Hi all,

My company is looking into alternative methods of degreasing metallic parts following various NDT inspections (to remove oils, contaminants, fluorescent and magnetic penetrants etc). We currently use 2 large industrial degreasers which use perchloroethyelene, however we are aiming to replace one of these due to it's age and therefore environmental impact.

A suggestion has been made to replace the largest degreaser with a new, smaller unit which would eliminate the environmental impact of perchloroethyelene.
The suggestion is to introduce 2x acetone wash stations in a nearby room.

We're still figuring out what exactly the system would look like but in general:
2x Wash stations with internal storage for around 30L acetone.
Acetone will be pumped from storage container using a compressed air pump and through a spray gun.
The acetone will wash over the part and flow back into the storage container. A filter will be place either before the spray gun and on return to the storage container.

Issues and controls I forsee:
Potential for explosions or fire - Ensure all equipment is earthed. Switches and lights are intrinsicly safe. 
Static electricity - Could use some advice on this as we'll be pouring acetone to fill the storage container and using a spray gun.
Vapour build up above the liquid solvent in the storage container - Could this be an issue?
Exposure - There is an extraction system in place in the suggested room, but this would be modified by a suitable contractor for use with acetone. Hood sizes may be an issue because of the large sie of the baths. Weight - The shafts weight upwards of 150kg but weight ratings will be built into the structure of the stations.

We're working through all of the possible issues, even if that means the end results is not proceeding with the idea.

Any thoughts and questions are more than welcome! 

Originally Posted by: Hsquared14

I've seen some units being used in automotive and aerospace parts manufacturers which use a water based emulsion to remove the grease and other debris.  I don't recall what the chemicals in the emulsion were but I'm pretty sure that citrus extracts played a part and the resulting grease was skimmed off the top of the water by an automatic weir system and treated to produce a solid residue.  Might be worth looking at?

Thanks for the suggestion. We've used aqueous washing in the past, but due to strict cleaning specifications we're unable to use anything water or detergent based, so solvents are our only option.

Originally Posted by: Ian Bell2

You need to complete a risk assessment under the Dangerous Substances and Explosives Atmospheres Regulations (DSEAR) HSE Acop L138.

From that you will be able to determine the ATEX rating of electrical equipment, the extents of any hazardous areas generated, if you do put electrical equipment inside a hazardous area the required rating e.g IIA T1 Cat 1/2/3 depending on the hazard zone assessment.

I shudder at your comments about getting a contractor to modify the existing extraction without further analysis... acetone is quite volatile.

As part of your assessment you should complete an ignition assessment as well and consequence assessment.

Also develop your emergency procedures for the plant.

Happy to help

Great advice, thank you.

As for modifying the current LEV, we wouldn't carry out any changes until we know exactly what the process is going to be. What that final process actually is is changing regularly.

Originally Posted by: chris.packham

You mention a spray gun. Will this be hand held? If so how will you protect the operator? Simply providing PPE might not be compliant with the requirements of COSHH and PPE regulations.

It will be hand-held, although we're not sure what pressure it will operate at. There's a chance that it will only need to gently flow over the part to degrease it, in which case the risk of splashes will be low.
​​​​​​​An interesting point though, thanks.

Edited by user 20 February 2020 16:44:45(UTC)  | Reason: Typo

Originally Posted by: JohnW

Acetone is highly flammable and any process will be a significant fire risk, it evaporates quickly at room temperature so any leak will present a spark-ignition hazard and a respiratory/ nausea hazard to employees

I have precision engineer clients who use a Dowclene 1601 process, a fully-contained high temperature process (160degC) special equipment e.g. Amsonic. Expensive but ensures the quality required by the aerospace industry.

John

A don't have access to the MSDS' at the moment but if I'm not mistaken that's the modified alcohol option?

This is the alternative we've been looking into, however the investment would be around £250k, which isn't easy to get authorised.

Originally Posted by: Climhazard

Originally Posted by: Hsquared14

I've seen some units being used in automotive and aerospace parts manufacturers which use a water based emulsion to remove the grease and other debris.  I don't recall what the chemicals in the emulsion were but I'm pretty sure that citrus extracts played a part and the resulting grease was skimmed off the top of the water by an automatic weir system and treated to produce a solid residue.  Might be worth looking at?

Thanks for the suggestion. We've used aqueous washing in the past, but due to strict cleaning specifications we're unable to use anything water or detergent based, so solvents are our only option.

I have seen aqueous units in use for aerospace applications and in particular for parts used in satellites - cleaning specifications don't get stricter than that and they were the preferred cleaning method specified by the customer.  No detergents were involved and there was zero residue on the finished article. 

I have recently visited a workplace where degergent based degreasing was used on safety critical aerospace components. For me one major benefit of this approach is that it is far easier to provide adequate PPE than it is for a solvent such as acetone. 

Given the emphasis on LEV as has been stated, you will lose much of the acetone in the extraction system. What recovery system will you have as I cannot imagine that you will be considering discharging the acetone laden air into the general atmosphere? What will you do then with the recovered acetone? 

Humbrol Airfix used to make paints for model airplanes. They used to have a factory on Hedon Road, Marfleet in Hull. I say used to, because in 1989 they had a spill of acetone. Some genius was moving a drum of the stuff around the site on a fork lift. It was, of course, unsecured and it fell off the forks and the entire contents spilt on the floor. Somebody then decided that two YTS trainees (remember those?) aged 17 and 18, should mop it up, using clothes etc. They could not see the extent of the spill so they turned on the lights. There was an explosion and one trainee (the 17 year old) was killed and the other had what we now call, life changing injures(https://www.itv.com/news/calendar/2018-07-06/nhs-70-a-lasting-bond1/) I can’t remember the fine but it probably ran into hundreds of pounds.( yes the good old days) .

Acetone is very volatile and highly flammable. If it is allowed to form an aerosol it becomes explosive. This is why people on this forum are so nervous about using it as in any sort of spray. Is it really the only solution or is it just something that a particular client is fixated on?

Originally Posted by: fairlieg

Originally Posted by: A Kurdziel

....Some genius was moving a drum of the stuff around the site on a fork lift.....

I know you didn't mean that!

One or both of us is being sarcastic! 

Originally Posted by: Climhazard

A quick update for those of you interested.We are now going ahead with the acetone wash stations based on the fact that it would be extremely difficult to control every potential ignition source in ... .

Edited by user 28 February 2020 16:15:49(UTC)  | Reason: Typo

Just use correctly rated DSEAR/ATEX rated equipment Group 2 IIA T1 Cat 1/2/3 depending on Ga/Gb/Gc protection following your hazardous area classification study.

No sense of adventure,