need help:cannot switch off the potatoes chipper motor

[tcfreeman08]

Hi all,

Catering equipment: I tried press the E-stop button couple of times, however, the potatoes chipper cannot switch off the motor, unless plug-off. No installation drawings or diagrams. What's going wrong?

1.Are the operator safety has some problems?

2.The contactor?

3.The hopper safety interlock?

Model: IMC PC1, single phase, 0.45 kW, 0.33 hp, about ten year young

Does anyone know how to repair?

Thanks!

 

[moose man]

i had the same problem on a power press problem was emerg stop supply was going down to earth so made circuit n/c. As it metal flexi if so look to see it it not kink or place meter on negtive side of the transformer and earth supplying contactor i did tha and was getting 110v down to earth problem was kink in the flexi con which ad spliced the line

 

[oldtimespark]

link to pdf for similar

model does it start on the start button

 

[netblindpaul]

I've had a similar common fault with certain makes of e-stop where the n/c contact on the back of the stop is clipped on and falls off!

 

[Lee321]

call an electrician? pay him ?

 

[Andy™]

does it start automatically when plugged in?

 

[ProDave]

All INCORRECTLY designed emergency stop systems, certanly DO NOT comply with the machinery directive.

This sort of very basic emergency stop is a legacy from the past. Any recent machinery should have a propper EM stop system that will not fail to stop due to a SINGLE failure.

This normally means TWO contactors in series, two pole EM stop buttons, and a safety relay monitoring all functions that won't start the machine if it detects a fault. The safety relay also monitors the auxilliary contacts of the contactor.

That's how it should be done now (for at least the last 10 years). Whether it is, is another matter.

I spent 10 years designing and building industrial machinery and used to know the machinery directive and it's consequences quite well.

 

[Apache]

You could just make a lot of chips in the mean time?

 

[sparkytim]

Plenty of vinegar on mine! :^O :^O

 

[SPECIAL LOCATION]

Couldn't stick a bit of fish and pie on as well please!:BlushingO) :innocent

:x

 

[netblindpaul]

ProDave, just a couple of comments,

The SIL of a system is dependent upon the hazards and risks is it not?

A single channel e-stop system without safety relays is still allowable even today on certain equipment.

However, you are 100% correct in saying that the machine may not comply with the machinery directive, but that is not really the users concern, their concern is PUWER98 is it not?

IF the machine is CE marked the maker is stating that it complies with the EHSR's of the machinery directive, and it is their responsibility to comply.

The user cannot take this for granted, but as long as they have shown due diligence in their purchase of the machine - reputable maker, relevant paperwork etc. then they may have.

Once the machine is installed and in use that is when PUWER98 & MHSWR kick in.

They then must undertake suitable & sufficient RA's, a PUWER98 assessment etc.

Don't forget also the current mix up over EN954 & the new machinery directive!

That has really cleared things up!!! NOT.

Apart from that, this is a very dangerous fault which does need investigating!

 

[ProDave]

Don't forget also the current mix up over EN954 & the new machinery directive!

That has really cleared things up!!! NOT.

Apart from that, this is a very dangerous fault which does need investigating!

AS I'm no longer in the industrial machinery business, I don't know the details of EN954. I do know when I left the industry 8 years ago there were more directives on the way and I was not sorry to leave.

My job had shifted from being an electrical designer, to reading, digesting and worrying about the hundreds of directives that apply to industrial machinery, particularly when we sold worldwide and had to comply with different regulations in different countries. In short, most of my work had become compliance paperwork and I hated it.

But yes I am familiar with the risk assessment process to determine the category of safety system needed, and don't forget the safety system is not just the estop, but any guarding and interlocking as well.

In this case I would argue the safety system is inadequate. But that doesn't surprise me. While my company tried very hard to comply with the regs, I did frequently encounter equipment in use in customers premises that IMO did not comply with the various directives and in some cases were down right dangerous. That was a particular issue when integrating one of our machines into another machine, we had to insist the other machine was bought up to standard first.

 

[roys]

So what is the bets on the fault?

I go for welded contactor.

 

[ProDave]

So what is the bets on the fault?I go for welded contactor.

Almost certainly, which is why a high integrity EM stop circuit has 2 contactors and a safety relay monitoring them. In the case of a welded contactor, the safety relay would detect that (by monitoring the auxilliary contacts) and would refuse to energise the second contactor, so the machine would not start until the fault was fixed.

 

[oldtimespark]

Have come across many different types of safety relay but I think the most common I have seen is made by pilz there are lots of different makes about, how was it done before safety relays were available? On the pdf it is called an on/off switch not emergency stop only semantics.

 

[ProDave]

Have come across many different types of safety relay but I think the most common I have seen is made by pilz lots off different makes about, how was it done before safety relays were available?

Exactly like this machine is I suspect.

A simple contactor with a hold on contact, energised by a start button. A normally closed single pole EM stop switch would interrupt the power to the contactor and it would open.

But as in this case, that's not reliable. A single wiring fault or a welded contact would cause the stop circuit to fail to stop.

Thats why safety relays and properly designed EM stop circuits were devised. And yes pilz is probably the largest safety relay manufacturer, though there are plenty of others.

 

[oldtimespark]

I can vaguely remember it being done with capacitor timing circuit and if the circuit did not charge no circuit would be energised.

 

[tcfreeman08]

thanks all

will try

 

[sparkyrj]

This is the reason why emergency stop buttons are supposed to be regularly tested to make sure that they are working.

 

[Andy™]

This is the reason why emergency stop buttons are supposed to be regularly tested to make sure that they are working.

maybe it was tested, didnt stop it, and how he has posted asking how to fix it?