Suitability of carbon steel as material for lean MEG handling pump

[balven]

The pump in question receives lean MEG from the MEG Regeneration Package. Relevant details are as follows -

Design temperature : (26 / -7 deg. C)
Fluid composition -:
MEG : 85 wt %
Produced water : 15%
Chlorides : 20000 ppm (approx.)
H2S : Negligible
CO2 : Negligible (removed in the MEG Regen. Package)
O2 : Negligible (oxygen scavenging is done in the
MEG Regen. Package)

Design life to be considered : 30 years

As there is no CO2, general CO2 corrosion will not be significant. Also, in the absence of oxygen, pitting due to chlorides does not seem a threat.

Considering all these factors, carbon steel looks to me a suitable material of construction for the pump. Can anyone confirm my understanding? If you wish to share any information, opinion or experience in this, it will be much appreciated.

Thanks in advance
Balven

 

[mrfailure]

MEG exposure does not look to be an issue. However, I might be concerned about an exposure to 2% chlorides in fluid from a corrosion standpoint.

Aaron Tanzer

http://www.lehightesting.com

 

[SJones]

The attached may be of some relevance to your research.

Steve Jones
Materials & Corrosion Engineer

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

 

[gr2vessels]

Hi Balven,
the MEG at 85% concentration is not really corrosive, but the chloride concentration is huge, you can expect very high corrosion rates on carbon steel and austenitic stainless steel material. I believe for the given temperature, the duplex stainless steel will be ok, but I would rather prefer SAF 2507, super duplex material to be on the safe side.. Just remember that 20,000 ppm of chlorides is similar to the sea water concentration of chlorides.
Also, I have some doubts over the chlorides concentration you stated. normally, the 20,000 ppm concentration of chlorides is consistent with the 'pure' produced water, but in only 15% of produced water, I suspect the chloride concentration in the Lean MEG is much lower. Please review your data and come back if you need further help.
Cheers,
gr2vessels

 

[balven]

Thanks all for your responses.

Yes, the chlorides concentration is very high (this data comes from the MEG Regeneration Package supplier), but will chloride be a significant threat to carbon steel in the absence of oxygen? There is a provision for oxygen scavenger injection in the Regen. Package. Also, there is hardly any CO2.

balven

 

[mrfailure]

Chlorides will still be a big threat. Corrosion will still occur even without oxygen, and in any event you have some oxygen present in the 15% water. You also have to think what may be in your system when you shut down - often corrosion is most active from water vapor containing remnant high-chloride solution whenever the system is turned off.

Aaron Tanzer

http://www.lehightesting.com

 

[SJones]

MEG at 85% is not really corrosive...huge chloride concentration...expect very high corrosion rates

Have a look at NACE 2007, Paper 07116 where Conoco observed 0.06-0.09 mm/year for X65 at 108 deg C with around 28,000 ppm chloride and 89 ppb oxygen. They did get some pitting though!

Steve Jones
Materials & Corrosion Engineer

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