Emergency Power for Overhead Crane

If the crane has a suitable brake, it should be able to maintain its position forever. Who is "somebody"?

You don't trust Somebody to give you advice?

Why not ask Somebody what they meant?

What makes you think that Somebody knows squat about overhead cranes and emergency power in the first place?

Somebody once said that, "only a fool believes what Somebody says without proof."

It is not recommended to leave loads suspended for any length of time! It damages the ropes where they pass through the sheaves.

For once somebody may be right.

And also the brakes are usually friction tupe brakes. If loaded to almost rated capacity (as is likely if you take out say LP casing or the rotor) I am not sure for how long will the brake last without slipping.

BTW the rated load testing of the Cranes as a part of safety checks, we leave the rated load on for quite some time though to check this aspect.

But all in all the emergency generators should be well able to take the crane load in case of emergencies. They are afterall not that much.

I agree with somebody.

Leaving a load suspended is (in many places) also against the Law/Rules.

The crane can't pull that much power, especially when it is dropping a load using gravity. Maybe a proper sized UPS (Uninterrupted Power Supply) can give the operator enough time to safely drop the load until power is restored. This way you don't need a generator... Just a couple batteries to supply control power for a limited time after loosing power. The UPS is automatic as well, which wont require any dangerous downtime to fire up a generator. They have become much more economical from years past.

Depends on the industrial safety regulations for lifting devices in your area for your application.

Cranes brakes automatically apply if the power fails locking the load in position.

Usually it is illegal to leave a suspended load unattended so supports are put under the load until the power returns, a lift truck takes the load down, or if there is manual overrides on the crane the load can be positioned and lowered manually.

That guy "somebody" does it again! Who the hell is he?

Ok.. what are YOUR safety rules in the turbine room in regards to a suspended load and suppling emergency power to the crane?

No, a suspended load will not damage the ropes, the pulleys or anything else for that matter, as if they did then the crane would fail during normal function, PROVIDING you have NOT exceeded the "Safe Working Load" limit.

A safety power supply to the crane is a great idea if you have no back up for it as, if your safety rules forbid the continual suspension of a load on a crane then you will need to place that load on the ground. Safety first!

Yes if the power is cut to the crane, the crane will halt.. VERY ABRUPTLY, that in itself will put an abnormal strain on the lifting chains if lowering, (NOT the crane), start the load swinging if it crane was travelling at the time in either direction.

Also if you have a VERY large crane in which a driver sits, you need to get him off, or provide him with a safety rope to absail down. (not a good idea as you gotta get him back up there once the power is restored)

It is not recommended to suspend load for very long time. It will affect brake liner, wire rope life also it is risky. Better to install standby generator.

From one of the OHSAS hand-books on safe crane operation extract,

If power failure is to be long term and a load is suspended on the hook, these requirements may apply:

- Advise a person authorised to investigate the problem.

- Stay at the controls until the load is landed.

- The area beneath the suspended load should be suitably barricaded off to prevent personnel entering the area.

- Emergency lowering of the suspended load may be performed as per the manufacturer's instructions.

in our power plant.

we dont have emergency supply given to overhead cranes in our turbine shed.

but is it utmost necessary ?

my conscience says NO, since it is always used for major shutdown activities which are rare in a continuos running plant.

BUT, you may decide it as per your plant and the need of crane and its process.

Better is safe than sorry. it depense on the weight you are working with, i supose.

GA to post #9

Ref Tonys' comment and others following:

It is possible for cables to take a set around sheaves over time. This can lead to winding irregularities - so abrasion in laying on the drum - so damage to the cable.

However, it takes many hours to reach any significant level. Temperature, humidity and lubrication are also a factors.

A skilled operator will notice any set, and cycle it out. An unskilled operator can render the entire cable to dangerous rubbish.

To other posters: If the friction brake is not slipping already, it will not slip. _{This is just straight forward coefficient of friction/stiction, basics.}

The big threat is the suspended load lowering unexpectedly due to power restoration.

Or worse, some momentary resupply, gives the load a good jerk _{(typically breaking slings, not cables, cranes or hooks)}

This of course presumes it is possible to leave the crane controls in 'up' or 'down'. With most modern cranes this is "impossible", but you never know what confusion a power failure may cause mid duty in contactor based systems.

Hence; per AP1, the area under the load should be barricaded and the crane manned.

A further note is; if the load is multiple items - like a bundle of pipe - what happens if it falls, like where stuff maybe flung, must be considered in terms of barricade and prohibited area.

Ref the Topic Question: Is it an absolute 'necessity' to provide standby power?

That depends on;

A. how long the 'random outages' usually last

B. what is the cost of not being able to use the affected area

C. if the load is suspended near where power restoration work needs to be done - then standby is obviously very necessary.

D. if it's not, see A and B