ASTM Piping Materials for Carbon Dioxide service 1

[vic56]

We are designing a process unit that has a gas flow with the following composition : 14mol%CO2,84%CH4,the rest is Ethane, Propane, Butane and Pentane. The various lines operate at 75 barg with temperatures ranging from 50°C to 230°C with a water content of 0.2 to 1.7 mol% and a 1% vapour fraction. Could anyone comment on our intention to use 304 material for the pipelines ?
We have another line operating at 75 barg and 300°C with the same composition but with no water present, we were considering using carbon steel for this line. Any thoughts ?

 

[SJones]

Onshore (coastal, industrial, rural) or offshore? The biggest corrosion threat to the 304 and the carbon steel will be external, particularly if you have to insulate. Apart from that, strength at 230 deg C may render 304 uneconomic against, say, S31803 duplex SS.

Steve Jones
Materials & Corrosion Engineer

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

 

[vic56]

It is for an onshore, industrial location, Steve. Do you agree that carbon steel is unsuitable for this CO2 + H2O composition ?

 

[SJones]

Vic,

It depends what you mean by unsuitable. Carbon steel could be very suitable if you only need the line for 6 months. The general approach is to assess suitability based on life cycle costing. To that end, you need some means of predicting how long your carbon steel line will last and whether, or how many times, it will have to be replaced during the lifetime of the facilities. Then, as you know it will degrade in service, there will be the operating expenditure of having to perform inspections to ascertain the level of technical integrity and so on and so on. The first port of call is to determine the expected corrosion rate of carbon steel. It is a relatively common question and various threads can be reviewed:

thread338-121748

Thread601-115896

Thread338-111687


Steve Jones
Materials & Corrosion Engineer

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

 

[vic56]

Steve, much appreciate you taking the time to provide this excellent response.