3E Common Exam Questions Flashcards
What is a blowdown tank and what are the piping connection requirements
A blowdown tank is used to collect blowdown water and temper it before going out the drain. 1” MINIMUM 21/2” MAXIMUM BLOWDOWN TANK VENT SHOULD BE OF SUFFICIENT SIZE TO RELEASE FLASHING STEAM. MAWP BLOWDOWN TANK: 50 PSI BLOWDOWN TANK DISCHARGE LINE:NPS 2” MINIMUM SIZE GAUGE GLASS PRESSURE GAUGE THERMOMETER
What is specific heat
Specific heat is the heat required to raise one pound of any substance 1℉
What is a pressure vessel
A PRESSURE VESSEL IS A CLOSED VESSEL IN WHICH THE SOURCE OF PRESSURE IS EXTERNAL TO ITSELF. ANY PRESSURE VESSEL NOT IDENTIFIED AS A BOILER
How do you plug a firetube/watertube
UP TO 10% OF THE TUBES CAN BE PLUGGED BEFORE REPLACEMENT IS REQUIRED.
IDENTIFY LEAKING TUBE(S) AT BOTH ENDS AND MARK.
(THIS STEP MAY REQUIRE A SQUEEZE/HYDRO)
DRAIN BOILER BELOW LEAKS. LOCK OUT/TAG OUT BOILER.
HAVE CORRECT WEDGE SHAPED TUBE PLUGS ON HAND.
APPLY LOCTITE OR PIPE DOPE TO TUBE PLUG.
USING SMALL SLEDGE HAMMER DRIVE PLUG INTO TUBE.
SOLID TUBE PLUGS WILL BE DIFFICULT TO REMOVE LATER ON.
PERFORM SQUEEZE TO ASSURE TIGHTNESS.
How do you replace a boiler tube
REPLACEMENT OF BOILER TUBES IS BEST LEFT TO PROFESSIONALS!
REMOVE DAMAGED/LEAKING TUBE.
CLEAN UP TUBE HOLES WHICH MAY BE DAMAGED IN THE REMOVAL PROCESS.
INSERT NEW TUBE.
EXPAND TUBE INTO TUBE HOLE (ROLLING) USING TUBE EXPANDER.
(IT IS POSSIBLE TO OVEREXPAND TUBES - USE CAUTION)
BEAD OVER TUBE ENDS (FIRETUBE)
FLARE TUBE ENDS (WATERTUBE)
CONDUCT SQUEEZE TO DETERMINE TIGHTNESS.
Hydrostatic pressure test
A FULL HYDROSTATIC PRESSURE TEST MUST ONLY BE PERFORMED UNDER THE DIRECTION OF THE AUTHORIZED INSPECTOR.
(A BOILER SQUEEZE AT/BELOW NORMAL OPERATING PRESSURE CAN BE PERFORMED ANYTIME BY PLANT OPERATORS)
REMOVE/GAG SAFETY VALVES
REMOVE/ISOLATE APPURTENANCES UNABLE TO WITHSTAND TEST PRESSURE
FILL BOILER UNTIL WATER COMES OUT BOILER VENT
(WATER TEMP. 70℉ MINIMUM 120℉ MAXIMUM)
RAISE PRESSURE WITH FEEDPUMP. USE HAND PUMP FOR CLOSE CONTROL OF PRESSURE
HOLD TEST PRESSURE PER INSTRUCTIONS OF AUTHORIZED INSPECTOR
USUALLY THE PRESSURE IS REDUCED TO MAWP FOR CLOSE VISUAL INSPECTION
ACCUMULATION TEST
AN ACCUMULATION TEST IS NOT NORMALLY PERFORMED BY PLANT OPERATORS (NOT DONE 600 PSI AND ABOVE)
AN ACCUMULATION TEST IS NOT PERFORMED ON BOILERS EQUIPPED WITH SUPERHEATERS, REHEATERS OR HIGH TEMP. HW BOILERS
ISOLATE BOILER AT MAIN STEAM STOP VALVE(S)
FIRE BOILER (INCREASE FIRING RATE TO MAXIMUM AS PRESSURE INCREASES)
CONTINUE TO FIRE UNTIL SAFETY VALVE(S) LIFT
OBSERVE HIGHEST PRESSURE OBTAINED
BOILER PRESSURE SHOULD NOT EXCEED MAWP + 6%
What are the benefits of water walls
WATERWALL HEATING SURFACE IS TAKEN AS “EXTENDED SURFACE”
THE PORTION EXPOSED TO THE PRODUCTS OF COMBUSTION
BENEFITS INCREASE IN BOILER HEATING SURFACE REDUCED REFRACTORY AREA LESS AIR INFILTRATION IMPROVED CIRCULATION INCREASE IN BOILER EFFICIENCY
ECONOMIZER/AIR-PREHEATER EFFICIENCY GAIN
ECONOMIZER
A 1% GAIN IN EFFICIENCY
FOR EACH 10℉ RISE IN
FEEDWATER TEMPERATURE
GAIN CAN BE 1 – 15%
GAIN IN EFFICIENCY DECREASES
AS TEMPERATURE INCREASES
AIR-PREHEATER
A 1% GAIN IN EFFICIENCY FOR EACH 40℉ RISE IN
COMBUSTION AIR TEMPERATURE
GAIN CAN BE 1 – 10%
GAIN IN EFFICIENCY DECREASES
AS TEMPERATURE INCREASES
What can you do with your 3rd’s
Third class, to have charge of and operate a boiler or boilers not exceeding, in the aggregate, 150 horsepower when solid fuel is burned or not exceeding, in the aggregate, 500 horsepower when steam is generated by the use of liquid or gaseous fuel, electric or atomic energy or any other source of heat and an engine or engines not exceeding 50 horsepower each or to operate a second class plant under the engineer in direct charge thereof.
Define potential and kinetic energy
Potential is energy pocessed by reason of position or deformation, kinetic is energy pocessed by motion
What are the 3 types of heat transfer
Radiation - heat transfer by light waves without a material carrier
convection - heat transferred by currents in a fluid
convection - heat transferred molecule to molecule
How to determine engine hp
P.L.A.N. 33,000 P = MEAN EFFECTIVE PRESSURE L = LENGTH OF STROKE A = AREA OF HP PISTON N = NUMBER OF STROKES/MIN. SIMPLE ENGINE = 40 PSI, CONDENSING ENGINE = 50 PSI COMPOUND ENGINE = 70 PSI VARIABLE SPEED USE AVERAGE SPEED
How do we determine turbine hp
BASED ON EXTERNAL DIAMETER OF STEAM SUPPLY PIPE LESS THAN 1 ¾ INCHES = < 9 HP > 1 ¾ - 3 ½ INCHES = 50 HP > 3 ½ - 5 INCHES = 150 HP > 5 INCHES = UNLIMITED HP
How many btu’s in a mechanical hp hour
1,980,000 / 778 = 2,545
How many btu’s in a kilowatt hour
2545 /.746 = 3,413
BTU’ Input
33,475 /.80 = 41,840
ASSUMES 80% BOILER EFFICIENCY
One kilowatt
1.34 HP (1000/746)
ONE BTU
778 FT/LBS. OF WORK
JOULE’S EQUIVALENT
Define boiler heating surface
The parts of the boiler with water on one side (wet steam) and products of combustion on the other. measured on the hot gas side always expressed as square feet
What are the safety valve requirements as to the number and capacity of a boiler that contains 625 sq ft of heating surface and is operating at 125 lbs pressure
2 safety valves required over 500sq ft of heating surface or for an electric boiler 1,100 kw. One or more pressure relief valves on the boiler proper shall be set at or below the maximum allowable working pressure (except as noted in PG-67.4).If additional valves are used the highest pressure setting shall not exceed the maximum allowable working pres- sure by more than 3%. The complete range of pressure settings of all the saturated‐steam pressure relief valves
on a boiler shall not exceed 10% of the highest pressure to which any valve is set.
How is the heating value of fuel determined
Ultimate analysis, (lab + dulongs formula)
Bomb calorimeter
Proximate analysis + graph
When are 2 or more safety valves required on a boiler
Over 500sq ft of heating surface or for an electric boiler 1,100 kw. One or more pressure relief valves on the boiler proper shall be set at or below the maximum allowable working pressure (except as noted in PG-67.4).If additional valves are used the highest pressure setting shall not exceed the maximum allowable working pres- sure by more than 3%. The complete range of pressure settings of all the saturated‐steam pressure relief valves
on a boiler shall not exceed 10% of the highest pressure to which any valve is set.
When using 2 safety valves how are the safety valves mounted and how are they set
When two or more pressure relief valves are used on a boiler, they may be mounted either separately or as twin valves made by placing individual valves on Y‐bases, or duplex valves having two valves in the same body casing. Twin valves made by placing individual valves on Y‐bases, or duplex valves having two valves in the same body, shall be of approximately equal capacity.
When not more than two valves of different sizes are mounted singly the relieving capacity of the smaller valve shall be not less than 50% of that of the larger valve.
What is a safety valve
An automatic pressure relieving device actuated by the static pressure upstream of the valve and characterized by a full opening pop action. Used for Gas or Vapor Service.
What is a safety relief valve
Used where a gas/vapor or liquid service. (Example: Economizers)
How do we determine minimum safety valve relieving capacity requirements
4 ways
Table pg-70, often referred as appendix table a-44
Accumulation test
Maximum fuel burned formula (code formula)
Maximum evaporative capacity by measuring the feedwater
How would you order a new safety valve
Take the information off of the old one
How would you start a boiler using #6 fuel oil
IT MAY NESSECARY TO RECIRCULATE OIL TO GET PROPER TEMP.
(OIL SHOULD BE 180-200℉)
CHECK LINE UP OF GAS (PILOT) VALVES.
LINE UP ATOMIZING STEAM/AIR. (DRAIN CONDENSATE FROM LINES)
ESTABLISH DRUM LEVEL. ALLOW FOR SWELL.
PURGE FURNACE BEFORE LIGHT-OFF ATTEMPT.
WITH OIL AT PROPER TEMP. AND PRESSURE ATTEMPT LIGHT-OFF
IF BURNER DOES NOT LIGHT, ISOLATE MAIN FUEL, PURGE AND TRY AGAIN.
ONCE BURNER IGNITES, ADJUST AIR DAMPERS.
Describe cold end corrosion
Corrosion that occurs in the low temperature components of a boiler such as economizers and air pre heaters, induced draft fans, and flues
What causes cold end corrosion
Caused when the temperature of the metal drops below the sulfuric acid dewpoint of the flue gas
How would you conduct a Bacharach fyrite test
THE BACHARACH FYRITE TEST KIT INCLUDES A CLOSED CYLINDER CONTAINING REAGENT AND TUBING TO TRANSFER FLUE GAS SAMPLE FROM BREECHING/STACK TO CLOSED CYLINDER.
ZERO OUT GRADUATED SCALE ON CYLINDER.
CONNECT TUBING FROM BREECHING/STACK TO CYLINDER.
PUMP BULB TO TRANSFER FLUE GAS TO CYLINDER.
(FOLLOW GUIDELINES – THE BULB MAY HAVE TO BE SQUEEZED 15-20 TIMES)
4) REAGENT IN CYLINDER ABSORBS SPECIFIC GAS (O2/CO2). SHAKE WELL.
5) USING SLIDE RULE, ENTER FLUE GAS TEMP. AND PUT POINTER AT SPECIFIC READING.
6) READ COMBUSTION EFFICIENCY IN WINDOW
How do we determine combustion efficiency
Boiler heat balance,
Portable analyzers, ORSAT AND BACHARACH FYRITE, Electronic analyzers such as a continuous emissions monitoring (CEM)
What are the losses in a boiler
Heat loss out the stack , 10% Water vapor (from burning hydrogen) Unburned fuel in the ash Incomplete combustion Moisture in the fuel Moisture in the combustion air Radiation
What is electrolosis
A PROCESS BY WHICH ELECTRIC CURRENT IS PASSED THRU A SUBSTANCE TO EFFECT A CHEMICAL CHANGE. ELECTROLYSIS OF AN AQUEOUS SOLUTION OF SODIUM CHLORIDE YIELDS SODIUM HYDROXIDE AND CHLORINE GAS. HYDROGEN CAN BE SEPARATED FROM OXYGEN BY THE ELECTROLYSIS OF WATER
What are some common tests on feedwater in power plants
P or m alkalinity Conductivity PO4 residual O2 residual PH Hardness
For high purity plants ph Phosphate Silica Coinductivity Cation/Specific conductivity
Why do we treat feedwater
Prevent sludge from depositing on boiler
surfaces
Prevent scale from forming on boiler surfaces
Prevent corrosion of boiler metal
Prevent carry over with the steam leaving the boiler
What are Chlorides
CHLORIDE IONS (CHLORIDES) ARE MINERAL SALTS THAT CAN CAUSE SCALE ON BOILER SURFACES AND ARE USED TO MONITOR CYCLES OF CONCENTRATION AND CONTROL BLOWDOWN RATES.
THE CHLORIDE TEST IS MOST CONVENIENTLY DONE ON THE SAME SAMPLE AS THE P-ALKALINITY TEST DONE ON BOILER WATER.
(THE CHLORIDE TEST WILL NOT WORK ON HIGH pH BOILER WATER)
What is a volute pump
A CENTRIFUGAL PUMP THAT HAS AN INCREASED AREA OF THE PUMP CASING THAT CONVERTS HIGH VELOCITY TO PRESSURE.
What is required NPSH and Available NPSH
REQUIRED NPSH (NPSHR) IS SET BY THE PUMP MANUFACTURER AND IS THE DISTANCE (HEAD) REQUIRED TO PREVENT CAVITATION. AVAILABLE NPSH (NPSH3) TAKES INTO ACCOUNT VALVES, FITTINGS, STRAINERS, ETC. (FRICTION) THAT WILL REDUCE NPSH.
What are wearing rings
Usually sit on both sides of the impeller, prevents leakage around it and protects the pump from damage by targeting the wearing rings
Lantern rings
Water is directed over the lantern rings and it is directed to the packing to keep the packing cool
How many BTU’s are in a boiler horsepower? A kilowatt hour?
There are 33475 BTU’S in a horsepower and 3413 BTU’S in a kilowatt hour
What is cold end corrosion
The corrosion that develops in the low temperature components of a boiler such as economizers, air preheaters, induced draft fans, scrubbers and flues. Cold end corrosion occurs when the temperature of the metal drops below the sulfuric acid dew point. The temperature at which sulfuric acid will first condense varies from between 240 and 330 degrees F. Cold end corrosion is prevented by monitoring the temperature of the flue gas to ensure that exiting flue gas temp is above 330 degrees F
Explain why it is necessary to treat boiler feedwater
Prevent sludge, prevent scale, prevent corrosion, and prevent carryover
Name four (4) things you would find on a boiler stamp.
Serial Number
BTU Input
Tube Size
Heating Surface
Explain the five (5) headings on the steam tables
- Absolute Pressure
- Temperature
- Specific Volume, The amount of space the material will occupy in cubic feet per pound
- Enthalpy, Total heat available for work measured in BTU’S /LB
- Entropy, Total heat unavailable for work
A boiler has 3 inch diameter tube holes pitched 5.25 inches apart. What is the ligament efficiency
Ligament efficiency = P-D/P
5.25-3/5.25 = .428
Explain what happens to steam pressure, volume and velocity thru a steam turbine Curtis Stage
As steam passes through the first stage nozzle there is a large pressure drop increasing the volume and velocity of the steam. The high velocity steam is directed to the first row of moving blades giving up some of that velocity to rotate the rotor. The steam then travels through a redirecting blade which sends the steam into a second set of moving blades
What is the purpose of a thrust bearing? Name two types of thrust bearings
Used to absorb axial movement of the rotor, Two types of thrust bearings are the Kingsbury and the Tapered Land bearing
What is the definition of latent heat
Latent heat is heat added to a substance that causes a change of state without a corresponding change in temperature
What is erosion? What is corrosion?
Erosion is the wearing away of metal due to mechanical forces and corrosion is the wasting away of metal from chemical forces
Explain the steps necessary to start a non-condensing steam turbine.
- Make ready driven piece of equipment (feed pump, fan, compressor, etc)
- Check lubrication on turbine, check open turbine casing drains, open turbine exhaust valve fully wide
- Crack open throttle valve and roll the turbine to 200 – 300 RPM and trip turbine
- Relatch turbine and roll up to 500RPM and sound out.
- Continue roll up until governor takes over, you are now at full speed/no load
- Put driven piece of equipment in service
- Close turbine casing drains
Find the heating surface of a water tube 4” (inches) in diameter and 16’ (feet) long
Outside diameter in feet (always measured on the hot gas side) X 3.14 X length of tube X number of tubes
4’’/12 X 3.14 X 16’X1 = 16.74 cu ft
Convert the following fractions to decimal: 1/4 23/28 7/16
¼ = .250
23/28 = .821
7/16 = .437
Explain the operation of a volute centrifugal pump
As the impeller of a centrifugal pump rotates water enters the center of the impeller and is thrown outward by centrifugal force. The water leaves the impeller at high velocity and is converted to pressure in the volute section of the pump
How do you conduct a hydrostatic test on a boiler
Note: A full hydrostatic pressure test must only be
performed under the direction of the authorized inspector
- Remove or gag safety valves if removed install blank or blind flange
- Remove or isolate appurtenances unable to withstand test pressure such as gage glass
- Shut main steam stop and blowdown valves and loto boiler
- Fill boiler until water comes out the boiler vent. Min temp 70F, Maximum temp 120F in no case can the temperature be lower than atmospheric
- Raise pressure with hand pump for close control of pressure. Test pressure should be at 1.5 times the MAWP
- Hold pressure per instructions of authorized inspector
- Usually the pressure is reduced to MAWP for close visual inspection
Reference ASME Code section #7 for guidance
A boiler has two (2) individually mounted safety valves. What are the sizing requirements
The relieving capacity of the smaller valve shall not be less than 50% of that of the larger valve
What is CO2, SO2, N2, O2, and NH3
CO2, Carbon Dioxide SO2, Sulphur Dioxide N2, Nitrogen O2, Oxygen NH3, Ammonia
What is meant by “critical speed” in a steam turbine
Certain speeds that cause excessive vibration due to harmonic imbalance. Pass through critical speeds quickly by increasing the ramp rate on the turbine
Name three (3) ways to determine boiler efficiency
- Boiler heat balance
- Portable analyzers, ORSAT and BACHARACH FYRITE
- Electronic Analyzers, CEM’S (Continuous Emissions Monitoring)
Explain the operation of a centrifugal mechanical governor
With the turbine at rest the flyballs will be at the inner most position causing the valve to be wide open. As the turbine comes up to speed centrifugal force will cause the flyballs to move towards the outer position, compressing the spring and causing the valve to move towards the closed position.
- What is deaeration?
The removal of oxygen in feedwater by mechanical seperation / chemical addition using sodium sulfite
*Start a small non condensing turbine.
- Make ready driven piece of equipment (feed pump, fan, compressor, etc)
- Check lubrication on turbine, check open turbine casing drains, open turbine exhaust valve fully wide
- Crack open throttle valve and roll the turbine to 200 – 300 RPM and trip turbine
- Relatch turbine and roll up to 500RPM and sound out.
- Continue roll up until governor takes over, you are now at full speed/no load
- Put driven piece of equipment in service
- Close turbine casing drains
What is the board of boiler rules
A group within the DFS that deals with the construction, installation and inspection of boilers. Meet infrequently every year
Who is on the Board of boiler rules
Ed Kawa, Chief of boiler inspections, and representatives of operating engineers, boiler manufacturers, insurers, and users of boilers
A water tube boiler with 66 tubes 3” O.D. and 18’ long. Find the heating surface.
3/12x3.14x18x66=
Why is there a pressure drop in a Curtis stage turbine?
As steam passes through the nozzles there is a pressure drop increasing the velocity of the steam, the steam is directed through the moving blades to turn the rotor.
How is oxygen removed mechanically
Oxygen is removed mechanically by a deaerator. As condensate and make up water enters the top of deaerator its directed over a series of trays, steam makes direct contact with the water which liberates greater than 99% of the oxygen non condensable gases which exits out the vent
Removes o2 and non-condensable gases
Stores feedwater
Heats feedwater
Low pressure area for chemical addition
Provides proper NPSH to boiler feed pumps to prevent cavitation
What is pitting? How can you tell if the pitting is active or inactive?
Pitting is the formation of small holes in the surface of the boiler plates, caused by oxygen and poor circulation or an acidic condition with the boiler water.
Shiny metal surface indicates active pitting, Inactive pitting has a layer of magnetite (orange brownish color)
What is cavitation? -or- What is net positive suction head available and required
Cavitation is defined as the sudden formation and collapse of low pressure bubbles in the pump due to mechanical forces, NPSH is the minimum NPSH required to prevent cavitation set by the manufacturer, Available NPSH is actual NPSH taking losses due to piping
Name 7 things you will find on a Mollier Chart
Lines of constant Enthalpy Lines of constant Entropy Lines of constant pressure Lines of constant quality Lines of constant temperature Saturation line Degree of superheat Standard atmosphere
What is the coefficient of expansion for carbon steel
.00000734 in/ft for 1 deg F
What is kinetic energy? Potential energy
Kinetic energy is the energy that a body has due to its motion, potential energy is energy posessed by reason of position or deformation
Perform an accumulation test in detail
Test should not be performed without notice given to the inspector.
Shut all steam discharge outlets from the boiler and force the fires to the maximum.
The safety valves shall pop and relieve all steam generated without the steam pressure rising 6% above the highest set valve pressure but in no case more than 6% above the MAWP.
This test is not to be done on a boiler with a superheater or reheater
Regarding superheaters, what is radiant pass and convection pass. What loads do they operate best at
Radiant superheaters absorb heat from the direct radiant heat from the flames, Convection superheaters absorb heat from the products of combustion passing over it, located somewhere in the gas passage before the stack. Radiant superheaters work best at low loads, convection superheaters work best at higher loads
How many btu’s in a horsepower hour? Kilowatt Hr
2545 btu’s in hp hr and 3413 in KW hr
What can you do with a third class engineers license
Have charge of and operate a boiler or boilers not exceeding in the aggregate 150 hp when solid fuel is burned or not exceeding in the aggregate 500 hp when steam is generated by the use of liquid or gaseous fuel, electric or atomic energy or any other source of heat and an engine or engines not exceeding 50 hp each or to operate a 2nd class plant under the engineer in direct charge thereof
License requirements
Operators are responsible for the boilers during their shift under the engineer in charge.
Completes and signs the operators log book on a daily basis, records made available to the district inspector upon request
Requirements for reportable accidents
Owner / user or engineer in charge of steam boilers or engines shall notify the Mass emergency management agency within 24 hours of the event
Requirements for accepting / leaving a position
All engineers or fireman in charge of steam boilers or engines shall notify the dfs within 7 days of the location of the boilers and / or engines of which he is in charge. When accepting a position as engineer or fireman in charge the dfs need to be notified withinRequirements for an engineer in charege 7 days
Requirements for engineer in charge
Make daily visits to the plant and leave daily written instructions to the operating personnel made available upon request to the district inspector
Review the operators log book daily and perform his duties at the facilities five working days per week
Welded repair info / requirements
All welded repairs require documentation. An R1 form must be completed by contractor and the engineer in charge has to make sure everyone that is supposed to get a copy gets one, (dfs).
An R1 Form is for a welded repair
An R2 Form is for an alteration
Mechanical repair to boiler external piping systems. What are requirements
Completed under the supervision of the engineer in charge, engineer in charge needs to fill out a form obtained from the dfs recording all work performed. records are kept on file at the location of the boiler and be accessible to the division and authorized inspectors. Repairs need to meet original code of construction. Completed forms and attachments submitted to dfs within 7 days of completion of repairs
Nox limits
20 ppm at alnylam, state limit is 30 ppm for nrwer boilers ( constructed after 2000) 70 ppm for older boilers. Mass law supersedes federal law in environmental matters
Opacity limits
In no case shall exceed 20% opacity for a period or aggregate period of time in excess of 2 minutes during any 1 hour period provided that at no time during said 2 minutes shall the opacity exceed 40%
Visible emissions (old standard), CMR-310 SEC 7
1 on chart for a period or aggregate period of time in excess of 6 minutes during any 1 hour period provided that at no time during said 6 minutes shall the shade density or appearance be =/> no 2 on chart (ringleman scale)
What is a third class plant
Up to 150 bhp when solid fuel is burned, up to 500hp when liquid or gaseous fuel is burned, operate engines none of which=h exceed 50 hp
What is a 2nd class plant
Unlimited bhp and engine none of which shall exceed 150 hp
What is the largest engine a third engineer can operate
Up to 150 hp under the engineer in charge, can be in charge of a 5o hp engine or turbine
What are the three types of boiler inspectors
Ins company inspectors
Shop inspectors (work for manufacturer)
DFS inspectors
If in charge of a plant can you stand watch 5 miles away
Yes, you can only be in charge of 1 plant but can stand watch for as many as you can get to, no set limit to being an operator
What is the board of boiler rules
A group within the dfs that deals with the construction, installation and inspection of boilers, they meet infrequently every year
Who is on the board of boiler rules
Ed Kawa, chief of boiler inspectors
Representatives of operating engineers
Boiler manufacturers and insurers
users of boilers
Periodic attendance, non continuous attendance , continuous attendance
Periodic boilers operating at 9 - 250 hp in the aggregate
non continuous attendance, boilers operating at 251 - 500 hp in the aggregate
continuous attendance, boiler operating over 501 hp
Main difference between non continuous and periodic
Non continuous requires remote monitoring equipment to alert the operator
Can a first fireman operate a steam turbine
Yes up to a 50 hp turbine
HP of turbine in a first class plant
Unlimited hp
4 reasons why you would use condensers
reduce back pressure on the steam turbine which increases the heat (enthalpy) drop through the turbine (more btu’s available to do work)
reclaim high quality condensate
condensate is dearated in the condenser
All steam drains are routed to the condenser
Describe a surface condenser
Use water from oceans, rivers, streams as the cooling medium. they are shell and tube heat exchangers with the water going thru the tubes and the condensing steam surrounds the tubes, condensate collects in a hot well and is picked up by condensate pumps. Circulating water pumps pump water from the condenser to cooling towers where heat is rejected to atmosphere. Inlet and outlet temperature is important on single pass surface condensers due to discharge temperature limits. In mass the limit is 98 deg F
What is ph, if ph goes from 10 to 11 what does this mean?
PH is the logarithm of the reciprocal of the hydrogen ion concentration. If ph goes from 10 to 11 it becomes 10 times more basic
What are some of the problems with surface condensers
Tubes plugging with material
Name 3 types of surface condensers
Single pass
Two pass, can have higher discharge temperatures using cooling towers to discharge to atmosphere, (rejects heat to atmosphere) (does not use seawater)
Split/divided condenser, allows for cleaning one side while keeping unit on line. allows for cleaning while keeping the turbine online
What is laning in regards to surface condensers
The omission of whole sections of condenser tubes force steam deeper into the shell so the tubes do more work
Name components of a surface condenser
Shell Exhaust nozzle (hood) Expansion joint Impingement plate (reduce erosion) Water boxes (lined to reduce erosion) Tubes Tube sheets Steady Plates Hotwell
What material are condenser tubes made of
For freshwater the tubes are constructed of alloys of copper, aluminum, admiralty metals, and/or stainless steel
For seawater, titanium or stainless steel
Name some reasons why condenser tubes are bowed
Allow for drainage
Reduce vibration
reduce tube erosion from rubbing on steady plates
How are condenser tubes installed
They are installed using a combination of packing and ferrules and are usually flared at the inlet. Floating tube sheets are also used to allow for expansion and contraction of the tubes
How are condensers supported
Condensers and turbine are rigidly supported with expansion joint between them
Hung from the turbine (smaller units), expansion is downward. all connections have expansion joints
Rigid connection with condenser supported by springs. All connections have expansion joints
What typical auxiliary equipment would you find on a condenser
Travelling screen
Circulating water pump (use cutlass bearings)
Water box priming system, used on ocean systems, pulls air and non condensable gasses out of the condenser using a vacuum pump
What happens when you have a sudden reduction in steam in a condenser
Causes a vacuum
What prevents a vacuum from forming in a condenser
Air removal equipment
- Vacuum pump and steam jet air ejectors are used to maintain vacuum. advantages of steam jet air ejectors over vacuum pumps are they are cheaper to operate (not electrically driven and nothing is wasted, virtually all steam returned to process
Explain how a steam jet air ejector works
Steam jet air ejectors work on the principle that steam passing through a restricted area (nozzle) will experience a velocity increase (pressure drop) that will create a low pressure area across the suction tube drawing non condensable gasses into the diffuser section which converts velocity to pressure
why do we use a loop seal
A loop seal is required to return recovered condensate from the inter/after condensers to the hotwell which is at a higher pressure. A leg (drip leg) is provided to prevent the condensate from the hotwell to be drawn into the inter/after condenser. You need a loop seal to create a higher pressure to return the condensate from the inter / after condenser to the hotwell. The height of the loop seal will provide sufficient pressure (usually between 6 - 9 feet) to prevent flow from the hotwell to the inter/after condenser. *** not all plants direct condensate from the after condenser to the hotwell
Why use vacuum pump in condensers and what are the downsides vs steam jet air ejectors
Vacuum pumps are used to pull air and non condensable gasses from the condenser, the downside of using vacuum pumps are that they require electricity ( costly to operate)
What are some water side (tubes) problems with condensers..
Issues with condensers causes an increase in back presssure in the turbine
Water side leaks contaminate condensate
Tube leaks (difficult to locate)
-temporarily plug tubes with sawdust
- condenser hydro is often used with dye to pinpoint leaking tubes
- Gas (freon) is used by pulling vacuum and checking sections of tubes and placing a gas analyzer at air injector outlet
Dirty tubes
travelling screen dirty
circulating water flow issues
high water level in hotwell
problems with water box priming system
Name some problems with condensers on the shell side
Vacuum breaker leaks Expansion joint leaks loop seal lost problems with air removal equipment valve packing leaks pump seral leaks
How would you respond to rising back pressure in a condenser
Reduce load on the machine
put extra air removal equipment into service
check seal system (proper pressure)
check circulating pumps
check temperature rise across the condenser
Check water level (water box priming )
What do they mean by condensate depression
Under cooling / sub cooling
What is macro fouling in a condenser
Debris on tube sheet causing a decrease of water flow and temperature rise in the condenser
What is micro fouling
Debris in condenser tubes resulting in a decreased temperature rise across the condenser
What is hogging
Allowing steam and non condensable gasses to vent to atmosphere to reduce the time required to pull vacuum on condenser
What is the purpose of an impingement plate on a condenser.
As steam reaches the end of the turbine water droplets form, to remove them impingement plates are used to protect the tubes from high velocity water droplets hitting the tubes, impingement plate need to be replaced often
Where would you use an air cooled condenser
Air cooled condensers are used primarily where water availability is a problem, an air cooled condenser can be used anywhere and are frequently used to satisfy 0 discharge requirements
How does a direct acting air cooled condenser work
Functions the same way as a radiator, steam exhausted from a turbine is directed into the tube banks with fans directing cool air over the tubes, the condensed steam is collected in a tank and condensate pumps return the condensate to the system
What are some disadvantages of using an air cooled condenser
Major disadvantage is the loss in turbine efficiency due to higher backpressures which is dependent on ambient air temperatures
Air cooled condensers use a lot of electricity
What type of tubes are used in an air cooled condenser
Finned tubes to optimize cooling ability to condense steam
What is a direct acting air cooled system
It is when exhaust from the turbine goes directly to the acc, the steam gets condensed and is returned to the system
What is a indirect dry cooling system (cooling towers)
Classified as Natural draft (hyperbolic), forced draft, and induced draft
- Natural draft uses a hyperbolic tower that creates air flow due to the venturi effect of the design with the height of the tower determining the amount of air flow. The advantage of this system is no fans are used
- Forced draft towers use a fan located at the base of the tower forcing air up through the tower
- induced draft towers use a fan on top of the tower that pulls air into and through the tower
What are some problems associated with cooling towers
- evaporation
- Drift, (water falls outside the basin)
- blowdown (cooling towers require a lot of blowdown)
Losses can be substantial with 5 - 15% make up for each loss, while it is rare to see 45% loss, make up in cooling towers between 25 - 30% is quite common
Formula for calculating cooling tower requirement
Large volumes of water are required to condense steam, the formula is Q= H-(Tc-32)/T2 - T1 Q= quantity of water H= Enthalpy of exhaust steam Tc= Temperature of the condensate T2=Temperature of the leaving water T1= Temperature of the entering water
Steam exhausts to a condenser @ 1100 btus/lb, the hotwell temperature is 100deg F and the entering cooling water is 80 deg F with a 10 deg rise across the condenser. How much cooling water is required
Q= H-(Tc-32)/T2 - T1
1100-(100-32)/90-80
1032/10 = 103.2 LBS OF WATER PER LB OF STEAM
How do you start a surface condenser
Open suction valve(s) and start circulating pump
Open discharge valve(s)
Close all condensate drains/vents
Start water box priming system
Place air removal equipment in operation, put seals on turbine, pull vacuum
Operate condensate pump as needed during startup, roll turbine
As load increases remove extra air removal equipment
Heating systems
1 pipe system are when the steam supply and condensate return all happens in 1 pipe, more economical to build than 2 pipe systems. downside is water hammer
2 pipe systems are when the steam supply and condensate returns are in 2 separate pipes, most plants today use 2 pipe systems
2 types of return systems
dry return system condensate and airin condensate return line
wet return system condensate lines below the normal water level, they stay flooded and corrosion is reduced
Hartford loop (loop seal) minimizes low water level conditions in home heating boilers. it allows for the return of low pressure condensate to a boiler at a higher pressure without the use of a pump
Loop seals today are seen in steam jet air ejectors which pull air and non condensable gasses out of the condensers. Pressure at the steam jet air ejector is lower than pressure in the hotwell of the condenser so a loop seal is required to deliver low pressure condensate from the steam jet air ejector back to the hotwell
How is a vacuum prevented in a deaerator
By using a vacuum breaker
Explain how a deaerator works
Condensate returns to the top of DA and pass through nozzles which break up condensate to a fine spray which cascades over baffles. Steam entering from the bottom scrub the O2 and non condensable gasses before going out the vent. The condensate then drops into the storage area of the DA providing positive suction head to the boiler feed pumps
Why is there a pressure regulator on the steam supply to the DA
To maintain the pressure in the DA, typically 5 - 10 psi and heat the feedwater.
What information is found on the boiler stamp and where is it located
- Manufacturers serial number
- Certified by _______Name of manufacturer
- MAWP
- Heating surface
- Year built
- Fire tube the stamping is located on either side of the the shell near the NOWL and as near as practical to the front tube sheet
- On water tube boilers the stamping is on a head of the steam drum near and above the manhole.
- Superheaters, Economizers, and waterwalls have their own boiler stampings
How is moisture separated in a fire tube boiler? In a water tube boiler?
Moisture is separated by a dry pipe in fire tube boilers and cyclone separators, baffle plates , and scrubbers in water tube boilers
Where in the boiler are radiant and convection type superheaters located
Radiant superheaters are located in the furnace section of the boiler in direct line of sight with the boiler, convection type super heaters are located in the back gas passages that doesn’t see the fire
At what loads do radiant and convection type superheaters perform best
Radiant super heaters perform best at low loads while convection superheaters perform best at high loads, these two types of superheaters are frequently used together to get a more uniform temperature profile
Relieving capacity of safety valves on superheaters
Super heater safety valves can account for up to 25% of the boiler and is always set at the lowest pressure to assure steam flow through it
How do you prevent overheating of super heater during start up
Start up super heater at low fire, when you get steam out the vent or super heater drains you can increase load
What are the benefits of superheated steam
No moisture
More BTU’S per lb of steam
Travels longer distances without condensation
How do we control super heat temperature
- Attemperators (desuperheaters) spray water into the steam, water evaporates and lowers steam temp
- Tilting burners
- Bypass dampers
- Using a combination of both radiant and convection type superheaters
- Flue gas recirculation
What is the overall gain in using super heaters
2 - 5 %
What are the benefits to the turbine when using superheated steam
Less erosion on turbine blades and less steam flow due to higher enthalpy
What does high and low CO2 indicate
High CO2 indicates high combustion efficiency and low CO2 indicates low combustion efficiency
At which temperature will sulfuric acid first condense (acid dewpoint)
240 - 330 deg F
Explain cold end corrosion
Temperature of the metal in economizers , air preheaters induced draft fans, may drop below the sulfuric acid dewpoint. It is important to keep these surfaces at temps than the acid dewpoint of the flue gas, especially during start up when these components are cold
What does cold end corrosion look like
Rust colored corrosion that occurs on economizers and air preheaters
Is cold end corrosion an issue when burning natural gas
No, natural gas has no Sulphur in it
Explain block and bleed in regards to gas piping
Block and bleed is an NFP requirement. there are 2 maxon valves with a vent valve between them to atmosphere. When valves are closed the vent valve will be open, when valves are open vent valve will be closed
List the piping components of a typical arrangement for burning #6 oil
Oil Tank suction strainers pressure gage pumps heaters (Steam and Electric) pressure gage discharge strainers low oil temp switch high oil temp switch low pressure switch pressure regulating valve SSOV burner
What is draft
Difference in pressure between 2 points that causes gas or air to flow
How is draft measured
By a manometer
What are 2 types of manometers
U-tube
inclined tube
2 types of draft
Mechanical draft, powered driven fans
Natural draft, height of the stack and dampers
