Boiler cleaning and repair; Building construction and repair; Building maintenance and repair; Construction and repair of buildings; House building and repair; Installation and repair of air conditioning apparatus; Installation, repair and maintenance of condensing apparatus, steam condensers, radiators for motors and engines, air reheaters, boiler tubes; Installation, repair and maintenance of heating equipment; Maintenance and repair of heating installations; Maintenance, repair, replacement and tuning of components, parts or systems in steam and gas turbine generators; Oil well casing, tubing, and drill pipe installation; Pipeline installation and repair; Pump repair or maintenance; Repair and maintenance of feed or booster pumps; Repair or maintenance of air-conditioning apparatus ; Repair or maintenance of boilers; Repair or maintenance of chemical plants; Repair or maintenance of chemical processing machines and apparatus; Repair or maintenance of mining machines and apparatus; Repair or maintenance of nuclear power plants; Repair or maintenance of power distribution or control machines and apparatus; Repair or maintenance of power generators; repair or maintenance of storage tanks; Repair or maintenance of vessels; Repair or maintenance of water pollution control equipment; Repair or maintenance of water purifying apparatus; Underwater repair