316L Stainless Steel for Plant Air System 1

[azahari]

Hi All

Currently, the plant uses galvanised carbon steel for its plant air system. However, over the years, some part have thinned and had pin hole leaks at several places where we had to bandage it.

I am looking to replace the badly affected header section. However, I am trying to see if I can get away from using galvanised carbon steel. We do not have the facility to fabricate galvanised spool safely. Previously, spools were fabricated on site and then sent out to get them galvanised.
This is troublesome (plant is remote and located few hundred miles away from the city & main industrial areas).

I am thinking of replacing the galvanised steel with 316L Stainless steel. Anyone have experience with them? Any thoughts.

 

[unclesyd]

is your line corroding from the OD or ID?
Is there any specific reason to pick 316L?
What sizes and pressures are you talking about?

We have a plant wide stainless steel breathing air system and probably 30 of the plant air (120#) in SS due to external corrosion in certain process areas. We also have considerable instrument air (90#)in Aluminum.
All our process air is in CS due to sizes and pressures.
All our SS is 304L just because this is the plant standard for the grade.

 

[azahari]

The Plant air header is basically 40mm NB pipe & fittings. Corrosion is mostly from internal. Probably due to the poor performing dryer system over many years. Changing the dryer is out of the question at this stage.

Pressure is about 7 bars.

I have no real reason to select 316L other than it is easily available. But 304L might be a good option because I can get them easily too.

I am just wondering, is your CS piping for plant air galvanised? Do you suffer the same fate on the system as the plant I am working at?

How about the 304L? Any corrosion issue with the plant air?

Thx

 

[rneill]

Carbon steel is commonly used for "dry" air systems but it sounds like your system is not really that dry. In a wet air system, galvanized carbon steel would be the normal thing but austenitic stainless steel should be fine too (304, 304L, 316, or 316L).

 

[unclesyd]

No, the big piping is not HDG it is CS painted with an epoxy + urethane coating system.
Some of our old plant air and breathing air system inside our manufacturing building is HDG. We just HDG pipe and fittings and assembled the system. HDG pipe has Zinc on both sides so you will be covered on corrosion to some extent.
In your new system make sure everything is sloped and put you in coalescing filter if you don't replace your dryer.


One of them brain things just came and went.
I just checked with someone who has just installed some Transair Al compressed air piping in his machine shop. They also have it SS.
This system being sold by Parker, who are all over the world so you may have access to a source. The ROI is very good.

http://www.transair-usa.com/roi.php

 

[EdStainless]

I am seeing Victaulic PressFit SS put in for air service in many plants. 304 is probably good enough.
Better drying and draining are key to long term performance.
Our plant saves a fortune in reduced maintenance by switching to SS. It has helped us keep our air systems much cleaner.

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Plymouth Tube

 

[11echo]

So I have to ask, you'd be replacing every bit of the galvanized carbon steel? IF not and you tried to tie the S.Stl to the C.Stl. you be fighting galvanic corrosion at those locations.

 

[strider6]

usually, i mean offshore, for dry air carbon steel and for wet air stainless steel to avoid also the possibility to have corrosion product in the air system, if you are close to the sea i'll use a 316 and not a 304..

S


Corrosion & Rust Prevention Control

 

[stanweld]

Most of our projects in the past 5 - 8 years specify 304L for above ground air systems. There have been many leakage problems reported with press fit systems.

 

[EdStainless]

Stan - are your leaks due to corrosion or improper installation? We have had one joint leak out of about 500.

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Plymouth Tube

 

[stanweld]

Improper installation and improperly manufactured fittings.