AWS F4.1:2017

This standard informs the reader of the necessary safe practices to be followed in the cleaning and preparation of containers and piping for welding or cutting. It describes various methods for cleaning, including water, steam, hot chemical and mechanical, and techniques to be used for their proper preparation, such as inerting.
Scope : Introduction. Explosions, fires, and health hazards may result if welding, cutting, heat, friction, impact, or other hot work is applied on containers that are not free of hazardous substances, such as combustible, reactive, or toxic solids, liquids, vapors, dusts, and gases. No container shall be presumed to be clean or safe, but containers can be made safe for work, provided the safe practices prescribed herein or their equivalent are followed. 1.2 Scope. These safe practices shall apply to the preparation for welding or cutting of metal containers and piping. For the purposes of this document, references to precautions for welding or cutting are also intended to apply to all metal working operations (i.e., brazing, grinding, soldering, thawing pipes, using heat guns, using spark-producing power tools, straightening, thermal spraying) involving heat. Cleaning of used containers is necessary in all cases before welding or cutting. The term container, as used herein, includes piping. The safe practices presented here are not intended to replace either regulatory standards or more stringent practices of industries that have expert knowledge of handling hazardous substances. Even a water tank should be considered hazardous unless a qualified person has declared it safe to weld or cut. Consequently, safe practices presented here are not intended to apply to the following:1 (1) Containers and confined spaces that can be entered by workers (see ANSI Z117.1, Safety Requirements for Confined Spaces). (2) Containers that have contained radioactive substances (3) Compressed gas containers (4) Containers that have held explosive substances (such as nitrocellulose, pyroxylin solution, etc.) (5) Tanks, bunkers, or compartments on ships (6) Gasometers or gas holders for natural and manufactured gases (7) Outside, above-ground, petroleum storage tanks (8) Containers holding flammables that are to be repaired while in service 1.3 Safety. Safety and health issues and concerns are addressed in this standard. Safety and health information is available from the following sources: American Welding Society: (1) ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes (2) AWS Safety and Health Fact Sheets (3) Other safety and health information on the AWS website Material or Equipment Manufacturers (1) Safety Data Sheets (SDS) supplied by materials manufacturers (2) Operating Manuals supplied by equipment manufacturers Applicable Regulatory Agencies Work performed in accordance with this standard may involve the use of materials that have been deemed hazardous, and may involve operations or equipment that may cause injury or death. This standard does not purport to address all safety and health risks that may be encountered. The user of this standard should establish an appropriate safety program to address such risks as well as to meet applicable regulatory requirements. ANSI Z49.1 should be considered when developing the safety program