You may be able to observe boilermakers or workers who use similar skills as they work on construction projects or repair and maintenance jobs. For example, welders and equipment operators lifting heavy objects with elaborate rigging can sometimes be seen working at sites where large buildings are being erected. High school shop courses, such as blueprint reading and metalworking, can give you an idea of some of the activities of boilermakers. With the help of shop teachers or counselors, you may be able to arrange to talk with people working in the trade. Information may also be obtained by contacting the local union-management committee in charge of apprenticeships for boilermakers.

Some boilermakers and mechanics work at or near the site where the boiler, tank, or vat is installed. Such sites include petroleum refineries, schools, and other institutions with large heating plants; factories where boilers are used to generate power to run machines; factories that make and store products such as chemicals or beer in large tanks; and atomic energy plants. Others work in shops or factories where boilers and other large vessels are manufactured.

Boilermakers who do layout work usually work in a shop or factory. These workers follow drawings, blueprints, and patterns to mark pieces of metal plate and tubing indicating how the metal will be cut and shaped by other workers into the sections of vessels. Once the sections are fabricated, other workers at the shop, called fitters, temporarily put together the plates and the framework of the vessels. They check the drawings and other specifications and bolt or tack-weld pieces together to be sure that the parts fit properly.

In doing the final assembly at the site, boilermakers first refer to blueprints and mark off dimensions on the base that has been prepared for the finished vessel. They use measuring devices, straightedges, and transits. They attach rigging equipment, such as hoists, jacks, and rollers, to any prefabricated sections of the vessel that are so large they must be lifted into place with cranes. After crane operators move the sections to the correct positions, the boilermakers fine-tune the alignment of the parts. They use levels and check plumb lines and then secure the sections in place with wedges and turnbuckles. With cutting torches, files, and grinders, they remove irregularities and precisely adjust the fit and finally weld and rivet the sections together. They may also attach other tubing, valves, gauges, or other parts to the vessel and then test the container for leaks and defects.

Boilermakers also work in shipbuilding and in repairing the hulls, bulkheads, and decks of iron ships. In a typical repair, boilermakers first remove damaged metal plates by drilling out rivets and cutting off rivet heads with a chipping hammer. Then they take measurements of the damaged plates or make wooden patterns of them so that new plates can be made. They install the new plates, reaming and aligning rivet holes, then fastening on the plates by driving in rivets. Sometimes similar work is done on ships' boilers, condensers, evaporators, loaders, gratings, and stacks.

Boilermakers also maintain and install blast furnaces, water treatment plants, air pollution equipment, storage and process tanks, smoke stacks, heat-resistant materials in fireboxes or pressure vessels, and massive piping used to send water to and from hydroelectric power generation turbines in dams.

Field construction boilermakers work outdoors and move from one geographic location to another. They join construction teams in erecting and repairing pressure vessels, air pollution equipment, blast furnaces, water treatment plants, storage tanks, and stacks and liners. They can be involved in the erection of a 750,000-gallon water storage tank, the placement of a nuclear power plant reactor dome, or the construction of components on a hydroelectric power station.

Boilermaker mechanics maintain and repair boilers and other vessels. They routinely clean or direct others to clean boilers, and they inspect fittings, valves, tubes, controls, and other parts. When necessary, they check the vessels to identify specific weaknesses or sources of trouble. They update components, such as burners and boiler tubes, to make them as efficient as possible. They dismantle the units to replace worn or defective parts, using hand and power tools, gas torches, and welding equipment. Sometimes repairs require that they use metalworking machinery, such as power shears and presses to cut and shape parts to specification. They strengthen joints and supports, and they put patches on weak areas of metal plates. Like fabrication and installation work, all repairs must be done in compliance with state and local safety codes.