Start/Stop Station control

I have been asked to make some changes to a start/stop station control logic. We have several sets of conveyors feeding one another. The first conveyor in the set, a merge table, occasionally has to be stopped. Currently the stop button(NOT ESTOP)at the merge table panel/op station is used to stop the merge table as well as all of the conveyors downstream. Operations has asked that the local machine stop button only stops the merge table.

I am fine with this since there is a global estop at the panel that stops the entire packaging room. However, i feel like having a stop button to stop all downstream equipment is still valuable. My idea is to program a hold delay to stop all downstream. So a momentary press of the stop button will stop the local machine(merge table), but a 3 second hold of the button will stop all downstream conveyors. Of course buttons would be field tagged as such.

I am just wondering if this is generally acceptable? Any rules, codes, standards against this? Just to reiterate, this is not affecting the safety circuit at all.

It doesn't matter if it's acceptable to us, but is it to the person paying the bill (or wages)

Sounds like the OP is just asking for advice.
Sometimes you have to protect the customer from themselves. In this instance it seems to be reasonable. In my limited conveyor experience, the last conveyor starts first, so stopping the infeed shouldn’t cause a problem down the line.

I think your proposed solution is fine for a non-safety application, but personally I have found that our operators tend to get frustrated with functions where you have to hold a button in for a certain amount of time. Another option would be to set it up so that if they push the button twice within a set period (say 3 sec) then it would stop all conveyors--that would allow them to do it quicker if they're in a hurry.

FluxCap said:

Sounds like the OP is just asking for advice.
Sometimes you have to protect the customer from themselves. In this instance it seems to be reasonable. In my limited conveyor experience, the last conveyor starts first, so stopping the infeed shouldn’t cause a problem down the line.

Click to expand...

Yes just looking for advice, or rather just an open conversation about best practices. Which is why we are all here right?

Thanks for for playing along.

kolyur said:

I think your proposed solution is fine for a non-safety application, but personally I have found that our operators tend to get frustrated with functions where you have to hold a button in for a certain amount of time. Another option would be to set it up so that if they push the button twice within a set period (say 3 sec) then it would stop all conveyors--that would allow them to do it quicker if they're in a hurry.

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I originally had planned it that way... But since the sequence requires a 3 second hold as well I decided to go for continuity. Tested this morning with OPs, they're happy. Case closed.

Thanks for your input, sometimes just nice to hear some confirmation.

Why not keep the existing stop PB for system stop and add a switch interrupting the coil to stop the local conveyor.

you MUST look at the entire line !
i'm not sure if I am reading your posting correctly.
let's say you have 10 components in the assembly line.
#1 is your merge table and #10 is the final product being unloaded.
if that is the case, you can stop all conveyors downstream.

if #4 is your merge table, you have to stop #1,2,3 that feeds the merge table to prevent parts from being fed to the station that is stopped and injuring someone.

in my applications, I stop the stations upstream of the stopped station and let those downstream continue to run. But, I don't know your application.

james

James Mcquade said:

you MUST look at the entire line !
i'm not sure if I am reading your posting correctly.
let's say you have 10 components in the assembly line.
#1 is your merge table and #10 is the final product being unloaded.
if that is the case, you can stop all conveyors downstream.

if #4 is your merge table, you have to stop #1,2,3 that feeds the merge table to prevent parts from being fed to the station that is stopped and injuring someone.

in my applications, I stop the stations upstream of the stopped station and let those downstream continue to run. But, I don't know your application.

james

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This is good to note, but he did say that the merge table is the first conveyor in the system.

Personally, I wouldn't program one button to have more than one function. It will be confusing for any new person coming onto the line.

If funds are available, I'd push for a simple HMI that would display all conveyors, have a main stop/start button as well as individual buttons for each one.

If there's no budget, I'd add a secondary button for the application you described.

the term merge table to me implies there is something feeding the table, thus my post. I can be wrong, but better to err on the side of caution.
james

Vlad Romanov said:

Personally, I wouldn't program one button to have more than one function. It will be confusing for any new person coming onto the line.

If funds are available, I'd push for a simple HMI that would display all conveyors, have a main stop/start button as well as individual buttons for each one.

If there's no budget, I'd add a secondary button for the application you described.

Click to expand...

This is what I was thinking as well, I did a similar project using SCADA and it allowed the maintenance crew to keep an eye on it as well. (Usually one of the only systems that calls people out all the time.)

This is a fairly complex conveyor system. Logic is place to handle start/stop/jams of all individual conveyors.

Yes there is something feeding the merge table. There are product PEs and jam sensors to handle upstream product flow. A stop of the merge table also stops upstream feed.

There is already a well programmed HMI to handle all individual HOA functions.

There is a budget. Running wire to and possible conduit is not in the scope. The original ask was just to isolate them local stop from the downstream. Which I did. I just thought having a way to locally stop the downstream was useful, but not required.

Just asking if my way was "commonplace" since we don't use this method elsewhere. I just thought having the option was nice and ops would appreciate not having to walk to the HMI.

James42005 said:

This is a fairly complex conveyor system. Logic is place to handle start/stop/jams of all individual conveyors.

Yes there is something feeding the merge table. There are product PEs and jam sensors to handle upstream product flow. A stop of the merge table also stops upstream feed.

There is already a well programmed HMI to handle all individual HOA functions.

There is a budget. Running wire to and possible conduit is not in the scope. The original ask was just to isolate them local stop from the downstream. Which I did. I just thought having a way to locally stop the downstream was useful, but not required.

Just asking if my way was "commonplace" since we don't use this method elsewhere. I just thought having the option was nice and ops would appreciate not having to walk to the HMI.

Click to expand...

Rule of thumb, don't do things people don't ask you to do. This sounds like a "nice feature" to you, but I'd ask if they want it before doing anything. I use to have a guy that would do a lot of "nice feature" work that'd I'd remove later. He never asked to do it before hand... just added **** that nobody knew about and generally were poor ideas and implementation.

James42005 said:

This is a fairly complex conveyor system. Logic is place to handle start/stop/jams of all individual conveyors.

Yes there is something feeding the merge table. There are product PEs and jam sensors to handle upstream product flow. A stop of the merge table also stops upstream feed.

There is already a well programmed HMI to handle all individual HOA functions.

There is a budget. Running wire to and possible conduit is not in the scope. The original ask was just to isolate them local stop from the downstream. Which I did. I just thought having a way to locally stop the downstream was useful, but not required.

Just asking if my way was "commonplace" since we don't use this method elsewhere. I just thought having the option was nice and ops would appreciate not having to walk to the HMI.

Click to expand...

That makes more sense.

I haven't seen it done the way you've described (one button for two functions), but I wouldn't be concerned about anything besides operator confusion. It may be "unconventional" but doesn't impact any of your E-Stop circuitry and allows them to save some time/effort, so it's got an approval from me.

Cheers,
Vlad