Advice on designing an electrostatic-proof building please.

[Mark42]

I’m converting a steel Portacabin-type box into a lab for static-sensitive equipment and materials.

If there are any ESD gurus on here, I’d appreciate any advice please!

I’ve ripped out all the vinyl, floored it with aluminium treadplate, clad the walls in painted aluminium sheets, and left the ceiling in the original painted steel.

Worktops will be in Trespa anti-static material, there’s a metal fume cupboard, and metal cupboards and shelving. Everything is bonded together, and earthed TT. Earth impedance is good.

I’m also intending to run a bonded metal (copper or maybe ali) strip all round the worktops, with little sockets for plugging in flying earth leads for loose equipment, wrist straps and so on. Conductive shoes will be worn, and no plastics or other insulators allowed in the building.

But this is all new to me: have I missed anything? The most dangerous errors are those you don’t know you’ve made!

And one specific question please:

Is it OK to use 10mm John Guest plastic plumbing pipe (Polybutylene), tucked away under the worktops? I need to run ring mains of mains water, Type 2 pure water, vacuum, and gas. There are no great flow velocities. It’s so much nicer to install, and easier to amend. Is a little bit of plastic pipe which will never be touched really a problem?

 

[pc1966]

You might find the floor is mostly wood over some steel cross-beams, so make sure the building is Earthed to the ground immediately below to keep ant E field down from that source.

Keep the place humidified (within reason) to lower any charge build up of stuff you have not thought about.

Folk moving about are a significant source, so you will have to take care of the types of clothing worn (i.e. keep to natural fibres like cotton/wool and not polyesters, etc) or have semi-conductive overalls.

If worried about the pipes (and flow in an insulators is a risk) then look to screening them by having a mesh cover under the worktops or possibly look at conductive paints, but they won't stick terribly well to plastic, etc. To be honest going for copper pipes and equipotential bonding them is a far safer choice if you need to keep E fields down through materials like wood, or anti-static plastics that are barely conductive (static dissipative), etc.
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Doh, just re-read and you have conductive floors already!
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If it is more than just low electric fields (i.e. you are trying to avoid sparks, etc) then you need to look also at tools and those tend to be expensive for stuff made from beryllium-copper alloys.

Same applies for electrical switches, motors, etc, you would need to look at intrinsically safe ones designed for explosive atmospheres.

There are probably some folk with experience in the oil industries who can tell you more about such standards & practices.
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Also for wiring you would be looking at stuff in metal trunking, metal conduit, SWA cable, or far simpler to handle using Flexishield cable so all circuits are within an earthed shield. Strip lights, etc, might need to have CPC-bonded wire mesh over them depending on how much field you can tolerate.

 

[DPG]

Speak to a company called Vermason.

Consider air ionisers. Also they will need to regularly test things like foot straps and wrist straps, so a tester will be needed. Probably down to them that though.

 

[Pete999]

I’m converting a steel Portacabin-type box into a lab for static-sensitive equipment and materials.

If there are any ESD gurus on here, I’d appreciate any advice please!

I’ve ripped out all the vinyl, floored it with aluminium treadplate, clad the walls in painted aluminium sheets, and left the ceiling in the original painted steel.

Worktops will be in Trespa anti-static material, there’s a metal fume cupboard, and metal cupboards and shelving. Everything is bonded together, and earthed TT. Earth impedance is good.

I’m also intending to run a bonded metal (copper or maybe ali) strip all round the worktops, with little sockets for plugging in flying earth leads for loose equipment, wrist straps and so on. Conductive shoes will be worn, and no plastics or other insulators allowed in the building.

But this is all new to me: have I missed anything? The most dangerous errors are those you don’t know you’ve made!

And one specific question please:

Is it OK to use 10mm John Guest plastic plumbing pipe (Polybutylene), tucked away under the worktops? I need to run ring mains of mains water, Type 2 pure water, vacuum, and gas. There are no great flow velocities. It’s so much nicer to install, and easier to amend. Is a little bit of plastic pipe which will never be touched really a problem?

Have the electrical supply isolated from the mains, M/A set or Isolating transformers. insulate both inside and outside, use wave guides for any entry point to the building.
Raise the building floor from the main floor, air condition to a70deg and 50% RH or as near as possible, use DP mcbs etc.

 

[DPG]

Have the electrical supply isolated from the mains, M/A set or Isolating transformers. insulate both inside and outside, use wave guides for any entry point to the building.
Raise the building floor from the main floor, air condition to a70deg and 50% RH or as near as possible, use DP mcbs etc.

I wouldn't have thought that most of that would be needed for an anti static environment.

 

[Mark42]

You might find the floor is mostly wood over some steel cross-beams …

Exactly correct. It’s pretty rubbish construction actually. I’m adding 25mm Celotex, then a 3mm ali treadplate floor glued down, with bare aluminium wires laid underneath the sheets, all terminated at a main bonding point. I’ve no idea if this is a standard way of doing things, I made it up.

… Keep the place humidified (within reason) to lower any charge build up of stuff you have not thought about. …

Great idea.

… have semi-conductive overalls …

Yes, we’re doing that.

If it is more than just low electric fields (i.e. you are trying to avoid sparks, etc) then you need to look also at tools and those tend to be expensive for stuff made from beryllium-copper alloys.

Exactly correct. It’s all about preventing sparks. The lab is for sensitive explosives.

Same applies for electrical switches, motors, etc, you would need to look at intrinsically safe ones designed for explosive atmospheres.

I think there’s no need for that as it’s for solid explosive materials sitting on a desk on in a flask, not explosive atmospheres, which is an entirely different thing.

Also for wiring you would be looking at stuff in metal trunking, metal conduit, SWA cable, or far simpler to handle using Flexishield cable so all circuits are within an earthed shield.

Flexishield is a great idea. Thanks. It appears you can’t buy cut lengths so I’ve ordered one roll of 2.5 which I’ll use for everything (inc lighting!)

The easiest installation would be one run of dado-rail multi-compartment trunking around the walls, terminating directly into the DB. I’m researching this today. It appears a metallic version is very difficult (and expensive!) to source. Or I'm thinking quality 100 x 50 metal trunking, with accessories cut into the lid, which is economic enough and fully shielded, but would look a bit sh!te

Strip lights, etc, might need to have CPC-bonded wire mesh over them depending on how much field you can tolerate.

I was going to use 3 No. LED IP-rated strips, the type with all the electronics in a metallic enclosure.

I need to keep the cost down so I’m not looking at intrinsically-safe equipment unless I really need to.

… If worried about the pipes (and flow in an insulators is a risk) then look to screening them by having a mesh cover under the worktops or possibly look at conductive paints, but they won't stick terribly well to plastic, etc.
To be honest going for copper pipes and equipotential bonding them is a far safer choice if you need to keep E fields down through materials like wood, or anti-static plastics that are barely conductive (static dissipative), etc.

Agreed but there are other reasons why copper is not a good idea, chemically. Many of the regs for this kind of thing were written sometime in the Cretaceous (probably by actual dinosaurs), before plastic pipework existed. I’ll do some research on the static properties of John Guest pipes, which are either polybutylene or polyethylene first.

I like your metal cage idea, that’s cheap and easy to fabricate.

Thanks for the excellent advice!

I'll post photos once it's done in a few weeks ...

 

[DPG]

Ah, in your OP you said it was for static sensitive equipment. I assumed they were repairing electronic equipment. I see it's actually explosion risk you are looking at. That's a whole different ball game with it's own regulations.

 

[Mark42]

... If worried about the pipes (and flow in an insulators is a risk) then look to screening them by having a mesh cover under the worktops ...

Any idea how dense a mesh cover needs to be to provide electrostatic screening? Would something as simple as bonded mesh cable basket hung on wall clips, directly over the runs of plastic pipes work?

Very easy to buy and fit. If cut into short modules, easy to unclip to make changes to the push-fit pipework.

It would also prevent touching, so even if the pipes carried an electrostatic charge, it can't go anywhere?

I do like simple solutions

 

[pc1966]

I think there’s no need for that as it’s for solid explosive materials sitting on a desk on in a flask, not explosive atmospheres, which is an entirely different thing.

I have a strong suspicion that is likely to be a rather controlled occupation. Getting advice from a bunch of randoms on an internet forum is not something you can depend upon!

Flexishield is a great idea. Thanks. It appears you can’t buy cut lengths so I’ve ordered one roll of 2.5 which I’ll use for everything (inc lighting!)

It is half way between SWA and normal round cable to work with. It tends to stay in place when you bend/set it. It is not "flexible" - it is intended for fixed wiring. However, unlike SWA where you need to carefully fit a gland for the outer armour/CPC, for Flexishield you can use a normal IP68 style plastic gland so far easier to use.

Read the stripping instructions, basically you score the outer sheath and then bend it to split the plastic and aluminium foil, then pull it off. With gloves, and some force.

You can score with a knife if careful, but this sort of tool is far safer & repeatable:

RS PRO Triple Action Wire Stripper, 4.5mm Min, 29mm Max | RS

uk.rs-online.com

The easiest installation would be one run of dado-rail multi-compartment trunking around the walls, terminating directly into the DB. I’m researching this today. It appears a metallic version is very difficult (and expensive!) to source. Or I'm thinking quality 100 x 50 metal trunking, with accessories cut into the lid, which is economic enough and fully shielded, but would look a bit sh!te

Unitrunk make covers for the 100mm and 150mm wide trunking pre-punched for single and double switches/sockets:

Products | Total Cable Management Solutions - trunking, cable tray and ladder: Unitrunk

www.unitrunk.co.uk

While trunking is hard to work with, it is touch and long-lasting. Just remember to use grommets and/or glands for cable in and out, and to ensure it is bonded to your MET.

As you found, also massively cheaper than metallic dado rail style options.

Agreed but there are other reasons why copper is not a good idea, chemically. Many of the regs for this kind of thing were written sometime in the Cretaceous (probably by actual dinosaurs), before plastic pipework existed. I’ll do some research on the static properties of John Guest pipes, which are either polybutylene or polyethylene first.

I like your metal cage idea, that’s cheap and easy to fabricate.

Or wrap it in aluminium self-adhesive tape.

Thanks for the excellent advice!

I'll post photos once it's done in a few weeks ...

We look forward to seeing it.

Also we can discuss where you are likely to appear next:

• Derek Lowe's blog "Things I Won't Work With"
• The Darwin Awards

Ladies, gentlemen, and internet randoms, place your bets

 

[Pete999]

pc1966 there a lot of "RANDOMS" on this forum that have a lot of knowledge, judging from your reply you think are insignificant, chose your wording carefully.

 

[pc1966]

pc1966 there a lot of "RANDOMS" on this forum that have a lot of knowledge, judging from your reply you think are insignificant, chose your wording carefully.

Sorry if I offended anyone, that was not my intention.

It was more the point that if the excrement were to impact on the air-moving apparatus, standing up in a court and saying "But the folk on forum XYZ said this was safe!" is not going to go down well.

 

[davesparks]

Is this a licenced explosives factory?

If it is then I know what the OP means about the rules being antiquated, our fireworks business has a factory licence, the explosives factories act of 1875 is the appropriate law. Although it has been updated a few times since then!

 

[pc1966]

Just to add I consider myself as one of the "internet randoms" here.

 

[DPG]

Just to add I consider myself as one of the "internet randoms" here.

I'm proud to be an internet random. Is there a badge for it?

 

[davesparks]

Just to add I consider myself as one of the "internet randoms" here.

I'm pretty random myself.

 

[Mark42]

Is this a licenced explosives factory?

If it is then I know what the OP means about the rules being antiquated, our fireworks business has a factory licence, the explosives factories act of 1875 is the appropriate law. Although it has been updated a few times since then!

Close. The Explosives Act 1875, AKA 'The Green Book' written by the rather splendid Col. Majendie. I've had my copy for over 40 years. Beautiful, precise law which nearly all made sense. Now almost entirely repealed and replaced by a succession of European-inspired Acts and Statutory Instruments which are impenetrable, daft in parts, and contain typos.

And yes, this is an authorised explosives site, it's what I do. (Electrickery is an adjunct, primarily for personal use).

You're in the fireworks business? We must know of each other. CBI EIG? IExpE?
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Unitrunk make covers for the 100mm and 150mm wide trunking pre-punched for single and double switches/sockets

Brilliant. Well-found! Doesn't look too bad either. A bit of etch primer and a coat of paint and it will both look pro, and save me a few quid . Thanks for the tip.

Or wrap it in aluminium self-adhesive tape.

Good idea. Or stainless cable braid as used on vehicle fuel hoses. And I just found this:

Metallised spiral wrap for use in the food industry. I've e-mailed the manufacturer to ask it it's actually conductive and hence anti-static.
Would be dead easy to install.

... Also we can discuss where you are likely to appear next:

Derek Lowe's blog "Things I Won't Work With" ...

Is that the bloke with the azidoazides which go off if you 'look at them in a funny way'?

Ha Ha, bloody amateur. Here is me enjoying destroying heavily peroxidised Tetrahydrofuran found earlier this year in a Kent lab. A fine day out. Yeah, and now I'm waiting for a chorus of, 'All the gear but ...'

I do rather enjoy my work.

 

[Mark42]

... Getting advice from a bunch of randoms on an internet forum is not something you can depend upon!

Wrong.

I have much more respect for people like those on this type of forum who, like me, actually build stuff than for any number of supposed 'experts' who have done little but read the manual. And I often find those enforcing regulations read the manual only yesterday.

And advice sought does not always have to be taken

 

[static zap]

I know photon energy gets involved in some unstable reactions ,maybe we can include quantum mechanics for if some-one was actually looking/filming ..satellite passing over !
(when a good conductor can meet another conductor )-- 500k -1 M in all sockets could reduce arc from a hand held metal object waved too near a socket... always a compromise between discharge time and reducing current in any small arc ! -- I'm no expert but was wary of being personally earthed
with anything lower than 1MOhm.

 

[pc1966]

Good idea. Or stainless cable braid as used on vehicle fuel hoses. And I just found this:

Metallised spiral wrap for use in the food industry. I've e-mailed the manufacturer to ask it it's actually conductive and hence anti-static.
Would be dead easy to install.

Good ideas in both cases.

Is that the bloke with the azidoazides which go off if you 'look at them in a funny way'?

Yes, his articles are both informative and amusing, with the ones on hideous chemicals usually the best of both:

In the Pipeline by Derek Lowe | Science | AAAS

Derek Lowe’s editorially independent blog on drug discovery and the pharma industry.

blogs.sciencemag.org

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Wrong.

I have much more respect for people like those on this type of forum who, like me, actually build stuff than for any number of supposed 'experts' who have done little but read the manual. And I often find those enforcing regulations read the manual only yesterday.

And advice sought does not always have to be taken

As long as you understand things and filter the advice it is fine!

This forum has a policy of avoiding step-by-step guides for DIY and being very cautious about any advice on the USA forum, etc, to avoid it coming back to bite them if it all goes horribly wrong and things get litigious.
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Also to add you probably will need the building to have a lightning conductor arrangement, at least all explosive stores I have seen have that.

And relating to that is having SPD fitted to the incoming distribution board. With a lighting conductor in use it should be a Type 1+2 to deal with the much higher surge energy in the event of a direct hit (not just induced spikes) and they cost a lot more (single phase in the £300 region, not the £70 region for Type 2 only). Examples include:

DV M TN 255 | Dehn, DV Modular Surge Protector 255 V ac Maximum Voltage Rating 50kA Maximum Surge Current Lightning Arrester | RS

uk.rs-online.com

Type 1+2 Lightning Current and Surge Arrester (KM1+2-25-1+1 SC) - Kingsmill Industries

System: Single Phase TT/2 Pole Nominal Voltage: 230V AC

www.kingsmillindustries.com

Type 1+2 Lightning Current and Surge Arrester (KM1+2-12.5-1+1 SC) - Kingsmill Industries

System: 1 Phase TT/2 Pole Nominal Voltage: 230V AC

www.kingsmillindustries.com

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I'm no expert but was wary of being personally earthed with anything lower than 1MOhm.

Quite right, most ESD wrist earth straps are of the order of 1M for that very reason! For example:

RS PRO ESD Grounding Wrist Strap & Cord Set With 10 mm Socket, 10 mm Stud | RS

uk.rs-online.com

Also in such environments it is not uncommon to use 10mA RCDs as well just to lower the risk further.

 

[DPG]

Close. The Explosives Act 1875, AKA 'The Green Book' written by the rather splendid Col. Majendie. I've had my copy for over 40 years. Beautiful, precise law which nearly all made sense. Now almost entirely repealed and replaced by a succession of European-inspired Acts and Statutory Instruments which are impenetrable, daft in parts, and contain typos.

And yes, this is an authorised explosives site, it's what I do. (Electrickery is an adjunct, primarily for personal use).

You're in the fireworks business? We must know of each other. CBI EIG? IExpE?
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Brilliant. Well-found! Doesn't look too bad either. A bit of etch primer and a coat of paint and it will both look pro, and save me a few quid . Thanks for the tip.



Good idea. Or stainless cable braid as used on vehicle fuel hoses. And I just found this:

View attachment 59918
Metallised spiral wrap for use in the food industry. I've e-mailed the manufacturer to ask it it's actually conductive and hence anti-static.
Would be dead easy to install.

Is that the bloke with the azidoazides which go off if you 'look at them in a funny way'?

Ha Ha, bloody amateur. Here is me enjoying destroying heavily peroxidised Tetrahydrofuran found earlier this year in a Kent lab. A fine day out. Yeah, and now I'm waiting for a chorus of, 'All the gear but ...'

View attachment 59920

I do rather enjoy my work.

Looks interesting!

Did you buy the suit off the guy from Boney M?