H2S, Material Requirements for Wet H2S Service, Phosphorous 1

[PressEquip]

Many oil and gas plant owners and operators have their own material specifications that relate to steel plate exposed to wet H2S service.

Often these client specification are partly based on the following:
- NACE MR0175/ISO 15156-1:2015 Petroleum, petrochemical, and natural gas industries - Materials for use in H2S-containing environments in oil and gas production
- NACE MR0103/ISO 17945-2015 Petroleum, petrochemical and natural gas industries - Metallic materials resistant to sulfide stress cracking in corrosive petroleum refining environments.

Often the client specification for steel plate will have a limit on Phosphorous, P <=0.012% or <= 0.015%

Does anyone know if there are other NACE or EFC standards that list a Phosphorous limit? Where did the information/research to limit Phosphorous come from?

Thanks in advance for your time and response!

A Fan of EngTips, share the knowledge

 

[Dhurjati Sen]

Dear PressEquip,

Phosphorous present in the steel is in the form of non-metallic inclusion that reduces the toughness of the steel. Secondary steel-making procedures are employed to reduce it to the limits you mentioned thereby making the steel "clean".

Also, the phosphorous inclusions act as active sites for hydrogen atoms to nucleate and cause blistering, HIC, etc.

Refer Section 5.1.2.3 of API RECOMMENDED PRACTICE 571 for further information.

Regards.

DHURJATI SEN

https://www.nace.org/people/dhurjatisen

 

[Metalero]

The restriction is due P element is an easy to segregation element, so the increase of phosphorus mass fraction will lead to the increase of banded structure, thus increasing the sensitivity of the steel HIC.
That restriction came from multiple studies that stablished guidelines for the selection of line pipe steels for sour gas/oil service.