Interconnecting existent CS pipe networks with new piping expansion in SS (304L) 1

[EAbreu]

Good day to you all,

I´m a piping engineer in charge for the detail engineering of interconnecting to new MDF machine in an industrial wood transformation facility. Right now I have 2 situations to decide upon:

Expansion of a compressed air network (DN50 - DN100) made of CS piping, where I would like to use SS (304L) piping in the expansion areas. The compressed air network receives clean and dried air suited for pneumatic appliances (control valves, pneumatic cylinders, etc.)

Expansion of a fire water main (DN150/DN250) made of CS piping, where the client would like the expansion to be in SS (304l) - DN100/150 branch). Right now the older portions of the fire water main (35/40 years old) is having several

In these 2 situations, the connection between dissimilar material piping spools fill be flanged, using a flat fiber ring for air and water service, and the bolting material in SS (A2-70, for ex.). The extension of these piping network expansion is substantial.

Please advise the issues I could have implementing these 2 solutions, as I am specially concerned about corrosion.

Many thanks in advance for your help.

Kind regards

 

[MJCronin]

My recommendation:

Connect the dissimilar metal piping sections with a flange isolation kit ... mostly to resolve arguments from armchair supervisor engineers

The kits are cheap and, although the actual galvanic elecrical potential is small, they will prevent arrogant butthole MBA managers from displaying their cursory and incomplete knowledge of metalurgy...

(the small galvanic potential means that corrosion rate is very, very slow)

https://www.westatlantictech.com/pages2/flange-isolation-kits.php

MJCronin
Sr. Process Engineer

 

[EdStainless]

Why 304? You may well be disappointed with the results.
Connected to a CS system the 304 will end up with iron deposits covering the ID surface.
And in the long run this layer of rust will have a high risk of causing corrosion.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

Don't forget the firewater main experiences stagnation as well which is doubly a negative for stainless.

 

[EAbreu]

Dear MJCronin,

I was looking for a solution to insulate de metal from direct contact between both flange materials, and tehe gasket used would be naturally insulated.
Do you have any reference to a brand that works with EN/DIN flanges, as I am working in Europe with EN standards?

Many thanks & kind regards

 

[EAbreu]

Dear EdStainless,

If I would select 316L will this be much better than 304L?
The plant is in the interior, in a dry place not suffering from marine corrosion.
For the case of the compressed air network I am aware that some contamination may occurr.

Many thanks & kind regards.

 

[EAbreu]

Dear TugboatEng,

Regarding the fire water main, I will suggest to the client to use carbon steel for the new branches, and galvanized steel for the dry columns.
The danger of blowing an old fire water main is too high in this case.

Many thanks & kind regards.

 

[LittleInch]

EAbreu,

We're not a bunch of procurement engineers here.

Simply search insulating flange kits EN xxxxx flanges.

Also do some research into galvanic corrosion so that you know what people are talking about.

To get it you need some sort of liquid circuit. If the connections are inside and not subject to condensation or rain then they shouldn't corrode.

I have never ever heard of fire main built in Stl Stl. Cast iron, carbon steel, PE, GRE, but never Stl stl. Is your client made of money?

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

 

[EAbreu]

Dear LittleInch.

In fact I've heard here in Portugal about some facilities using a stainless steel fire water main. Honestly for me carbon steel should be ok in this case with a minimum water treatment.
The client suggested this because he has currently a big issue in the oldest part of the fire water main.

Many thanks & kind regards,

 

[LittleInch]

Well a 35/40 year old main has exceeded its design life so no wonder it's getting a few leaks.

Time to replace it, but not in Stl stl.

Can't he line the existing main?

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

 

[EAbreu]

Dear all,

Regarding the compressed air network, I will move the compressors, driers and buffer tank to a new location, so that the new spools in stainless steeç will connect to the carbon steel existing network, so in this case, maybe the corrosion and contamination would be minimized. What do you make from this solution?

Many thanks & kind regards.

 

[TugboatEng]

If you are adamant about using corrosion resistant piping, there are a few copper alloy options that would eliminate all of the problems associated with stainless steel.

For an example, I can purchase class 200 copper nickel pipe and join it using MIL-F-1183 socket braised fittings for about the same materials price as schedule 40 type 316 stainless steel. And, joining the copper nickel pipe with the socket braze fittings is a lot less expensive in terms of labor and is better suited for field installations. There are also press-on options that cost more per fitting but greatly reduce labor costs.

 

[EdStainless]

I just did the work on a fire main system all in 2205 because of issues they have had with stagnant water in 316.
I would rather use CuNi for stagnant water.
316 is common in compressed air systems, usually with something like Vitaulic PressFit.
I have done compressed air systems in brazed typeK Cu also.
The last few places that I have worked and zero steel compressed air piping.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

For the fire main, plastic may also be an option. CPVC has approval in some jurisdiction.

 

[Dhurjati Sen]

Do find out the dates of commissioning and occurrence of the first leak in the existing carbon steel fire water network.
Hopefully, that would deter you in any material upgradation.

For compressed air, again, apply the same logic as above and detest from changing the existing material spec.

DHURJATI SEN
Kolkata, India