High temperature application material 3

[asv80]

We have a high temperature heat exchanger application and would like your comments on material selection. The mean metal temperatures is about 1540°F. We are trying inconel as a material and find we get very thick tube sheets. If anyone used materials around these temperatures please give your comments.
Thanks in advance.

 

[EdStainless]

Inconel is a trade name for a family of Ni based alloys.

What kind of corrosion issues are you facing?
Traditional solid solution strengthened alloys like X or 625 simply do not have much strength above 1400F.
If you really need more strength then you need to use an age hardened aircraft alloy.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[asv80]

EdStainless:

The main reason for using the inconel is because of the temperature. The fluids used are high temperature exhaust gases from methane combustion with some chloride gases like HCl.

What is an age hardened aircraft alloy?

Thanks.

 

[metengr]

Can you provide more information as to the process involved with this heat exchanger design? Material selection is based on various service conditions besides operating temperature.

In general, I would recommend only using ASME B&PV Code, Section II material. Does this heat exchanger fall under ASME B&PV Code, Section VIII, Div 1 requirements? At your stated mean metal temperature, your material selection for a tubesheet will probably be limited to materials with a maximum design service temperature of 1650 deg F. I believe ASME SA-564 Ni-alloy forging specification would be your best option for tubesheet material.

Under SA-564, the maximum design temperature for UNS 06230 and UNS 08810 is 1650 deg F. Again, I want to stress that you need to review all potential high temperature corrosion mechanisms that would influence final selection of material for the tubesheet.

 

[metengr]

The ASME Specification is SB not SA, a typo on my part.

 

[asv80]

Metengr:
The process fluids are flue gases from burning exhaust gases with natural gas. It is a mixture of various gases, CO2, CO, N2, H2O, HCl, CH4, etc. The gases on the shell side operate between 1600-1400°F, the tube side gases are between 100-800°F. the objective of the heat exchanger is to heat the tube side gases up to 800°F. We calculated the mean metal temperatures to be ~1500°F on both shell and tube.
Our material selection is to be for both the corrosive environment because of chlorides and the high temperature. The unit will be under ASME code.
We are considering materials like SB166, SB 167, SB 564, as there are different forms required for us - plates, tubes and pipes. But the stress values are less at these temperatures and gives unusual thick tubesheets.
Thanks.

 

[unclesyd]

We have a similar situation on a nitric acid plant on what is called the turbine gas heater.
The tubesheet temperature is kept within reason by 12" thick cast monolithic insulation on the hot side (shell side) of the tubesheet. The tubes are shielded at the hot gas inlet by a corrugated skin over the tubes. The tube bundle shell is a boiler.

I'll try to get the exact MOC tomorrow.

They have a name for this type tube bundle and I have seen pictures of this type on the web.

 

[metengr]

asv80;
I would agree with unclesyd that some type of shell side refractory may be your best bet to reduce exposure to gas side temperatures so than your mean metal temperature of the tubesheet is kept as low as possible.

 

[asv80]

unclesyd:
It would be great if you can give more information on the insulated tube sheets. Thanks

 

[EdStainless]

I have seen high temp heat recovery units, it is a delicate balance between strength and corrosion resistance.
Insulating the TS is a good idea.
Do you know what sulfur levels you will be dealing with? I presume you will have some excess air, so the application will be oxidizing?
What diameter tubes are you looking at using?


= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[tomwalz]

Heat Treating magazine publishes a list of High Temperature alloy suppliers

We usually start with High Performance Alloys 800 472-5569 Try Scott of Jerry Pyle.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessor.com

 

[asv80]

EdStainless:
Sulfur levels are not known (may not be present, main corrosive gases being chlorinated compounds). The tube size is 1".

tomwalz:
We will contact and see they can suggest materials for our application.

Thanks

 

[stanweld]

You may wish to explore using Inconel Alloy 617 for this service. Contact Special Metals for particulars.

 

[unclesyd]

I have been promised the materials list tomorrow.

This particular bundle had a internal floating head. The cold gas comes in through the a pipe that straddles the tube bundle centerline and traverses the bundle to the internal head and is returned through the tubes and into the external head and then sent to the HP side of the unit. The exit conditions are 250 psig @ 1250?F. The external head is also jacketed and is part of the boiler. The tubesheet is about 24" in front of the entrance of hot gases from the burner chamber which allows the insulation to be effective in keep the hot gases of the tubesheet.

The tubesheet as stated before is insulated by standing the bundle vertically and a 12 wide band is tacked to the tubesheet to serve as a mold. Several injection nozzles are arranged around the periphery and one of the following materials is pumped in or poured in from the top.

Fiberfax QF-180 and LDS and GPS Moldable and Pumpable.

http://www.unifrax.com/web/UnifraxH...9398CB1B895D1C6C85256C71004C76F2?OpenDocument

Dale Johnson @ Plibrico (863) 519-5044 has handled all the insulation jobs.

 

[asv80]

unclesyd:
thanks for the description. would you have any sketches of the unit that will make better understanding and other sources of reference.

 

[unclesyd]

I got some pictures (3) and try to find a place to park them where you can see them.

The tubes are Inconel 800 and the tubesheet is 800HT 3.75" Thick

The original tubesheet was 321 SS and didn't last very long.

We can try this
Go to

http://www.winkflah.com

The albums name is tubesheet and the password is “insulation”

 

[unclesyd]

Hello out there!

Did this link and sharing thing work?

unclesyd

 

[metengr]

unclesyd;
It did not work for me. For some reason, this link had re-directed me to a free-print-share-photos.com web page with Kodak advertising and software. I could not find your file.

 

[unclesyd]

metengr,
All the trouble I had getting the pictures I've got to show them to somebody.

The website is:

http://www.winkflash.com

The album is name is "tubesheet" and the password is "insulation".


I typed it instead of copying it, bad.

Its a digital photo storage and print type place that my granddaughter uses for us to see and print her kids pictures, of course at our expense.

 

[asv80]

unclesyd:
How do I find the album. Is it the username and password? Thanks for the trouble to find the pictures. You can email me the pictures also.
Thanks.