Please criticise!

johnboy6083 · Sep 14, 2011

Hi lads, ive just drawn a simple starter for a 1ph pump.

Can you please view this, and criticise it, so that i may learn?

There is 1 glaring error, which i know about, and didnt have any tip-ex to erase. I also know that fuses are not shown, and thatbthe 24V transformer is not shown.

Thanks,

John

oxocube · Sep 14, 2011

The big problem with your drawing is its invisible.

ian.settle1 · Sep 14, 2011

You said criticise but we can't as oxo said there's no diagram

johnboy6083 · Sep 14, 2011

sorry fellas, its now been added!

oxocube · Sep 14, 2011

Looks ok but you got the pump neutral connected to the 24v neutral and you should also show at least one normal stop button. And the removeable 'stop' link shown is not ok for normal stops because it will operate the epo operated lamp.

Also, controls should always where possible monitor the actual status. You have drawn 'pump stopped' 'pump running' lamps controlled by a relay on the stop circuit, its not a true and factual indication. On a pump it is much better to have differential pressure switches, these are fitted across the pump and are a true indication of whether the pump is pumping correctly or not and can also be used to monitor blockages or a major leak, simlar thing can be done with flow switches.

Likewise with a fan the important thing to know is, 'is it delivering the correct amount of air' this can be montored by a proximity switch calibrated to count the number of times the fan blades pass per second, it it matches the commissioning speed theres nothing else you need to know.

Always monitor the effect of the piece of machinery.

johnboy6083 · Sep 14, 2011

cheers oxo. Tghe 24v neutral is the problem which i couldnt find tippex to erase! lol.

Im familair with pressure switches and trandscucers, with my current job, but didnt want to get into that level of complexity on this drawing yet. Ill draw another one when ive got time, and try and incorpororate suction and delivery pressure switches.

i thought i had added a normal stop button, labelled "panel stop".

can you elaborate about the removeable link please mate?

The idea, as far as im concerned, would be to take the stop circuit to a set of din rail terminals, and then link them manually, so that in the future, e-stops can be added without modifying the panel.

thanks for your advice mate. Im trying to learn more about process control.

silva.foxx · Sep 14, 2011

With Word use this file to play with rather than drawing out. You'll need to apply oxocube's suggested corrections. regs// s.f

Knobhead · Sep 14, 2011

First off what is the ESR doing other than turning a light on. You change the function of the light to E-Stop healthy.
IR1 and SR1 can be done away with by using auxiliary contacts on KM1.

Sorry I’ve thrown away ¾ of your drawing.

Will send you a drawing later

johnboy6083 · Sep 14, 2011

ESR could be used to control other things that may need stopping at the same time. Maybe not applicable with a pump, but maybe with other machinery.
agree with using auxillary contacts for running lights, i just didnt think, although ive use them like that before.

oxocube · Sep 14, 2011

silva.foxx said:
With Word use this file to play with rather than drawing out. You'll need to apply oxocube's suggested corrections. regs// s.f

Please tell, how did you do that in word?

johnboy6083 · Sep 14, 2011

silva.foxx said:
With Word use this file to play with rather than drawing out. You'll need to apply oxocube's suggested corrections. regs// s.f

liking your word drawing mate. did it take you long to do? is this a recognised method of presenting simple drawings?

oxocube · Sep 14, 2011

johnboy6083 said:
i thought i had added a normal stop button, labelled "panel stop".

can you elaborate about the removeable link please mate?

Sorry, never twigged 'panel stop' as the normal stop and thought where you said 'additional stops' they were normal stops, and in that postion they would 'incorrectly' operate the 'epo operated' relay.

netblindpaul · Sep 14, 2011

johnboy,
Good attempt.

Personally I would not bother with the e-stop relay unless it was a dedicated safety relay and the system required it.
In which case you would need a reset for the esr.

I'm not happy at the way the esr would re-close on releasing the e-stop, my own interpretation of the law and the standards, along with how I have been trained and mentored through my career, pushes me away from this type of operation.
If you look at the other thread on PUWER by Archy then look at the document from HSE you will see the references to the standards and guidance, and it may even be in there, that "releasing an e-stop must not re-energise anything".

The Notified Body I work with also do not like this and it is doubtful would 3rd party CE mark a machine with such a design.
I would never sign off a design with this feature.
I would repair a machine to this standard, depending on the cost to modify to an acceptable function.

Even though it is a simple single phase pump, what it is pumping should have a feedback into the design of the control system.
e.g. low pressure ambient temperature clean water, a "simple machine"; hot concentrated nitric acid, not a "simple machine"!

johnboy6083 · Sep 14, 2011

good point about the e-stop not re-energising anything upon reset. ill have another go when ive got time,and see if i can improve, using al of your comments.

Knobhead · Sep 14, 2011

You did say criticise. In a way I think we’ve been a bit cruel. But keep at it because it’s the only way you’ll learn.

The best way is to borrow bits and bobs out of stores and build it on the bench. Then your playing in the real world.

I will get that drawing done for you, with pressure sensors and pink fairies on top if you want them :santa5:

netblindpaul · Sep 14, 2011

Tony,
I hope we have not been cruel, my posts are not intended as cruel.

I just hoped to point the OP along and justify some of my points on the way.

It was intended as constructive and honest.

silva.foxx · Sep 14, 2011

johnboy6083 said:
liking your word drawing mate. did it take you long to do? is this a recognised method of presenting simple drawings?

Less than it took you to sketch, scan and stick it on here!

It's cheap, universal and simple to use. Copy that file and fiddle with it. Copy, drop and drag the coils and switches and join up with lines.

regs// s.f

johnboy6083 · Sep 15, 2011

i think all the critism is constructive. if you all said it was fantastic, then how would i learn from that?

Thanks for the advice, and later today when ive had some kip ill try again, using silva's method of drawing.

Knobhead · Sep 15, 2011

This is how I’d do it but you can add more whistles and bells if you want.
PS = Pressure switch
KMT = Start up timer to allow pressure to build.

View attachment 7774

Knobhead · Sep 16, 2011

Was in a silly mood during the night so came up with this for you.

View attachment 7777

PS pressure switch
T1 start up timer
R1 system start latch relay
KM1 contactor
V1/O inlet valve open
V1/C inlet valve closed
V2/O outlet valve open
V2/C outlet valve closed
R2 valves open
R3 valves closed
S1 inlet valve solenoid
S2 outlet valve solenoid
L1 system stopped
L2 system running
L3 valves opening/closing