Power Eng 1st Class key terms

A documented process that reviews and approves modifications to equipment, procedures, chemicals, or software before implementation, so that new hazards are identified and controls updated before the change goes live.

A systematic team study of a process unit to identify hazards, causes, and consequences, and to recommend safeguards. Common methods include HAZOP, what-if, and failure modes and effects analysis.

A structured brainstorming technique that applies guide words such as no flow, more pressure, or reverse flow to each node of a piping and instrumentation diagram to find deviations, causes, and consequences.

A semi-quantitative risk method that compares the demand frequency of an initiating event with the combined risk reduction of independent protection layers to judge whether risk meets the plant tolerance criteria.

A final verification, performed before introducing hazardous chemicals or energy, that construction matches design, procedures and training are complete, and all PHA and MOC action items are closed.

The construction code for power boilers and high-temperature water boilers, setting rules for materials, design, fabrication, inspection, testing, and stamping. Jurisdictions commonly adopt it as the legal basis for power boiler construction.

The design and construction code for piping in electric power plants and industrial steam systems, covering wall thickness, support, flexibility analysis, fabrication, examination, and pressure testing requirements.

A consensus code governing in-service inspection, repair, alteration, and rerating of boilers and pressure vessels, including requirements for authorized inspection agencies and the use of R and VR stamps.

The highest pressure at which a boiler or vessel may legally operate, established by the designer using allowable stress values and minimum thickness rules under the applicable construction code.

A pressure test in which the component is filled with water and pressurized to a code-specified level, typically 1.5 times the design pressure, to verify strength and leak tightness before service or after repair.

An inspector employed or commissioned by the state or provincial authority who performs statutory inspections of boilers and pressure equipment and has authority to order repairs or prohibit operation.

The idealized thermodynamic cycle for steam power plants, comprising isentropic pumping, constant-pressure heat addition in the boiler, isentropic expansion in the turbine, and constant-pressure heat rejection in the condenser.

A modification in which steam is partially expanded in the turbine, returned to the boiler for reheating, then expanded again. It raises cycle efficiency and limits exhaust moisture at the last stages.

Extraction of steam from turbine stages to heat boiler feedwater in closed heaters, raising the mean temperature of heat addition and thereby improving cycle thermal efficiency.

The amount by which steam temperature exceeds its saturation temperature at a given pressure. Superheating raises cycle efficiency and reduces erosion from wet steam in turbine blades.

The thermal energy input required per unit of electrical energy produced, usually expressed in kJ/kWh or Btu/kWh. Lower heat rate means higher plant efficiency; it is the reciprocal of thermal efficiency.

The ratio of useful heat absorbed by the working fluid to the heat released by fuel combustion, determined either by input-output testing or by the indirect method summing stack, radiation, and unburned losses.

The air supplied beyond the theoretical stoichiometric quantity required for complete combustion, expressed as a percentage. Too little causes carbon monoxide and smoke; too much lowers efficiency through stack loss.

The exact mass of air needed to burn a unit mass of fuel completely, with no oxygen or combustible left over. It is the reference point for calculating excess air and combustion efficiency.

A closed-loop control that continuously measures oxygen in the flue gas and adjusts combustion air flow to hold a target excess-air level, compensating for fuel heating value and load changes.

A post-combustion emission control that injects ammonia or urea into flue gas passing over a catalyst, converting nitrogen oxides into nitrogen and water. Performance depends on temperature window and ammonia slip control.

A particulate control device that charges ash particles in a high-voltage field and collects them on oppositely charged plates, then removes them by rapping into hoppers.

The temperature at which water vapor and acid vapors in flue gas begin to condense. Operating metal temperatures below it causes sulfuric acid corrosion, especially when burning sulfur-bearing fuel.

A feedwater control scheme using steam flow, feedwater flow, and drum level signals so that level is held during load swings while rejecting false level indications caused by swell and shrink.

Transient drum level changes caused by pressure shifts that alter the volume of steam bubbles in the water. Rising load lowers pressure, swells the level, and can mislead single-element controls.

An independent protective function, assigned a safety integrity level, that drives the process to a safe state when a dangerous condition is detected, such as a boiler trip on low water.

The logic and hardware that supervises burner light-off, monitors flame, and executes a safety shutdown on loss of flame or other permissive faults, following a defined purge and trial-for-ignition sequence.

A forced flow of air through the furnace and gas passages at a specified rate and duration before ignition, intended to clear accumulated combustible gases and prevent furnace explosion.

The standard for prevention of furnace explosions in multiple-burner boilers, specifying interlock logic, purge requirements, flame detection, and trip response for burner management systems.

The inlet pressure at which a pressure relief valve begins to open under bench-set conditions. It must not exceed the maximum allowable working pressure and is verified by an authorized testing facility.

An operating test confirming that relief devices keep boiler pressure from rising more than the code-allowed percentage above maximum allowable working pressure when the unit is at full firing rate.

Admission of water or cold steam into a hot turbine, causing rapid differential cooling, rotor bowing, and potential catastrophic damage. Prevention relies on drain systems and temperature-based interlocks.

An independent protective device that closes the main stop valves when rotor speed exceeds a set point, typically 110 percent of rated speed, preventing destructive blade and rotor failure.

A relay function that trips a generator breaker when the machine draws real power from the system instead of delivering it, indicating a lost prime mover or drive failure.

A distance-based or impedance relay scheme that detects loss of field excitation, which causes the generator to absorb reactive power and can overheat the rotor and stress the system.

The process of matching a generator's voltage, frequency, phase angle, and phase sequence to the bus before closing the breaker, avoiding damaging current and torque transients.

A feedwater heater that strips dissolved oxygen and other gases by heating water to saturation and venting the released gases, reducing corrosion in the boiler and condensate system.

Localized corrosion caused by dissolved oxygen attacking steel, producing deep pits that can penetrate tube walls. Control depends on deaeration, chemical oxygen scavengers, and maintaining protective films.

A form of stress corrosion cracking in boiler steel exposed to concentrated sodium hydroxide at high stress and temperature, often near riveted seams or tube rolls. Control uses coordinated phosphate treatment and stress relief.

Low-temperature corrosion occurring when sulfuric acid condenses on cold metal surfaces such as air heater elements or stack linings, driven by sulfur in fuel and moisture in flue gas.

A structured investigation method, such as fault tree, five-why, or barrier analysis, that moves past immediate causes to identify systemic management and design deficiencies and prevent recurrence.

A risk diagram that places a single top event at the center, threats and preventive barriers on the left, and consequences with mitigating barriers on the right, showing how controls link to outcomes.

A written authorization specifying atmospheric testing, isolation, ventilation, attendant duties, and rescue arrangements required before a person enters a boiler drum, vessel, or other restricted space.