80bar RO duplex 2205 s.s grooved pipe

[13ProjectManager]

Building an industrial RO to operate up to 80bar pressure with duplex 2205 s.s pipe. The RO pressure vessels have groove coupling port connectors. I understand no fabricators can roll groove sch40 duplex pipe with std hydraulic roll groove machines as the duplex 2205 is too hard. Cutting the groove in the pipe wall is the other option but will this reduce the pressure rating? the coupling bolts snugly around the groove so in theory should build up the wall thickness again but can anyone give me a steer on pressure ratings or pipe charts for 1.6mm cut grooves in 2" and 2.5" sch40 pipe thank you.

 

[EdStainless]

Go to the tech data from the coupling manufacturer.


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P.E. Metallurgy, consulting work welcomed

 

[13ProjectManager]

thank you EdStainless,

yes, have done this - the 83bar LQueen coupling datasheet mentions the groove depth to be 1.6mm for both 2" and 2.5" pipe. they also show min wall thickness of 3.9mm for the 2" pipe and min WT of 4.78mm for the 2.5" pipe. But its not clear to me if they are calling for a sch40S pipe which is 3.9mm WT for 2" and 5.1mm for 2.5" before or after the pipe is grooved.

I am trying to find this out from the manufacturer but would like to do the due diligence checks on duplex 2205 pipe wall strenghts from industry trusted stds/codes etc; but struggling to find a lot of detail specifically for duplex 2205 (there is plenty for 304/316 ss)

Duplex 2205 is much stronger so im needing help to confirm the equivalent min wall thickness of duplex 2205 to operate at 80bar please. The spools have been designed on 40S pipe and trying to keep it at that but the groove cut detail was TBC on final detailed design where we at now. Need to confirm if the increased strength of duplex 2205 will satisfy the slightly thinner wall after the 1.6mm groove has been cut

if the min wall thickness of 3.9 and 4.78mm called for by coupling manufacturer is after the 1.6mm groove has been cut then this would mean the required pipe would need to be 80S which we trying to avoid if possible.

 

[EdStainless]

Even if those dimensions are before grooving you would need min wall pipe (where the nominal in the spec is the minimum allowed).
This would be a special item.


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P.E. Metallurgy, consulting work welcomed

 

[13ProjectManager]

Yeah ok thanks. Trying to research roll grooving instead of cutting...do you know if the rolled grooved section could be weakened because the duplex is harder.....(if we can find a grooving machine to do the 40S pipe)

 

[LittleInch]

Got a drawing or sketch of this?

What's the purpose of the grooves?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[13ProjectManager]

The grooves hold the victualic coupling on the pipe. It's a smart design and very common for reverse osmosis prrssure vessels and pipework. Victaulic website has many downloads showing groove details. The groove is typically about 8mm wide and 1.6mm deep

 

[LittleInch]

It's a collar groove - Ok I thought they we axial grooves.

The coupling will nt provide any strength to the pipe - in fact the opposite as it will have a force on the edge of the groove and you need to consider stress concentrations at that point.

I would either weld on a different end connector or find another way to connect your flexible?

Got any pictures or drawings of this coupling? As you say there are many options so would help to know which one you are looking at.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[13ProjectManager]

thanks LittleInch please see the coupling datasheet [URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1682848400/tips/LQueen_Grooved_Couplings_Sizes_Pipe_Specs_Sonac_RO_lxpd0u.pdf[/url]

 

[EdStainless]

I have seen them rolled into lighter gage 2205, but not sch40.
I don't know that it can't be done, just never seen it myself.
I have seen heavy wall stubs used on the ends of lighter gage pipe, but that is a real pain.

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P.E. Metallurgy, consulting work welcomed

 

[13ProjectManager]

Thanks Ed, yeah I'm finding same! Any seawater RO is typically high pressure and duplex 2205 seems to be more common now too so sure there must be companies out there doing this tyope of application just hard to find them! Do you know if there are any pipe charts available showing max operating pressure for a given wall thickness for duplex 2205 please

 

[EdStainless]

You have to figure out pressure ratings based on your applicable codes.
Figuring Yield pressure and Burst pressure is easy enough.
Just make sure that you use the minimum wall and max OD from the pipe specs.
Many people use Barlows formula, but it is overly conservative.
I prefer the Lame method.
Scaling these down to service pressures is the next step.
For a first estimate I look at Burst/3.5 and 2/3xYield.

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P.E. Metallurgy, consulting work welcomed

 

[13ProjectManager]

Thank you

 

[MJCronin]

A rare disagreement with EdStainless ...

IMHO, the allowable pressure for these 2205 tube should be based on the formulae and allowable stresses of B31.3.

For an 80bar (1160psig) RO unit, this is clearly a high piping system that requires a detailed engineering effort....

https://www.pipingengineer.org/pipe-thickness-calculator/

MJCronin
Sr. Process Engineer

 

[EdStainless]

MJC, I have seen RO units designed to a number of different Codes.
It depends on where you are and which parts of the system you are talking about.
I was just trying to give him a place to start, a little reality check and not the final design.


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P.E. Metallurgy, consulting work welcomed

 

[13ProjectManager]

Thank you mjcronin, that is helpful. I was hoping for a supplier of duplex pipe chart showing max pressures for a given wall thickness and then we can subtract the 1.6mm groove depth to confirm. It seems like duplex 2205 is significantly stronger than 316 and most charts I can find are for 316

 

[EdStainless]

The charts are just approximations.
Like MJC said, you need a real design.

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P.E. Metallurgy, consulting work welcomed