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Mersey  
#1 Posted : 12 September 2019 18:32:48(UTC)
Rank: Forum user
Mersey

Hi, This is an area that I'm not too aufait with. One of the sites I visit has a dedicated airline with filter for their air hoods, however I have discovered that this clean air supply is also used on some machinery , ( lucky for the machines getting filtered air) I'm concerned that there could be contamination and this is bad practice, I want the to pipe another air supply in and change the couplings accordingly so they are impossible to mix up. I'm after the right guidance documents, or acops for this subject I want to learn more about the checks involved in maintaining this type of equipment and the rules around connecting clean air supplies to machinery Many thanks
chris.packham  
#2 Posted : 12 September 2019 22:00:27(UTC)
Rank: Super forum user
chris.packham

My questions would be: If the filtered compressed air was being fed to both the respiratory equipment and machinery where could the contamination occur? How would any external contamination gain entry to the system? Of course, without more detailed knowledge of the design of the system it is difficult to answer this question from here. 

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CptBeaky on 13/09/2019(UTC)
stevedm  
#3 Posted : 13 September 2019 05:50:23(UTC)
Rank: Super forum user
stevedm

The guidance from EIGA is that the supply should be independant..HSG 53 Appendix 3..is also a reference but doesn't answer your question...I only work with independant supplies....

https://www.eiga.eu/index.php?eID=dumpFile&t=f&f=179&token=e43b839015d9ba331be1e996acf0a519d8db248a

http://www.sfeg.co.uk/sites/default/files/Breathing%20Air%20Quality%20Info%20Sheet.pdf

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Mersey on 17/09/2019(UTC)
chris.packham  
#4 Posted : 13 September 2019 08:20:13(UTC)
Rank: Super forum user
chris.packham

Steve - does this mean that you have a completely separate air compressor system for the breathing air?

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Mersey on 17/09/2019(UTC)
CptBeaky  
#5 Posted : 13 September 2019 08:40:50(UTC)
Rank: Super forum user
CptBeaky

I can't see where the contamintion risk is. Can someone explain it to me in case I come up against this in my role?

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Mersey on 17/09/2019(UTC)
hilary  
#6 Posted : 13 September 2019 09:14:30(UTC)
Rank: Super forum user
hilary

Where exactly are the filters?  On our filtered air, we have one airline from the compressor which splits and downsizes as it goes through the factory, one arm goes to a set of yellow filters above the paint booth and the airline that exits these filters goes to the breathing apparatus, but the airline continues past this point to other parts of the factory. 

Even if this were not the case, given that the compressed air is probably at 30psi as an absolute minimum, how is the contamination going to get back up the airline from the machinery to affect the breathing apparatus?

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Mersey on 17/09/2019(UTC)
stevedm  
#7 Posted : 13 September 2019 09:33:07(UTC)
Rank: Super forum user
stevedm

Originally Posted by: chris.packham Go to Quoted Post

Steve - does this mean that you have a completely separate air compressor system for the breathing air?

That is pretty much what EIGA promote...not sure I fully agree with the statement....so long as the quality and relaiability of the system can be guaranteed I don't really see a problem...however the supply of breathing air should really only be supplied from a system designed for that purpose...I do have dual systems be they conform to the spec for breathing air..we have had many a debate that we are wasting good air... :)

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Mersey on 17/09/2019(UTC)
Granlund40055  
#8 Posted : 13 September 2019 09:42:26(UTC)
Rank: Forum user
Granlund40055

If you carry out the checks on the quality of the breathing air specified in appendix 3 of HSG to which Stevedm referred, then this should determine if there are any contaminants in the breathing air supply. (and that the filtering system is doing what it should and filters changed at the appropriate intervals etc etc).

http://www.hse.gov.uk/pUbns/priced/hsg53.pdf

If the filtered air also goes to other equipment, while unlikely, could there be a risk of some back flow when the compressors are turned off at the weekend? or if there is a ring main? - just a thought

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Mersey on 17/09/2019(UTC)
chris.packham  
#9 Posted : 13 September 2019 09:44:44(UTC)
Rank: Super forum user
chris.packham

The problem with most normal air compressors is that the air coming from the compressor is virtually saturated with water vapour and a small amount of lubricating oil carried over from the compressor. The water vapour condenses as the air cools in the pipework and also when the air expands when used at the work site. This can present a problem so most systems have a water separator system immediatly after the compressor. The tiny amount of oil is not normally removed by this and is carried over. In some situations this is used to help lubricate the air motor/piston in the equipment. In some systems it is removed at the compressor station and the appropriate lubriaction carried out by a system at the place of use. However, for breathing air the oil has to be removed and this is normally done using a high performance filter system in the breathing air supply pipework. If the oil is removed at the compressor then, provided that the pipework is in good condition, then there is no way that contamination should be able to get into the air system. To answer the question on air pressure, this is normally around 7-8 bar in the pipework and is reduced by a pressure control system to the desired pressure and the point of use.  I used to work in the air compressor business (many years ago) so if anyone needs more, M me with contact details and I will respond. Chris

thanks 3 users thanked chris.packham for this useful post.
Dave5705 on 15/09/2019(UTC), mihai_qa on 15/09/2019(UTC), Mersey on 17/09/2019(UTC)
hilary  
#10 Posted : 13 September 2019 10:00:49(UTC)
Rank: Super forum user
hilary

Yes, we have a dryer and separator at the compressor and then filters at the breathing air point.

CptBeaky  
#11 Posted : 13 September 2019 10:18:28(UTC)
Rank: Super forum user
CptBeaky

Originally Posted by: hilary Go to Quoted Post

Yes, we have a dryer and separator at the compressor and then filters at the breathing air point.

This is the same as our set up (for a spray room). This is why I am confused as to what the contamination issue is. If, for example, we used the filtered point for a machine then plugged the breathing airline back in, would there be a contamination issue?

hilary  
#12 Posted : 13 September 2019 10:46:22(UTC)
Rank: Super forum user
hilary

Originally Posted by: CptBeaky Go to Quoted Post
Originally Posted by: hilary Go to Quoted Post

Yes, we have a dryer and separator at the compressor and then filters at the breathing air point.

This is the same as our set up (for a spray room). This is why I am confused as to what the contamination issue is. If, for example, we used the filtered point for a machine then plugged the breathing airline back in, would there be a contamination issue?

I don't know how contamination could occur either.

chris.packham  
#13 Posted : 13 September 2019 14:29:17(UTC)
Rank: Super forum user
chris.packham

If I were designing and installing such a system, at the breathing air offtake I would have a separate connector (upstream of the filter for the breathing air) for other air use. I would arrange that the standard connector for the factory would be of a separate design to that of the breathing air connection point so that only this could be connected to the breathing air. 

Dave5705  
#14 Posted : 15 September 2019 07:00:28(UTC)
Rank: Super forum user
Dave5705

If you are concerned about using breathing air for tools (cost of treatment filtration ) would it not be possible with a little re-plumbing to split the air immediately after the compressor and before the air dryer/filters? That way the filtered air would only be used for breathing apparatus and the filters would process less air and last longer? Or have I got the wrong end of the stick?

Kate  
#15 Posted : 15 September 2019 14:15:28(UTC)
Rank: Super forum user
Kate

It reads to me that the concern is that oil etc from the machines could backflow into the air system and get into the air used for breathing - is that the right end of the stick?

Dave5705  
#16 Posted : 15 September 2019 20:31:43(UTC)
Rank: Super forum user
Dave5705

Kate, maybe you are right and I got the wrong end. I suppose this is one for a compressed air expert, but I thought the risk of contamination would be eliminated by the filter and dryer being on the 'breathing air' side of a backflow check valve. To me, it is possible that contamination could feasibly occur if the compressor was turned off and a pressurised line was allowed to backflow unchecked. I wouldn't have thought using breathing air from an undedicated breathing-quality airline was a good idea.

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Mersey on 17/09/2019(UTC)
Mersey  
#17 Posted : 17 September 2019 14:26:12(UTC)
Rank: Forum user
Mersey

Thats correct Kate, I suppose ultimately it comes down to a risk assessment

Originally Posted by: Kate Go to Quoted Post

It reads to me that the concern is that oil etc from the machines could backflow into the air system and get into the air used for breathing - is that the right end of the stick?

stevedm  
#18 Posted : 18 September 2019 07:42:52(UTC)
Rank: Super forum user
stevedm

Sorry for the late reply...I have had a look at two installations just to make sure we were running on the same lines..(excuse the pun)...so yes single compressor yes single line coming out of compressor...which is then diverted..one for breathing air one for instrument air.(we still have a independant line - but that is just us apparently!)..they have 2 'surgical grade' filters (Once I have the link to the spec I will post it) on the breathing air line, with the appropriate NRVs...which gives us the purity required to comply with the breathing air standard...so although EIGA references are good and other nations do mandate independant supply (US) we don't seem to do that in the UK..I am happy, having reviewed two customer systems against our own, that the setup is ok and complies...you might want to get further advice from you vendor on the maintainance and the type of filters...but generally single line diverted looks to be ok

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