Hot Tapping in Oil Refineries: Corrosion and Material Concerns

The purpose of hot tapping is to add connections on piping or equipment without depressurization or disruption of normal process operations. Hence, hot taps involve welding on items while they are in service. Although not desirable, owners are faced with situations in which hot tapping is the best option. With due regards to safety, owners rely on published industry standards, such as API RP 2201 Safe Hot Tapping Practices in the Petroleum and Petrochemical Industries and ASME PCC-2, Repair of Pressure Equipment and Piping, Article 2.10, for guidance on hot tapping. These standards provide excellent guidelines on the safety reviews, design details, welding procedures, testing, etc., and cover some special restrictions for hot taps due to the specific service and/or base materials. However, there are numerous additional hot tapping cases which arise in the refining industry, and the purpose of this paper is to highlight considerations due to potential corrosion or environmental cracking risks and/or due to refinery materials with special welding requirements. Examples are hot taps in services containing sour water and on low alloy Cr-Mo steels. The considerations and suggested special requirements are explained.