Sulfuric Acid Pipeline 1

[skoutso]

Hi you all,

I'm currently involved in the design of a 5 km 6" pipeline that transports 98-99% wt. sulfuric acid.
I'm interesting to know what codes/standards are applicable to the design of such a system and what are the best practices to follow for specific issues related to operation, inspection, maintenance etc.

 

[BigInch]

ANSI B31.3 or B31.4 would usually do. In which country will this pipeline be installed?

First, follow the general operating practices for pipelines.
Which specific issues?



**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[skoutso]

Hi BigInch,

I'm a petroleum guy too, and I've built quite a few oil and gas pipelines with ANSI and other oil standars/practices.
The "specific issues" I'm trying to get a reply are:
1. Should the PL be burried or installed aboveground (for better inspection etc.)?
2. What kind of leak detection system applies better for each installation (burried of aboveground)?
3. What kind of corrosion monitoring applies better to a sulfuric acid PL?
4. Should the PL designed for pigging or not (I assume water is used to push the pig during PL inspection)

These issues are not covered by ANSI. Hope you got an idea of what I'm looking for.

Thanks anyway.

 

[donf]

Skoutso,

My experience with your application is limited, however a huge red flag popped up when I read your issue number 4.

Very, very carefully review using water for testing, pigging, etc. in an acid line. If you must, make sure the piping (especially low points) can be drained and thoroughly dried, and VERIFIED that it's dry before introducing acid.

Regards,

donf

 

[skoutso]

Many thanks donf.

 

[BigInch]

I doubt you'd do an inline inspection in acid. I would imagine that the line would have to be flushed of all acid first, as even with many pigs, you'd still get one hell of a reaction with wall film layers as the pigs pass. I'd drain it to a holding tank, dry flush the pipe with water containing a base sufficient to neutralize any remaining wall film and perhaps push the pig with N2. But, would you really need to run a pig on a 6 km pipeline anyway. Other than that, I wouldn't see much difference in any of the other items. If its all in secure territory, burial wouldn't necessarily give much advantage if temperatures are not extreme, there's no reason not to use differential volume leak detection, unless you're not metering in and out. If you have SCADA and a hydraulic model you could compare readings with the model for leak detection. But if you don't, you can't. If you can, there's no reason not to do all three. Likewise there's no reason not to use coupon corrosion monitoring, sniffing, or sensors along the right of way. Other than running pigs in acid, I don't see where the rest of those decisions would really be much different between a regular pipeline or an acid pipeline. Economics probably has the major influence, but I don't run acid lines either. Maybe someone else has a different opinion.

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[skoutso]

Thanks again BigInch.

I'm not running acid pipelines either. That's why I'm looking for best practices and BATs. I would not just rely on intuition and experience alone when it comes to safety.

 

[BigInch]

I don't think safety issues are so different. After all, the biggest danger by far is from 3rd party damage causing leaks and explosions, and if you only have 6 km, perhaps your risk exposure to 3rd party damage is very much reduced in relation to a typical pipeline. The balance of risk factors is relatively smaller.

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[ash9144]

The only time water should be introduced to an acid pipeline of that length is the day it is taken out of service for demolition. I've never known of an acid line being pigged either.

Above ground is the way to go. Small leaks can be detected easily and quickly. Below ground they could leak for some time and create weak acid around the pipeline resulting in major failure.

Normal thickness readings and periodic Xray should provide good data on life time and predictive maintenance.

 

[BigInch]

If there is no public access, yes above ground. With easy public access, I'd think about underground, or a big fence.

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[unclesyd]

For a H2SO4 line of that size and length I would definately get some assistance from someone well versed in the art of transporting the material.

As stated above water is a NO/NO as it will cause horrendous corrosion while it dilute the acid and will dissolve the Iron sulphate film that provides the major corrosion protection against the H2SO4. Inhibited water is not the answer.

The is a a major problem with O2 corrosion or grooving in the top quadrant of the pipe. As mentioned above this is usually monitored by RT. Normally in smaller lines provisions are made for rolling the line 180° to mediate the effect of the groove.

Velocity has to be controlled.

Heat input has to be controlled as well as freeze protection.

Slope of the line has to taken into account for draining the line.

There is a possibility of having to have a N2 purge.

If there are people you might have to consider double containment.

Tankage at both ends has to have all the right stuff.

 

[itsmoked]

I want to see the look on the face of the errant petrol thief on this one..

Keith Cress
kcress -

http://www.flaminsystems.com

 

[stanier]

Keep water well away from the H2SO4 pipeline.

If buried leak detection can be monitored by use of tracer wire. But by the time it leaks you will know because your custody transfer flow meters will be showing a discrepancy.

Those acid lines I have been exposed to were equipped with pigging facilities. Pigs were N2 driven.

Station facilities need specialised equipment to be able to maintain them. This includes peristaltic pumps to be able to empty at low points.

Orica (nee ICI) published design guides for handling the fluid in Australia. Check with your material supplier and you will be surprised the amount of information they can provide. Also try and inspect some existing facilities.

Vopak operate acid shipunloading lines.

 

[MJCronin]

Skout....

I am having a lot of trouble understanding how this pipeline makes any sense. When sulfuric acid moves, it can erode/corrode carbon steels rapidly

What material do you intend to use for this pipeline ?

If the answer is carbon steel, how long do you expect it to last ? (and what type of corrosion allowance are you using ?)

You see, I have seen a lot of small bore stainless piping systems in process plants... especially in applications where the acid velocity is 5-12 fps.

Where I have seen carbon steel used for sulfuric acid service the velocity is much lower (2-5 fps) and a 0.125 inch corrosion allowance is used.

So as I see it, your choices are large diameter, thick walled CS or expensive SS....

Wouldn't it be cheaper to use tankers to transfer the acid ?

-MJC

 

[sebastiancito]

you can use ONLY ZICOR for pipes.
Zicor is expensive but is too resistant to the corrosion.
maybe you can use PVRF too.
If money isn't a problem, i prefer use a zicor pipe with a second container in 316SS with a preassure swicht for leak deteccion like the mass flowmeters. This is the requeriments sugested by the standars.
I'm using zicor pipes for acid sulfuric in 99,98 and 93% in a zinc plant.
sorry, my english is bad at this moment.

 

[MJCronin]

Sebastion..

Do you mean the material "ZeCor-Z"..????

I believe that ZICOR is a popular medication in the USA for nasal problems or heart attacks or something.

?????

-MJC

 

[sebastiancito]

Mj see below.
Zicor in spanish. zecor in english.
Is a SS with a low charge of silice.
Best regards.

 

[moltenmetal]

You don't need high silicon stainless steels for ambient temperature concentrated sulphuric acid. Those steels are needed for higher temperatures such as in an acid plant, particularly for the 93% acid.

At ambient temperatures you can either use carbon steel with a large corrosion allowance and VERY low velocities, or ordinary austenitic stainless steels.

For a buried line, unless the size is huge I would imagine stainless would be the choice.

 

[MJCronin]

molten.....

I agree...

But that sounds a lot like what I suggested ?

Then, you have to ask yourself, will a stainless steel pipeline of this length make economic sense....

-MJC

 

[SeanB]

We have a sulfuric acid plant at the refinery where I work. We are continuously plagued by leaks in the lines. Many of the lines that are leaking are carbon steel - which is acceptable for 98% sulfuric acid as long as you limit the velocity to less than 3 ft/s. The problem is when you introduce fittings such 90 ° elbows where the localized higher velocities and turbulence strip the protecttive layer off the pipe. Any pipe that has been leaking we have been replacing with Alloy 20.