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Wash Tank Venting


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#1 cos

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Posted 04 March 2009 - 03:14 PM

Hi All,

I have a project that requires modifying an existing 200GAL wash tank and automating an addition of booster solution.
Currently the tank is used as a wash tank for our CIP system. It contains a 3" overflow line on the side directed to floor drain and a 2" ubend vent on top of the tank directed to open drain.
Due to lack of extra ports I need to use the 2" line currently used as a vent.
I was thinking of modifying the connection to the verflow line and place a Tee to attach the 2"vent. Is this relocation feasible?

As far as the function of the wash tank, CIP solution is heated up to 55 degree C in the tank and circulated to the equipment requiring CIP.

I did look into ASI 2000 guidlines, but was not able to come up with a solid conclusion if this is feasible or if I can simply enlarge the overflow opening.

Any feedback would be helpful.

Cos

#2 proinwv

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Posted 04 March 2009 - 04:02 PM

COS, your application is not fully understandable, so let me make a couple of basic comments.

Your vent must be capable of handling the transfer of air/gas into and out of the tank under the several conditions described in API2000.

The overflow must be capable of handling the full pump flow into the tank.

Any compromise here could lead to a tank failure.

With that you need to be able to calculate the capacity of your vent and overflow piping and assure that under the worst conditions you will not exceed the tank MAWP or MAWV.

#3 Art Montemayor

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Posted 04 March 2009 - 07:31 PM


COS:

I would strongly recommend you study and strictly apply what Paul has written in his response.

If you are doing pilot plant or processing plant operations within the USA for a leading pharmaceutical firm, then I believe you fall directly under the dictates of OSHA and the safety codes in your region or location. If my assumptions are correct, then you should be doing your project with a detailed Piping and Instrumentation Diagram (P&ID), showing every line and piece of equipment connected to the subject tank. The tank itself has to be accurately identified as to its Maximum Allowable Working Pressure (MAWP) and its Maximum Allowable Working Vacuum (MAWV). You need this certified data in order to correctly identify and size the required venting nozzles, lines, and/or devices that you may have to put on the tank. And you need to have this information in a technically documented fashion in the event the tank suffers any mishap due to over pressure or excessive vacuum. I believe this is a legal requirement – but even if were not, you would be leaving the operation wide open for legal prosecution should a mishap take place.

The P&ID should be maintained in an “as-built” condition – i.e., it should be an accurate description of exactly what is found in the process as to size, pressure & temperature rating, capacity, all instruments, all controls, and all incoming feeds as well as all outgoing flows. OSHA demands this in order to ensure that all operations are safe and of no danger to the operators and to the general public. You should be well prepared to prove that your design and operations are inherently safe.

I believe your basic data is incomplete because your sketch does not show any heater and yet you say you are heating the tank. This fact, plus other details such as the upstream sources of the fluids entering the tanks should be identified. If there are hazardous scenarios related to these situations you have to identify what is the worse case scenario and identify its size of flow rate and potential pressure (or vacuum). Additionally the tank has definite pressure and vacuum limitations and these have to be identified and documented. I would never assume that someone else has calculated or identified these values and that the tank is “OK” for the new application. This procedure is known as Management of Change (MOC) and it is a requirement of OSHA when hazardous substances are involved.

I strongly recommend you create or obtain certified calculations or information for the tank, the flows, the operations, and all fluids involved. Once the P&ID is created, you then can reason and logic out a series of potential pressure or vacuum hazards and identify the worse case. I have developed an Excel workbook that details a lot of possible scenarios for storage tanks. You can use the SEARCH feature in our Forums, find it, and download it for free.

I believe your project is going to take a little more work than just assuming that your tank is OK and that everything is alright. That’s why Paul’s recommendations should be studied and applied.

Good Luck.


#4 Qalander (Chem)

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Posted 05 March 2009 - 12:30 AM


Dear COS,

Please follow in letter and spirit the recommendations of Our 'Paul' and 'Art'.Or otherwise visit www.csb.gov to see (GOD FORBIDDING)the possible recourse.

Some good process safety hints available from excellent site www.iomosaic.com

Hope this proves useful help& a guidance bit.

Best Regards
Qalander

#5 cos

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Posted 05 March 2009 - 08:06 AM

Hi All,

Thanks for all the insite. It looks like I need to do a little more research.
The links and info will surely help.

Regards,
COS




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