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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Condensate drips from an HCl pickle line cover
Q. I'm a maintenance manager at a steel pickler. We pickle with HCL. We have recently installed fume covers or hoods over the granites in our 4- bath pickle line. Each bath is 45 feet long. Since installing the covers, we have been getting acid drips from condensation developing on the covers and dripping. The acid bath temperatures run between 175 to 190 degrees. Acid concentrations run between 12% to 1.5%. The fume scrubber CFM has checked out with the manufactures original design specifications (12,000 cfm). However, with adding the covers, I do not know if we need more of a draw from our scrubber to eliminate the drips or do we need drip ledges and drip pans to catch the condensate? Currently the condensate drips test at 11% HCl in our last bath. Does anyone have any ideas on how to stop the drips?
Todd C [surname deleted for privacy by Editor]Pickler - Ghent, Kentucky, USA
2004
A. Hi Todd,
I'm somewhat confused. You said that you had put covers over the 'granites' ... but what in the hell are granites? I'm not a plater... but have designed many a (plastic) hood.
Then you infer that the scrubber is working OK ... may I suggest you leave it WELL ALONE because if you increased the airflow a) the scrubber may not like it at all ! b) your fan hp would jump c) your heating costs in winter would rise = more $$$ costs d) an increase in airflow would probably NOT be good enough.
If you can explain just what 'granites' are or do, then maybe one could come up with some answers.... but I presume you don't mean tank covers.
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
2004
Q. The granites are original equipment from the manufacturer. The acid section of the line is covered by granite slabs that cover the width of the pickling tanks. There are 52 sections of granite that cover the 180 ' of acid tanks. In the lines original form, every acid section (45' ft from squeegee roll to squeegee roll) had three 10" ducts coming out from the granites and tied into the fume scrubber. These granite slabs had a hole cut out. The acid sections are separated by squeegee rolls that had a small cover that hooked an 8" duct into the fume scrubber.
The new covers that are dripping cover the entire 45' section. Fumes come from the seams were the granites fit together and the three holes are now open.
- Ghent, Kentucky, USA
2004
A. Todd,
Thanks for the reply ... now I read this 5 or 6 times but being somewhat dense, couldn't quite understand it.
Is there any way you can take some photos of this or sketches so that one could have a visual? I would be delighted to try to help you if I am allowed to. There would be no charge (well, maybe a Rolls or a Bentley)
Cheers!
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
2004
A. Maybe I don't understand something, but it sounds like you have
'sealed' the tank with a lid and only have an exhaust from the tank. Without some air flow allowed over the surface of the tank to transport the vapors (acid and water)out, the condensation will build and the drips will form.
If I am understanding this right, I suspect that you are forming a negative pressure between the liquid surface and cover but have a very, very low stack velocity.
- Conroe, Texas
2004
A. Over the years my company has designed and fabricated many HCl pickle covers for the steel industry, in several cases the client was concerned about the drips from inside the cover, all we did was install a vertical drip plate near the outer edge of the cover, this would allow the condensate to drip back into the tank.
Kenneth Kensington- Hastings, Michigan, USA
2004
A. If I'm reading this correctly, Drip shields are the best solution to divert drippings back to the tank. Also you may explore an air push system (simple. Chem-Air piping placed around the perimeter of the tanks and perforated with about 1/32" holes to force more fumes towards your pulling exhaust system, control the air flow and balance to your liking) Hence the name, Push-Pull system. I would also like to see some pics. Good luck. Shaun
Shaun ShoemakeBuda, Texas U.S.A.
2004
A. Drip shields take many different forms, from a piece of plastic pipe or hose with a split in it, hammered over the two adjoining tank walls, to a piece of soft plastic lining material glued to the tank, to nicely engineered PVC weldments.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004
A. Charnockite {a natural stone] does not react with acids and heat - wear resistant, can make pickling lines which will stay permanently.
Venkateshwaralu- Bangalore, Karanataka , India
2005
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