What is the best materials for 2500 F operation? 5

[EdDanzer]

We need to have a horizontal pipe in a 2500°F environment. What is the best material to use so that is does not droop from it’s own weight?

Thanks in advance, Ed Danzer

 

[IRstuff]

??? Aren't you pretty much limited to refractory metals and ceramics?

TTFN

 

[unclesyd]

If you can use ceramic here is on supplier who’s products I’ve used but never dealt with personally.

http://www.techceramics.com/products.html

Is your atmosphere in and around the tube going to oxidizing or reducing?

 

[stanweld]

Probably the least expensive refractory metal would be Niobium (Columbium) alloys (C-103, etc.)with an appropriate disilicide diffusion coating, assuming exposure to an oxidizing environment.

 

[davefitz]

probably the best bet is an air cooled or steam cooled co-axial pipe.

2500 F is the same temperature as the inlet to an advanced, modern gas turbine . All the best brains in that business have been working on finding such an alloy for at least 2 decades, and the best they could come up with are (a) single crystal ceramics and (b) air cooled or steam cooled blades.

 

[hacksaw]

what is the tube diameter and separation between supports. the fluid and its state on either side of the wall is also useful

 

[EdDanzer]

Thanks everyone for your information.
The pipes extend a short distance into a cement kiln. For this experiment the customer has chosen to use Inconel 601, it only has to run 3 days, but be ready to install March 12. I suggested air or water cooling, but the proto type testing time frame has ruled this out. After this first test we will be looking at ceramic, refractory metal as well as cooling if further work is to be done.

Thanks again,
Ed Danzer

 

[SMF1964]

EdDanzer:

Be aware that nickel alloys will self-destruct extremely rapidly in the presence of sulfur at the temperatures you are talking about. The nickel reacts with the sulfur to form an intermetallic phase that is liquid at this temperature and the alloy will go away as fast as this reaction can take place.

 

[hacksaw]

Inconel is a very poor choice for that application. The sulfidation process will make short work of it. Life time is hours not days at kiln temperatures.

Are oyu using the tube for gas sampling or in a closed end arrangement for temperature measurement?

 

[EdDanzer]

There is a 2” sch. 40 pipe that transmits a 190db shock wave into the heat zone and across is a 1” sch. 40 pipe with a microphone at the cool end. They measure time of flight of the sound wave and provide a temperature reading. This system is used in coal fired boilers with good success.

 

[hacksaw]

Don't doubt success in coal fired boilers, but they have a lot less sulfur to deal with. The self aspirating aspect of your penetrations will help, but there are other alloys better suited to that service. Good luck!

 

[EdDanzer]

Thanks for the input SMF1964 and hacksaw!
Could the Inconel be chrome plated, or have a spray coating applied to increase life? This is something that may fit into the construction time constraint. We should receive the material by Tuesday, and only have to thread one end of each pipe.

 

[rmw]

It has been a long time since I worked with a kiln, but in the early days of oxyten analyzers, I stuck a many of one into those into the back ends of kilns, with great success. What is the burner material made of? There are other components in the vicinity of where you wish to put this device on the burner end. What are they made of? Naturally, they are cooled by the combustion air, as well. Is there any way to make a pipe within a pipe arangement, where you could aspirate some cooling air. High temperature TV cameras are also commonly used in kiln burner areas, and they have a lense tube with a cooling tube passing air down the outside path of the concentric tubes to cool the whole mess, and constantly clense the lense.

To the best of my memory, most of those materials were Inconel, or similar.

Why not go with that type of concept?

rmw

 

[hacksaw]

I think, Ed is using penetrations on a diameter of the kiln with the nozzles/protection (or sight) tube projecting into the kiln just past the refractory.

Most kilns run on induced draft, so the pressure is slightly negative. You'll get some sifting through the protection tube, but as long as you have proper purges protecting your transducers it is not a big problem.

Inconel is unsuited to the service. Typically it will burn-off to within a inch or two of the refractory face, depending on the gas temperatures and the amount of sulfur in the system. That may be adequate for a trial run, but not for the long term. There are cheaper materials if a sacrifical tube was being considered.

We used infrared systems with closed end tubes, but the ultrasonic measurement is the new kid on the block these days.

 

[EdDanzer]

Hacksaw,
We are penetrating the side of the kiln.
The first test went ok, now they want to change lengths, and increase life. Has anyone tried Chrome plating the Inconel for corrosion resistance and wear?
There is reluctance to try ceramics because of the shock wave from the 190db signal generator.

 

[hacksaw]

Ed,

Forget Cr plating. There are a few alloys that can take you to 2200F, but their life time is limited and the strength is way down. With time most metals will burn off to within an inch of the hot face of the refractory lining anyway. So use a cheap solution.

Are there ceramics better suited to your application? Yes and they're really tough and the cost is not too bad, but their use presents a host of design problems that have to be worked through.

Kiln temperature has been the holy grail of control, but equally elusive to implement. There are other, more complex, and inferential control schemes being used.

Good luck,