Reference

Power engineering glossary

Plain-language definitions of the jargon that trips up newcomers — so a term in a lesson never stops you cold. Built for SOPEEC 4th- and 3rd-class students.

Boilers

Firetube boileralso: fire-tube, HRT: A boiler in which the hot combustion gases pass through tubes that are surrounded by the water. Common in heating plants; simpler and lower-pressure than watertube designs. A horizontal-return-tubular (HRT) boiler is one classic firetube type.
Watertube boileralso: water-tube: A boiler in which the water flows through tubes that are surrounded by the hot combustion gases — the reverse of a firetube. Handles higher pressures and steaming rates, so it dominates power generation.
Tubesheetalso: tube sheet: The thick plate at the end of a boiler or heat exchanger that the tubes pass through and are sealed into. It holds the tube ends and separates the gas side from the water/steam side.
Stay / Stay tubealso: staybolt, stay bolt: A rod, bolt, or reinforced tube that braces flat or weakly-supported boiler surfaces so internal pressure cannot bulge or rupture them. A telltale hole drilled through a stay leaks if the stay cracks, warning the operator.
Refractory: Heat-resistant brick, castable, or lining material used in furnaces and combustion chambers to withstand very high temperatures and protect the surrounding steel.
Furnace: The enclosed space in a boiler where fuel is burned. The heat released here is transferred to the water to raise steam.
Economizer: A heat exchanger that recovers heat from the boiler flue gas to preheat the incoming feedwater, improving efficiency. It must stay below the steaming temperature so it heats water without boiling it.
Superheater: A bank of tubes that adds further heat to saturated steam leaving the drum, raising it above its boiling temperature to produce dry, high-energy superheated steam.
Steam drum: The vessel at the top of a watertube boiler where steam separates from the boiler water. Feedwater enters and steam leaves here.
Downcomer: An unheated tube that carries cooler, denser water down from the steam drum to the bottom of a watertube boiler, driving natural circulation as heated water rises in the risers.
Blowdown: Deliberately removing some boiler water (continuously or intermittently) to control the concentration of dissolved solids and remove sludge, protecting the boiler from scale and carryover.

Fittings & Safety Devices

Safety valvealso: relief valve, PSV: A spring-loaded valve that opens automatically to release steam or pressure if it rises above a set limit, protecting the boiler or vessel from over-pressure. It is the most important boiler safety device.
Water columnalso: gauge glass, sight glass: The fitting and glass tube that let the operator see the actual water level in the boiler. Maintaining proper water level is critical to safe operation.
Low-water fuel cut-offalso: LWCO: A control that automatically shuts off the burner if the boiler water level falls dangerously low, preventing the catastrophic overheating that low water would cause.
Fusible plug: A plug with a low-melting-point metal core fitted in some boilers; if water level drops and the crown sheet overheats, the core melts and releases steam as a warning.
Feedwater: The treated water supplied to the boiler to replace the water lost as steam and blowdown.
Check valvealso: non-return valve: A valve that allows flow in one direction only, automatically preventing reverse flow — for example, stopping boiler pressure from pushing back into the feedwater line.
Steam trap: An automatic device that drains condensate (and air) from steam lines and equipment while holding back live steam, keeping the system efficient.

Plant Equipment

Centrifugal pump: A pump that uses a spinning impeller to throw liquid outward, converting velocity into pressure in the surrounding casing (volute). The most common plant pump for high-flow service.
Positive-displacement pump: A pump that moves a fixed volume of liquid per stroke or revolution (e.g. reciprocating or gear pumps), delivering steady flow against high pressure regardless of system resistance.
NPSHalso: net positive suction head: Net Positive Suction Head — the suction pressure available at a pump above the liquid’s vapour pressure. Too little NPSH lets the liquid flash to vapour and causes cavitation.
Cavitation: The formation and violent collapse of vapour bubbles in a pump (or valve) when local pressure drops below the liquid’s vapour pressure — it erodes metal and causes noise and vibration.
Compressor: A machine that raises the pressure of a gas by reducing its volume. Reciprocating, rotary-screw, and centrifugal are the main types used in plants.
Heat exchanger: A device that transfers heat between two fluids without mixing them — e.g. shell-and-tube or plate types. Used for heating, cooling, and heat recovery throughout a plant.
Condenser: A heat exchanger that cools exhaust steam back into water (condensate) so it can be reused as feedwater and so the turbine can exhaust to a vacuum for efficiency.

Thermodynamics & Steam

Saturated steam: Steam at the boiling temperature corresponding to its pressure, in equilibrium with water. Add heat and more water boils; remove heat and some steam condenses.
Superheated steam: Steam heated above its saturation temperature for a given pressure, so it carries extra energy and is dry — preferred for turbines because it avoids condensation damage.
Latent heat: The heat absorbed or released when a substance changes phase (e.g. water boiling to steam) without any change in temperature.
Sensible heat: Heat that changes a substance’s temperature without changing its phase — what you add to warm water from 20 °C to 90 °C.
Enthalpy: The total heat content of a fluid per unit mass (internal energy plus pressure-volume energy). Steam tables list enthalpy so engineers can size and balance equipment.
MAWPalso: maximum allowable working pressure: Maximum Allowable Working Pressure — the highest pressure a vessel or boiler is rated and stamped to operate at safely under code.

Water & Chemistry

Scale: A hard mineral deposit (mainly calcium and magnesium) that forms on heat-transfer surfaces from impurities in the water. It insulates the metal, wastes fuel, and can cause overheating.
Carryover: Boiler water droplets carried out with the steam, often due to high water level or high dissolved solids. It contaminates steam lines and can damage turbines.
Deaerator: Equipment that removes dissolved oxygen and other gases from feedwater (usually by heating and venting) to prevent oxygen corrosion in the boiler.
pH: A measure of how acidic or alkaline water is. Boiler water is kept mildly alkaline to protect the steel from corrosion.

Electrical

Transformer: A device that transfers electrical energy between circuits through magnetism, stepping voltage up or down. It works only on alternating current.
Power factor: The ratio of real power (doing useful work) to apparent power in an AC circuit. A low power factor means current is being drawn that does no useful work, wasting capacity.
RMSalso: root mean square: Root-Mean-Square — the effective value of an alternating voltage or current; it is the DC value that would deliver the same heating power.
Synchronous speed: The speed of the rotating magnetic field in an AC machine, set by the supply frequency and the number of poles. Induction motors run slightly below it (the difference is called slip).

Instrumentation & Controls

Transmitter: An instrument that senses a process variable (pressure, level, flow, temperature) and sends a standardized signal — commonly a 4–20 mA current — to the control system.
Controller: The device that compares a measured value to a desired set point and adjusts a final element (like a control valve) to drive the difference to zero.
Control valve: A valve, usually driven by an actuator on a controller signal, that throttles flow to regulate a process variable such as level, pressure, or temperature.
Live zero: Using a non-zero value (e.g. 4 mA) to represent the bottom of a signal range, so the system can tell a true zero reading apart from a broken wire (0 mA).

Codes & Operations

ASME: The American Society of Mechanical Engineers, whose Boiler and Pressure Vessel Code sets the construction and inspection rules widely adopted in Canada (e.g. Section I for power boilers, Section IV for heating boilers).
CSA B51: The Canadian Standards Association code for boiler, pressure-vessel, and pressure-piping construction and registration in Canada.
SOPEEC: The Standardization of Power Engineer Examinations Committee — the body that standardizes power-engineering certification exams across participating Canadian provinces.
Chief Engineer: The certified power engineer in overall charge of a plant’s operation and safety. The plant’s size (capacity) and the engineer’s certificate class determine who may hold the role.
Purge: Forcing air through a furnace before light-off (and after shutdown) to clear any unburned fuel or combustible gas, preventing a furnace explosion.
Lockout / tagoutalso: LOTO: A safety procedure that isolates and locks an energy source (electrical, steam, etc.) and tags it, so equipment cannot be started while someone is working on it.

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