wireless network. Also thought about lazer distance between, but not sure if alignment will be a problem...

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Anyone have any working sites that achieve the long travel tracking accurately and reliably ??

I don't see why this should be so difficult. I would find a mechanical engineer that would work out the formulas for load and bending as a function of positions and load and adjust the positive and negative travel limits on-the-fly accordingly.

Peter Nachtwey said:

I don't see why this should be so difficult. I would find a mechanical engineer that would work out the formulas for load and bending as a function of positions and load and adjust the positive and negative travel limits on-the-fly accordingly.

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Its the "where is the gantry" measurement over a 200M span I'm looking for. Like I said, can throw an encoder on a wheel with calibration pints dotted along the way, but was looking for a known method which is proven...

We have had customers use rack and pinion connected to a multi turn SSI absolute encoder but only for about 20-25m. I would still consider the same idea on a bigger system but it might be good to have a position feed back on both sides of the gantry to measure skew and vote.

A long time ago I did system systems with rack an pinion. The problem we ran into was that any bump could make the pinion gear skip off the rack. You probably wouldn't have this problem.

As was stated above it doesn't matter if you can tell where the cranes are if you don't know how heavily loaded each is. You may be able to park all 10 unloaded cranes right next to each other and be OK. So unless you know what load is on each crane you run the risk of making a system that the operators see as unreasonably restrictive.

Keith

New info (as of about 40 minutes ago...) that all cranes will break the building irrespective of loading... The positions relative is the critical thing.. They apparently pulled a million out of the building costs by adopting this methodology...

my first thought was, they are yoking with you. It would mean a crane can never pass the other one. So hoisting is not the issue but the load and its position.
You will need to do X and Y position and the weight hanging , and this for every crane.
The position must be done absolute so incremental is no good.
Use a Gray coderail with for example 8 bits (200meter/127 is < 2m distance that is oke. it is cheaper as 10 laserrangefinders(however this is possible, (you need to find 5 paths for the laser.and enough free room not to interact any of them)
you will need same on gantry, just to be allowed to run cranes with low load.
you will need a loadcell on each crane,
a lot of communication to a central computer, and/or between each crane.
so you are sending the pos and load and you receive if a movement in a particular direction is allowed. On each crane make 3 lights: yellow for restriction of movement, and a red one for overload. green for operation is possible.
In central computer make a model. if display the load as circle around the crane, that way if two circles touch each other you will have to stop both cranes from moving in 2 directions, do not interact with hoisting as this can be dangerous (and is not allowed).

Lemming, why are you worried about this when it is a new building/Install? crane sales/engineering issue/crane sales, or management? Why do you have to come up with the answer/resposibility

duckman said:

Lemming, why are you worried about this when it is a new building/Install? crane sales/engineering issue/crane sales, or management? Why do you have to come up with the answer/resposibility

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It was designed by choice to save cash... No responsibility, but have been asked if we can sort. The load is no factor, thou obviously heavily loaded would be worse. I'm not worried about the logic, just the accurate positioning.

Will probably run with an encoder and run the wheel on a toothed tracked or chain...

shooter said:

my first thought was, they are yoking with you.

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Your right, I thought it could have been April first when i was told the building was designed like this...

Will probably end up with encoders like you suggest... Thanks for the suggestions..

shooter said:

Use a Gray coderail

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Didn't read this properly first time, code rail seems an ideal option, but will have to see how much ideal costs....

Thanks