Basic Power Plant Operations

What three factors affect natural circulation in a boiler?

1) amount of heat produced 2) Height of the boiler 3) Pressure at which the boiler operates

How many watts are in a megawatt?

1,000,000

5 additional components to the turbine lube oil system

1. AC Auxiliary pump 2. DC emergency pump 3. AC turning gear pump 4. turning Gear 5. Vapor Extractor

The 2 ways the position of the servo valve is afected?

1. Action of the governor 2. Action of the Hydraulic actuator

4 major types of pollution

1. Air pollution 2. Water Pollution 3. Thermal pollution 4. Noise Pollution

3 steps if automatic boiler controls system fails

1. Analyze the situation 2. Take corrective action 3. Decide if need to go into manual

List two things that a boiler in a plant does:

1. Burns fuel to produce heat 2. Uses heat to convert water to steam

3 Functions of all bearings

1. Carrying loads 2. Reducing Friction 3 Positioning moving parts

List the 3 general steps to follow if an emergency condition occurs in your plant

1. Determine what is going on 2. Put the plant in a safe condition 3. Perform follow up action necessary to return plant back to normal

3 major parts of a gland seal exhaust system

1. Gland steam condenser 2. A glad steam exhauster 3. Connecting Pipe

Abilities necessary for an operator to deal with an emergency:

1. Know the plant's emergency procedures 2. Know the systems and equipment well enough to take whatever corrective measures are necessary 3. Be able to analyze what is happening

What two steps can an operator take if an automatic system fails to adjust a flow rate properly?

1. Make adjustments to one of the auto control systems 2. Take manual control of the system

4 common oil lubrication systems?

1. Oil ring 2. Forced Lubrication 3. Constant Level Oiler 4. Drip Feed

List the 6 elements necessary for controlled combustion

1. Oxygen 2. Fuel 3. Heat 4. Chemical Reaction 5. Turbulence 6. Time

List two reasons why circulation is necessary in a boiler

1. Provides a constant supply of water to be turned into steam 2. Carries heat away from the waterwalls

The 4 main parts of a turbine lube oil system

1. Reservoir 2. main lube oil pump 3. Booster pump 4. Oil coolers

Two general types of bearings

1. Sliding surface bearings 2. Rolling Contact Bearings

4 main parts of a typical gland seal system

1. Steam supply line 2. steam supply control valve 3. steam leakoff line 4. steam leakoff control valve

Two common ways of controlling feedwater flow

1. Turbine Pump turbine Control Valve/vary speed 2. Motor Pump Feedwater Valve

An imbalance in the steam and feedwater low rates may result in:

1. Water filling up the condenser and backing into the Turbine 2. A drop in the water level in the boiler drum 3. The boiler tubes melting 4. The boiler filling with water and water being carried over to the turbine

2 most common methods of greasing a bearing

1. grease gun 2. grease cup

Two most common types of lubricant used in power plants

1. oil 2. grease

3 ways to check the level of oil in an oil ring lubrication system

1. sight glass 2. dipstick 3. spill hole

What 4 important flow rates must be monitored during load change?

1. steam 2. Feedwater 3. Fuel 4. Air

What is the ratio of volume reduction in the condenser?

1600-1

Typical turbines operate at ewhat RPM

1800 or 3600

What is a grease fitting?

A small rounded projection on a bearing housing to inject grease from a grease gun. The tip of the grease gun must fit it.

What is the oil ring lubrication system?

A system that is used on surface sliding bearings. the lower half of the sliding surface bearing is an oil reservoir with an oil ring around the shaft.

What effect does the dropping pressure of steam into water in the condenser have?

A vacuum is created due to it taking up less space.

What is a gland steam exhauster?

A vacuum pump that draws a vacuum on system, puling the air and team from the glands to the gland steam condenser.

Why do you wnat to keep the temperature of flue gas abouve the dew point?

Acid gases are less corrosive than the condensed acids.

Hydraulic _______ are used to open and close turbine valves

Actuators

Where does secondary come in at the burners?

Air registers from the windbox

Why are tie-lines an important aspect of power production?

Alternating current used in homes and businesses cannot be stored in batteries for future use. It has to be supplied when needed.

Excess Oxygen

Amount of oxygen in the gases going to the stack

Saturation Temperature

At a given pressure, the temperature at which water boils

Main Lube Oil Pump

Attached to the turbine and driven by the turbine shaft. supplies oil to the turbine control system and the booster pump

The level and flow in a boiler are usually controlled _____

Automatically

What two types of movement do bearings limit?

Axial and Radial

Methods of oil filtration

Bags, skimmers, centrifuges, and screens

Boilers that use both forced draft and induced draft fans are called __________

Balanced draft fans

DC Emergency Pump

Battery operated. supplies oil when AC power is unavailable. Used to supply oil long enough for turbine to coast down after loss of AC power.

Radial Bearing

Bearing Surface in a Bearing Housing

Where is the thermal energy made?

Boiler

3 major components of the steam cycle

Boiler Steam Turbine Condenser

List the three components of a fossil fuel plant where energy conversions take place.

Boiler, Turbine, Generator

How is load change begun?

By operating the turbine governor to increase or decrease the control valve openings

How do superheaters increase the efficiency of boilers?

By using heat that would otherwise be lost up the stack.

Two most common alternatives to steam seals?

Carbon seals and water seals

Turbine lube oil system reservoir

Central collecting point for all the oil used in the system

What happens to the governor when turbine speed decreases?

Centrifugal force on the spinning governor decreases, The spring pulls the weights inwards, the brackets press down on the rod and crossbeam, the servo valve opens, oil goes into the actuator, the control valve opens more, more steam flow, turbine speed increases

What is the definition of load change?

Changing the supply of power to equal demand

What cools the steam in the condenser?

Circulating water flowing through tubes

First step when installing a spigot or barrel pump?

Clean top of the barrel and the pump

A system where a fluid is used over and over is called a _________ system.

Closed loop system

What regulates the fuel flow in coal burners?

Coal feeder

What does a substation do?

Combines electric power from multiple sources together in one location

Best safety practice is

Common sense

A large heat exchanger that is part of the steam cycle is the _______

Condenser

Boilers that have boiler water circulation pups on the downcomers are called _________

Controlled Circulation Boilers

Two disadvantages of fossil fuel plants

Cost of fuel and more complicated

What are the major stationary parts of the turbine?

Cylinder and diaphragms

2 reasons why you don't want Air inleakage

Decreased efficiency and possible cracks due to temperature difference

What are Blowdowns?

Drains that are opened during boiler operation.

What is a benefit of the vacuum created in the condenser?

Draws more steam through the turbine and into the condenser. Increasing the efficiency.

Gland seal exhaust system

Draws off steam leaking past the second seal of the turbine glands before it can escape.

A _______ lubricator supplies a steady supply of fresh oil to a bearing.

Drip Feed

Two most common types of boilers

Drum type and once thru

Before steam is sent through the outlet pipes of a drum, it is usually sent through ________ to remove additional water that is not removed by the moisture separators.

Dryers

Axial Movement

End to end

In the steam cycle, the flow rates of steam and feedwater must be _________.

Equal

If there is not enough time for complete burning of the fuel, combustible materials could build up in the later stages of the boiler or in the stack and cause an _____________

Explosion

What fans provide the secondary air?

FD fans

True or False: A condenser circulating water system that is an open system uses water over and over again.

False

True or False: Economizers are heat transfer devices that use hot flue gas to heat combustion air

False

True or False: Natural Circulation boilers can operate at higher temperatures and pressures than controlled circulation boilers of the same size.

False

True or False: Turbines may be impulse or reaction, not not both.

False

True or false: Reheaters add energy to steam by increasing its temperature and pressure

False

True or False: When a turbine's generator is connected to a power system, its speed is essentially constant and controlled by the governor.

False, Grid

True or False: If feedwater flow is greater than steam flow, the boiler will boil dry.

False.

Pressure in the steam cycle is highest in the _________, and lowest in the ____________.

Feed water system, condenser

In order for a unit to operate safely and efficiently, the steam flow must equal the ______ flow, and the ______ must equal the combustion air flow.

Feedwater Fuel

How does an economizer work?

Feedwater passes through the tubes, and flue gas flows around the outside of the tubes

What is an oil wedge?

Film of oil that reduces friction

The main lube oil system is a good example of a _______ lube system

Force fed

For proper combustion to take place, the boiler needs a continuous supply of _______ and ______.

Fuel and air

If the steam flow and feedwater flow are increased, the _______ flow and combustion _______ flow must be adjusted accordingly.

Fuel and air

Difference between Coal burner and gas boiler

Gas supply enters burner gas manifold and out the gas spuds

Other name for control valves

Governor valves

How does a grease gun work?

Grease is injected in the bearing housing through a grease fitting. You have to remove drain plug first to let old grease drain out.

Steam moves from areas of _________ pressure to areas of ________ pressure.

High to low

Impulse vs reaction vs combination Turbines

Impulse- force of steam causes movement Reaction- expansion of steam turns the blades Combination- most common. First stage is impulse, last is reaction, and in between is a combo

Hydraulic Actuator Form and function

Includes a hydraulic cylinder with a piston with a spring on top. Without oil the pressure of the spring keeps the piston pushed down and closed. Pumping hydraulic oil in controls the amount the valve opens by applying opposing force to the piston.

Effect of amount of heat produced on natural circulation?

Increased Heat, Increased temperature difference, increased natural circulation

Effect of height of boiler on natural circulation

Increased height, Increased Weight difference, Increased Natural circulation

Effect of Pressure of boiler operation on natural circulation

Increased pressure, decreased density difference between steam and water, decreased natural circulation

A pressurized furnace boiler uses the pressure of incoming air from the FD fan to push flue gas out the stack, in a balanced draft boiler, an additional fan, called an _______, accomplishes this.

Induced draft

rolling contact bearing

Inner ring rolls with shaft outer ring is stationary. rolling elements between. lube prevents contact

Steam flows from the reheater to the turbine to the turbine through _______ valves and _______ valves

Intercept and reheat stop valves

What does the reset feature do in a tpical turbine controlsystem?

It gives a certain amount of information to the control system to allow speed adjustments to be made in small increments

What must be done to a barrel with a spigot?

It must be turned on its side.

What do attemperators do?

Keep the final temperature of the steam from becoming too hot and overheating the superheater tubes by injecting water into the steam

Why is the turning gear important?

Keeps turbine from bowing as it cools down.

A typical gland seal is made up of several ______

Labyrinth seals

Composition of a sootblower

Lance tube with nozzles, feed tube, and a valve

What is a steam chest?

Large housing between the stop valves and control valves

Constant Level Oiler

Like a gravity feeder

Who tells you how much load your unit should be generating?

Load dispatcher/Resource coordinator

Lube oil coolers

Located between booster pump and bearings. Heat exchangers that use the flow of water to cool the oil. Pair. one for cooling one for backup.

What are three advantages of fossil fuel plants?

Location flexibility, Can be sized for desired output, not rain dependent

What conditions cause an automatic trip?

Low Lube oil pressure, turbine overspeed, excessive vibration

Turbine pressure at low load vs high load

Low load is a vacuum at later stages High loads only last few stage under vacuum

What is film lubrication?

Lubrication in between bearing surfaces to prevent contact

Major source of thermal pollution

Major condensers

What are some operator responsibilities in regards to the Turbine Lube Oil System?

Make sure in auto, check temps at multiple locations: (bearings, bearing supply and return lines, cooler inlet and outlet), Check oil purity

In a typical natural gas burner, gas is fed under pressure to a burner _________.

Manifold

What is the difference between a electrohydraulic control system and a mechanical hydraulic control system?

Mechanical hydraulic has flyweight governor and get oil from main lube oil system. Electrohydraulic has an electronic governor and gets its oil from an independent oil source.

Two major systems commonly used to control turbine speed are

Mechanical hydraulic system and electrohydaulic control systems

How do you determine the correct fuel/air ratio

Monitoring oxygen that leaves the stack

Why would you want to raise the temp of the steam above saturation temp?

More efficient

The highest demand for power is generally around:

Morning and evening

What type of pressure is a vacuum?

Negative Pressure

Steam temperature can be raised above the saturation temperature only if there is _____________________.

No water

To open a control valve in a typical control system,

Oil must be forced under the piston in the hydraulic cylinder to counter the fource of the piston spring

When are stop valves open or closed.

Open during normal operation, closed during shutdown or emergencies

When are boiler drains opened and closed?

Opened after shut down because during operation natural circulation would be interrupted. (Some open during startup example being superheater drains to remove extra water and maintain flow)

When are boiler vents opened or closed?

Opened only during startup to remove access air in system and closed as soon as steam startes to come out.

What is the best time to tale temperature readings of a bearing?

Operating temperature

In a turbine that is under a vacuum, _______________.

Outside air tries to leak in

What effect does too much grease in a bearing have?

Overheat

What is the function of primary air in combustion?

Picks up the finely ground coal, dries it out, and carries it to the burners

Booster Pump

Powered by the discharge of the main lube oil pump and supplies oil to the suction of the main lube oil pump and to the turbine bearings

Precipitators vs Scrubbers

Precipitators remove particulates, scrubbers remove particulates and gases

What does a load dispatcher of resource coordinator do?

Predicts demand, monitors condition of the power system, coordinates the output of the power plants so that supply always equal demand

Steam flows from the boiler to the turbine because of differences in ________

Pressure

The turbine overspeed trip:

Prevents the turbine exceeding the maximum rated speed

Primary vs Secondary superheater

Primary is usually convection Secondary is in hotter path

What does the condensate-feedwater system do?

Provides a continuous flow of water from the hotwell to the boiler after the steam exiting the turbine has been condensed or cooled back to the condensed state.

What is the function of secondary air?

Providing enough air to support combustion

In a typical coal burning plant, coal is transported to a plant by a conveyor system and then fed into a _______, where it is ground into a fine powder.

Pulverizer

The makeup water system _______ water and stores it in tanks until it is needed.

Purifies

Radiant vs. Convection Superheaters

Radiant- Direct line of sight of flames Convection- Get heat from gases

How are NOx levels limited?

Regulating Boiler temp by recirculating flue gas through the furnace and adjusting the fuel/air ratio

What regulates fuel flow in a gas burner?

Regulating valves

Function of surface blowdown

Removes drum contaminants

What does a sootblower do?

Removes soot from the waterwall tubes using compressed air or steam

Retractable vs Fixed Sootblowers

Retractable usually in hotter areas

Before steam flows from the HP section of the turbine to the IP section, it is often ______?

Returned to the boiler for reheating in the reheater

The turbine shaft, wheels, and blades are collectively called the _______

Rotor

If water and steam are present together, the temperature of both the water and the steam will always be at _________

Saturation Temp

How does a labyrinth seal work?

Sets of grooves and ridges that correspond make it difficult for air to pass through and leak.

Radial Movement

Side to Side

Turning Gear

Small motor and gear arrangement that keeps the rotor rotating while it cools

What is a nozzle box or block?

Special type of diaphragm before first wheel. It contains nozzles instead of blades. the nozzles direct steam from steam inlet to first wheel.

What happens to the turbine speed when the generator is not connected to the power system?

Speed of turbine is controlled by turbine control valves

What happens to the turbine speed when the generator is connected to the power system?

Speed remains constant

What is between the primary and secondary superheater?

Spray Attemperator

lIST THE 3 PHASES OF TURBINE OPERATION

Startup, shutdown, and normal operation

The amount of __________ to the turbine and the amount of _______ to the boiler must be equal.

Steam and water

What does the gland seal system do at high load?

Steam leaks into glands causes increased pressure, steam supply valve closes, steam leakoff valve opens, steam goes to main condenser

What does the gland seal system do at low load?

Steam supply cpntrol valve opens, low pressure steam is supplied to glands, steam flows towards outer seal.

In a turbine under a positive pressure, ________________________

Steam tries to escape

The valve before the steam inlet to the turbine that remains fully open during normal turbine operation is called the _________ valve

Stop

Two valve types before steam inlet

Stop valves and control valves

What all valves close with a trubine overspeeding trip?

Stop valves, control valves, reheat stop valves, and intercept valves

AC Auxiliary Pump

Supplies oil during startup and shutdown when shaft is too slow for main lube oil pump to be effective. Also for when normal oil supply is interrupted.

The ________ of power must always equal the _________ for power.

Supply and demand

tapered roller bearing

Supports both axial and radial loads

A combination of pipes and equipment connected together to perform a function is called a _______.

System

What determines the amount of electric power produced by the generator?

The amount of steam flowing through the turbine

How does a grease cup function?

The cup of grease is mounted on the housing and turned to force grease into the housing.

What supplies water to the waterwalls?

The lower headers from the down comers from the drum

What happens to the pressure of steam is condensed to water?

The pressure drops

What is it called when the actuator provides feedback to the governor by moving it?

The reset feature

What must be done while using a barrel pump?

The vent cap must be taken off.

Other name for stop valves

Throttle valves

One power company is often connected to another power company by:

Tie-lines

Where is the condensate in the gland steam condenser taken?

To the main condenser

A sudden shutdown of the turbine is called a

Trip

True or False: A perfect fuel and air mixture is impossible to maintain, so a little extra air is supplied to make sure that all the fuel is burned.

True

True or False: A servo valve controls the flow of oil into hydraulic actuators.

True

True or False: Before a turbine can be run at full load, it must first go through a warmup period.

True

True or False: During startup, drains must be opened in the turbine and its associated piping to prevent water buildup

True

True or False: Feedwater heaters are heated by extraction steam.

True

True or False: Generators are machines that convert mechanical energy to electrical energy.

True

True or False: In a fossil fuel plant, pressure and thermal energy in steam are converted to mechanical energy in a turbine.

True

True or False: Most generating units have specific limits on rate of change for load

True

True or False: Once combustion starts, it is usually maintained by the burning fuel, and the ignitors are turned off.

True

True or False: Some burners can be tilted to allow for raising and lowering the flame to increase and decrease steam temperature

True

True or False: Some variation in lube oil temperature is normal, but rapid temperature changes usually indicates trouble.

True

True or False: Two of the major jobs that a boiler drum performs are receiving feedwater for the boiler and collecting steam from the boiler before it goes to the turbine.

True

True or false: In order for oil to mix with air, it must first be atomized.

True

True or false: When steam first enters a condenser, it takes up a lot of space, but, as it condenses, the space it takes up is dramatically reduced.

True

Cross-compound turbine

Turbine sections mounted on different shafts

Forced oil lubrication systems

Uses a pump to continuously circulate oil through the bearings

What controls air flow to the burners?

Vanes or dampers on the FD fans or by varying the speed of the fans

Vents vs drains

Vents are on top of equipment Drains are on bottoms of components

Instrument for measuring vibrations.

Vibrometer

A hydroelectric plant uses mechanical energy from ____ to turn a generator

Water

What is natural circulation?

Water moving from lower header up through waterwall to drum because cold water weighs more than hot water or steam.

Where is the steam produced?

Waterwalls

The electricity that a power plant produces is measured in

Watts

Turning Gear Pump

When AC power is available after shutdown and turbine is placed on turning gear.

Why are intercept and reheat stop valves necessary?

When Turbine stop and control vavles close, there is still a lot of steam in the reheater that could flow to the turbine.

The term "excess air" refers to the amount of air going to the ____________.

Windbox

The pairing of one diaphragm and one or two wheels is called

a stage

Two basic methods of removing oil from a barrel

barrel pump and a spigot

Excess Air

extra air supplied to the windbox by FD fans

Term for the relative amounts of fuel and air in the furnace

fuel/air ratio

Continul fluctuation of turbine speed while the controls ystem searches for the proper speed is an undesirable conidion called

hunting

2 responsibilities of operator

monitor info being dispatched and stay alert for potential problems

Drip Feed lubricator

oil slowly drips into a bearing

When are control valves open or closes

partially open normally

Definition of bearing surface

parts of a bearing that come into contact with a moving part

Where are scrubbers located?

path of flue gas between boiler and stacks

The reset feature on a turbine control oil system does what?

prevents hunting

instrument to measure bearing temperatures

pyrometer

2 types of air preheaters

regenerative and tubular

thrust bearing

resist axial thrust

Rolling contact thrust bearing

rotating and stationary rings are parallel to each other instead of wrapped around each other

A governor controls a _____ valve, which regulates the amount of oil going to hydraulic actuators

servo

Vapor extractor

small fan or blower on top of reservoir to remove oil vapor and other combustible gases

True or false: a trip circuit shuts down the turbine by bleeding all the oill off the hydraulic actuator

true