DC 3rd Class Test Flashcards
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Questions and Answers

The component in which liquid vapor by absorbing heat is called?

evaporator

What is the best answer for an electrical grounding method?

Metal stake driven 8 feet into the ground.

A _____ valve should be used for throttling purposes?

Globe

What is the acceptable range for residual sodium sulfite in the boiler maintain?

<p>30-70</p> Signup and view all the answers

What is the BTU content of a gallon of #4 fuel oil?

<p>146,000</p> Signup and view all the answers

What does a zeolite water softener system use as a means of regeneration?

<p>brine</p> Signup and view all the answers

What are the 4 steps for a Zeolite Rejuvenation water softener process?

<p>Backwash, Brine, Rinse, Service</p> Signup and view all the answers

Where is medium temperature liquid found?

<p>Condenser</p> Signup and view all the answers

Where is high temperature vapor found?

<p>At the discharge of the compressor or condenser</p> Signup and view all the answers

What stays are used to support the burner chamber in a scotch marine boiler?

<p>Diagonal stays</p> Signup and view all the answers

What type of safety valve is this?

<p>(Full) Crosby nozzle-type safety valve</p> Signup and view all the answers

Where do you get a superheat reading?

<p>Take suction line pressure</p> Signup and view all the answers

Name the wire that connects all components of a system to a physical ground or water pipe?

<p>Grounding electrode conductor</p> Signup and view all the answers

Where do you get sub-cooling reading?

<p>Take liquid line pressure</p> Signup and view all the answers

On the boilers that have both quick opening and screw type blow down valves, where must the Quick opening valve be located?

<p>closest to the boiler and followed by the screw-type valve</p> Signup and view all the answers

High pressure boilers equipped with quick opening and screw type valves are blown down how?

<p>By opening the Quick opening valve first and closing it last.</p> Signup and view all the answers

ASME Code defines a slow opening valve as what?

<p>One requiring at least 5 full 360 degree turns between full open and close position.</p> Signup and view all the answers

A 300 Horsepower boiler operating at 100 psi has a load of 75% with 80% condensate return and 5% blow down. Find the amount of chemical needed for the day period.

<p>835, 40 gallon</p> Signup and view all the answers

During a 24 hours operation how often should you check the water level?

<p>once per shift</p> Signup and view all the answers

How often do you check the high limit switch?

<p>Annually</p> Signup and view all the answers

What is the recommended time for a complete external inspection of a boiler?

<p>once per shift</p> Signup and view all the answers

What is the first thing to do when shutting down a boiler?

<p>To turn off the fire</p> Signup and view all the answers

A flow control should be blown down when?

<p>once per shift</p> Signup and view all the answers

How often should you check the Low Water Fuel Cut off?

<p>once per shift</p> Signup and view all the answers

Why is oil added to the refrigerant?

<p>lubrication of the compressor</p> Signup and view all the answers

Recycled and filtered refrigerant can be used where?

<p>By the same owner in the same type of equipment</p> Signup and view all the answers

Data printed on the equipment nameplate would include manufacturer, model, and serial number and _________________?

<p>Stamp of approval from commissioning authority</p> Signup and view all the answers

How many BTUs does it take to raise 10 lbs of steam from 40 to 41 degrees?

<p>1 BTU</p> Signup and view all the answers

When working on a boiler, permits should be required?

<p>For every shift</p> Signup and view all the answers

How many things do safety controls protect against?

<p>Over pressure, Over Heating, Fire side explosions</p> Signup and view all the answers

What chemical compounds in water cause permanent hardness?

<p>Calcium Sulfate and Magnesium Silicate</p> Signup and view all the answers

What chemicals are used to combat corrosion?

<p>sodium sulfite and hydrazine</p> Signup and view all the answers

You have boiler water that is found to have a pH of 5. What compound do you add to neutralize?

<p>bases</p> Signup and view all the answers

What produces soft scale?

<p>calcium carbonate and magnesium carbonate</p> Signup and view all the answers

With normal oxygen and low alkalinity, what is added to boiler water?

<p>Neutralizing Amines</p> Signup and view all the answers

What is hard forming scale?

<p>silica</p> Signup and view all the answers

Which chemicals are used to combat scale?

<p>Combined Phosphate Treatment</p> Signup and view all the answers

Which compound is not heat produce?

<p>Nitrogen</p> Signup and view all the answers

What takes no actual action in combustion?

<p>Nitrogen</p> Signup and view all the answers

With hydroxide present & normal oxygen levels, which chemical will cause problems?

<p>Chlorine</p> Signup and view all the answers

What mechanical device is used to remove scale from fire tubes?

<p>A Tube Rattler or Vibrator is used</p> Signup and view all the answers

Who can make adjustments or repairs on a safety valve?

<p>Qualified person from Manufacturer or Representative</p> Signup and view all the answers

What mechanical device is used to remove scale from water tubes?

<p>A Tube Turbine is used</p> Signup and view all the answers

In a duct air handling system, how does a space thermostat control building temperatures?

<p>Mixing the air from hot &amp; cold ducts in a mixing box serving the space</p> Signup and view all the answers

The removal of moisture from air using a cooling coil is called _________ dehumidification?

<p>Passive</p> Signup and view all the answers

In a multi-zone air handler unit, how does the zone thermostat control the zone temperature?

<p>Dampers that control the air flow from the hot &amp; cold duct</p> Signup and view all the answers

An air handler unit that has hot & cold air ducts connected to __________ is called a __________ air handler unit?

<p>molding boxes, dual duct</p> Signup and view all the answers

An air handler unit supplies a constant supply air temperature of 55 degree F to building spaces and includes a coil called _____ air handler unit?

<p>terminal reheat</p> Signup and view all the answers

An air handler unit that provides heating, cooling, ventilation, and air conditioning to more than one building or area and has its cooling & heating Coil in separate side-by-side ducts is called a _______ air handling unit?

<p>multi-zone</p> Signup and view all the answers

In a dual duct air handling system space thermostatic controls building temperatures by? Moving the air from the hot & cold duct in a molding box serving the space.

Signup and view all the answers

A boiler is rated at (86,250 lbs, 88,250 lbs, 96,250 lbs) of steam per hour. What is the equivalent boiler horsepower?

<p>2500 HP = 86,250 / 34.5 = 2500 lbs</p> Signup and view all the answers

What is the area of a steam engine cylinder reading 10 x 24, when the piston is only travelling at 2/3 of the way?

<p>160</p> Signup and view all the answers

What is the total force acting on a 4 inches diameter safety value disc with a boiler pressure of 12 psi?

<p>150.79 TF= P x A</p> Signup and view all the answers

The expansion tank on a closed loop system should be located?

<p>Suction side of the pump</p> Signup and view all the answers

What is the primary purpose of a crank case heater on a reciprocating chiller?

<p>To prevent refrigeration migration</p> Signup and view all the answers

What is meant by the percent of (skip, step, and slip) in a pump?

<p>The difference in theoretical capacity compared to the actual capacity</p> Signup and view all the answers

Which of the following type of pumps can be started with the discharge valve closed?

<p>Centrifugal</p> Signup and view all the answers

The vertical distance from the center line of the pump up to the top level of the supply tank is called?

<p>Static suction head</p> Signup and view all the answers

Where in a system is a foot valve value installed and what is its purpose?

<p>Located below the normal level of the tank attached to the end of the suction line of the pump, used to keep suction line full to facilitate starting.</p> Signup and view all the answers

In a multi-zone air handling unit, how does the zone thermostat control the zone temperature?

<p>Dampers that control the air flow from the hot &amp; cold deck</p> Signup and view all the answers

What is meant by a pump becoming steam bound?

<p>When the static pressure at the suction of the pump falls below the vapor pressure corresponding to its temperature.</p> Signup and view all the answers

Which of the following is a positive displacement pump?

<p>reciprocating</p> Signup and view all the answers

What does the whistle on the top of the water column indicating?

<p>High and low water condition</p> Signup and view all the answers

The heart of a refrigeration system is the _______?

<p>compressor</p> Signup and view all the answers

Refrigerant flow into the evaporator is controlled by ___________?

<p>Metering device</p> Signup and view all the answers

A reciprocating compressor operating with refrigerant R-410 head pressure of 476 psi and a suction pressure of 118 psi. What is the compressor's compression ratio?

<p>3.7 476+14.7 / 118+14.7 = 3.760</p> Signup and view all the answers

The part of the refrigeration system that absorbs heat into the system is controlled by the ______?

<p>evaporator</p> Signup and view all the answers

What is the replacement refrigerant for R-12 medium and high temperature refrigeration application?

<p>134 A</p> Signup and view all the answers

The color for an R-134A refrigerant cylinder is _______?

<p>light blue</p> Signup and view all the answers

The color for an R-410A refrigerant cylinder is _______?

<p>rose</p> Signup and view all the answers

Which of the following is a flanged joint between two or more furnaces and may be located in the center of the furnace, with no more than 18 inches apart?

<p>Adamson Ring</p> Signup and view all the answers

Which of the following statements is true concerning fire tube and water tube boilers?

<p>A water tube boiler's biggest advantage over a fire tube boiler is its flexibility to increase capacities and pressure.</p> Signup and view all the answers

A chief engineer is preparing for a mud drum inspection. Which of the following will you not do?

<p>Set up a 110 volt lighting for inspection</p> Signup and view all the answers

What do you use to bank off a boiler and bring it back online without using the shut-off valve?

<p>Automatic stop valve</p> Signup and view all the answers

What is not an advantage of an economic boiler over a conventional HRT Boiler?

<p>Space, ability to increase capacity, flexibility</p> Signup and view all the answers

What do you call the chemicals that are used to test water for hardness?

<p>Reagents</p> Signup and view all the answers

What do the three 'T's of combustion stand for?

<p>Time, Temperature, Turbulence</p> Signup and view all the answers

What do you do to attain complete combustion in a boiler?

<p>Increase secondary air</p> Signup and view all the answers

Air leaking into the inner and outer parts of the boiler, what will happen?

<p>Decrease boiler efficiency</p> Signup and view all the answers

By clicking on the exhibit, the picture is a display of (page 365 BOG)?

<p>Full nozzle reaction type safety valve</p> Signup and view all the answers

What controls the steam pressure and monitors the combustion air intake?

<p>Fuel, air, water</p> Signup and view all the answers

What happens to the water in a boiler that is at 80% load and all of a sudden, the flame goes off?

<p>Water will shrink and cause a low water condition</p> Signup and view all the answers

What is installed between the boiler drum and the steam gauge to create a protective watertight seal for the gauge?

<p>Siphon</p> Signup and view all the answers

What is the replacement refrigerant for R-22?

<p>R-410A</p> Signup and view all the answers

Which valves to the boiler are opened and closed during blow down?

<p>By opening the Quick opening valve first and closing it last.</p> Signup and view all the answers

How and why tube ends on a fire tube boiler are secure?

<p>Tube ends are beaded to allow for greater expansion and control of the tubes.</p> Signup and view all the answers

What is not an advantage of the economic type boiler over the conventional type boiler?

<p>Allows greater flexibility expansion and contraction</p> Signup and view all the answers

An accelerated circulation water tube is characterized by?

<p>Heated downcomers</p> Signup and view all the answers

Why is platinum used in RTD (Resistive Temperature Device)?

<p>Because of its stability at high temperature</p> Signup and view all the answers

In HVAC systems controlled by a thermostat, what is the difference?

<p>The difference between the set point and the temperature at which the switch turns the systems off</p> Signup and view all the answers

What is the purpose of a suction accumulator?

<p>It contains liquid refrigerant to allow evaporation prior to entering the compressor</p> Signup and view all the answers

What must be submitted to the code official when field assembly of boilers is required?

<p>Boiler inspection report</p> Signup and view all the answers

A boiler has 2800 furnace temperature and 600 stack temperatures reading. What is the boiler efficiency?

<p>78.57 Input - loss x 100 divided by Input (2800 - 600) x 100/ 2800 = 78.57</p> Signup and view all the answers

What do you call a reading from the center of an impeller across to the gauge?

<p>Static pressure</p> Signup and view all the answers

What is the heart of a refrigeration system?

<p>compressor</p> Signup and view all the answers

Which coal has the biggest level of fixed carbon content?

<p>Anthracite = 14,000</p> Signup and view all the answers

What is the cause of high excess in a condensate return tank with temperature up to 20 degrees above normal?

<p>Steam traps are stuck open</p> Signup and view all the answers

Water inlet into a building is 100 psig. If no booster pumps are used, what will be the pressure on the 10th floor, if the building is 10 feet per floor?

<p>43.3 2.31 = 1 psi, 100 psi = 100/2.31 = 43.3 psi</p> Signup and view all the answers

Where is the total hardness of a softener reading 0.5 grains?

<p>(17.1 x 0.5 = 8.6)</p> Signup and view all the answers

How many BTUs are needed to raise 2 lbs of water from 32 °F to 212 °F?

<p>360 BTUs</p> Signup and view all the answers

Study Notes

Heating and Cooling Systems

  • An evaporator absorbs heat to convert liquid into vapor.
  • Grounding methods utilize an 8-foot metal stake driven into the ground for electrical safety.
  • Globe valves are ideal for throttling applications.
  • Medium temperature liquid is typically found in a condenser, while high temperature vapor is at the discharge of a compressor or condenser.
  • The centrifugal pump can start with a closed discharge valve, while reciprocating pumps are positive displacement types.

Boiler Operations and Maintenance

  • Acceptable residual sodium sulfite range in boilers is between 30-70 ppm.
  • BTU content of a gallon of #4 fuel oil is 146,000 BTUs.
  • Blowdown procedures for boilers involve opening quick opening valves first and closing them last.
  • Chemical needs for boiler treatment can be calculated based on evaporator rates and condensate return.
  • A thorough external boiler inspection is recommended once per shift, along with checking water levels and safety controls.

Water Chemistry in Boilers

  • Permanent hardness in water is caused by compounds like calcium sulfate and magnesium silicate.
  • Corrosion in boilers can be combated by chemicals such as sodium sulfite and hydrazine.
  • Soft scale is formed from calcium carbonate and magnesium carbonate, while hard scale is primarily silica.
  • A neutralizing agent should be added to raise the pH of acidic boiler water.

Refrigeration and Air Handling Systems

  • Refrigerant migrations are prevented by using crankcase heaters and oil mixed with refrigerants for lubrication.
  • In refrigeration systems, the compressor is the critical component, while metering devices control refrigerant flow into evaporators.
  • R-134A is a replacement refrigerant for R-12, marked with light blue cylinders, while R-410A is identified by rose-colored cylinders.
  • Air handling units that provide heating, cooling, and ventilation are categorized by configurations like multi-zone and dual duct systems.

Pressure and Flow Dynamics

  • The specific gravity of fluids can be defined in terms of pressure, such as calculating pressure loss over height in buildings (2.31 feet = 1 psi).
  • A sighon installation between boiler drums and steam gauges creates a protective seal to prevent steam escape.
  • Superheating and subcooling realities in refrigerants are measured by comparing suction and liquid line temperatures to their respective pressure/temperature charts.

Safety Protocols and Regulations

  • Safety valves must only be adjusted by qualified personnel.
  • Annual maintenance includes checking high limit switches, while low water fuel cut-off checks should occur per shift.
  • Boiler operation permits are required for each shift to ensure compliance with safety standards and regulations.

Energy Consumption and Efficiency

  • Boiler efficiency ratings can be calculated — for instance, a boiler with an input of 2800°F and a stack temperature of 600°F reflects an efficiency of 78.57%.
  • Understanding and applying the combustion principles, represented as the three “T”s (Time, Temperature, Turbulence), is critical for optimal efficiency.
  • Energy calculations for steam generation can quantify required BTUs for temperature changes in varying quantities of water.

Additional Terminology

  • "Reagents" are used in testing water hardness, while "diagonal stays" support burner chambers in boilers.
  • The difference between actual and theoretical pump capacity is referred to as skip, step, or slip percentages.
  • Water's thermal expansion and behavior under varying temperatures are crucial for maintaining system integrity and efficiency.

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This quiz consists of flashcards designed to help you prepare for the 3rd Class DC exam. Each card presents a question related to electrical and boiler systems, focusing on fundamental concepts such as evaporators, grounding methods, and valve types. Test your knowledge and reinforce your understanding of critical topics in this field.

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