Related science. Flashcards
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- Density of ice?
57.4 lb/cu.ft.
- The weight of a unit volume of substance?
Density.
- Density of air?
.075 lb/cu.ft.
- Density of copper?
552 lb/cu.ft.
- Density of steel?
489.5 lb/cu.ft.
- Density of lead?
710 lb/cu.ft.
- Density of mercury?
849 lb/cu.ft.
- How are all substances composed?
Elements are the basic materials of which all substances are composed.
- How many elements are known to exist?
Currently, there are 115 elements.
- Name parts of periodic table of the elements?
- The vertical columns called periods.
2. Horizontal rows - groups.
- Name groups of periodic table of the elements?
- Alkali metals.
- Alkaline earth metals.
- Transition metals.
- Nonmetals.
- Inert gases.
- What is rare earth elements?
Elements which differ in electron configuration from that of the next lower or higher atomic number only in the number of electrons in the second from the outside shell.
- What is a transition element?
An element which differs one lectern configuration from that of the next lower or higher atomic number only in the number of electrons in the next to the outside shell.
- How is the atomic weight of an element based on?
The total number of protons and neutrons in the nucleus of the atom.
- What is general similarity between atomic weights of various elements and the densities of the same elements?
The weight of a specific volume of each element would remain in the order shown on the periodic table.
- How are all elements composed?
Of atoms.
- What is an atom?
The smallest particle of an element which can exist either alone or in combination with other elements.
- Definite regions - energy levels or orbits in which electrons move about the nucleus?
Shells.
- How is acetylene stored?
In a liquid, acetone.
- What is molecule?
The smallest part of either an element or compound which retains the properties of the original substance.
- What is heat?
A form of energy due to the molecular motion of substance. A measure of the total kinetic energy of all the molecules contained in the substance.
- Range of thermometers?
- Alcohol - for low temperature work.
- Mercury - up to 400*F.
- Pyrometers (the space above the mercury is filled with an inert gas under pressure) - from -60F
to 1000F. - Electric resistance pyrometers - from -330F to 1300F.
- Metallic thermometer.
- How much space does stern require under the same temperature as water?
About 380 times as much.
- How does water expend when heat is applied?
At the rate of approximately .00023%for each degree of temperature rise.
- How does water expand when it freezes?
1/12 its volume.
- When are Rankine and Kelvin temperature scales used?
When working with gases whenever pressure and volume are part of the calculations.
- How are heat calculations, involving a large number of Btu as with the Btu output of a large capacity steam generator?
In therms: 1 therm is equal to 100,000 Btu.
- What are average temperatures of cold water and setting on a water heater?
55F and 140F.
- What are three terms that directly related to a temperature change in a known substance where the three states of matter are involved?
- Specific heat.
- Sensible heat.
- Latent heat.
- What is specific heat of water. Air alcohol and steam?
1, 0.24, 0.602, 0.48.
- What is specific heat of a substance?
The ratio of its heat capacity to that of water.
- The formula to determine the quantity of sensible heat required to raise or lower the temperature of any substance?
H=SxWx(T1-T2) H-Btu of sensible heat, S-specific heat, W-weight in pounds (T1-T2)- temperature difference.
- How much heat is required to raise the temperature of 100 lb of ice from 20F to 32F?
The specific heat of ice is 0.5.
H=0.5x100x(32-20)=600 Btu.
- More convenient formula for computing Btu/hr?
H(H2O Btu/hr) = 500xO(gpm)x(T1-T2).
- If 970 cfm of air flows across the heating coil of a unit heater and the temperature of the air increases from 70* to120*F, how many Btu of heat are transferred per hour?
W=970cfm x .075 lb/cu. ft. x 60min/hr = 4365 lb/hr.
H=.24x4365x(120-70)=52.380 Btu/hr.
- What is the total amount of heat that must be added to one pound of ice at 0F to convert it to steam at 212F?
1 lb of ice at 0*F to 32*F - 16 Btu. 1 lb of ice at 32* to water - 144Btu 1 lb of water at 32* to212*-180Btu. 1 lb of water at 212* to steam - 970.4 Btu. All together:1,310.4 Btu - 1 lb ice at 0*F to steam at 212*F.
- How is the process of changing from the solid to the liquid state called?
- Fusion.
- Melting.
- Liquefaction.
- How is the temperature at which the solid change to the liquid called?
The melting point.
- What substances do not have a definite melting point?
Non crystalline substances such as glass, wrought iron, and solder.
- How is the latent heat that is added to cause a change of state from a solid to a liquid called?
The latent heat of fusion or the latent heat of melting.
- Melting and freezing point plumbing substances?
Wrought iron - 2732-2912*F. Steel - 2588*F. Copper - 1983*F. Brass - 1866*F. Bronze - 1688*F. Lead - 620*F. Tin - 449*f. Ice - 32*F
- The law of heat exchange?
The total number of Btu lost by the warmer substance whisks the total number of Btu gained by the cooler substance.
Heat lost = heat gained.
- What is the unit ton of refrigeration?
The heat absorbed by the melting of a ton (2000 pounds) of ice in an 1 hour period: 12,000 Btu per hour.
- What is the flow of air (cfm) that must pass the hot water heating coil, if the temperature drop is 40F. The water flow rate is 10 gpm and the air temperature increases from 60 to 130*F?
Heat loss=heat gain.
H(water)=500xO(gpm )x^T=500x10x40=200,000.
H(air)=1.08xO(cfm)x^T=200,000.
O(cfm)=200,000/1.08/^T=200,000/(1.08x70)=2645.5 cfm.
- How is the process of converting a liquid into a vapor called?
Vaporization.
- Different forms of vaporization?
- Boiling.
- Evaporation.
- Flashing.
- What is boiling?
All of the liquid is hot enough so bubbles reach the surface freely, vaporization occurs throughout the liquid with visible disturbance.
- Boiling points plumbing substances?
- Zinc -1,661*F.
- Mercury-675*F.
- Water - 212*F.
- Alcohol - 173*F.
- Freon - (-21.7)*F.
- Ammonia - (-28)*F.
- What is the name of the latent heat involved in a change of state from a liquid to a visor, or vice versa?
The latent heat of vaporization.
- What is the latent heat of vaporization of water at sea level?
970.4 Btu.
- How many must Btu of heat be removed from each pound of water vapor to cause it to condense to a liquid?
970.4 Btu at sea level.
- What is meant by the term evaporation?
Process of changing a liquid to a gas below the saturation temperature and only at the surface of the liquid
- Factors which govern the rate of evaporation?
- The extent of the free surface of the liquid.
- The temperature.
- The pressure exerted upon the surface of the liquid.
- The degree of saturation of the space above the liquid.
- The volatility of the liquid.
- The number of air changes.
- Cooling of water as the water evaporates when air blow across it speeded surface?
Evaporative cooling.
- Give an example of evaporative cooling and how it can be used to cool condenser water?
The cooling tower is used to cool condenser water so it may be recirculated again. The water is sprayed through the cooling tower where a portion of it evaporates. The evaporation removes the heat from the remaining portion of water.
- The temperature and pressure hot condensate at the steam trap inlet?
15 psig and 250*F.
- How do liquids and solids expand on heating?
Liquids have higher coefficients of expansion.
- How does mercury expand on heating?
It is fairly uniform between 32F and 212F.
- The coefficient of water expansion?
0.00024.
- Formula for expansion volume?
EV = V1x(T1-T2)xCE. EV-expansion volume. V1-original volume. ^T-temperature change. CE-coefficient of expansion.
- One hundred gallons of gasoline are measured at 32F. What will be the increase in volume of the gasoline at 86F?
EV = 100x(86-32)x0.0006 = 3.24 gal.
- What is the value of the coefficient of cubical expansion for all gases?
.002035 per 1 degree Fahrenheit.
- The gas low?
The absolute pressure exerted by a gas is in direct proportion to the absolute temperature:
P2 = P1xT1/T2.
- 10 cubic feet of air is heated from 60F to 180F at a constant volume. What is the final pressure if the initial pressure is 20 psig?
P2 = (20+14.7)x(180+460)/(60+460) = 42.7 psia =42.7-14.7 = 28 psig.
- The combination gas law?
P1xV1/T1 = P2xV2/T2.
- A gas occupies a volume of 6 cubic feet at standard temperature and pressure. What volume will it occupy when the pressure is 15 psig and the temperature is 80*F?
V2 = P1xV1xT2/(P2xT1) = 14.7x6x(80+460)/(29.7x(32+460)) = 3.26 cu. ft.
- What are two terms closely related to liquids?
Solution and suspension.
- What is solution?
A homogeneous mixture (thoroughly mixed) of two or more substances, the composition of which may vary to a maximum limit, called the saturation point.
- What is the saturation point?
A maximum limit of composition of two or more substances.
- What is the hydrogen bond?
Water molecules are electrically attracted to each other because of their shape.
- What is capillary action?
The liquid is raised or lowered as a result of the combined forces of adhesion, cohesion and surface-tension on the liquid.
- What are three physical properties of pure water?
It is odorless, colorless, and tasteless.
- Name a scale for measuring the acidity or alkalinity of water?
The pH scale read from 0 to14. 0.
- Why is it important to know the pH value of water?
To determine if the water supply must be chemically treated to make it potable for human consumption. Water which is acidic is very corrosive.
- Which water is acidic?
With a pH of 5 or lower.
- A pH value of water suitable for use in piping systems and safe for human consumption?
7.0 - 10.5.
- What causes deposits within pipelines and can cause them to close off completely?
Calcium.
- How does calcium, magnesium sulfates, bicarbonate a and other hardness particles can be removed from hard water?
By installing a water softener that employ the principle of iron exchange to attract (capture) and remove calcium and other hardness particles from the water solution.
- What is ion?
An atom or group of atoms or molecule with an unbalanced electrical charge as a result of having lost or gained one or more electrons.
- How does water softener work?
Ion exchange is a reversible chemical reaction between a solid and a fluid (water) mixture by means of which ions may be interchanged.
- What will be effected when the pressure of steam is changed?
- Temperature of vaporization.
- Sensible heat content ( heat content of the liquid).
- Latent heat content ( latent heat of vaporization).
- Total heat content (heat of the steam).
- Volume.
- Density.
- How does steam expand?
Saturated expands 1700times and superheated steam expands more.
- Heat content of saturated steam?
The sum of the sensible heat of the water, plus the latent heat of vaporization.
- Types of saturated steam?
Dry-saturated steam or wet-saturated steam, depending on the amount of water contained in the form of mist.
Superheated steam - saturated steam that receive additional heat
At same pressure.
- What is the condensing temperature of steam at 125 psig?
353*F.
- What is the name of the number of Btu required to raise the temperature of one pound of water from 32*F to the boiling temperature?
Heat in water.
- Compare the difference in the amount of latent heat liberated when one pound of steam is condensed at 35 psia and at 140 psia?
35 psia - 939.0 Btu
140 psia - 868.0 Btu
Difference=939-868=71 Btu.
More heat is liberated, 71.0 Btu, at 35 psia.
- How many Btu are required to change one pound of water at 182*F into steam at 115 psia?
Total heat of steam at 115 psia - 1190 Btu
Heat in water at 182*F - 150 Btu
Heat required Btu = 1100-150=1040 Btu.
- What is the volume of one pound of saturated steam at 70 psia?
6.0 cu. ft. per lb.
- When will condensation of steam take place?
Only after the point of saturation has been reached because condensation entails loss of heat and consequently power.
- When does saturated steam start to condense?
At once. The condensed water which covers the inside walls of pipes and steam cylinder causes a further loss of heat by radiation.
- What is hydraulics?
It covers the subject of liquids in motion.
- What is pneumatics?
The study of the mechanical properties of air and other gases (pressure, weight, expand ability, ect.
- Give three examples of piping systems that have :
1 liquids only;
2 liquids and gases combined;
3 gases only?
- Domestic hot and cold water, chilled water, heating hot water and sprinkler systems contain liquid water.
- Sanitary wast and vent piping.
- Air, ordinary natural gas, steam, vacuum, and oxygen piping.
- What does the term fluid mean?
A substance that has the ability to flow (like water).
- The relative thickness or thinness of a liquid that affect the rate at which a liquid flows?
Viscosity.
- What is the weight of substance?
The measure of the force of gravity on a substance expressed in units such as pounds.
- What is specific gravity?
The ratio of the density of a substance to the density of a standard of reference.
- What can be used to measure specific gravity?
The hydrometer method.
- What is the hydrometer?
A hollow glass tube which has been weighted with enough lead to make it float in an upright position with its stem out of the liquid. The specific weight of the liquid can be read on the scale etched on the side of the stem.
- What is the weight of an equal volume of the standard, such as water or air?
Specific weight of a substance.
- What are the standards for specific weight?
Water to compare the densities of all solids and liquids and air or hydrogen for gases.
- Weight of water?
62.4 lb per cu ft or 0.0361 lb per cu in.
- Specific weight of water, alcohol, Gasoline, ice, sea water?
Sea water - 1. 026, Water - 1, Ice - 0. 917, Alcohol - 0.79, Gasoline - 0.7.
- Specific weights of mercury, lead, copper, brass, aluminum?
Mercury- 13.6, Lead - 11.38, Copper - 8.8, Brass - 8.39, Aluminum - 2.67.
- Specific weights of steel pipe, wrought iron, cast iron?
Steel - 7.84,
Wrought iron - 7.7,
Cast iron - 7.2.
- Specific weights of concrete, brick, cork?
Concrete - 2.2,
Brick - 1.8,
Cork - 0.24.
- What is adhesion?
The property they causes dissimilar materials to be attracted to one another.
- 3 way find specific weight of a substance?
SW = density of a substance /density of water = weight of substance / weight of equal volume of water = weight on air / loss of weight in water.
- Where is capillary negligible?
In tubes greater than 1/4” diameter.
- Give an example illustrating how some liquids are characterized by the phenomenon, of seemingly overcoming gravity, called capillarity?
Mercury is more cohesive than adhesive. If tube is inserted into a container of mercury, the liquid inside tube will actually be lower than the surrounding liquid.
- The treatment of liquids at rest is known as?
Hydrostatics.
- How do liquids exert pressure?
In all direction: downward, sidewise, and upward.
- Name the pressure that is produced by the weight of the water below the surface of water which is exposed to atmospheric pressure?
Static head, static pressure, hydrostatic head or hydrostatic pressure.
- Psia?
Pounds per square inch absolute.
- Formula for the pressure exerted by a liquid?
It is directly proportional to its density: P=HxD, P-pressure, H-height, D-density.
- Formula for pressure produce by water head?
P(psi) = H’x.433(psig/ft.hd.) = H”x.0361(lb/cu.in).
- The Laws of liquid pressure?
- It is directly proportional to the height of the liquid
- Liquid pressure is directly proportional to the density of the liquid.
- It is independent of the area or shape of the container, it is also independent of the direction.
- Manometer?
Manometer.
Ma’nome^te^r.
- Hot water temperature for commercial kitchen and sink for kids?
Commercial kitchen - 140*,
Children use - 110*.
- Parts of metallic dial thermometer?
- Bimetallic coil.
- Pointer actuated by coil.
- Scale (*C or *F).
- The level of the water in the elevated tank is 50’ above the top of a 6” horizontal water main. What is the total force acting on the bottom of the 6” vertical pipe connecting the tank to the water main if the tank is 12’ in diameter and is 30’ in length?
TF = AxP = (.7854xdxd)x(H'x.433psi/ft.hd.) = (.7854x6x6)x(50x.433) = 612.14, or TF = AxHxD = (.7854xdxd)x(50xD) = (.7854x.5x.5)x(50x62.4) = 612.61 lb.
- Types of manometers?
- An open manometer with a column of mercury or painted water.
- A Bourdon tube gage.
- Pascal’s law?
Pressure applied anywhere Tia body of confined or enclosed fluid is transmitted with undiminished force in every direction. This pressure acts at right angles to every portion of the surface of the container, with equal force upon equal areas. Fluids comprise both liquids and gases.
- If the 100’ high 2” stack is converted from an open system toa closed system and has an additional 50 psig pressure added at the top, how will this affect the pressure in the rest of the stack?
- When the system is pumped to a pressure of 50 psig at the bottom?
- At the top of the stack, the pressure is 50 psig + 0 = 50 psig.
At the bottom is 50 + 43.3 = 93.9 psig. - At the bottom of the stack we have 50 psig.
At the top of stack pressure will be 50 - 43.3 = 6.7 psig.
- What is the total thrust in lb on a 90* elbow on a 10” underground water main which will be tested at 200 psig? The thrust for a 10” 90* is 151 psig.
Total thrust = thrust x P = 151x200 = 30,000 lb.
- Vaga?
A balance scale:
- A rigid, uniformly dense beam.
- Weighing pans.
- Balance weights.
- How may a barometer reading in inches of mercury be changed to pounds per square inch gage?
By multiplying by .491 the density of mercury.
- Types of barometers?
- Torricellian tube and bowl (mercury).
2. Aneroid barometer.
- Atmospheric pressure at sea level?
30” Hg.
- Formula for absolute pressure?
Pa = Pg+Pat = Pg+Hg"x.491. Pa-absolute pressure. Pg-gage pressure. Pat-atmospheric pressure. Hg-pressure in inches of mercury.
- How does absolute pressure differ from gage pressure?
Gage pressure is read starting from zero for atmospheric one absolute pressure is measured from zero for a perfect vacuum.
- What is the abbreviation STP used for ?
To indicate standard temperature and pressure.
- What are STP numbers?
Temperature- 32*F;
Pressure- 14.7 psia or 29.921” of mercury.
- Types of tank used in closed hot water heating system?
- Compression tank.
2. Pre charged extension tank.
- Where may non-potable pre charged water expansion tanks be installed?
In a tee or any other suitable tapping in the heating system.
- Boyle’s law?
The volume of a confined gas is inversely proportioned to the absolute pressure exerted on it, provided the temperature remains constant:
V2/V1 = P1/P2.
- How can Boyle’s law be applied to an air chamber in a piping system?
You can determine how much air cushion remains in a 12” air chamber after it has been pressurized.
- A 1” diameter air chamber 12” long is installed Ina cold water system. How much air space remains after a pressure of 60 psig has been applied to the system? Make calculation in cubic inches. The system is at sea level.
V2 = V1xP1/V1. V1 = AxL = .78x12 = 9.36; P2 = 60+14.7 = 74.7 psia; V2 = 9.36x14.7/74.7 = 1.84 cu.in.
- What is often used to measure the draft in boilers?
A draft gage (the inclined manometer) with range of .10 to 1.0 in. W.C.
- What is compressed air used for?
For the operation of automatic controls on heating, cooling, ventilation and air conditioning equipment.
- Describe the operation of the pneumatic control system?
Compressed air operates the controlled devices, valves or damper operators on demand of the thermostat. Compressed air is provided by a compressor.
- Give the brief description of the use of a vacuum pump in the pipe trades?
To evacuate refrigeration systems.
- Types of vacuum pump?
- The piston type.
2. The sliding vane type.
- Is there a rule of thumb for estimating remaining space after systems are pressurized for air chamber?
15psig- 1/2 space remains; 30 - 1/3; 45 - 1/4; 60 - 1/5; 75 - 1/6 space remains.
- How does the three pressure measurements approximately relate within 15% accuracy?
1/2 psig = 1” W.C. =1” mercury column.
- Components of a dial type bourdon tube gage?
- Flexible bent tube.
- Link adjustment.
- Pivot.
- Segment gear.
- Rotating gear.
- Socket.
- Hy does an object that is immersed in a liquid, seem to weigh less than it does on dry land?
Water exerts an upward pressure, or buoyant force, upon objects.
- The law of flotation?
- A body sinks in a fluid if the weight of the fluid it displaces is less than the weight of the body.
- A submerged body remains in equilibrium, neither rising nor sinking, if the weight of the fluid it displaces exactly equals its own weight.
- If a body, when submerged, displaces a weight of fluid greater than its own weight, it will float.
- What is called buoyancy?
Upward support force equal to the weight of the liquid that has been displaced by the object.
- What does the mechanism of stop/start control on a sump pump use?
Two weights at different levels in the sump.
- How is water flow measured in the pipe trades?
The most common flow units are: 1. Gallons per minute (gpm); 2. Gallons per hour (gph). Other frequently used units are: 3. Cubic feet per minute (cfm); 4. Pound per hour (lb/hr).
- What is the definition of velocity of flow?
The rate of motion per unit of time.
- What is the pressure measured at any point while water is flowing which is read on a pressure gage installed in the piping?
The flow pressure?
- What is bigger flow pressure or static?
Flow pressure is always less than the static due to friction loss.
- What is meant by the term velocity head?
The decrease in the potential energy, or static head.
- What are six factors which govern pressure drop caused by friction in a piping system?
- Viscosity of fluid.
- Length of pipe.
- Velocity of flow.
- Size and type of pipe.
- Number and type of fittings and valves.
- Number and degree of bends.
- Where is laminar flow an important factor in a piping system?
It is especially desirable upstream from metering devices and pressure regulating valves.
- What is used to provide the laminar flow necessary for accurate low measurement?
Straightening vanes:
- One-piece.
- Honeycomb.
- Where is turbulent Dow desirable in piping?
In water heating devices as the mixing action of the fluid provides a better heat transfer. A fin tube baseboard heating element has the built-in obstruction which causes the desired turbulence.
- How does a fluid act as it flows in a pipeline?
- Laminar flow is in slightly slopping horizontal sewers or open drainage ditches, streams, or canals.
- Turbulent flow occurs in most pressure piping such as domestic water lines or pumped liquid lines.
- How does flow occur in piping system?
- Unsteady flow - varies from a maximum at the time of greatest use to a minimum of no flow at all when no fixture are being used.
- Steady flow - a constant rate of fluid flow (hot water recirculating line).
- How can the volume of flow be determined?
By measuring the pressure on each side of the orifice
, or the Venturi, the volume of flow can be determined from charts or tables which have been calculated by the use of a formula.
- What are some methods which can be used to measure rate of velocity?
- For water flowing in an open channel time the movement of an object being carried with the flow for a known distance.
- By means of a propeller device.
- The Pitot tube.
- What is the average velocity In an ordinary pipeline?
About 80% of the maximum velocity.
- The operation of a Pitot tube?
The impact of the water flowing into the opening in the submerged leg causes the water level in the upright leg to rise to a point where the head of water above the surface of the flowing stream exactly balances the pressure due to the impact ( velocity) of the water on the submerged leg.
- How is the velocity determined from velocity head of a Pitot tube?
A chart gives values velocity of a fluid for each movement of velocity head.
- Bernoulli’s theorem?
In a piping system under steady flow, the sums of velocity head, the pressure head, and the elevation head are equal at each point within the pipe line.
- What is the total head at the halfway point and at the bottom of the pipeline? W.H. is 100’, a velocity head is10’.
1. The total head at the half way point equals:
Evaluation head - 50'
Pressure head - 50'
Velocity head - 10'
--------
110'
2. The total head at the bottom equals:
EH-0" + PH-100' + VH-10' = 110'.- What is hydraulic ram?
A device is used to pump water from a source to a storage tank at a higher elevation without the use of electricity, gas or other energy.
- Describe the operation of a hydraulic ram?
The supply water flows into the ram body through a drive pipe, and passes out through the impetus valve until the column attains sufficient speed to raise this valve to its seat. A small quantity of this water is forced through the check valve into the air chamber. After the impetus and check valves are close, the air , being then at a pressure greater than that due to the head in the dis charge line, forces this small quantity of water into the supply tank.
- Extremes for difference between elevation and fall in a hydraulic ram system?
Min 6’, max 12’.
- How would journeymen working in the pipe trades make use of the principle that pressure varies inversely with velocity?
The discharge from a smaller nozzle at a very high velocity will cause the pressure at the nozzle outlet to be very low. By creating these below-atmospheric pressures at the Venturi tube, the fluid surrounding the nozzle will be sucked into the stream and mixed with the high-speed jet. This principle is applied in the jet pump and the common gas burner.
- What is orifices use?
To measure flow and to regulate flow.
- How is flow through orifices regulated?
The orifice which creates the high velocity jet is carefully sized so that gas, supplied at a constant pressure, will pass through it at a set rate, as required by the burner.
- Parts of jet fitting for pumping well water?
- Wide tube with low pressure well water.
- Thin pipe with pumped water to jet nozzle.
- Jet nozzle that causing pressures below atmospheric.
- Venturi fitting where mixture of jet water and well water increase in pressure.
- Wide pipe to storage tank and pump.
4.
- Where is a flow regulator (regulating orifice) found?
In the cold water supply piping to a domestic hot water heater.
- Why a flow regulator is sometimes found in the cold water supply piping to a domestic hot water heater?
The rate of flow is limited by the orifice in the flow regulator to the rate of recovery of the heater.
- Typical piping arrangement of flow regulator and tempering valve?
- Cold water supply valve.
- Flow regulator.
- Cross fitting to:
A. Heat source;
B. tempering valve;
C. Drain valve. - (A) Heat source.
- Hot water to tempering valve (has cold, hot and mix water connections).
- Mix water to tempered hot water line to fixtures.
- Hot water supply valve.
- Ow does gas burner work?
High velocity gas jet producing low pressures (vacuum). Primary air enter burner. Mixture of primary air and gas increase pressure in Venturi tube and burn in outlet using secondary air.
- How is flow through orifices measured?
Orifice plates are carefully manufactured, and through experimentation it has been dater mined exactly what the flow will be for each pressure differential.
- What I a weir?
A dam in an open channel constructed so that the dam has an evenly shaped notch through which the water flows.
- How are weirs used to measure flow?
It can readily be determined by measuring the depth of the water in this notch and consulting the flow data.
- How are weirs used to regulate flow?
Flow through water-softening equipment is regulated by setting the float valve to maintain a certain depth of over-flow at the weir, to control the rate of back-washing.
- What are some of the factors which cause resistance to flow in pipelines?
- If you double the velocity of a fluid, the resistance will be increased by nearly four times.
- A thick liquid, like heavy fuel oils can be heated to lower its viscosity and thus reduce its resistance to flow.
- Roughness and smoothness of pipe walls.
- The amount of corrosion and deposits depends on the composition of the fluid and action of the fluid on piping material.
- What effect does the arrangement of pipe and fitting have on resistance to flow in a pipelines?
- The longer the pipe the greater its resistance.
- The sharper the bend, the greater the resistance.
- Changes in pipe sizes made with bushings also cause more resistance to flow than do the gradually sloping changes of reducing fittings.
- What does high velocity flow cause in a piping system?
- Water hammer.
- Increased friction loss.
- Erosion.
- How does high-velocity flow cause erosion in a piping system?
Fluids traveling at very high velocities wear away the material of the pipe walls.
- Where is erosion by high velocities a particularly important?
In the thin-walled tubing of hot water heat exchanges.
- A physical law inertia?
Matter resists change in its velocity.
- What causes water hammer?
Inertia and the non-compressibility of liquids.
- When does water hammer occur?
Water is traveling in a pipeline at high velocities and is suddenly halted by a quick-closing valve.
- Factors contributing to water hammer?
- Velocity.
- Size of pipe.
- Length of pipe.
- High pressure.
- How can water hammer be controlled or prevented?
- Providing an air chamber adjacent to the point of sudden shut-off, where a cushion of air can absorb the shock of the water hammer.
- Manufactured shock absorbers which mechanically prevent water hammer by means of a bellows, pistons, or diaphragm. They have the advantage of never becoming waterlogged.
- What may be defined as any state of matter of a particular composition or make up?
A substance.
- What is an element?
An element is any of more than 100 fundamental substances that consist of atoms of only one kind , and singly or in combination constitute all matter which can not be reduced by chemical means.
- What is a compound?
A compound is a substance composed by uniting two or more simpler substances or similar elements by ordinary chemical action in definite pre portions.
- What are the basic materials of which all substances are composed?
Elements.
- List five elements commonly used in the piping industry, and give their chemical symbol?
- Lead (Pb).
- Copper (Cu).
- Iron (Fe).
- Tim (Sn).
- Oxygen (O).
- What is an atomic weight of the heaviest element known : ununoctium (Uuo)?
293.
- What is the smallest particle of a substance which retains the properties of that substance and is composed of one or more atoms?
A molecule.
- Because molecules take more space (increased movement) when they are heated, long runs of pipe have to be designed to withstand these forces. Expansion is one of the most powerful forces known. How is expansion controlled in piping systems?
By using either an expansion loop or a specially designed expansion fitting.
- What temperature is water most dense at?
39*F.
- What is absolute zero be calculated in *F?
-460*F.
- List three terms that directly relate to a temperature change in a known substance?
- Specific heat.
- Sensible heat.
- Latent heat.
- What is a calorie?
The amount of heat required to raise the temperature of 1 gram (0.035 oz) of water 1* Celsius.
- Is the specific heat of ice 1.5?
F. S=.53.
- What are two terms closely related to liquids?
Solution and suspension.
- What is meant by the term solution?
A homogeneous mixture (thoroughly mixed) of two or more substances, the composition of which may vary to a maximum limit, called the saturation point.
- What causes suspension of particles on a liqui?
Solids not dissolved in a liquid.
- What makes the water molecule very stable?
Hydrogen bond.
- What are the physical properties of pure water?
It is odorless, colorless and tasteless.
- A scale for measuring the acidity or alkalinity of water and refers tithe active hydrogen atoms of water?
The pH scale.
- What is an ion?
An atom or group of atoms or molecule with an unbalanced electrical charge as a result of having lost or gained one pr more electrons.
- What would happen if the pressure were suddenly released from an enclosed vessel of water at 300*F and 100 psig?
Flashing of steam.
- What number of Btu will be involved when 50 lb of water at 32F changes to ice at 32F?
H=HltxW=144x50=7200 Btu.
- How many Btu are required to change 20 gal of water at 212F to steam at 212F?
H=HltxW=970.44x20x8.33= 161.668.64 Btu.
- Twenty cu.ft. of air is heated from 80* to180*F at a constant volume. What is the final pressure if the initial pressure is 10 psig?
P1/P2 = T1/T2 P2 = P1xT2/T1 = (20+14.7)x(180+460)/(80+460) = 41.13 psia =41.13-14.7 = 26.43 psig.
- What is the word work when discussing machines?
The product of force times distance: FxD = W.
- What is mean to do work upon the body?
A force acts upon a body and moves it.
- What does the term power mean in a technical sense?
The rate of doing work.
- What is unit of power?
Horsepower (hp).
- What does horsepower mean?
Rate of work 550 ft.-lb per sec or 33,000 ft.-lb per min.
- Formula for power?
P= TW/(550xT),
P-horsepower (hp),
TW-total work (ft.-lb),
T-time (sec).
- What horsepower engine is required to raise 2000 gallons of water per hour from a well 200’ deep (disregarding efficiency and friction losses)?
P = TW/(33,000xT) = FxD/(33,000xT) = (2000x8.3)x200/ 33,000x60 = 1.676 hp.
- List the six basic classifications of simple machines?
- Lever.
- Pulley.
- Wheel and axle.
- Inclined plane.
- Wedge.
- Screw.
- What is the fixed point of a lever called?
The fulcrum.
- List three classifications of levers?
- 1st class - fulcrum between effort and resistance;
- 2nd class - resistance between fulcrum and the effort;
- 3d class - effort between resistance and fulcrum.
- What is mechanical advantage?
M.A. Is the ratio of the force that performs work to the force which is applied to a machine, disregarding friction.
- What is friction?
The resistance to motion between two bodies in contact.
- How does friction affect machines?
It wears their moving parts and causes them to become impractical even though they may, theoretically, have a mechanical advantage.
- How do we determine the mechanical advantage (M.A.) of a lever?
The length of the effort arm (EA) is divided by the length of the resistance arm (RA).
M.A. = EA/RA.
- One of the basic rules or lows of mechanics?
Work input is equal to work output (disregarding friction).
- Why does the additional force gained by the lever is derived from additional motion at point EA?
Because the effort arm is times as long as the resistance arm, point EA moved times as far as point RA, and the work input is equaled the work output.
- What does journey worker often uses to force pipe “home” instead CI pipe pulling tool?
A tunneling bar.
- What is M.A. for a pulling tool for cast iron compression gasket bell and spigot pipe?
RA = 2"; Handle has 30"; M.A. = EA/RA =( 30"+2")/2" =16.
- What is the M.A. of the shovel if from spud to lift arm are 3’ and from that arm to fulcrum arm 2’?
M.A. = 2’/(2+3) = .4.
- What is advantage of a third class lever?
A gain in speed or distance.
- Examples of third class levers?
- Broom.
- Tweezers.
- Ice cube tongs.
- Human forearm.
- Shovel.
- How does statement: work input equals work output, disregarding friction, apply tithe three classes of levers?
The gain in force resulting in loss of distance and speed (2nd). The gain of speed and distance results in loss of force (3d). The first class lever can be adjusted.
- How are pulleys used in the pipe trades?
Individually as well wheels, and in combination as block and tackle.
- What is the rule for determining the M.A. of pulleys?
The mechanical advantage of a block and tackle is equal to the number of strands of rope supporting the movable block.
- What is the total force acting on the top hook of pulley of 3 vertical blocks?
TF = WP+RF = 300+100 = 400 lb;
TF-total force;
WP-weight of pump;
RF-force required to raise pump.
- What is mechanical advantage gained by the pulley of 3 vertical blocks?
Not only reduces the force needed to raise the load, but also reduces the total force on the top hook.
- What is the wheel and axle?
The wheel and axle utilizes circular motion to accomplish two basic functions. The first is to transmit force, and the second is to change speed.
- Ratio of force, speed, wheel size of a simple wheel and axle machin?
F1xA1 = F2xA2; D1xV1 = D2xV2; C1xV1 = C2xV2; F-force; A-arm; D-diameter; V-velocity; C-circumference.
- What is the formula for determining the M.A. Of the wheel and axle mechanism like hand brace?
M.A. = radius of wheel at handle/radius of axle at bit.
- Types of the wheel and axle mechanisms?
- Wheels are on separated axle: V-belt mechanism for speed changes.
- Wheels are on the same axle for transmitting force and motion.
- Transmitting force and motion through wheels and axles?
FxLA = RxRA: F-force; LA-lever arm; R-result; RA-radius of charge wheel.
- Ratio for speed change of wheel with V-belt?
V1/V2=D1/D2=C1/C2;
V-velocity;
D-diameter of the 1 driver or 2 driven pulleys;
C-circumference.
- What is the function of most inclined planes?
Raise or lower heavy objects.
- The formula for determining the M.A. of the inclined plane?
M.A. = L/H:
L-length of plane;
H-height of plane.
- What is M.A. of ramp 4” heigh and 12’ long?
M.A. = L/H = 12/4 = 3.
- What are two uses of the wedge?
- As cutting tools (chisels, ect.).
2. To level equipment.
- How is the M.A. of a wedge determined?
It is the ratio of its length to its thickness:
M.A. = L/T:
L-length,
T-thickness.
- Three uses of the screw?
- Ditch jack.
- Drill bit.
- Pipe thread.
- What is M.A. Of a screw?
The circumference divided by the pitch: M.A. = C/P:
C-circumference;
P-distance between threads.
- Two basic classes of energy?
- Potential.
2. Kinetic.
- What is the difference between potential energy and kinetic energy?
Potential energy is energy that is stored for future use.
Kinetic energy is energy related or pertaining to motion.
- What is mechanical equivalent of heat?
778 ft.-lb = 1 Btu.
- How does Joule apparatus for use in finding out how much work must be done to produce one Btu.?
The weights turn a set of paddles immersed in a known weight of water. The constant padding of the water warms it by friction.
- How can heat energy be used to do work?
By combustion engines.
- Types of combustion engines?
External and internal.
- How does external combustion engines work?
Heat energy from the burning coal, oil, or nuclear reactor produces the steam and the steam pushes a piston or turns the blades of a turbine.
- How does the internal combustion engine work?
The mixture of gasoline vapor and air is exploded in a thick-walled cylinder. The heat energy causes the gaseous products to expand and and push against the piston with great force.
- What is high-pressure engine or a non-condensing engine?
By movement of the slide valve, steam is admitted alternately to the opposite ends of the cylinder, thus the piston is pushed back and forth because openings in the cylinder are connected alternately with the steam supply and the exhaust pipe by means of the sliding valve.
- Describe the operation of a condensing engine (low-pressure engine)?
Stationary engines are fitted with a condenser, in which the spent steam is condensed by means of a spray of cold water. A partial vacuum is formed in the condenser and the back ward pressure of the air against the escaping steam is much reduce, possibly to only one pound per square inch.
- How does steam turbine work?
High speed steam from nozzles strikes the rotating blades, is deflected and expends in the process. The stationary blades then catch the steam and direct it back against a second row of rotating blades.
- What is formula for calculating the efficiency of a machine?
The ratio of the output energy to the input energy: E = OP/IP; E-efficiency; OP-output power; IP-input power.
- Energy lost by machine?
- Wasted heat.
- The fuel is not completely consumed.
- The hot gases going up the chimney.
- Radiation.
- Friction loss.
- What is a metal?
A metal is an element that exhibits all or most of the following characteristics:
- Solid at room temperature.
- Opaque.
- Conductor of heat and electricity.
- Reflective when polished.
- Expands when heated.
- Symptoms of gradual mercury exposure?
Tremors, insomnia, memory loss, headaches, vision problems, irritability and nervousness.
- How is mercury poisoning treated?
By administering chemicals that bond with the mercury and remove it from the body as waste?
- What is an alloy?
A material or substance made up of two or more elements, at least one of which is a metal.
- Alloyed materials which are used in the manufacture of pipe?
Brass, stainless steel, silicon iron.
- Two types of synthetic materials?
- Thermoplastic.
2. Thermoset.
- Difference between thermoplastic and thermoset materials?
Thermoplastic can be heated repeatedly and reshaped thermoset materials cannot beer formed even if subjected to melting.
- Types of the synthetic materials used for piping?
Manufactured of a petrochemical base and are of the thermoplastic type.
- What are some of the most common synthetic piping materials installed by journey workers?
Thermoplastic: ABS-acrylonitrile-butadiene-styrene; CPVC-chlorinated polyvinyl chloride; PE-polyethylene; PP-polypropylene; PVC-polyvinyl chloride; PVDF-polyvinylidene fluoride; Thermoset: FRP-fiberglass reinforced polyester.
- A brief explanation of several characteristics pertaining to use the use of PVC and CPVC piping materials?
Have smooth, seamless interior walls and are light in weight.
Inert to attack by most acid, alkalis, salt solutions, alcohols.
Highly resilient, tough and durable products that have high tensile and high impact strength.
Self extinguishing and will not support combustion.
Non-toxic, odorless, and tasteless.
Have a low thermal conductivity factor.
Maintenance free.
- Applications for PVC and CPVC piping?
Potable water, irrigation, chilled water, deionized water, chemical drainage, plating and chemical processing.
They are not recommended for use in compressed air or gas service.
- How is joining of PVC and CPVC materials accomplished?
By solvent cementing, threading or flanging.
- What are the basic principles of solvent cementing PVC and CPVC pipe and fittings?
- The joining surfaces must be softened and made semi-fluid.
- Sufficient cement must be applied to fill the gap between pipe and fitting.
- Assembly must be made while the surfaces are still wet and fluid.
- Joint strength develops as the cement dries.
- What is primer for PVC and CPVC?
Tetrahydrofuran (THF) and MEK may be used.
- Use solvent cement?
PVC cement must be used with PVC pipe and fittings. CPVC with CPVC.
- What type of applicator should be used to apply the primer and solvent cement to PVC and CPVC piping materials?
Daubers should only be used on pope2” and below.
Brushes can be used on any diameter pipe, should have a width equal to at least 1/2 the diameter of the pipe.
Rollers can be used on 4” and lager diameter pipe and should have a length equal to a at least 1/2 the diameter of the pipe.
- List several factors which must be considered by journey worker when installing PVC and CPVC piping materials?
- Hot weather: cementing operation should not be attempted where temperatures exceed 100*F.
- Cold weather: primer and cements penetrate slower.
- Set time: the time required before moving or handling the assembled joint (30 min for 1 1/2”-3” at 60-100F).
- Cure time: the time is required before filling and pressurizing a system ( 2hr for 1 1/2-3” at 60-100*F up to 180 psig).
- How are flanged systems limited for thermoplastic piping materials?
To 150 psig system pressure at 73*F. Flanges can be installed on the pipe by either solvent cementing or by threading.
- Where should not threaded pipe and threaded fittings be used?
In high pressure systems or in systems where a leak could endanger personnel.
- What are six rules which should be followed for threading plastic pipe?
- Only pipe with a wall thickness of schedule 80 and above can be threaded.
- Use pipe dies disowned for plastic pipe.
- Use a strap type vise and wrench to hold the pipe or chain-type with a rubber sheet wrapped around the pipe.
- Insert wooden plugs into the end of the pipe to be threaded.
- Use a die that has a proper size guide to ensure it starts square.
- Lubricate the cutting die.
- How is polypropylene (PP) severely defeated?
Ultraviolet (UV) radiation and should be protected from direct exposure to the sun and other UV exposure.
- Why do we use polyvinylidene fluoride (PVDF)?
It further extends the operating temperature/pressure range of thermoplastic piping.
- Use of polyvinylidene fluoride (PVDF)?
It is not recommended for ketones , but is prefer in applications that demand high purity (electronic, pharmaceuticals, food and beverage processing.
- How do you join fiberglass reinforced polyester (FRP)?
Hardener mixed with a polyester resin and applied to the joint and then reinforced with fiberglass.
- What are four of the most common installation methods used to compensate for expansion and contraction of PVC and CPVC piping materials?
- Expansion loops which consist of pipe and 90* elbows.
- Piston type expansion joints.
- Flexible bends.
- Bellows and rubber expansion joints.
- What must be done to ensure the satisfactory operation of a PVC or CPVC piping system?
- Concentrated loads (valves, flanges, etc.) should be supported directly so as to eliminate high stress concentrations.
- In systems where large fluctuations in temperature occur, allowance must be made for expansion and contraction.
- Changes in direction should be supported as close as practical to the fitting.
- Hangers should not restrict pipe expansion or contraction and a clamp type hanger should not deform the pipe when it has been tightened.
- Hangers should provide as much bearing surface as possible.
- Valves should be braced against operating torque.
- PVC and CPVC lines must not be placed alongside steam or other high temperature pipe lines.
- Why are metals usually specified for temperatures above 140*F and pressures above 65 psig instead synthetic piping materials such as PE and PVC?
PE and CPVC have flex distortion temperatures which are relatively close to 140*F at 65 psig and would likely fail if either the temperatures or pressures were to be increased.
- What are the names of some fillers used in the manufacture of synthetic piping materials?
Silica-glass, graphite, clay, cotton flock, chopped rags, magnesium carbonate, magnesium silicate, mica, aluminum, sisal, wood flour, granulated cork, nut shell flour, perlite, calcium carbonate.
- Name the raw material in which metal is contained?
Ore.
- List the four most abundant metals found in nature?
- Aluminum.
- Iron.
- Magnesium.
- Titanium.
- What are the four metals most commonly used in manufacturing pipe?
- Steel.
- Cast iron.
- Copper.
- Brass.
- What are two general categories of piping materials?
- Mechanical.
2. Physical.
- What are mechanical properties of piping materials?
- Hardness.
- Toughness.
- Rate of expansion.
- Endurance limit.
- What are some of the physical properties of piping materials?
- Electrical conductivity.
- Heat conductivity.
- Magnetism.
- Density.
- 4 the best conductor of heat?
- Silver-100.
- Copper-92.
- Gold-70.
- Aluminum-48.
Glass 10-25, iron 16, steel 11.
