Tolerance of a stainless steel vessel

[drodrig]

Hi there,

We are ordering a coil which comes in a vessel with:

outer diameter: 9.2 feet - 2.8 meters
inner diameter: 7.9 feet - 2.4 meters
length: 10.8 feet - 3.3 meters

The material is stainless steel 304L

The manufacturer gives a tolerance of +/-5mm (0.2 inches) in the inner diameter and +/-10mm (0.4 inches).

Are these tolerances normal?

What if it was in aluminium?

thank you
regards,

 

[XL83NL]

Is that a 200 mm thick shell?

 

[drodrig]

hey
of course not.
I forgot to mention the wall thickness. It's 10mm (0.4inches)

The coils is inside the volume defined by the inner and outer diameters (with end-caps)

cheers,

 

[r6155]

Some information in Pipe Fabrication Institute PFI Standard ES-24 “Pipe bending methods, tolerances, process and material requirements”

http://www.pfi-institute.org

Regards
r6155

 

[drodrig]

Dear r6155 I checked the Standard, they talk about 8% difference between minimum and maximum diameters (in ovality)

In the case of 7.9 feet - 2.4 meters would be 7.6 inches - 192mm.

This looks way too much for me, wouldn't it?

thanks
regards,

 

[r6155]

drodig
8% is the ovality of a pipe bend, not the coil.

Regards
r6155

 

[MJCronin]

Some fabrication tolerances are contained in the code:

https://app.aws.org/forum/topic_show.pl?tid=16261

Some, must be as agreed to in the purchase documents

http://www.eng-tips.com/viewthread.cfm?qid=150064

Some are contained in a book called the "Pressure Vessel Handbook"

http://www.inspection-for-industry.com/pressure-vessel-dimension-inspection.html

There are probably DIN and NORSK documents out there ...

MJCronin
Sr. Process Engineer

 

[racookpe1978]

You are doing the ordering, so you are in a position to set your tolerances for your work.
However, setting tight OD bend tolerances will cost more money over "just accepting industry normals" .

Can you live with the difference in OD's in your heat exchanger in your application? (Special supports, extra welding, harder to slide the HX out through a manhole or hatch?) If you can live with their proposal, use it. If not, call them to come and give you their reasons for the current tolerances, their schedule and their new price for tighter tolerances on the bending.