NIULPE Class 3 flashcards
NIULPE Class 3 · Build recall with a focused review session.
31 cards. Read the term and the definition here. The deck at the top of this page is optional.
- MAWP
- Maximum allowable working pressure, the highest pressure at which a boiler or pressure vessel may be operated, stamped on the nameplate and used to set safety valve pressure.
- Fusible plug
- A brass fitting with a low-melting alloy core installed in the crown sheet or firebox; it melts near 445 °F to warn of low water and prevent overheating of pressure parts.
- Water column
- A vertical fitting connected to the boiler at water and steam spaces that mounts the gauge glass and low-water cutoff, keeping their connections clear of sludge and foam.
- Staybolt
- A rod threaded into two plates to hold them together against pressure loads; it is designed to bend rather than pull apart when the plates flex with temperature.
- Stoichiometric air
- The exact amount of air needed to burn all fuel completely with no excess oxygen; for natural gas it is about 17.3 pounds of air per pound of fuel.
- Excess air
- Air supplied above the theoretical requirement to ensure complete combustion; too little produces CO, too much wastes heat up the stack.
- Trial for ignition
- The limited time (about 10 seconds for gas, 15 seconds for oil) during which the burner may prove flame before the fuel valve must close.
- Three-element control
- Drum level control that uses steam flow, feedwater flow, and drum level signals together to correct for shrink and swell during load changes.
- Hydrostatic test
- A pressure test using water at 1.5 times MAWP for new construction or 1.25 times for in-service repairs, held to inspect joints for leaks.
- Ultrasonic thickness testing
- A nondestructive method that measures remaining wall thickness with sound waves; readings are compared to nominal thickness to detect corrosion loss.
- Post-weld heat treatment
- Controlled heating of a completed weld to relieve residual stress and drive off hydrogen, required for thick sections and certain alloys.
- Joint efficiency
- A factor (E) in pressure vessel design equations that accounts for the strength lost at welded or riveted seams compared with solid plate.
- Corrosion allowance
- Extra wall thickness added to the calculated minimum so the vessel can lose metal to corrosion over its design life and still be safe.
- B31.1 and B31.3
- ASME piping codes: B31.1 covers power piping in boiler plants, B31.3 covers process piping in chemical and refinery service; their stress rules differ.
- Rupture disc
- A one-time pressure relief device that bursts at a set pressure; often installed ahead of a relief valve to protect it from corrosive or fouling fluid.
- Rankine cycle
- The thermodynamic cycle of a steam power plant; efficiency improves with higher steam pressure and temperature and with lower condenser pressure.
- Turbine heat rate
- The heat energy input required per unit of electrical output, usually Btu per kWh; a lower heat rate means a more efficient turbine cycle.
- Overspeed trip
- A protective device that stops steam or fuel to a turbine when speed reaches about 110% of rated speed, preventing catastrophic rotor failure.
- NPSH
- Net positive suction head, the absolute pressure margin above vapor pressure at the pump suction; available NPSH must exceed required NPSH to avoid cavitation.
- Affinity laws
- Pump scaling rules: flow changes with speed, head with speed squared, and power with speed cubed when impeller diameter is held constant.
- Compressor surge
- A flow reversal that occurs when compressor flow drops below the surge line; an anti-surge valve recycles flow to keep the machine stable.
- 4–20 mA loop
- An analog signal standard where 4 mA represents the live zero and 20 mA full scale; a 0 mA reading indicates a broken wire.
- RTD Pt100
- A resistance temperature detector with 100 ohms at 0 °C and about 0.385 ohms per degree Celsius change, used for accurate temperature measurement.
- Safety integrity level
- A SIL rating (1 to 4) assigned to a safety instrumented function based on its required risk reduction factor, with SIL 3 about 1,000 to 10,000.
- Oxygen pitting
- Localized corrosion caused by dissolved oxygen attacking steel; prevented by deaeration plus a chemical oxygen scavenger such as sodium sulfite.
- Conductivity blowdown
- Control of boiler blowdown rate based on measured dissolved solids conductivity, keeping solids low enough to prevent carryover and foaming.
- Caustic embrittlement
- Stress corrosion cracking of steel at high stress and high caustic concentration, historically in riveted seams; avoided by coordinated phosphate treatment.
- Full-load amperes
- The current a motor draws at rated load and voltage, listed on the nameplate and used to set overload protection at about 115 to 125 percent.
- Locked-rotor current
- The high inrush current, typically five to seven times full-load current, that flows while an induction motor is starting and before it accelerates.
- ASME Section I
- The ASME code section covering power boilers, including rules for design, materials, fabrication, inspection, and the required safety valve capacity.
- R stamp
- An ASME Certificate of Authorization that allows a repair organization to repair or alter pressure-retaining items in boilers and pressure vessels.