My first question is 80°C is the temperature of what?
The air temperature might be 80°C but the components could well be hotter.
Also during the curing process does the product give off any sort of fumes/vapours etc?
30 minutes is a hell of a long time to being doing any sort of manual work at this sort of temperature. Heat exhaustion would obviously be an issue
Can the guys stand up straight in the oven, or would they be working bent over?
Overall I'd be very wary about putting people into such an environment.

David - welcome to the forum.

Though you don't mention it, I trust that attention is also being given to why the chain drive comes off from time to time in a bid to avoid down time and the need for entry into the oven while hot. If the new oven is a proprietary one, the manufacturers should be able to help diagnose the cause and suggests appropriate modifications.

Also, hopefully, other forum users with experience of similar ovens may be able to respond to this thread and comment if problems with chain drives are relatively common or not. If they're not, this adds weight to the likelihood that there is a problem with your oven's drive and that it can be resolved.

There is a lot about heat stress on the HSE's website. They also have a risk assessment pro forma you could use to determine the risk and the precautions you need to take - see link below. If you have to do this on a regular basis and cannot rectify the fault once and for all and do away with the task I suggest you (or an occupational health advisor) undertake some Wet Bulb Globe Thermometer (WBGT) tests/sampling so that you can create an informed safe system of working. Hope this helps.

Sorry forgot the link - see below

http://www.hse.gov.uk/te...tress/riskassessment.pdf

There was also a couple of fatalities a few years ago when 2 maintenance guys entered an oven in a bakery.

Get a copy of BS EN 563:1994 Safety of Machinery - Temperatures of touchable surfaces.

If the 80C you mention is the metal temperature, you will get burns to unprotected skin with about 0.5s - so effectively straight away.

The BS suggests the burn threshold starts at about (the burn threshold) is between 64-73*C

Above that, more or less instant burn.

If you anticipate a longer contact period between the metal and the body of 1minute, then the temperature of the surface drops to 51*C

I think you need to find a away of cooling the oven down more quickly, a different way of doing the job or providing thermal protection to the guys doing the job.

As other have said, you also need to consider the risk of breathing very hot air and potential internal injuries to the throat/lungs etc.

This may not help!! The original query was about a chain drive coming off its (I assume drive sprocket) - as this would seem to be a relatively random event, pre start maintenance doesn't help.

The full answer is to determine why the chain comes off and find a engineered solution to stop it coming off.

I've actually been there and done this back in the 80's, it was a 3 man job, even back then, mind, it was us that decided we wanted a safety man outside and would not do it without!

You cannot do if for more than 5 minutes.

You need to be covered up to protect yourself from the heat.
Which makes you get hot quicker IYKWIM.

You can't go in @ 80 deg, you simply can't breathe, we tried!

If it is close to the door, and you can hold your breath you might get away with it, we would do this for jammed hangers.

If the chain came off, we would shut the burners down and leave the fans running as many doors open as we could manage then it would be down to us to decide when we went in and came out.

Even back then, the official line was that it should be cooled down totally.

We would do it on our terms, and often got a job and finish out of it.
No one got hurt, luckily, but, we all were a close knit team, who really watched out for each other.

If you are getting regular chains coming off then you really need to look at the mechanics and plan a down shift, or out of hours works to find out why.

Wear, in the chain, sprockets, or bearings, misalignment due to the bearings failing, or the chain sagging due to stretch or wear, creep due to the materials continually operating at elevated temperatures, thus loosing their tensile properties due to the thermal effects, and physically stretching, or overloading were the normal reasons our chains started detaching themselves from the sprockets.

Normally because we had a run to failure maintenance policy as we were so short staffed no PPM's were done.

IF, we had less breakdowns, by luck, we would go on to PPM's and there was a noticeable increase in plant reliability, then of course we would have a major, that would soak up all our resources, no PPM's so reliability fell again.

If this is new kit, and this is happening already, then lord help you when it gets a bit of real wear & use!

HTH.

Take on board what bob and paul say.
Get some data, whats the temperature of the air AND surfaces over time once the heat has been removed
Can people get out
Can the drive be isolated
Can the heat be isolated
Why is they drive failing

Personally speaking I would;
1) get the install company to sort the drive out, if not then
2) relocate the drive to outside of the oven, if not then,
3) access by permit only to include, time heat source isolated, cooling time of X minutes, PPE list, isolation, etc, etc

It's sounds to me that we are using humans in a harsh environment to correct poor mechanics. Get the plant right first - it's going to cost a lot in downtime, training, PPE, SoP, permits etc. Why not just pay for a decent mechanical drive.

From experience in an industrial oven baking resin powder onto steel components.
Air temperature 70-90C.
After the first breath through the nose, the nose dries out. After that it hurts.
Breathing through the mouth in ok, until that dries out, the tongue starts hurting first.
After the person comes out he/she will have trouble with the first breaths of cold air.
Why would you even consider sending a person into that heat anyway..get it sorted by the installation company, and bill them for the dow
n time.

Sauna anyone?

Typical operating temps 70-100 degrees C, no clothing, no physical activity, no work in awkward areas, no use of tools. How long do casual users (i.e. not regular and acclimatised) stay? Perhaps 15 minutes.

Industrial oven: turn the above "no's" to "yes", add dust and vapours, pressure from production to get the job done = very unpleasant working environment.

Please add my voice to those advising that the problem be solved at source.