3XX or inconel stainless tubing with high yield strength and small size 1

[aroundhere]

The equation I normally use to calculate pressure rating for tubing tends to become unreliable when getting below .50". Over 1" thru 5, and it is spot on. I need a .250 od stainless tube that will withstand 15,000 psi. If I use .125 for an id, my equation states I need a yield stength of 40ksi. Most 3XX series stainless doesnt have these types of yield stengths. Again, the equation I always use for larger diameters seems to not be valid on smaller sizes. The smaller diameter tubing tends withstand higher pressures than the formula gives. Maybe the tubing is just higher yield than spec'd due to cold working? Anyway, can anyone suggest any type of stainless tubing in this size with higher yields, or where to buy it? The challenge with this part is that it is almost 2 ft long. Cant drill a .12 hole 2 ft deep in 17-4, then turn between centers. I suppose you could attempt if you haveplenty of $$. thanks guys.

 

[CoryPad]

Get in touch with Plymouth Tube, they will be able to help you with this:

http://www.plymouth.com/

 

[EdStainless]

What is your max temp?
What about corrosion resistance?

There are a number of stainless grades with yield over 40ksi.
The autenitic 21-6-9 (S21904) has min yield of 60ksi and min UTS of 100ksi.
This alloy would be my first choice, and your walls could be a lot thinner.

If you want higher corrosion resistance AL-6XN (N08367) has 45ksi min yield, 100ksi min UTS.

Either of these could be made as welded and drawn tubing 0.250" OD x 0.050-0.060" wall.
The 21-6-9 is what aircraft hydraulic lines are made of.

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Plymouth Tube

 

[aroundhere]

The temps will be a max of 350F. I am looking for a tubing off the shelf if available. I can probably get by with .25 x .09 id. I can then use a stainless of around 35ksi yield. Im not at my desk at the moment so I havent ran the numbers. Corrosion resistance is a must. I will also need to turn the ends down a few thousands to hold a tolerance and a 32 finish since they will be sealed with static orings. This tool is not going to be h2s or sour well certified, but one always knows these are possible. We try to stay away from the cold worked stainless due to stress cracking over time, but sometimes the options are not there to pick and choose. I will contact Plymouth. I see that one company has inconel-600 tubing in stock. I need to take a look at the exact properties. It is more expensive, but does not really give much more in yield strength.

thanks guys

 

[EdStainless]

The 600 will be soft, not much gain over 304/316 in strength.

I wasn't even suggesting cold worked material.
You will find 21-6-9 in inventory places at 120 min yield/142 min UTS because this is the aerospace spec material.
At that strength 0.250" x 0.035" might be all of tube that you need.

How much do you need? We could always make something. Even a small amount maybe as a lot charge.
If I was doing this from scratch I would go with AL-6XN because of the great corrosion resistance.
0.25" x 0.080" would have a burst of >64ksi and yield >29ksi. Not bad safety margins.

Another option would be 625, it should be stronger than 300, but not by a lot.
You will have a tough time finding tubing in stock that is is heavier than 0.035" wall.


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Plymouth Tube

 

[tbuelna]

aroundhere-

Try contacting Autoclave Engineers. They specialize in the very high pressure tubing, fittings, valves, etc. that you require.

Regards,
Terry