API RP 939-C-2019
Guidelines for Avoiding Sulfidation (Sulfidic) Corrosion Failures in Oil Refineries (SECOND EDITION)

Standard No.

API RP 939-C-2019

Release Date

2019

Published By

API - American Petroleum Institute

Latest

API RP 939-C-2019

Scope

This recommended practice (RP) is applicable to hydrocarbon process streams with sulfur-containing compounds@ without the presence of hydrogen (H2)@ which operate at temperatures above approximately 500 ??(260 ?? up to about 1000 ??(540 ??. There is considerable debate in the industry as to the correct threshold temperature for H2-free sulfidation@ and in a change in this edition@ the API 571 threshold of 500 ??(260 ?? is adopted herein. Experience has shown that little significant corrosion will occur at operating temperatures below 500 ??(260 ?? for H2-free sulfidation services without the influence of naphthenic acid corrosion. Mercaptan corrosion@ particularly in condensate service@ has been reported below this temperature but is not explicitly covered in the Second Edition of API 939-C. For H2-containing services@ the threshold temperature is set at 450 ??(230 ??. A lower threshold limit for sulfur content is not provided because significant corrosion has occurred in the reboiler/fractionator sections of some hydroprocessing units (which do not contain H2) at measured sulfur or hydrogen sulfide (H2S) levels as low as 1 ppm. Corrosion of nickel (Ni) base alloys in hot H2S environments is excluded from the scope of this document. In addition@ while sulfidation can be a problem in some sulfur recovery units@ sulfur plant combustion sections and external corrosion of heater tubes due to firing sulfur-containing fuels in heaters are specifically excluded from the scope of this document.

API RP 939-C-2019 history

• 2019 API RP 939-C-2019 Guidelines for Avoiding Sulfidation (Sulfidic) Corrosion Failures in Oil Refineries (SECOND EDITION)
• 2009 API RP 939-C-2009 Guidelines for Avoiding Sulfidation (Sulfidic) Corrosion Failures in Oil Refineries (FIRST EDITION)