Losing voltage at E stop

[wade88]

I think i have been a total fool. I have over looked the insanely obvious....... i shall take myself outside and beat myself with a cricket bat.

 

[Silly Sausage]

I applaud your thread timing Ben....during Tony's afternoon nap! :smilielol5:

 

[Robotstar5]

I'd replace the contactor with a safety contactor, use an N/C aux contact in the reset line of a safety relay. The safety relay would monitor the E-stops and the PLC feed to the contactor coil would go through one of the safety outputs, 13-14 etc.

 

[Brightspark2]

To improve the tray mount it on brackets rather than straight to the wall, then you can get cable ties behind. Also manufacturer the top bend rather than just sticking two piece's side by side. Will look a lot better and more professional.

Now I'm not calling your work as I don't like doing that, its just tips for next time :daisy:

 

[vaughant]

Wade don't wind yourself up about it mate,a basic stop start circuit is a question my boss (now former) added to the archer trade test and apparently the majority of sparks got it wrong,which for a control man like me is scary but then again I'd never made off a barrier gland until my last trip offshore so it's different horses for different courses.

But basically your e-stops are just a daisy chain in line to your a1 or coil + on the contactor.

Generally pilz style relays are used as its harder to bypass them but not impossible.

 

[Knobhead]

I applaud your thread timing Ben....during Tony's afternoon nap! :smilielol5:

I'm awake now, unfortunately it's 02:00! I'm not even going to comment on this travesty. I just hope it doesn't develop in to a tragedy!

 

[wade88]

Yay Tony's here!

Brightspark, i did mount the tray on spacers, you just can't see them. As for the top bend, it's pretty ugly for sure. Bit of a tray noob, so ill do a better job next time.

Vaughant, thanks mate, i've got it down now, made a really silly error, really face slapping moment, but it's all good now.

Robostar, due to my lack of experience in this area, i didnt think to look to get a dedicated safety contactor, figured the one i have would suffice (which it will) although i appreciate it is not idea for the scenario, i will source a new contactor asap


Thanks again lads, really appreciate the feedback...and you tony, big kisses

 

[Spoon]

I thought one of your work mates was going to help with the design of this? One that has lots of experience in machine safety directive and safety circuits?
Again (just cause I curious and it is important) are the mesh guards on the mixer fixed (Bolted closed) or hinged (for maintenance)?
If there has been a full safety report and there is no chance of injury to people do you still need an Emergency Stop circuit? Could you just not use a Stop Circuit?

I quite understand why Tony is not saying anything.... I hope you are being supervised by your work mate who has experience in machine safety directive and safety circuits

 

[wade88]

My colleague is from a different company, he came down for a day to help me with a bucket lift conveyor i was having some issues with and then talked me through the design of this.

It's ok, i understand why people may be dubious to make comment, thats fine.

Bolted closed mate.

 

[Spoon]

Im just trying to help you out a bit mate and hope that you dont end up getting yourself into lots of trouble if things go wrong.
Its good that the guards are bolted closed.
When you did your risk assessment what Category of stop was needed for your design?

 

[wade88]

Yea and i appreciate it fella for sure.

Not really sure what you mean by category of E stop Spoon, like i said, new to this area, but i decided after writing the SOP for the process and scrutinising it, although i dont necessarily feel E stops are essential, if i am honest i weanted to put them in because i never have before and wanted to give it a go and couldn't see the harm in doing so, but i opted for standard, latching, twist reset E stops.

Again, I can only apologise that my threads may wind the veterans amongst you lot up no end, but i have no where else to turn for help on these matters than this forum quite honestly, and although thats a rather scary prospect and 95% of you guys wil have just sighed in desperation, i still feel that by coming here and asking my stupid questions, at least its better than not asking, not knowing what i am doing, and just doing it wrong..... wronger....

I am not a total plank, i promise, im quite competent, but there are many many things for me to learn, i am just trying to do that, albeit a little unorthodox.

 

[vaughant]

Yea and i appreciate it fella for sure.

Not really sure what you mean by category of E stop Spoon, like i said, new to this area, but i decided after writing the SOP for the process and scrutinising it, although i dont necessarily feel E stops are essential, if i am honest i weanted to put them in because i never have before and wanted to give it a go and couldn't see the harm in doing so, but i opted for standard, latching, twist reset E stops.

Again, I can only apologise that my threads may wind the veterans amongst you lot up no end, but i have no where else to turn for help on these matters than this forum quite honestly, and although thats a rather scary prospect and 95% of you guys wil have just sighed in desperation, i still feel that by coming here and asking my stupid questions, at least its better than not asking, not knowing what i am doing, and just doing it wrong..... wronger....

I am not a total plank, i promise, im quite competent, but there are many many things for me to learn, i am just trying to do that, albeit a little unorthodox.

Nothing wrong with asking fella but you will always receive some aghast replies as really in a control style apprenticeship like I (and no doubt many others in this section) did,the first thing you learn about any machine is how to stop it and then how to start it.
The safety circuit is always the first part of pretty much any control design because the idea being when you hit the "big red button" you cut everything off as you don't know in that split second whether there's a jammed hand,split hydraulic hose under pressure,burning motor etc,you just know you want the whole machine to stop there and then hence the importance of it and in all honesty it's good to see your trying to incorporate that into your work,but be aware there's a LOT to the safety side of it and there's some really clever bits of kit out there which make it safer for the operator which is what it's all about really.
In ford even the majority of bolted guards had limit switches on them directly linked to some sort of safety device as someone got crushed in another plant by opening a fixed door while the machine was running.
No safety system is 100% foolproof,but it's designed to make you think about why your bypassing it,which often you have to in a controlled environment,rather than just jumping in head first.
I think it's a bit like when the more installation biased sparks get very wound up when folk don't use the correct size earthing etc,I've found in most industries where I've worked it's a case of "use what we've got" rather than always using the exact for the job,often it tends to be larger than required but this is not always the case.

 

[Spoon]

Not really sure what you mean by category of E stop Spoon,

Have a read of this.
View attachment Risk_Assessment.pdf

 

[wade88]

Thanks guys. Spoon, thats great, i have printed that off and bound it into my H&S folder, i am attending a NEBOSH International Cert course next month, so that will definitely give me a good leg up on all of this.

The risk assessments i carry out are based around the guidance provided and templates available online at HSE: Information about health and safety at work as thats been my only point of reference since doing this job.

Good news it however, i just tested the circuit, and it all works fine. Start/stop, the main E stop, forward reverse and all my E stops on the hopper all work. So im pretty pleased with that.

Vaughant you are absolutely right on all accounts, i have no insisted at work here to have almost free rein on my own purchasing accounts so i buy what i want when i need/want it, to allow me to purchase the correct stuff for the job, as spoon has pointed out however and a few others, what i feel is right for the job, may be and often probably isnt, but what i have got this time is working, and it is all safe.


In time and as a gather more experience, i will pick these things up along the way i guess.

Thanks again everyone

 

[KAS1]

I remember when people would employee a design engineer to do the electrical design work (if the inexperienced trainee / electrician wasn't up to it) and then install the electrical installation to a spec lol