240v Control Curcuit

[Nazza]

Our company is working on a piece of machinery which has come from China.
We are ensuring the electrics are safe.

The control side of the electrics is 240v. All the components in the system are CE marked and from reputable brands.

1 electrician says we should remove all the control system and replace for 24v.

Another says the control system is fine at 240v as long as it is wired up correctly.

The machine is a fairly simple wrapping machine. Functions on the control curcuit include on of buttons etc.

We have been reading the machinery directive and the low voltage directive and all we can find is the phrase "it should be intrinsically safe"

So, my question is whether 240v in a control circuit could be considered safe and legal providing it is wired up correctly and the componenets are reputable brands with CE marks.

 

[LeeH]

Yes it's safe although not generally used here.

Having all the components CE marked doesn't make the machine compliant or safe by a long shot.

Why does it need to be intrinsically safe?

Your company is putting the onus on themselves on behalf of a customer who bought a non CE marked machine?

Good luck with that if it turns south.

 

[LeeH]

People go to jail when things go Pete Tong.

CE marking - Work equipment and machinery - http://www.hse.gov.uk/work-equipment-machinery/ce-mark-summary.htm

We use PILTZ and Laidlers (TUV) for our CE.

 

[Pete999]

Our company is working on a piece of machinery which has come from China.
We are ensuring the electrics are safe.

The control side of the electrics is 240v. All the components in the system are CE marked and from reputable brands.

1 electrician says we should remove all the control system and replace for 24v.

Another says the control system is fine at 240v as long as it is wired up correctly.

The machine is a fairly simple wrapping machine. Functions on the control curcuit include, if it's in an Explosive environment it's not just the starter or control circuit that should be intrinsically everything else concerning the machine should be treated the same.

We have been reading the machinery directive and the low voltage directive and all we can find is the phrase "it should be intrinsically safe"

So, my question is whether 240v in a control circuit could be considered safe and legal providing it is wired up correctly and the componenets are reputable brands with CE marks.

Why should it be Intrinsically? what sort of environment is the Machine situated in?

 

[Nazza]

No your right just the electrics doesn't make the machine compliant.

We look at all areas of the machine in order to make it compliant including mechanical systems, guarding, electrical systems etc.
We self certify the equipment, collate our own technical files and keep these updated with what we have done.

We use the advice of a HSE consultant specialising in CE marking and he has provided us with the necessary guidance in ensuring our business is capable of doing this.

However, as you can appreciate different situations always arise, and as a business we are constantly learning.
This is a situation that has cropped up a few times, and the answers are fuzzy. This is the reason im here to try and get some varied responses.

We have 3 electricians working in our company, 1 who is very experienced.

When we build machinery in house we always use a 24v control circuit and a 24v safety circuit.

Recently we have been working on some machinery which has originated from China. We are working on it to ensure its fit for the European market.

On the electrics the control circuits are 240v and we are trying to understand clearly the justification for removing this in replacement for a 24v curcuit. We do not want to make something unsafe but understand clearly the reasons.

If you read through the machinery directive or the low voltage directive for the answer they do not state clearly. The nearest justification we could find was that the control system must be "intrinsically safe", which begs the question what is the definition of intrinsically safe in the context of a machine control system.

 

[Besoeker]

Our company is working on a piece of machinery which has come from China.
We are ensuring the electrics are safe.

The control side of the electrics is 240v. All the components in the system are CE marked and from reputable brands.

1 electrician says we should remove all the control system and replace for 24v.

Another says the control system is fine at 240v as long as it is wired up correctly.

The machine is a fairly simple wrapping machine. Functions on the control curcuit include on of buttons etc.

We have been reading the machinery directive and the low voltage directive and all we can find is the phrase "it should be intrinsically safe"

So, my question is whether 240v in a control circuit could be considered safe and legal providing it is wired up correctly and the componenets are reputable brands with CE marks.

I wouldn't have thought it would need to be intrinsically safe. That usually refers to equipment that has to operate in hazardous areas where you have a hazardous atmosphere.

Your application seems more like it should have a specific Ingress Protection rating. More commonly referred to as an IP rating.
It's two digits the first being protection against solid objects, the second protection against liquids.
Most relays, pushbuttons, and indicator lamps etc are IP2X for industrial controls. The X is unspecified - generally, you don't have to contend with water getting on to them..............
IP2X means the components are protected against solid objects greater than 12mm - keeps your dirty digits off them.
So that's the components.

Enclosures for the controls like pushbutton stations would usually have a higher IP rating. We usually used IP43 for control panels.
Protectiion againt solid objects greater than 1mm and sprays of water up to 60 degrees from the vertical. It really depends on the environment in which they are expected to operate.

 

[Nazza]

@Pete999

The machine would be used in a factory environment packing dried goods.

There would be 1 operator feeding product into the equipment.

 

[Pete999]

@Pete999

The machine would be used in a factory environment packing dried goods.

There would be 1 operator feeding product into the equipment.

So is there a dusty atmosphere? Intrinsically safe is as said previously reserved for explosive atmospheres, fuel storage, dusty areas etc
http://liftequipmentsafety.blogspot.co.uk/2008/12/what-does-it-mean-to-be-intrinsically.html

 

[Nazza]

No the atmosphere isn't dusty.

I interpreted "intrinsically safe" as meaning that the system is safe even if it fails (a button breaks leaving a wire exposed which presents a risk of 240V shock?) for instance.

Or is it true that the IP rating is the most important thing and in practice having a 240V control circuit is acceptable (providing it has sufficient IP rating which we would do anyway)

A domestic light switch has 240v behind it, for example, and that is acceptable.....

 

[Pete999]

Nothing wrong with 230v control circuit.

 

[Besoeker]

No the atmosphere isn't dusty.

I interpreted "intrinsically safe" as meaning that the system is safe even if it fails (a button breaks leaving a wire exposed which presents a risk of 240V shock?) for instance.

Or is it true that the IP rating is the most important thing and in practice having a 240V control circuit is acceptable (providing it has sufficient IP rating which we would do anyway)

A domestic light switch has 240v behind it, for example, and that is acceptable.....

Intrinsically safe has to do with hazardous atmospheres.

I'm with Pete. A 230V control circuit is fine.
Two provisos.

The safety aspect. Live parts should be protected against accidental human contact. We fitted door interlocked fuse switches on panels so there live access was prevented. Anything that could potentially still be live like external interlocks were fully shrouded and labelled.

The other is customer specifications. My background is industrial and mainly variable speed drives. Project technical specifications ranged from just a performance spec (you decide how to make it do what they want it to do) to those that tell you how many threads must be visible on a nut and bolt connection after it is tightened up. I even had one that had 40 pages on how to make packing cases for kit that had to be exported - including diagrams and instructions of the correct angle to drive the nails in.

Excuse my digression but there is a relevant point. Some customers will specify the control voltage. It's their standards that take precedence provided that they don't contravene any official industry regulations. Most of our customers would specify 110Vac or lower.

The point is that you may wish to check what your customers will accept.

 

[mache]

Intrinsically safe has to do with hazardous atmospheres.

But the term is not exclusive to hazardous area classification / concept descriptions.
It is an entirly acceptable and correct way to describe the requirement of a piece of equipment or tooling that it should not allow harm or injury to be incurred whilst operating the machine in the manner for which it was designed for and that under simple fault condition remains safe to the operator or those around.

 

[Pete999]

Intrinsically safe has to do with hazardous atmospheres.

But the term is not exclusive to hazardous area classification / concept descriptions.
It is an entirly acceptable and correct way to describe the requirement of a piece of equipment or tooling that it should not allow harm or injury to be incurred whilst operating the machine in the manner for which it was designed for and that under simple fault condition remains safe to the operator or those around.

http://www.omega.com/temperature/Z/pdf/z131-148.pdf

 

[Pete999]

http://www.omega.com/temperature/Z/pdf/z131-148.pdf

In addition non ferrous tools must be used. or use to be in my day. I even have my intrinsically safe test lamp somewhere.

 

[mache]

http://www.omega.com/temperature/Z/pdf/z131-148.pdf

Hi Pete,
Yes well aware that the terminology is used in hazardous area protection concepts.....but it is not exclusive to that use and can be used for other purposes

 

[Lagentium]

Out of curiosity what is the normal working voltage in China? Are they building machines to suit our market and firing them over? I don't think it's a case of making sure the system complies with legislation over here for a 230v control circuit, rather than thinking would somebody want to buy a machine with a 230v control circuit. Depends on the cost of the equipment, I would be sending down an engineer to have a look at any kit I would be looking at buying if it's top dollar, if there are ones on the market with 24v ones? I know what I'd choose as a buyer really. Darkwood will be along to give his point of view at some point as its area of knowledge really.

 

[Lagentium]

Plus I cant imagine a wrapper being in an IS area, they are usually in a safe zone

 

[Pete999]

Out of curiosity what is the normal working voltage in China? Are they building machines to suit our market and firing them over? I don't think it's a case of making sure the system complies with legislation over here for a 230v control circuit, rather than thinking would somebody want to buy a machine with a 230v control circuit. Depends on the cost of the equipment, I would be sending down an engineer to have a look at any kit I would be looking at buying if it's top dollar, if there are ones on the market with 24v ones? I know what I'd choose as a buyer really. Darkwood will be along to give his point of view at some point as its area of knowledge really.

Complete list: Three-phase electric power (voltages/frequencies) - World Standards - http://www.worldstandards.eu/three-phase-electric-power/

 

[Nazza]

@Lagentium

What is it you have against a 240v control circuit on a machine.

The Chinese do build machines for our market, but they need work doing to them.
Not only to make them safe, but sometimes to make them work.

 

[Besoeker]

http://www.omega.com/temperature/Z/pdf/z131-148.pdf

Spot on.