HIC Vs Absolute Pressure 2

[Hosseink]

Friends,
With reference to table 1 of ANSI/NACE MR0175/ISO 15156-2, it is understood that no special requirement is needed when total absolute pressure is below is 0.45 MPa. Does it mean that even HIC/SWC are not the failure mechanisms when the pressure is not high enough?
Please note that I am aware of part 8 which addresses HIC/SWC but it mentions trace amounts of H2S and as indicated in A.2.2.2 trace amount means partial pressure of H2S.
So, my judgement is that when pressure is no more than 0.45 MPa there is no chance for HIC/SWC no matter how much partial pressure of H2S is.
Am I right?
Thanks,

 

[SJones]

You could invoke Table 1, as per interpretation 2005-31 at

http://isotc.iso.org/livelink/livel...c=ll&objId=3340364&objAction=browse&sort=name

but you may also like to note the pressure of the HIC test detailed in NACE TM0284.

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]

You might also like to note that the 0.45 MPa exclusion applies only to crude oil storage and handling facilities.

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.

 

[Hosseink]

Thanks a lot. The file was very helpful.
1. The first two interpretations imply that crude oil and water handling facilities are permitted exclusions for pressure below 0.45 MPa because there is small traces of H2S available. So in these cases no precautions is required for HIC, SSC or other failure mechanisms. For other services or for pressure above 0.45, precautions are to be seen.
2. I have just one matter in mind. In old versions of NACE, maximum 0.45 MPa for total pressure was exemption for SSC and SCC regardless of H2S partial pressure and service. Now I suppose we have this exclusion only for crude oil and water handling facilities and should be careful that there is just small traces of H2S in these service.
Please correct me if I were wrong.
Thanks.

 

[SJones]

1. Table 1 does not appear to be offering any specific reason as to why 0.45 MPa is deemed a threshold pressure which suggests that it is a carried over empirical approach from the original NACE MR0175.

2. Clause 8 points out that HIC can occur with even trace amounts of H2S. As the interpretations point out at every opportunity: "It is the responsibility of the equipment user to assess the suitability of the material and to ensure compliance with NACE MR0175 / ISO 15156."

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.

 

[Hosseink]

Thanks a lot. It really helped..