[labnetwork] Corrosive exhaust material of construction

Mon Dec 23 20:47:02 EST 2013

Iulian, Colleagues,

Having built, in 1984, and managed the facilities of the UC Microlab I 
have my answer to the question about ducting material.

We used Plasite coated galvanized duct. Around 2000 we had a duct fire 
over our LPCVD furnaces, gallons of accumulated pump oil in a lateral. 
Following the duct fire the duct was inspected by a third party for 
integrity, found mostly in excellent shape and put back into service. 
About 10 feet of the lateral was replaced because it was damaged and 
actually glowing red during the burn-off of that oil (rather impressive 
when your holding the fire extinguisher).

In 2011, when we moved to our new lab, those same ducts were inspected 
by a third party for integrity to see if they could be re-purposed. Note 
that both laterals and risers of this same ducting serviced our acid and 
etch wet process station. The main riser saw all of the accumulated 
exhaust. After 26 years of harsh service these ducts were deemed in 
excellent condition with more service life. To be fair there were some 
areas that needed repair. The uncoated dampers where the flexible PVC 
tubing from the wet process stations transitioned to the duct were 
corroded. These dampers were dynamic and areas of them weren't coated.

An added benefit to Plasite was when we needed to modify the ducting our 
HVAC contractors and our machine shop could fabricate new sheet metal 
and coat the modified pieces plus, in site coat the modified with Plasite.

I cannot give you a cost/benefit for other ducting. If anyone asks me 
for my recommendation I will, without hesitation recommend Plasite 
coated ducts for both their chemical resistance and for their 
fire-ratings as well as the added benefit of being reconfigurable at 
modest cost.

The taste of a pudding is in its eating,
Bob Hamilton

-- 
Robert Hamilton
University of California at Berkeley
Marvell NanoLab
Equipment Eng. Mgr.
Room 520 Sutardja Dai Hall
Berkeley, CA 94720-1754
bob at eecs.berkeley.edu
Phone: 510-809-8600
Mobile: 510-325-7557
e-mail preferred

On 12/23/2013 11:18 AM, Iulian Codreanu wrote:
> Many thanks to those who have provided input!
>
> To summarize the input:
> - Three sites have teflon-coated SS and two designers strongly 
> recommend it. I know of at least two other sites that have it.
> - Three sites have FRP
> - Two sites have coated galvanized steel (one with PVC, one with 
> Plasite?)
> - One site reported polypropylene
>
> I wonder why polypropylene is not more commonly used.  Abbie's 
> comments about explosions seem to be a good reason. Any other reasons? 
> Can anyone comment on its durability; in my mind "plastic" becomes 
> brittle after a while although I saw decades-old polypropylene wet 
> benches that seemed to be fine?
>
> Best regards,
>
> Iulian
>
> iulian Codreanu, Ph.D.
> Director of Operations, UD NanoFab
> University of Delaware
> 149 Evans Hall
> Newark, DE 19716
> 302-831-2784
>
> On 12/21/2013 12:46 AM, Abbie Gregg wrote:
>> Thanks for the lead in Julia,
>> A few comments. The Teflon lined stainless steel which is 
>> flanged/gasketed/bolted or welded is especially important if you are 
>> combining potential effluents containing pyrophorics or hydrogen (eg 
>> CVD or LPCVD exhaust/purge) in the same duct as the wet hood (acid or 
>> base) effluent, because you have the risk of explosion, fire and 
>> corrosion in the same exhaust stream.
>> Also we have been able to modify the Teflon lined stainless in the 
>> field at many jobs, it just takes special skills and a kit from PSP 
>> to do a tap in the field for modifications. This material is a long 
>> lead item and also quite expensive,  but it has been much safer than 
>> any other material. FM prefers it because it is "factory made" rather 
>> than wrapped or coated in the field.
>> We did use Plasite coated heavy gauge galvanized ductwork in the same 
>> application at a couple of Northern CA projects but this was not 
>> preferred because the plasite is coated at the fabrication shop and 
>> there can be voids, think areas or other quality control problems 
>> that are hard to find. It is also heavier.
>> If there is no risk of overheating, fire, or explosion and only 
>> corrosion resistance needed, the Fiberglass reinforced plastic "field 
>> fabricated" duct is good if made by talented fabricators, although 
>> any Fire in the facility will also destroy it,  and it makes really 
>> awful destructive and corrosive smoke when it burns. PVC has  similar 
>> characteristics, and neither of these materials meet the 25/50 flame 
>> and smoke spread requirements of some H-5 codes. (depending on IBC 
>> year, I believe).
>> Best regards,
>>
>> Abbie Gregg
>> President
>> Abbie Gregg, Inc.
>> 1130 East University Drive, Suite 105
>> Tempe, Arizona 85281
>> Phone 480 446-8000 x 107
>> Cell 480-577-5083
>> FAX 480-446-8001
>> email agregg at abbiegregg.com
>> website www.abbiegregg.com
>>
>> CONFIDENTIALITY NOTICE:   All information contained in or attached to 
>> this email constitutes confidential information belonging to Abbie 
>> Gregg, Inc., its affiliates and subsidiaries and/or its clients.  
>> This email and any attachments are proprietary and/or confidential 
>> and are intended for business use of the addressee(s) only.   All 
>> other uses or disclosures are strictly prohibited.  If the reader is 
>> not the intended recipient you are hereby notified that the perusal, 
>> copying or dissemination of this email is strictly prohibited. If you 
>> have received this communication in error, please notify the sender, 
>> and delete all copies of this message and its attachments immediately.
>>
>>
>> -----Original Message-----
>> From: labnetwork-bounces at mtl.mit.edu 
>> [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Aebersold,Julia W.
>> Sent: Thursday, December 19, 2013 3:57 PM
>> To: Iulian Codreanu; Fab Network
>> Subject: Re: [labnetwork] Corrosive exhaust material of construction
>>
>> Teflon lined stainless steel was designed and implemented for our 
>> acid exhaust system.  Our cleanroom has been in place since 2006 and 
>> was designed by Abbie Gregg.  She would be a great source for this 
>> type of information.
>>
>> Cheers!
>>
>> Julia Aebersold, Ph.D.
>> MNTC Cleanroom Manager
>> Shumaker Research Building, Room 233
>> 2210 South Brook Street
>> University of Louisville
>> Louisville, KY  40292
>>
>> 502-852-1572
>> http://louisville.edu/micronano/
>>
>> -----Original Message-----
>> From: labnetwork-bounces at mtl.mit.edu 
>> [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Iulian Codreanu
>> Sent: Thursday, December 19, 2013 1:52 PM
>> To: Fab Network
>> Subject: [labnetwork] Corrosive exhaust material of construction
>>
>> Dear Lab Network,
>>
>> I, once again, seek your wisdom.  Could you please share with me the 
>> type of material used for your corrosive exhaust system, how long you 
>> had it in operation, if you had any problems with it, and what you 
>> would do differently of you were in a position to do so?
>>
>> Thank you very much for your help.
>>
>> Iulian
>>
>> -- 
>> iulian Codreanu, Ph.D.
>> Director of Operations, UD NanoFab
>> University of Delaware
>> 149 Evans Hall
>> Newark, DE 19716
>> 302-831-2784
>>
>>
>> _______________________________________________
>> labnetwork mailing list
>> labnetwork at mtl.mit.edu
>> https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork
>>
>>
>>
>> _______________________________________________
>> labnetwork mailing list
>> labnetwork at mtl.mit.edu
>> https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork
>
>
> _______________________________________________
> labnetwork mailing list
> labnetwork at mtl.mit.edu
> https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork