TEMA

[picasa]

There is an old HX which was designed back in 1970's per TEMA. I have thru the latest inspection report on this HX, thickness values for tubesheet, shell, channel, tubes etc. I need to check that these thicknesses are ok. I believe I need to use TEMA. As a second check, I want to also check these thicknesses per UHX.

I read UHX and I liked the well-described procedure. Now I am trying to read TEMA (1999 edition) The procedure does not seem that well-laid-out. With UHX, I can follow the instructions well, but will TEMA, I am lost. I dont know where to start.

Can someone relate to my point of view? Can you please give me some instructions. Sample calcs done per TEMA will be great, but I dont have them.

 

[picasa]

What does it mean when you say code for a particular HX is: TEMA B - ASME Section VIII? I dont understand the B part.

 

[Christine74]

TEMA "B" standards apply to unfired shell and tube heat exchangers for chemical process services.

What type of exchanger is this (fixed tubesheet, "U" tube, floating head, etc.)? For some types of exchangers, the TEMA tubesheet calculation is very simple, but it's somewhat complex for others.

-Christine

 

[picasa]

This is AEU type.

 

[Christine74]

The "U" type is the easiest type of tubesheet to calculate, whether you use TEMA or ASME UHX.

First you check to see if shear controls using the formula in RCB-7.133 (it won't unless its very high presssure).

Then you calculate you "G" per VIII-1 Appendix 2. Most of the time this will be equal to the tubesheet diameter minus the gasket width.

Then you calculate the ligament efficiency for your tube pattern per RCB-7.132.

This leaves you with

T = ( 1.25 * G / 3 ) * SQRT ( P / n * S) + CAt + CAs

Where CAs is the shell-side corrosion allowance and CAt is the greater of the tube-side corrosion allowance or the pass partition groove depth.

 

[picasa]

Thanks a lot!
What sections of TEMA do I need to focus on for design of a AET type HX.

 

[waskillywabbit]

I'd start w/ Section 10 RGP "Recommended Good Practice" if you are unfamiliar w/ TEMA.



Brian
Pressure Vessels and Autoclave Systems

http://www.mcabeeconstruction.com

The above comments/opinions are solely my own and not those of McAbee Construction.

 

[picasa]

In TEMA, you have a T ype of floating head that is Pull through floating head. ASME SEction VIII UHX gives three types of floating heads in figure UHX-14.1. How do you match these classifications. In other words, how do I find the right type of floating head in Fig UHX-14.1 that matches with the T type of floating head in TEMA.

 

[picasa]

I am looking at drawings for an old HX (AET type) designed per TEMA. Tubes are connected to the tube sheet using a rolled and grooved joint. I am looking at TEMA 1999 edition and I dont find any figure that describes that type of joint. ASME UHX latest edition shows the expanded tube joint which is similar. Does older (older than 1968) TEMA code address that type of joint between tube and tubesheet. On that joint what I see is using some type of device the tube has been metal-to-metal meshed into the tubesheet material in the form of a groove. That is how sealing is attained. No welding that I see.

If I want to repeat the design using the latest ASME UHX, how do I account for this type of joint between the tube and tubesheet?

If I want to check the design per TEMA (Note that the HX originally was designed per TEMA older than 1968), how do I account for this type of joint between the tube and tubesheet.

 

[picasa]

Shell is 33" I.D. When shell is made out of plate, for the range 30" to 39", TEMA 1968 requires that plate thk needs to be 7/16" min. In this case shell is 7/16" per TEMA. Now, over time shell has corroded thus corrosion allowance can no longer be specified as 1/8" which is required per TEMA R-1.5. Will this pose any problem in rerate of this HX?