Pipeline Material Selection - Carbon Steel vs. Corrosion Resistant Alloys 3

[danago]

Hi,

I am currently working on a project in which the default option is a pipeline with internal CRA lining. We believe that this option is excessively expensive, so are looking to recommend that a carbon steel pipeline be constructed instead. To answer this question I am looking for guidelines or studies that may help in deciding whether we could in fact use just carbon steel. Is anybody able to suggest sources of information regarding cost differences of different pipeline materials (upfront, and ongoing maintenance costs), where different materials are appropriate or any particular case examples of where carbon steel pipelines are used (also ideally with operating conditions).

Kind regards,
Daniel

 

[SJones]

Do you believe that whoever came up with CRA lining as the "default option" did not consider carbon steel in the first place and ruled it out? Maybe they didn't, since 'option' implies that other possibilities are still on the table. Surely, there must be some documentation justifying the selection, there's not many an operator who jumps straight to a CAPEX intensive option without a good analysis. Normally, it's the other way around and the accountants win the 'how lucky do you feel' battle leaving the poor operations people to fight to hold the dissolving carbon steel together.

It's all about what belief is held in the corrosion prediction model employed, the risk tolerance of the owner, the quality of the lifecycle costing and the faith in being able to run a tight corrosion control programme.

http://www.nickelinstitute.org/Tech...sofCarbonSteelandCRACladFlowlines_14035_.aspx

http://www.iso.org/iso/home/search.htm?qt=15663&sort=rel&type=simple&published=on

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[weldstan]

To answer your question, you need to provide the service conditions. Clad steel pipe, solid corrosion resistant alloy pipe or carbon steel pipe with corrosion allowance could be addressed based on corrosion type (general, pitting, SCC, etc.) that each would experience under the service conditions.

 

[zdas04]

Fluid conditions, volume flow rate expected, pipe sized under consideration would all be useful in helping you to make this call.

Sometimes CRA is necessary on a particular project. The next project grabs that file and sees that CRA might be useful. After a few generations of this, no one knows why your construction costs are so high and no one remembers why the CRA is required. Requirements for a particular project can generally be adjusted.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[BigInch]

CRA can be 6 to 8 times the cost of normal carbon steel.

calculate your corrosion rate, carbon steel life and then how many times you will have to make replacements. Calculate the replacement costs for the carbon steel during the entire system lifetime. For example, if you have a well that is only expected to have a 5 year lifetime and need only a short pipeline, carbon steel pipe with a corrosion allowance might be the way to go. If the well is expected to last 20 years, or your pipeline is long, you're going to need to replace it 4 times.

you must get smarter than the software you're using.

 

[danago]

Thanks for the responses, they are very useful.

To give a little more context: I have a background in chemical engineering, however I am currently working as a management consultant for an O&G operator. Consequently, I am not necessarily trying to perform rigorous technical engineering calculations, but rather trying to demonstrate to my client that carbon steel may be better economically. They did of course do some analysis before settling on CRA pipes, however they have a history of building things to a much higher standard than required, consequently overspending on CAPEX. Of course it may turn out that CRA pipe is required due to field conditions, however I want to open them up to the idea of increasing their risk tolerance a bit by using CS, so that they can re-run the technical engineering analysis with a different perspective in mind.

BigInch, that is exactly the type of calculation I'd like to perform at some stage. I will obviously require some more detailed information from the client to do that, however at this stage I am just going for an order of magnitude calculation. The other part of the work I am doing is to present to the client some examples of where other companies have made similar risk tradeoffs.

Thanks again for the responses so far. I will keep researching and post back here as I learn more information from the client.

 

[BigInch]

Not to discourage you, as that is exactly what should have been done already by somebody, but it will probably be a historic first to change from CRA back to CS. If they or you find that they really don't need CRA, they will be far too paranoid to change it. You might want to first consider how a cold beer would affect all of this.

you must get smarter than the software you're using.

 

[SJones]

The only way that you will get any definitive cost data is to go to the market with an enquiry. The above estimates appear to be a comparison for solid CRA pipe, not lined (you haven't mentioned the particular CRA). Whilst doing that, you might also like to try the cost of corrosion inhibitor and injection equipment and the cost of intelligent pig runs and maintenance pigging operations. Also you haven't mentioned the location of the pipeline, or the fluid that it transports (or the size, or the length for that matter). One man's building to a 'higher standard than required' is another man's ability to sleep easier at night. Most operators will not take the decision to go to CRA lightly - they have shareholders to report to. On the other hand, the industry is littered with the carcasses of those pipelines where everyone thought that the cheaper inhibition, and all that goes with it, is a doddle. Of course, there are some carcasses of CRA pipelines where poor quality control, or insufficient knowledge of material behaviour, has caught people out. Maybe the operator you are dealing with has some carbon steel carcasses they are still mourning.

How lucky do you feel?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[danago]

Thanks for the response. I do understand that the details I have given are insufficient to do any decent analysis - obviously if there was a change in direction then a much more thorough analysis would be required.

I know that there are different types of CRAs, but roughly how much more would it cost upfront (say, per kilometer of pipeline), relatively, to use CRA lining than just carbon steel? Would it be 2-3 times more expensive, or would it be closer to 10 times more expensive? Is it possible to get a feel for the order of magnitude comparison with minimal detail?

To get a very high-level order of magnitude understanding of how long a carbon steel pipeline would last compared to one with CRA lining, what would be the most important factors? Temperature, pressure and CO2 content? Again, I am just looking for a very rough estimate (i.e. would carbon steel need to be replaced every 5 years, or is it 20 years? etc.)

Coming from an engineering background myself, I know how frustrating and detail-insufficient my questions are - management consulting is a whole different game The information I am trying to gather is not for the purpose of performing any final economic analysis, but simply for my team's understanding of the order of magnitude differences between carbon steel and a corrosion resistant alternative.

I do appreciate your continued input!

 

[SJones]

The materials selection report for the pipeline should contain all of the information that you have requested (and more). Dig it out and take the time to read it. Here are some basic pointers to help your deliberations:

1. The manufacturing process for CRA lined pipe is: a) buy carbon steel pipe; b) buy CRA pipe of smaller diameter and probably 3 mm wall thickness but could be less (based on end user's risk perception!); c) insert CRA pipe inside carbon steel pipe; d) expand CRA pipe plastically and carbon steel elastically so that carbon steel springs back and grips CRA pipe; e) perform NDT. Remember: your carbon steel pipe now does not need a corrosion allowance, so you will have saved some carbon steel.

2. How much corrosion allowance would the carbon steel pipe have required? Good question - were you just going to leave it to rot, or were you going to deploy some other form of corrosion control? OK start with working out how corrosive is the transported fluid towards the unprotected carbon steel. Oh dear, there are at least 15 corrosion models I can choose from - which one will give me the "right" answer (the answer is - none of them, but some could be closer than others, but how would I know. Go with the one that has the fancy name - it must be good, maybe the one that costs 50,000 bucks is the best). Finally, you decide to go with the free one off the web with a nice looking GUI (so it must be good right?!!)

http://www.standard.no/en/sectors/e...norsok-standard-categories/m-material/m-5061/

but wait, the fluid has H2S and this model doesn't deal with H2S

http://www.ife.no/en/publications/2009/matkor/prediction

Now what?

3. Hey this stuff is really corrosive, but that chemical sales rep that was here last week had this magic formula that would get the corrosion down to nothing and was so simple that "Bubba and Bubba only had to squirt a bit in now and again." Fantastic - we'll go with that so we can use carbon steel, half a micron corrosion allowance, and our top performing corrosion inhibition team. Don't need no fancy alloys round here - we got it all sorted and we feel lucky.

A bit of fun, but hopefully you see why you are aking the impossible on an internet forum

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[SJones]

Asking even

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[LittleInch]

The real bit that can be "excessively expensive" is the clean up cost / environmental fine / loss of reputation / loss of production rights when your CS pipeline decides to finally give up the unequal struggle against corrosion and pressure, often in the most inaccessible place at a low spot (under roads, rivers etc). This can really break companies and if a bit more cost up front is what is needed, then long term value will go up.

Internally Clad is somewhere in the 2 to 4 times as expensive as CS for material and installation, but you gain a bit from no corrosion allowance and over the long term no corrosion inhibitor. Overall costs if you look at an entire system are much less, i.e. it costs the same amount of money to dig a trench for a C Stl line as it does for a clad line, etc.

However a recent case I was involved in was where some bright spark (maybe even a management consultant...) decided to "use up" the corrosion allowance he had calculated without inhibitor and save himself some OPEX costs. Sadly real pipe doesn't behave this way and the result before the CA was "used up" was a series of leaks.

Also bear in mind that replacement costs tend to come out of OPEX and if the well / filed is nearing the end of its life, this may not be economic, e.g. why spend $10MM replacing your flowlines when there is only $5MM of profit left in the place once you remove all the taxes and royalties etc. If you had just spent a little more in the first place this wouldn't be a concern and you could continue to produce as long as it was possible. Wells and fields often change with time and especially with injection can turn sour during field life. Do you want to change the system later on?

My points are that there anre many issues to consider when an operator is thinking about what types of pipe to use and thinking ahead to when flows and money are less, investing p front actually makes sense. They may occasionally over spec a system, but on balance, your excessive cost issue can seem to be a very short term solution.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[weldstan]

Another question to answer is, What is the planned length of service of the line?

 

[hacksaw]

what else could you expect from chemical engineers trying to do piping of all things...wow!

 

[zdas04]

danago,
Getting pretty tired of your evasions. You want specific answers to non-specific questions. Doesn't work that way. Every question you ask requires some knowledge of the application, any answer above is framed around people jumping through hoops to make up the details you refuse to provide. My advice is either to provide the details or ask site management to delete the thread.

If you job is 8-inch or smaller, you can save a ton of money and get outstanding results from Reinforced Thermoplastic Pipe (RTP). It is corrosion resistant and rated to very high pressures (everyone has ANSI 600 capable, several manufacturers have an ANSI 900 version). Bigger than 8-inch, poly liners work very well in carbon steel for a fraction of the price of stainless.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[SJones]

OK, to try and get back to more quantitative realms, here is some information that I stumbled across yesterday, quite by accident, whilst looking for something else:

Carbon steel seamless - USD 1700 per tonne
Carbon steel SAWL - USD 1150 per tonne
Carbon steel SAWH - USD 1050 per tonne
Carbon steel HFW - USD 1150 per tonne

CRA lined (unspecified CRA) - USD 11,300 per tonne or USD 700 per metre
CRA clad (unspecified CRA) - USD 12,700 per tonne

I can't vouch for these numbers, particularly the parity between HFW and SAWL, but it's better than nothing.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[Greg80]

Think about:
- Galvanized pipes which are not that expensive
- Plastic pipes suitable for your fluid
- Carbon steel with thick wall to be good for x years

 

[danago]

Thanks very much SJones, that information is very useful in giving me an idea of order-of-magnitude differences. Our client has shown interest in investigating this potential opportunity further, so they are pulling together the details required to progress this to the next step (i.e. technical details that we previously did not have).