K3.3-3.5/Notes Flashcards
Why do we purge?
- Safely introduced gas/fluid (gasifying)
- Safely remove gas/fluid to repair/abondon
Flaring is the controlled burning of natural gas through a flare stack. True or False?
True
U-tube manometer is also known as a ?
slack tube
Must measure the bottom of the meniscus on a slack tube/u-tube manometer. True or False?
True
What is the purpose of a combustion analysis?
ensure safety and efficiency
If a desiccant filter is brown it should be?
replaced
Where to measure for a combustion analysis?
At the breach before the draft hood
Can excess air be adjusted on a natural draft appliance?
NO
Can excess air be adjusted on a forced/induced/fan assist appliance?
Yes
Excess air greatly lowers the formation of CO by allowing CO to react with O2. True or False?
True
What is NOX?
Nitrogen pollutants generated by boilers (NO and NO2)
Why don’t we like NOX?
Results in production of ozone and acid rain
How is NOX formed? (two types)
Thermal NOX: nitrogen and oxygen react in flame
Fuel NOX: nitrogen and oxygen react in comb air
Two ways to control NOX?
- Post combustion
- Combustion control
What is the most expensive way to control NOX?
Post combustion control
Post combustion control techniques are generally not used on boilers smaller than 1000MBH. True or False
True
What is a post combustion control technique to mitigate NOX?
Selective and non-selective catalytic reduction
What is a combustion control technique to mitigate NOX?
Burner mods, flue re-circulation, water/steam injection
Installer shall instruct user in safe operation of appliance they install. True or False?
True
Installer shall ensure manufacturer instructions supplied with appliance are left with the user. True or False?
True
Net flue temperature?
difference between stack temperature and ambient temperature
The owner must be trained in safe start-up and operation of appliance. True or False?
True
Flue vent dew point is in what range?
120-150F
Causes of flue vent condensation? (4)
- over-sized venting
- low flue temps
- venting in cold area
- under-firing
Flue venting shall be sloped _______ the appliance at __” per foot
towards
1/4”
Pressure vessels are usually tested to ___MOWP
1.5mowp
What is refractory?
heat resistant material that lines high temperature areas
Mixing valves are usually preset to?
130F
Expansion tanks are typically pre-charged to?
12-15psig
For many stories, pressure must be added the expansion tank. True or False?
True
For expansion tanks, how many psig/ft must be calculated?
.433psig per ft
Example: 15psig / .433 = 34.64ft of head
Steam control zone valves work on the same principle as hydronic zone valves. The main difference is the?
valve body
Main purpose of steam traps?
allows steam to escape and keep the steam/water separate
Thermodynamic steam traps are only used in _____ pressure systems
high pressure systems
Common cause of steam trap failure?
dirt/scale not allowing valve to close
Good HSI has resistance of ___ to _____ ohms
30-200ohms
HSI resistance readings will be higher when the HSI is _______
warmer
Silicone nitride HSI are more reliable and last longer than silicone carbide HSI. True or False?
True
Replace HSI when resistance reads round?
70-90 Ohms
Typically furnace modulating percentage?
40-100% CAPACITY
What is the recommended gap size to ground for a spark igniter (ignition electrode)
1/8”
Which type of flame safeguard operates on flame rectification?
flame rod sensor
A good ______ is necessary to rectify a circuit
ground
Minimum flame rod ratio to ground is __:1 although 10:1 is recommended
4:1
What can happen if the flame rod touches ground/refractory?
changes the DC signal to AC
Flame rod sensor shall have no continuity from the sensor wire to ground. True or False?
True
Most controls will drop out of the flame rod sensor reads around __micro amps DC or less
2
During pilot operation the flame rod must read steady __micro amp DC
1
A smaller K factor passes less gas. True or False?
True
