MIC remaining life predictions in piping systems 1

[rolfsmi]

Dear All,

I would appreciate your help and input pertaining to remaining life assessments of MIC in piping systems. From my understanding MIC is both unpredictable and time independent which raises concerns when estimating remaining life from inspection data.

Q1: What is current practice for evaluation of the above?

Multiple damage mechanisms

Q2: When MIC is a potential damage mechanism in conjunction with a time dependent mechanism such as CO2 corrosion, how does one identify the driving damage mechanism and then estimate the remaining life?

Thank you,

RS

 

[SJones]

MIC can be predicted, rather the likelihood of MIC, by consideration of the fluid composition, particularly the aqueous portion, flow characteristics, and, of course, bacterial measurements. Predictive models are discussed in NACE Corrosion 2002, Paper 02235 and NACE Corrosion 2007, Paper 07515, for example. Some models, such as MICORP from Ohio University, attempt to give MIC corrosion rates which would suggest that the damage mechanism could be classed as 'time dependent,' but this is a tall order given the complexity of the physical and chemical processes occurring. One approach for remnant life prediction is to establish the MIC pitting rate from thickness measurement data timed at appropriate intervals once the onset of MIC has been identified from the generic inspection strategy for the system.

What drives the remnant life assessment is the inspection results - regardless of whether it is CO2 corrosion , MIC, oxygen corrosion, or whatever other degradation mechanism - and any other monitoring data that can generate pertinent information. The challenge is to derive useful degradation rates from the inspection data as is discussed in NACE Corrosion 2006, Paper 06380 and in Inspectioneering Journal, September-October 2013, A Discussion on the Piping Thickness Management Process - Part 5: Circuit Thickness Data Analysis

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.