Acid fumes... How do I measure and deal with them?

[tralala]

HI everyone.
Our machines are part of a large production line. In one stage one machine comes after an acid bath pool (Hcl, HF, H2S04, HNO3 mainly) which is supposed to be sealed to prevent acid fumes to come out. The problem is that the fumes still come out and corrode our machine.

I have 3 questiond and I hope you can help me...

How do I measure the concentration of the acids comming out? (mainly for alarm system)
Do I have to measure all acid independently or is it enough to measure the PH in the air?
Whats the normal way of getting rid of the fumes? With a filter, neutralizing the acid spraying basic fumes?

I hope you can help....
Cheers!
Trala

 

[IRstuff]

Fumes that are supposed to be contained generally require negative pressure, relative to the areas that are not supposed to be exposed. So, BIG honking exhaust fans that maintain the negative pressure are required. The exhaust fumes ought to be run into a scrubber, which dissolves the fumes into water, which is then neutralized.

At least, that's the way it was configured for semiconductor acid etch processing.

TTFN

FAQ731-376

 

[EdStainless]

You move lots of air. There is no practical way to neutralize the air.
Your machine that is supposed to be sealed should have direct ventilation so that it is always sucking air in. Yes cleaning all of that waste air is a pain, but it beats destroying equipment.
As for measurement there are a couple of ways. One involves using a pump to draw air samples through a small amount of water and then measure the pH. There are some conductivity measurements that could be used also, but they would read anything.

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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[tralala]

Thanks for the replies!

@IRStuff: We have the same problem as the machines that come after the semiconductor etching process! The etched parts are transported from the acid pool into our machine (after being air dryed). Our machine and the acid pool are just separated with a plexiglass plate with a hole, through which the etched parts are transported.

We were thinking of placing fans inside our machine to blow clean air (from outside the machine) directly into the hole conecting both machines. The idea is to prevent that the fumes leave the acid pool.

Do we need a special fan for this?
Can we use a normal one, since the air going though it is goin to be clean?

To measure the pH we've found sensors that doesnt require water.... they just measer the ph in the air. Besides... They are really compact!

Just another question... What is dangerous about acid fumes... Just the pH or also the acid they are made of? (the acid concentration should be under 1%)

Thanks you for your help!

Trala

 

[EdStainless]

Trust me the type of acid makes a lot of diff. and HF is about the worst.
Start with OSHA. There are workplace exposure limits.
Before you start trying to blow fresh air in make sure that you know where it will come out.
You may be better off using an acid resistant blower and sucking the fumes away. At least you have control then.

= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net