BD Second Class Boiler Attendant flashcards

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Second Class Boiler Attendant

A certified operator allowed to attend boilers up to a specified capacity, often 500 m² heating surface, under the supervision of a First Class attendant.

Boiler certificate validity

A boiler certificate is typically valid for one year and must be renewed after external inspection; internal inspection is required every two years.

Logbook requirement

The boiler attendant must record pressure, water level, blowdown, fuel used, and any abnormalities in the logbook every shift.

Fire-tube boiler

A boiler where hot combustion gases pass through tubes surrounded by water; limited to about 25 bar due to shell stress.

Water-tube boiler

A boiler where water circulates inside tubes with hot gases outside; suitable for high pressures above 100 bar.

Fusible plug

A safety device made of low-melting alloy that melts at about 230°C to release steam and warn of low water in a fire-tube boiler.

Water-wall

A furnace lining made of tubes carrying water, increasing radiant heating surface and protecting refractory walls from high temperatures.

Stoichiometric air

The minimum air required for complete combustion of a fuel; for coal it is about 7-8 kg air per kg coal.

Three T's of combustion

Time, Temperature (above 800°C), and Turbulence (mixing) are essential for complete and efficient combustion.

Chain-grate stoker

A mechanical stoker with a moving chain grate that feeds coal uniformly and removes ash continuously, used in solid-fuel boilers.

Atomisation

The process of breaking fuel oil into fine droplets (under 100 µm) using pressure or steam/air to ensure efficient combustion.

Warm-up period

Large boilers require slow warming over 1-2 hours to avoid thermal stress; air vents remain open until steam appears.

Blowdown procedure

Open the blowdown valve slowly, hold for 10-30 seconds, then close; repeat to control dissolved solids and conductivity.

Emergency shutdown

Trip fuel, close main steam stop valve, and manually open safety valve if pressure continues rising after fuel cut-off.

Low-water condition

When water level falls below the safe limit, immediately cut fuel; do not feed water until the boiler has cooled to avoid damage.

Scale

Deposits of calcium and magnesium salts on heating surfaces that reduce heat transfer and can cause tube overheating.

Deaeration

Removal of dissolved oxygen from feed water by heating to boiling point, often in a deaerator, to prevent corrosion.

Conductivity blowdown

Blowdown is controlled by measuring boiler water conductivity; typical limit for shell boilers is 3000-4000 µS/cm.

Economiser

A heat exchanger that recovers heat from flue gas to preheat feed water, improving boiler efficiency by 5-10%.

Saturated steam

Steam at the boiling point for its pressure; at 10 bar gauge, its temperature is about 184°C.

Superheated steam

Steam heated above its saturation temperature at the same pressure, improving efficiency and reducing condensation in pipes.

Steam trap

A device that removes condensate and air from steam lines while preventing steam escape; types include thermodynamic, thermostatic, and mechanical.

Water hammer

A pressure surge caused by condensate slugs accelerated by steam; prevented by proper trapping and drainage.

Safety valve

A valve that automatically releases pressure when it exceeds the set point, typically at or below the boiler design pressure.

Low-water cut-out

A protective device that automatically cuts fuel when the water level falls below the safe limit; must be tested regularly.

Boiler explosion causes

Low water, overpressure, defective safety valve, or scale-induced overheating can lead to catastrophic boiler failure.

Burn first aid

Cool the burn with running water for at least 10 minutes, cover with sterile dressing, and do not apply ointments.

Hydrostatic test

A test where the boiler is filled with water and pressurised to 1.5 times design pressure for 30 minutes to check for leaks.

Steam test

A test at full operating pressure to verify safety valve lifting and overall integrity, typically after major repairs.

Internal inspection

Examination of firebox, tubes, and shell for scale, corrosion, and cracks; requires cooling and cleaning of the boiler.

Boiler efficiency

Ratio of heat output in steam to heat input in fuel, expressed as a percentage; calculated by direct or indirect method.

Heat balance

An accounting of heat input distributed to steam, stack losses, radiation, blowdown, and unaccounted losses.