SA-210-A1 vs. SA-179 in air-cooled heat exchanger

[Hurmanetar]

Background:
In the ACHE industry SA-214 welded carbon steel (11400 PSI allow. stress at 350 F) is by far the most common material for finned tubes in non-sour applications. If a slightly higher allowable stress is required or if seamless is desired, then seamless SA-179 carbon steel (13400 PSI allow. stress) is used before jumping to stainless or duplex.

I recently came across a natural gas cooler on a compression package that had 5/8" OD .109" wall SA-210-A1 tubes and when I ran the calculations on tube thickness, I realized the tubes were 4 gauge sizes thicker than they needed to be to handle the pressure. SA-210-A1 has an allowable stress of 17100. Price for SA-210-A1 tubes was comparable to SA-179 so long as the tubes were in stock or min mill run quantity was met.

Question:
Does anyone know why SA-210-A1 tubes are not more commonly used in the ACHE and natural gas industries? Why is this tube material spec more commonly used for boilers? And why did the one ACHE application I came across have so much excess thickness?

I have asked these questions to a tube supplier and to an ACHE applications engineer and both gave the same response: SA-179 is more readily available whereas SA-210-A1 would usually have a to be a special mill run. But that doesn't really answer the question... chicken / egg... if more people asked for SA-210-A1 it would be readily available.

Is SA-210-A1 more susceptible to corrosion/cracking than SA-179 or SA-214 in natural gas applications? Is SA-179 superior in some way?

Any insights into the limitations / pitfalls / pros / cons in using SA-210-A1 tubes in natural gas / ACHE industry is appreciated.

 

[SnTMan]

Hurmanetar, you might wanna take another look at your yields, I think you have 'em crossed with allowable tensiles.

As to your question, why one and not the other, I don't know. Can you read the two material specs, maybe some clues there why one might be more available than the other.

Also unless you have the specs the cooler was originally built to, no way to know why that tube wall or material was selected.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Hurmanetar]

SnTMan, thank you for the correction on terminology. Don't know why I had "yield" in my head. I have corrected to "allowable".

 

[Dhurjati Sen]

Hurmanetar

A look at the chemical composition and hence the mechanical properties would lead to the answer. ASTM A 179 has more Sulphur and Phosphorus than ASTM A 210. That makes SA 210 costlier and cleaner.
The higher Carbon in SA 210 gives it higher strength than SA 179.

The requirements for the boiler cannot be met with SA 179, so SA 210 grade is used. However, SA 179 works well for most heat exchangers and air coolers.