Start/Stop for Remote vs Local

[ssommers 20]

Ok, I'm thru banging my head on this for today... !!!!! I've got a Reliance GV3000/SE drive that I need to start & stop either locally at the panel (2 PBs) or remotely (1 run signal, no stop signal). They'd like it to automatically turn on & off, but still be able to have the local start & stop work. The catch is that I can't trust the operators to remember use a selector switch for local vs. remote operation because they might walk away & forget about putting it back in remote mode. The machine is about 900 ft long so it's a good possibility. My best guess at a solution still includes the SS (see below). This is a new piece of equipment, so normally I'd have put it into the specs, but I wasn't here 6 months ago and it's on my floor waiting to be powered up. There is a PLC (all 120 VAC I/O) in the panel, but the drive is completely separate as far as controls go. I'll be adding isolation relays if I do use the PLC. I'd appreciate any & all ideas! Bedplate_puller_start_stop.pdf GV3000.pdf

[BobLfoot 302]

Your SS option looks like it will work to allow remote start-stop and local start-stop. My biggest concern is that a local operator can stop the system and be working on it and the remote can start it. Depending on the application you may for safety want to add a timer relay or use a plc to trigger start warning horns. Personally I'd use two PLC outputs one for Remote Start which comes on for run, and one for remote Stop which goes out to cause a stop. I'd then use the age old adage. Starts in parallel and stops in series. This means any stop can stop and hold the system stopped. And with no stops requested any start can start the system. I'd use SS type stop switches if the operator in moving into harms way while the machine is stopped.

[Groo 7]

'My biggest concern is that a local operator can stop the system and be working on it and the remote can start it. Depending on the application you may for safety want to add a timer relay or use a plc to trigger start warning horns.' hmmmm.. not looked at the problem but the reply above had me thinking about the different standards between countries. In the UK we would have to put a warning siren, plus flashing lights on equipment that can start automatically, that's initial start, resuming from energy saving doesn't require it. The other thing is stopping and working on it...... without isolating and locking??? is this really allowed in the states. Here there would be local rules that show someone how to work safely, as working safely is ultimately the workers responsibility, no-one should work on any machinery without first locking off and making it safe.

[Rodney 21]

I believe that you should only be able to start a unit from either local or remote. So if someone is looking to work on the unit he would switch the control from remote to local.

[BobLfoot 302]

Perhaps I should clarify myself. Working on a piece of machinery by maintenance is not allowed in the states without Lockot/tagou/try being completed. But what I was thinking of was a cross factory transport conveyor which would take material from Dept A to Dept B. And in the case I was invisioning the system would stop to be loaded or unloaded. In Dept A the local Dept it is loaded manually and the operator starts when the part is on the hangar. in Dept B a robotic cell removes the part and restarts the conveyor to await the next part. In this situation the Loading Operation would not require LockOut/Tagout/Try procedures to be completed, but would include some personnel safeties.

[ssommers 20]

I'm not worried about someone working on the motor or drive without lockout. They're really good about that here. And if they weren't, I'd be all over them for it! Safety comes first, regulations or not... The application is a tube being pulled thru 2 rollers (upper & lower). One of the rollers is driven at the same speed as the tube mill which forms the tube. This keeps a slight tension on the tube and prevents droop over the 900 ft run. The operator has to calibrate the speed of the roller with a handheld meter & potentiomenter from outside the guard when they change from one tube diameter to another. Thus the need for local control. The problem comes when they walk away from the puller station after calibration and forget to put the puller back into auto. The station is in the middle of the line and not where either of the 2 operators usually stand. I'm considering BobLfoot's signaling idea. The auto start signal is coming from the mill so the two machines start simultaneously. What if I send the auto-manual switch signal to the mill? At least the mill operator would know that the puller station is ready to start.

[BobLfoot 302]

It sounds as if it has merit. What is the downside of starting the mill with the puller in manual. Perhaps you want a pushbutton for manual at the puller which pulls in a relay for manual mode and a contact from the mill which can drop the relay for return to auto.

[Been Around 0]

also, you could use a seperate set of contacts from local/remote ss to power visual and/or audiable alarm that would be very hard to ignore. Or send signal to control room that will alarm or notify after a period of time in manual.. If you cant trust your operators to remember to change state of ss, It would not be wise to trust control system to hope no one is is physical danger. I have used manualmatic before, but only if operator cannot be placed in harms way. If system is that critical, maybe wait for period of time before auto switching into remote.(only after notifying with pause before starting) too bad we cant program operators SAFETY FIRST Could operator hold spring return pushbutton while calibrating??

[OkiePC 14]

If you end up with PLC control, just wire your pushbuttons and switches as individual inputs, and let the PLC turn on the start relay and hold closed the stop relay. Now your imagination is the only limit! You could have it go into auto whenever either AUTO button is pressed, or automatically when the mill is running and no buttons have been pressed for n seconds. Then you could do away with selector switches, unless you want to prevent one guy from hitting auto while the other guy is operating it manually. Or that, too could also be done in software: Give control to the station that has the most recent activity (with PLC timers) and lock out the other station for a few seconds... If you keep it hardwired, I believe there is a control method in the manual for the drive that will work with the two start buttons in parallel, and the stop buttons in series. I prefer the PLC method. You can bring in a "Mill Running" input and use it to trigger auto start too. And, add an output for your "AUTO" mode indicator lamps. Use lighted pushbuttons, so you can see the mode of operation by looking at any control station, and can see when auto mode begins at a glance no matter what triggered it. On a long line, a stacklight mounted high in the air might prove very useful. Red Flashing for fault, Green for Manual and Amber for Auto...just a thought... Paul

[BobLfoot 302]

I think Paul has hit the nail on the head for this post. If you have PLC control available and usable. Take full advantage of it.

[TimWilborne 108]

At 900' I sure hope it's got networked I/O

[ssommers 20]

ROTFLOL!!!!!! Nope. Nada. Nothing. Never even entered their minds. And it used to be mostly relays. They "upgraded" to a SLC5/03 on the tube mill section in 2000. And there are 2 fixed hardware SLCs at the coiler end. Total run from mill panel to coiler panel is about 1000 ft and there are at least 10 signals passing excluding e-stops. The new parts came in with another SLC5/03 - just to keep everything equally antique. There's an ultrasonic cleaner that's about 450 ft away from the new panel and the maker chose to home-run all that I/O too. That would have been a perfect candidate for Remote I/O. I just don't understand... As it stands, I'm going to a meeting today to inform them about the joys of DH-485 networking. It will mean they can buy a whole lot less wire, the electricians can hook up their laptop without going inside the control cabinet, the supervisor can get startup/shutdown reports that are accurate, and that coordinated startup procedure they've been dreaming about for years can actually happen. (Yes Virginia, no more voice intercom & signal flags!) Thanks to everyone who's answered. I've got quite a bit to digest & see how far I can push them into the 20th century. (I think going for the 21st century would be too much!) Now I must go prep. Thanks again!

[Money4Nothing 0]

You might want make sure that your voltage drop is acceptable on any long I/O wire runs. You may have to increase your conductor size. $

[TimWilborne 108]

Probably by a few sizes

[BobLfoot 302]

As well as sizing on your long conductor runs beware of crosstalk between power and i/o signals. Had a start stop circuit one time where the crosstalk from a 480 feeder induced enough current in the line to circumvent the stop button. Really hard to find at first. Just goes to show do not use an Omron 62A-432AN "ice cube" relay for your system MCr relay. Not a bad relay, but the coil holding current is way to low for the application.

[ssommers 20]

I found out after looking in all the panels that the makers didn't include any cables from the panels to machine jb's. It seems that's been a tradition here. Management requested that it comes in with no cables because they'd inevitably change their minds about where to put the electrical panel after it arrived here and rewire it anyway. So I effectively have "carte blanche" on wire & cable sizing & routing & anything else I see that needs changing... except that all the digital I/O stays 120VAC. (ugh!) I'll definitely use shielded cable & up size the wire in the long transmission cables for the ultrasonic cleaner. I'm also going to keep the inputs (pb's mostly) on one cable & the outputs on another. There's a lot of noise around here with induction welders & MG sets. There will be separate conduits or divided wireways for AC vs DC signals & Network cables. I'm not going to play that game because I have no time to deal with crosstalk issues. I did get thru to them on networking. I showed them how the synchronized start/stop for the pullers will work. The money they spend to setup the DH network will be about the same amount they would have spent on wiring for just that one function. And I found out that this particular app is fairly critical with the new tubing line because there's a place where the paint will probably be scraped off the tubing before it's dry if there is more than 1/4" of droop between pullers. It's going to be interesting to see how this works out. [sigh] I wish I'd been here about 6 months ago! I haven't had to deal with installing non-plug & play equipment in a very long time...