Steam Boiler

boiler endplates and tubes

A device for generating steam for power, processing, or heating purposes or for producing hot water for heating purposes or hot water supply. I’ve included the firebox within the overall steam boiler as it’s difficult to separate it descriptively.

boiler water level versus angle

Angle – the angle of the boiler to the horizontal, when used in transport it’s important to maintain the angle such that water is always over the crown of the firebox.

Blow Down Cock – A valve mounted low-down on the boiler, often around the foundation ring, which is used to periodically vent water from the boiler.

Chordal Thermocouple – A thermocouple installed in furnace tubes, designed to measure the effectiveness of water treatment within the boiler.

Cladding – In early practice this was usually wooden strips held by brass bands. Later they used asbestos matting as the insulation covered with rolled steel sheets.

Crinolines – The framework of hoops used to support cladding over a boiler. Named from the similar hoops under a crinoline skirt.

Dome – A raised location on the top of the main boiler drum, providing a high point from which to collect dry steam, reducing the risk of priming.

Downcomer – Large external pipes in many water-tube boilers, carrying unheated cold water from the steam drum down to the water drum as part of the circulation path.

Exhaust Injector – A feedwater injector that economizes on steam consumption by using waste steam, such as engine exhaust.

Field-Tube – A form of single-ended thimble water tube with an internal tube to encourage circulation.

Firebar – Replaceable cast-iron bars that form the base of the furnace and support the fire.

Fire Tube Boiler – A boiler where the primary heating surface is tubes with hot gas flowing inside and water outside.

Flue – A large fire tube, either used as the main heating surface in a flued boiler, or used as enlarged firetubes in a locomotive-style boiler where these contain the superheater elements.

Foundation Ring – The base of the firebox, where the inner and outer shells are joined.

Fusible Plug – A threaded metal cylinder with a hole that is sealed with a metal of low melting point that flows away if a pre-determined, high temperature is reached. Invented by Richard Trevithick. The hole is tapered so that the plug cannot be just blown out under high pressure. It is designed to melt when boiler is overheated, releasing a jet of steam into the firebox and alerting the crew. Reference: BS 1123:2006 “Fusible plugs for steam boilers and compressed air applications”

Galloway Tubes – Tapered thermic syphon water-tubes inserted in the furnace of a Lancashire boiler.

Gauge Glass – Part of the water level gauge, which normally consists of a vertical glass tube connected top and bottom to the boiler backplate.

Injector – A feedwater pump without moving parts that uses steam pressure and the Bernoulli effect to force feedwater into the boiler, even against its pressure.

Klinger Gauge Glass – A form of gauge glass where the water level is visible through a flat glass window in a strong metal frame, rather than a cylindrical tube. These were popular with some operators, and increasingly so for high pressure boilers.

Manhole – An oval access door into the boiler shell, used for maintenance and cleaning.

Mud Drum – A water drum, particularly one mounted low on the boiler whose function is primarily to trap mud from circulation.

Mudhole – A small manhole, too small for access but used for washing out the boiler, either as an inlet for a water hose or as a drain to remove mud.

Pressure Relief Valve – A type of valve used to control or limit the pressure in a system or vessel.

Safety Valve – An automatic valve used to release excess pressure within the boiler.

Scum Valve – A blow-down valve mounted at the water-level of a boiler, used to blow-down lighter oily or foamy deposits within a boiler that float on the water-level.

smokebox and lower chimney assembled

Smokebox – An enclosed space at the extremity of a fire-tube boiler, where the exhaust gases from the tubes are combined together and pass to the flue or chimney.

Image shows the smokebox for my miniature traction engine.

Steam Drum – A cylindrical vessel mounted at a high point of a water-tube boiler. This is where dry steam may separate above the water level, so that it may be drawn off without risk of priming. This has a similar to the function of a dome in a fire-tube boiler.

Steam Point – The temperature at which pure water can exist in equilibrium with water vapour at standard atmospheric pressure.

Super Heated Steam – Steam heated above its saturation temperature.

Tube Sheet – The portion of a heat exchanger or boiler in to which the tubes are rolled or secured.

Turner Gauge – A device used to measure the actual scale-thickness in boiler tubes.

Water Tube – A boiler tube through which the fluid under pressure flows.

Water Tube Boiler – A boiler whose primary heating surface is composed of many small tubes, filled with water.

About Nigel 380 Articles
I've been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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