Ideas sought for arresting the fall of a large mass

[RobertCasey]

Hi
We are developing a machine that involves a mass of the order of 300-400 tonnes suspended on cables. The mass will be lowered at a constant acceleration of about 0.5g to a maximum velocity of 12m/s. We need to have a secondary system that is able to trim the velocity of the mass should it exceed the maximum velocity, or to arrest its fall should the acceleration exceed the design value (i.e. if one of the suspension cables fail).

Does anyone have any ideas about how this could be done? We are thinking about secondary ropes that reel from drums at the top of the shaft and which are monitored and braked if neccessary, or maybe using caliper brakes just like a lift. Is there anything else that might be suitable, or has this situation been solved somewhere else already?

Any help is greatly appreciated.

 

[tc7]

Robert-
I just came upon this thread in searching for something else. I have worked with a few different water brakes in the distant past. Basically these are a paddle wheel or tubine wheel arrangement immersed in a tub of water of glycol and connected to a cable or tape reel. Very repeatable, very reliable and fairly low maintenance. I've seen them used in oil rigs for exactly your application and also military applications (which is my experience). These might be adaptable to your project. If you are still looking for ideas, I might have some for you. Write back if you do.
TC7

 

[chief]

i also have marine and oil rig experience. We use Baylor electric inertia brakes on the Drawworks hoist to arrest loads up to 600 tons. VFD drives with regenerative braking are now in vogue.EATON multi disc drag brakes are also now in use, these require water cooling. The water type brake went out of fashion many years ago but was reliable if primitive, it is in design a reverse torque converter.
To control speed descent, take a look at the lifeboat lowering systems which use a centrifugal brake pad arrangement to control lowering speed, the disadvantage here would be the high heat loads generated.

 

[PeteBennett]

Could always follow the Pyramid Builders lead, and use sand jacks in support. Cheap and cheerful, no moving parts, all you have to do is work out the flow orifice size.

 

[pablo02]

I, too, was thinking along the lines of "sancat" -- there is a similar ride in the US designed and built in Europe (in Ohio?) which uses a number of VFD's (regenerative motor loads) and PLC's to control the hugh mass as it swings... as I recall the VFD's were all ABB -- you might visit with them and other large VFD mfg. for guidance or suggestions..

if there is an opportunity in it for them, they'll be more than glad to assist you..

 

[chief]

Check out

http://www.airflex.com

which is the site for Eaton Industries brake components. These brakes can hold up to 1000 tons no problem, they are air operated and are air or water cooled. Used on offshore rigs for Drawworks braking and Anchor chain braking. It is a drag type to correct the rate of descent by means of air pressure control on the disc pads.

 

[RobertCasey]

Thanks for all the ideas - they are very welcome! The project has been delayed for a couple of years but is still going ahead so the pressure is off for the time being. We are still considering the use of the deadweight to accelerate the system but need to look at ways of reusing the energy lost in stopping the mass so the ideas about regenerative braking are very interesting. We are also looking at the use of accumulators to try and reduce the energy loss, and at ways of eliminating the ropes and sheaves.

 

[RDK]

How about some sort of air bag?

You could even have some fun with the exhausted air from the air bag. i.e. blow up a big balloon

Or a water bag that would drive a big fountain and shoot a jet of water into the air?






Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com