×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Starting Time For Conveyor/Crushers
2

Starting Time For Conveyor/Crushers

Starting Time For Conveyor/Crushers

(OP)
For a lime stone crusher and conveyor, what is the typical starting time for thier associated motors assuming these equipment are being started with load on them.

We have not received the torque and current vs speed for the motors and torque vs speed for the load and associated equipment and motor inertias. Therefore, a feedback from an experience fellow will be greatly appreciated.

RE: Starting Time For Conveyor/Crushers

Suggest you check with the OEM. Have yet to sucesfully have a OEM specify it for me, though I state what I have assumed and get them to approve.

RE: Starting Time For Conveyor/Crushers

Not all crushers are the same, and very few are capable of starting with any load on them at all. You need to describe the exact type of crusher.

Loaded restart on a rock conveyor is also very problematic, it depends on the angle, the length, width and load depth and the weight. There are no simple answers. Your OEM may have selected motors based on a specific performance criteria, if that didn't include loaded restart, it won't be capable of it. Most will not unless specifically instructed, it means seriously oversized motors which drives up the price.

As a very general rule regarding standard motors though, start times in excess of a few seconds require very careful engineering. You can do whatever needs to be done, but you really need to determine what you want to accomplish before you pick the motor.  

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Starting Time For Conveyor/Crushers

(OP)
Thanks for the points guys. I was hoping somebody on the operations and maintenance would somehow provide me a ball park as to the time it takes to start a conveyor. The main reason is for me to have a preliminary sizing for the fuses on those conveyors that are getting started by DOL (with some assistance from fluid couplings). But I believe if I size the fuse without the fluid coupling effect, it will be conservative enough not to nuisantly blow while the motor accelerates.

The fuse sizing is just preliminary to get some stocks reserved and we will later finalize after we get OEM response (hopefully quick).  

RE: Starting Time For Conveyor/Crushers

What sort of fluid coupling?
Generally they are selected to allow the motor to supply FLT + (potentially up to break down) by allowing the motor to run at rated speed prior to application of load.
If this is the case, then the starting time could be calculated using a=T (motor torque)/I (motor plus motor side of fluid coupling).
You can time step using Excel to calculate accurately, though if you have equivalent circuit of the motor you can calculate exactly, if you choose.
If you calculate neglecting the fluid coupling / assuming standard DOL, suspect you will have limited capacity to start the crusher (i.e. only FLT or slightly above cf up to breakdown) availible during the start.
 

RE: Starting Time For Conveyor/Crushers

If the crusher is suppllied with a fluid coupling, the typical starting time is 3-5 second. The motor is considered to be started essentially unloaded. Again it depends how stiff the supply system is and actual motor.  OEM can porovide you with typical startting time based on their past experience, but you would have to do the calculation yourself based on the information they provided and the system data. Typical centrifigal pump speed Torque curve can be assumed for the fluid coupling.   

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources