DC Third Class Stationary Engineer Flashcards

These flashcards cover key concepts and facts relevant to the role of a Third Class Stationary Engineer, focusing on system components, operational standards, and maintenance protocols.

What component in a refrigerant system vaporizes liquid by absorbing heat?

Evaporator

What is the best method for electrical grounding?

Metal stake driven 8 feet into the ground

Which valve is recommended for throttling purposes?

Globe valve

What is the acceptable range for residual sodium sulfite in boiler water?

15–30 ppm

What is the BTU content of a gallon of #4 fuel oil?

146,000 BTU

What substance is used for regeneration in a zeolite water softener system?

Brine

What are the four steps in the zeolite water softener rejuvenation process?

Backwash → Brine Draw → Slow Rinse → Fast Rinse

What device measures temperature by detecting electrical resistance changes?

RTD (Resistance Temperature Detector)

What is the purpose of a suction accumulator?

It stores liquid refrigerant to allow evaporation before entering the compressor.

What must be submitted to the code official for field assembly of boilers?

U-1 Manufacturer’s Data Report

What efficiency does a boiler with a 2800°F furnace and 600°F stack temperature have?

78.57%

Which type of coal has the highest fixed carbon content?

Anthracite

What causes a high condensate tank temperature (20°F above normal)?

Steam traps stuck open

What valve should be nearest the boiler in a blowdown line?

Quick-opening valve

Which valve is used to control the blowdown rate?

Slow-opening valve

How is a boiler hydrostatic test performed?

Fill boiler with 70°F water and raise pressure to 1.5× MAWP.

What does a 3-element feedwater regulator sense?

Water level, steam flow, and water flow.

What are on/off controls that activate using one variable called?

Discrete controls.

What are controls that use a range of dynamic values called?

Analog controls.

What valve is a poor choice if sediment is present in a system?

Gate valve.

What does the condenser in a refrigerant system do?

Changes refrigerant vapor to a liquid.

True or False: The evaporator is where refrigerant turns to gas and absorbs latent heat.

True.

What removes moisture from a refrigeration system?

Filter drier.

Why is oil added to refrigerant?

To lubricate the compressor.

How often should you check the low-water fuel cut-off?

Once per shift.

What causes permanent hardness in water?

Calcium sulfate and magnesium silicate.

What chemicals are used to combat corrosion in boiler water?

Sodium sulfite and hydrazine.

If boiler water has a pH of 5, what compound should be added?

Base.

What produces soft scale in water systems?

Calcium carbonate and magnesium carbonate.

What chemical combats scale?

Combined phosphate treatment.

What chemical does not produce heat in combustion?

Nitrogen.

What device removes scale from fire tubes?

Tube rattler or vibrator.

Who is authorized to adjust or repair a safety valve?

Qualified manufacturer or representative.

What mechanical device removes scale from water tubes?

Tube turbine.

How does a thermostat control temperature in an air-handling system?

By mixing hot and cold air in a mixing box.

What is the removal of moisture using a cooling coil called?

Mechanical dehumidification.

In a multi-zone air handler, how does the thermostat control temperature?

By modulating heating & cooling coil valves.

What is an air handler with separate hot/cold ducts side-by-side called?

Dual-duct air handler.

What is the boiler horsepower for 86,250 lb/hr steam?

2500 HP.

What is the pressure at the bottom of a 75 ft water column?

32.46 psi.

How do you convert 92°C to °F?

197.6°F.

How do you convert 60°F to °C?

15.5°C.

What is the flow rate through a 4” pipe at 12 ft/sec?

470 GPM.

What is the purpose of an expansion tank in a closed loop?

Absorb expansion & maintain pressure.

What is the purpose of a crankcase heater on a chiller?

Prevent refrigerant migration.

What is 'slip' in a pump context?

Difference between theoretical and actual flow.

Which pump can start with the discharge valve closed?

Centrifugal pump.

What is the definition of static suction head?

Vertical distance from pump centerline to top of supply tank.

What is relative humidity?

The moisture in air compared to its saturation level.

What should the temperature be when leaving a deaerator?

212°F.