48" flanges for distillation column 1

[Distill9]

I am working on a distillation column replacement, column is for obteining and alcoholic beverage, this column will work at atmospheric pressure and is 48" diameter and 30ft high.
Our current column has sectioned bodies with flanges, this is an old column which was localy manufactured without standard codes. I haven´t seen flanges this size (48") and the ones I've been quoted on are realy expensive, my question is if it is recomended to use flanges to join the new sectioned bodies of the column or is it better to weld bodies together.

Is there any standards specific for distillation columns?

 

[katmar]

Many columns were made this way in the old days because they did not have the mobile hydraulic cranes we have today to lift large sections into place, and it was easier to rig the columns in if they were in smaller pieces. If you do not need access to the trays for maintenance or cleaning then there is no reason not to weld them together.

However, a word of caution. Old column sections that were not stress relieved, or have been subject to a high chloride acidic environment, can crack very easily when you start welding them. Get an expert to check the section before you go ahead and weld them.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[Distill9]

The existing column will be replaced with a new one, my doubt is if I should weld it in site or have it manufactured in one piece and use a crane. Application has fouling tendency and has around 3500mg/L of fine suspended solids therefore periodic cleaning and maintenance will be done to the trays. Tray design I am considering is Koch Glitsch provalve with flexilock construction with tray manways.

 

[Montemayor]

Distill9:

I have done what you are proposing - although my column was considerably larger. It had body flanges that continuously leaked air (the column worked under partial vacuum) and it was ridiculously expensive to consider body flanges on a new column. I replaced it with a 100% stainless steel, prefabricated model that was dropped into position. As Katmar states, columns were made with body flanges due to some lifting constraints at the time. Today, there is no concievable reason to do that.

A 4 ft diameter x 30 ft, prefabricated column should be an easy pick and installed through a section of your roof. As you indicate, the Koch valve trays (which I also used) can be insertable through 24" manways and installed with bolted sections. Two or three manways should suffice for your tray installation and maintenance, although I don't know how many trays you'll have.

 

[Distill9]

I am considering 3 20" access manways for the 18 trays, one below first tray second above 9th tray and last one above tray 18.
Do you think 20" is adecuate? is there a standard size for access manways? and is there a recomended distance between each manway?

 

[Montemayor]

Distill9:

I do not think a 20" manway is adequate for a distillation tower. I believe you will have problems with tray components and internals making it through that dimension. But more importantly, an average maintenance person cannot, in my opinion, quickly and safely enter and exit the tower through that dimension. That is why I hold 24" as the minimum size for an effective manway.

There are no "standard" sizes for manways - just as there is no standard waist size for a human being. The recommended distance between manways is dictated by the type, size, and quantity of internals that you have installed inside.

 

[unclesyd]

Based on having traversed several thousand manways over time I heartily second the recommendation for 24" manways by Montemayor.
When I started working in the chemical industry there was a tendency to use the 20" for all us you folks but it didn't take long to change to 24" for engineer's egress.
Aside from all that and as stated above nearly all internals are designed for 24" manways and for a 20" will bring on adders.
Even on the 24" manway hold the nozzle as short as practical. Parts and people don't like to go through tunnels.

 

[rmw]

And put a rung for a hand grip inside and outside right above the manway. Often that is a great assist in both the entry and exit process.

rmw

 

[MJCronin]

Distill9...

I second the recommendations and concusions of Mr. Montemayer.

Additionally:

- The 30 foot long, 48 inch diameter column is very modest in terms of crane placement requirements.

- Do not install expensive "body flanges" in columns unless necessary for maintenance purposes. It is tough to beat the low cost and reliability of an "all welded construction.

- Specific details of construction, including tray placement, manway size, etc should be discussed with your fabricator, and....since this is your first column I suggest that you also consider the purchase of some texts on the design of process equipment.

I suggest that you contact the fine people at ENERFAB with some of your specific column questions.

http://www.enerfab.com/

-MJC