Carbon Steel for Instrument Air Pipe 1

[norzul]

Hi,

Is it common to have API 5L B (without galvanised) for the instrument piping material?

Based on my previous experience it should be pre-galvanised, however on my current project it is specified as API 5L B without galvanised?

Any advise

Thanks

norzul

 

[norzul]

What are the advantages & disadvantages of having galvanised?

 

[SJones]

If you have wet instrument air then the carbon steel will corrode and the corrosion products (rust) may end up damaging or blocking instruments. Galvanising can serve to prevent this process (for a certain period of time).

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[norzul]

I think our instrument/plant air is dry, since we have air dryer units downstream of the air compressors....its dewpoint is -40^oC

So its OK then...

Thanks

OK

 

[EdStainless]

Many plants use only stainless for all air lines. Dry air is never really dry, and dryers fail from time to time.
In the long term a lot of money can be saved by having a clean air system.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[NickE]

EdStainless- you are absolutely right. We are now fighting this exact situation. Sometimes in the summer the dryer isn't even turned on... (ARRGGG!) If I had the choice I would use stainless and heavy duty/high flow filtering right after the dryers. Then at each critical outlet I would dry and clean as described in this thread:

thread1036-137393

And notice rmw's statement at the bottom.

 

[norzul]

TQ for the advise/lessons learned....welll...it's a bit late for our project, already specified CS & in the final stage of procurement, construction in 2-3 months time.

Not much choice but to proceed with CS. In any project, besides quality, there are 2 other factors that need to be considered i.e. schedule & cost

Hope for the best....

 

[arto]

It's usually cheaper to do it right the first time...... ;-)

 

[Ashereng]

If the instrument air is wet, you may have other problems besides corrosion. Your instruments may also freeze.

Most places that I know of use carbon steel without galvanising. I don't know of any sites with all stainless steel instrument air piping system. Stainless steel pipes would cost a lot more. The welding would also be different I would think - although I am not familiar with stainless steel welding.

EdStainless, a quick question to you. What is the instrument air receiver/volume tank made of? If it is carbon steel, does that mean it has a liner?

 

[norzul]

After further investigation, I believe this is a matter of choice. We have been operating 2 refineries (100,000 BPSD each, sweet & sour) which had been in operation for more than 10 years already. Use CS for both, plant & instrument air. However, we do have filters & dryers downstream of air compressors. So far haven't heard any major problems on the filters, dryers & the entire air system except on one of the air compressor.

Our company standard also doesn't really emphasize on using galvanize or SS. My previous project, as I previously mentioned, specifying galvanized CS...I can't recall why...

 

[Ashereng]

norzul,

A quick question to you on the material of your instrument air receiver/volume tank. Is it also CS?

 

[norzul]

Most likely it is CS, but i'll double check tomorrow, already 12:43am time...going to sleep...

 

[norzul]

Can't find the eqpt datasheet, but from the PFD & P&ID, looks like CS

 

[EdStainless]

lined CS for tanks and such.
I hate to through a plug in here, esp since it isn't my product. I have seen a number of plants run air line using Victaulic Press-Fit

http://www.victaulic.com/docs/lit/pb-500.pdf

The last SS tube mill that I worked in ran all SS air (and all gass) lines with long runs of tubing and orbital welded joints.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[norzul]

TQ EdStainless....new knowledge for me

 

[Ashereng]

Thanks for checking norzul.

Thanks edstainless. Is it possible for you to indicate in what part of the world, and what specific industry, you have seen SS instr. air? If you can't, no worries.

It is just such a foreing concept (SS instr. air lines) to me, and my industry here.

I will now definitely keep my eyes open for a SS instr. air system.

 

[EdStainless]

The first place that I saw it was in air lines for paint spray booths, which must be kept very clean.
Since then I have seen it in drug plants, breweries, and even is some manufacturing plants that have a lot of air driven equipment. They say that it significantly reduces wear and failure of air cylinders and controls.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[Ashereng]

EdStainless,

Thanks for the context info. I learned something new today. You get a star.

These industries you mention are completely foreign (I typed it correctly this time) to me.

I can see industries such as breweries, drugs, painting, etc. being held to a different standard wrt cleanliness - and therefore SS instr. air systems.

In oil and gas, I guess you can say we are not so fussy. In fact, we don't even always use air all the time. We often also use propane (from bullets) and process gas (the gas we are shipping is also used for instr activation) when air is not available. Where gas of any sort is unavailable, we use self contained hydraulic systems.

Thanks.

 

[rmw]

The term 'clean dry air' is an oxymoron. (But I repeat myself.)

thread378-123404
thread378-122965

rmw

 

[norzul]

welcome rmw....I learn new word now..."oxymoron"