As a pipe welder in a per diem job, you complete the responsibilities of a normal pipe welder, but you have a contract in which you are paid per day rather than working in a full-time or part-time position. You may be at a different job site every day, traveling where your skills are needed. Your duties may have you welding pipes to certain specifications, handling equipment and tools, and observing safety regulations while you weld. A pipe welder who works per diem can repair pipes, bend and alter the material, and help alongside other projects.