Any Difference between SS316L and dual certified SS316/SS316L? 2

[Pavan Kumar]

Hi All,

I want to understand the difference between SS316L and dual certified SS316/SS316L. I am procuring piping in SS316L. The vendor is quoting for dual certified SS316/SS316L.

Thanks and Regards,
Pavan Kumar.

 

[1503-44]

No, other than the double certification. That means it can be either one, the other, or both, all at the same time.

 

[fel3]

One thing to keep in mind is that material specifications often overlap one another. So, a material that falls into the overlap can be certified for both. For a simplistic example, let's say one material specification requires a particular constituent to be 2%-5% of the total mass and another material specifications requires that same constituent to be 3%-7% of the total mass. All other things being equal, if your material has 4% of that constituent, if qualifies for both; 2.5% or 6%, it doesn't.

I have run across this before with bronze alloys (of which there seem to be infinite number), steel for water well casings, cement, and probably a few others I have forgotten about.
[ul]
[li]With bronze, I see this most often in manufacturer's "recommended specifications" for valves and pumps for service in water distribution systems. One manufacturer will call out one bronze alloy for some part, while their competitors will call out other bronze alloys. These alloys are usually from the same alloy family and often have overlapping specifications. Manufacturers will call out a particular bronze alloy in hopes you will use their specification for the project and thus limit the selection to their product. However, the likely overlaps usually mean at least some of their competitors will also qualify. The master specifications I use for public works projects have a broader envelope and rarely allow such proprietary designs.[/li]
[li]With steel for well casings, I was contending with a state regulator who said the well casing material I was proposing for a state-funded project (ASTM A139, Grade B) did not meet the state's water well regulations, even though it is one of the most popular steels used for well casings in this state. He was misinterpreting the regulations, of course, which he finally figured out after I wrote what amounted to a technical/legal brief proving my point. In fact, the proposed well casing material far exceeded the state's minimum requirements.[/li]
[li]With concrete, it all started for me when a subcontractor on a large project mistakenly used Type II cement (the most commonly used cement type around here) for about one hundred sewer manhole bases when our specs called out Type V cement, which is the most sulfate-resistant of the five cement types used in the USA. The government inspector had missed it and it was the prime contractor's site engineer who brought it to my attention. Rather than rip out all the manhole bases, he was suggesting a PVC liner to rectify the problem. Fortuitously, a few weeks earlier, our company's chief structural engineer had mentioned to me in an offhanded comment that some Type II cements also qualify as Type V. I called him to discuss this situation and he said that the mill the contractor was getting his cements from produced a Type II that qualified as Type V, but they had never certified it as such. He suggested I compare the two submittals I had received for Type II and Type V with ASTM C150 and see if this particular Type II also met the Type V requirements. The analysis was not too difficult, and sure enough this Type II also qualified as Type V. I contacted the site engineer and told him the cement was going to be OK and no PVC liner would be required, but I wanted a letter from the mill confirming that their Type II also qualified as Type V.[/li]
[/ul]

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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[1503-44]

Did you get your letter?

 

[XL83NL]

Mechanical properties for dual certified are (often) higher than single L-grade.

Huub
- You never get what you expect, you only get what you inspect.

 

[EdStainless]

There are only two differences in the spec for these grades.
1. The "L" has a lower C limit
2. The straight grade has a higher minimum strength.

What they are telling you is that they meet the lower C limit and still meet the higher strength level.
This is easy because there is likely a little N in the alloy which makes it stronger.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Dhurjati Sen]

You want 316L. Ensure that the vendor's piping spec matches with your requirement. You need not bother with dual / multiple certification.

DHURJATI SEN

 

[KevinNZ]

The design stress for 316L is lower than 316. If the material is dual spec 316/316L you can use the 316 design stress.

316 is Group 2-2.2. 316L is Group 2-2.3

 

[Pavan Kumar]

Thank you all for the valuable comments. The piping vendor is able to offer only the dual certified SS316/SS316L material which per your comments is better than SS316L. Also they don't seem to stock SS316L pipe material which is also more expensive. I have placed order for the dual certified material.

Thanks and Regards,
Pavan Kumar

 

[XL83NL]

We never spec 316L, always 316/316L (i.e. dual certified). One main issue of plain 316L is you want find it (easily) for most common items, like pipe, flanges, etc. The other advantage of dual certified is increased strength, vs reduced sensitivity to e.g. IGC.

Huub
- You never get what you expect, you only get what you inspect.

 

[fel3]

1503-44...

Yes, and quickly too. I got the letter a couple days later attached to an email from the contractor.

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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[1503-44]

That was a very good supplier!

 

[MickMc]

As pointed out by XL83NL it is more common to spec 316/316L and 304/304L and get the increased strength of former and weldability of latter. Dual certified are readily available from suppliers more probably than single spec as can be seen from your vendor offer.