Any recommendations on materials for storage and transport of propylene that is contaminated with up to 15ppm H2S? Planned use is in a DOT MC-331 vessel.
1) As propylene falls under the category of non-corrosive fluid, generally carbon steel(as basic grade) can be used as long as code(ex., ASME) which is based on strength calculation versus temperature allows it. Refer to below link as well.
2) Regarding the issue of H2S, in case there is liquid water present with H2S at any time including all the upset conditions, you need to apply the CS which is certified by NACE (ex., NACE MR 0103 for refinery and petrochemical) In other words, special requirements (ex., hardness limit) shall be applied for the CS so that it could be fitted for H2S containing environments.
3) If there is any stagnation expected or water accumulated such as tank or pressure vessel's boot section, you need to consider coating or cladding. However, No. 2 as above shall be applied even for the coated or cladded metal considering H2S can penetrated thru them and reach the base metal. Also, proper inspection interval for coating integrity shall be established as there is chemical corrosion expected in case there is coating failure and physical contact between CS and the accumulated water.
Thank you Lee for the info. I am in full agreement on your points 1 & 2. I posed the question because the customer is requesting the vessel be made of stainless, only they don't specify the specification nor grade. From their analysis there is no water nor Cl in the propylene.
The common grade of stainless steel will be SS 304L or SS 316L. However, before specifying the spec and grade, you had better check the reason why CS was excluded.
The ASTM spec for SS 304L and SS 316L is as below.
