1st Grade Study Before Test

Question 1

What causes freeze back on an ammonia compressor?

Answer 1

Improper charge or improper operation of metering device.

Question 2

How does an evaporator condenser work?

Answer 2

An evaporator consists of a steam coil in a tank. Water is fed to the tank and a float maintains a constant level. A pump circulates and sprays water over the refrigeration condenser. A fan draws in air through the side of the evaporative condenser housing and forces air out the top. Water droplets are cooled by evaporation and flow over the condenser.

Question 3

In regards to refrigeration what is superheat?

Answer 3

Temperature of vapor above its boiling temperature as a liquid at that pressure.

Question 4

What’s a reaction turbine and what’s it used for?

Answer 4

It is designed so there is considerable expansion in the rotating blades. Used for extraction for other pieces of equipment.

Question 5

Why is welding preferred over riveting on longitudinal?

Answer 5

Welded longitudinal joints are stronger than riveted joints, welding eliminates areas where sludge can form

Question 6

Manifold duplex water pumps?

Answer 6

Used for boiler feed service and is capable of handling water at high temperatures without cavitation. They are operated by two float switches set to start the water pumps at low and high water levels in the receiver. SPO 6th 345

Question 7

What are five basic methods used for protection of cross contamination of potable water

Answer 7

(1.) Air gap, no less than 1” and no more than 2 times the diameter of the pipe. (2.) An atmospheric style vacuum breaker (3.) a pressure style vacuum breaker (4.) reduced pressure style back flow preventer (5.) double check valve assembly.

Question 8

What is lagging? And how does it affect efficiency?

Answer 8

Lagging is an outer covering over a wall used for protecting the insulation from water or mechanical damage. To provide safety for personnel and minimize heat loss, thus improving efficiency.

Question 9

Which tubes on a sterling boiler are beaded?

Answer 9

Every other tube in the bottom row of the top drums for drainage, every other tube in the top of the mud drum. This prevents air pockets from forming.

Question 10

When installing a tube in a tube sheet how much of the tube should stick out pass the tube sheet?

Answer 10

T = thickness of the tube,
No more than 2T and no less than 1T and
no less than 1/8” or more than ¼”.

Question 11

Is it necessary to brace or stay a flat surface, and why?

Answer 11

Yes, to over come the bulging forces on the boiler plate.

Question 12

What is the average amount of water evaporated per square ft. of heating space?

Answer 12

34.5 lbs. per hour / 10 sq. = 3.45 lbs. per hour from & at 212ºF

Question 13

What is a Fyrite analyzer, where is it used, why is it used?

Answer 13

It is a flue gas analyzer to determine the amounts of O2 and CO2 in the flue gasses. Combustion gasses are sampled from the last pass or the breeching. It determines combustion efficiency.

Question 14

What is an orsat apparatus? Where is it used? Why is it used?

Answer 14

It is a flue gas analyzer that measures the percentage of carbon dioxide, oxygen and carbon monoxide in the gasses of combustion. It is placed in the breeching. It determines combustion efficiency.

Question 15

What useful purpose is nitrogen in a boiler?

Answer 15

In dry storage, nitrogen is used on the water-side.
In the fire nitrogen will control the burn ratio of fuel in the furnace.

Question 16

What is thermal efficiency and what is a good percentage?

Answer 16

It is the ratio of heat supplied by the fuel to heat absorbed by the boiler; a good percentage is 85%.

Question 17

What is volatile matter, and what is fixed carbon?

Answer 17

A form of combustible gasses – hydrocarbons – that are distilled off of coal when it is heated. Fixed carbon – coal that lies on the grate and burned there.

Question 18

What effect if any, does volatile matter in coal have on the smoke produced when coal is burned?

Answer 18

Coal with a high volatile matter content needs a larger combustion space for proper air to fuel ratio to prevent smoke.

Question 19

Describe the operation of the pulverizer.

Answer 19

Crushed coal is fed into balls or rollers rotating on a stationary grinding ring or fed into a housing containing a rotating element reducing the coal to power, primary air then carries the pulverized coal into the furnace.

Question 20

If you used 3 ton of coal in an 8 hour shift and averaged 150 Boiler HP what was the rate of evaporation?

Answer 20

One boiler HP = 34.5 lbs. of steam per hour
34.5 X 150 BHP X 8 hr. = 41,400 lbs. of steam an hour.

Question 21

What devices are in the fuel oil train to the boiler?

Answer 21

Thermometer, shut off valve, vacuum gauge, check valve, priming tee, duplex strainers, pumps, relief valve, isolation valves, pressure gauges, prv, metering valve, solenoid valves, oil heaters, nozzles.

Question 22

Name the parts of the safety valve.

Answer 22

Body,
Cap,
Blowback ring,
Spring,
Disk,
Lever,
Lifting gear,
Compression screw,
Spindle.

Question 23

How often should you operate a soot blower?

Answer 23

Depending on the type of fuel, it is done generally at the start of the shift and economizers and air preheaters once a day.

Question 24

Name three factors that cause scale?

Answer 24

High conductivity, high hardness, poor water treatment.

Question 25

Give three reasons to treat boiler water.

Answer 25

Reduces scale, prevents foaming and priming, and reduces corrosion and improves efficiency.

Question 26

Give three ways to put water back in your boiler.

Answer 26

Feed water pump, city water, tilt trap, injector.

Question 27

Name the parts of a centrifugal pump?

Answer 27

Impeller key to shaft, shaft, shaft sleeve, shaft bearings, impellers, impellers rings, O rings, seal rings, mechanical seals, grease seals, packing, casing.

Question 28

Describe the operation of the centrifugal pump.

Answer 28

The spinning impeller draws liquids into its center, and discharges it from its outer edge into a spiral casing, the velocity of the liquid is changed to pressure head.

Question 29

How is the discharge pressure of a stage of a centrifugal pump determined?

Answer 29

It is the calculation of impeller size. Impeller speed, friction losses and the size of the suction and discharge.

Question 30

What problems would you watch for when paralleling two centrifugal pumps?

Answer 30

Make sure the pump capacities remain the same, so one pump does not hog the load.

Question 31

Define Volumetric efficiency.

Answer 31

Theoretical intake minus the discharge, expressed in percentage of the intake. It is what you would call slip.

Question 32

Describe a motor driven rotary pump.

Answer 32

It is a positive displacement pump. It has rotating shaft or shafts with rotors consisting of gears, vanes, lobes, cams, screws, operating in a close fitting casing. They do not use valves in their design and they operate efficiently on both low & high viscosity liquids with a low NPSH requirement.

Question 33

Give seven advantages of a rotary pump.

Answer 33

a. Self priming b. Low NPSH requirements c. Can handle high viscosity liquids at a high efficiency d. Wide speed range e. Are available for low capacity, high head or high capacity applications. f. Capable of high suction lifts g. Slip is low

Question 34

What is a vacuum chamber?

Answer 34

It is the first chamber from the return line in the Redi-vac pump. It is a chamber installed on the suction side of the pump that smoothes out the flow of water to the pump. It works on the same principal as an air chamber.

Question 35

A 6 X 4 X 8 X 100 simplex pump will pump how many gallons of water in 5 minutes?

Answer 35

D X D X .7854 X length X frequency X minutes divided by cubic inches per gal. 4 X 4 X .7854 X 8 X 100 X 5 / 231 = 217.6 gallons D X D .7854 length frequency minutes cubic inches / gal. without considering the piston shaft.

Question 36

What is the piston diameter of a double acting simplex pump that has an 18 inch stroke, 30 strokes per minutes and will pump 500 gallons per minutes with 20% slip?

Answer 36

The formula for figuring gpm is D sq X ¼ pie X Double acting X length X frequency X efficiency divided by cubic inches per gal = 500 gpm ~ Reverse formula ~ 500 X 231 / .80 / 30 / 18 / 2 / .7854 = 170.2 which is Dsq sq. root of 170.2 rounded = 13.0 inches Not considering the piston shaft.

Question 37

What is aspirating?

Answer 37

A aspirating unit of it’s self is priming the pump by removing the air from the suction side.

Question 38

What is the difference between an impulse and a reaction turbine, name four types?

Answer 38

The impulse turbine is designed so the expansion of the steam occurs almost entirely in its stationary blades, and there is almost no pressure difference of the steam entering and leaving the stages. Types of Impulse: Re-entry flow, rotor, vertical, horizontal, de Laval Wilkinson, Zoelly, Pelton. The reaction turbine is designed so there is considerable expansion in the rotating blades and there is a pressure difference of the steam entering and leaving the stages. Types of Reaction: Tamden, Cross compound, single flow, double flow, Parsons, Allis chambers, Ingersal Rand.

Question 39

What forms of energy losses are in a turbine?

Answer 39

Steam leakage friction between stages, Eddy friction losses, Windage friction, Radiation, Mechanical friction, Steam velocity losses from last stages to condenser.

Question 40

How are turbine blades made and of what material are they made? How are they fastened in place?

Answer 40

Turbine blades are dropped forged steel, they are rolled and drawn sections of stainless steel. Rotating blades are secured by “T” root fastenings with lugs machined on the shank straddling the blade groove, and held against the shoulder in the groove by half round sections, caulked in place at the bottom. Stationary blades are anchored in straight sided grooves by a series of short keys, which fit into auxiliary grooves cut in the blade shank, and in the side of the main groove.

Question 41

How are rotors made?

Answer 41

Small turbines the rotors are machined steel disk shrunk and keyed onto a heavy steel shaft. Larger turbines have their rotors formed from a single piece forging including both journals and coupling flanges. Rotors must be statically and dynamically balanced.

Question 42

Can a turbine be run without a governor?

Answer 42

Yes, those on large ships that drive the screws, may be found without a governor.

Question 43

What are shroud rings?

Answer 43

Placed around the outer rim of the blades or nozzles, these rings are peened to the tenions to stiffen the blades and confine the steam to the blade path.

Question 44

What is seal stripping?

Answer 44

These are sealing strips between turbines stages to reduce leakage between stages.

Question 45

What is a dummy packing, dummy piston and where are they located?

Answer 45

A dummy packing is part of a labyrinth sealing device on a dummy piston. The dummy or balanced piston is a large disk that is part of the rotor, arranged to have a different pressure on each side creating a thrust action toward the high pressure side, balancing the end thrust. It is located between the impulse and the low pressure section.

Question 46

Define thin tipping.

Answer 46

Machining the tips of the turbine blades to a point, so they will make a harmonic noise alerting the operator if the rotors move radically and rub against the casing, which would cause damage to the blades.

Question 47

What is a grid type extraction valve and what is used on it?

Answer 47

This valve consists of a stationary port ring and a rotating grid. The rotating grid turns against the stationary ring and opens the ports in sequence. They give accurate control of the extraction steam pressure.

Question 48

What is the lowest flash point for oil used in a turbine?

Answer 48

325ºF

Question 49

Describe how you would align a turbine.

Answer 49

Use a straight edge to measure equal points on the shafts and couplings, they’re parallel. The shafts must be central and parallel, check by placing a straight edge parallel to shafts and the same across the rims of the coupling flanges, checking for equal distances at four places around the shaft, always the same places. Use a feeler gauge between the coupling flange faces, if measurements are equal at all points on the shafts and couplings they are parallel. Always follow the manufacture instructions.

Question 50

What is a Jet condenser? A barometric condenser? A water-leg condenser?

Answer 50

In a Jet condenser, water comes down from high pressure jets meeting the steam that enters on the side, together they drop into the hot well, which overflows by gravity, permitting non-condensable to escape. Two types are low level jet and a barometric jet. The barometric condenser is a condenser with a 34 foot plus tail piece. The weight of the water falling down the long tail piece draws a vacuum, reducing back pressure on the engine or turbine, increasing its efficiency. A water-leg condenser is a naval name for a barometric condenser, it has a 34 foot plus tail piece. The weight of the water falling down the long tail piece draws a vacuum, reducing back pressure on the engine or turbine increasing its efficiency.

Question 51

Explain how a disk flow condenser works.

Answer 51

Cooling water enters the top, cascading down over the disks. Exhaust steam entering from the side condenses when cooled by the water. Condensate and cooling water flow down the 35’ tail pipe into the hot well. Non-condensables are removed by a two stage ejector located in a vent condenser at the same height.

Question 52

How are Condenser tubes held in place?

Answer 52

Fiber or metallic packing on both ends held in place by a ferrule. Packed on the water outlet and expanded on the inlet. Rolled or expanded on both ends. It can be welded.

Question 53

What is a Vent condenser.

Answer 53

A small condenser located on the vent of a larger condenser pulling off air and vapor, to discard the air to the atmosphere, and the vapor is condensed and flows to the hot well.

Question 54

Define cooling tower and name two types.

Answer 54

It is a cooling pond equipped with louvered walls and arranged in one or more decks. Sprays are located on top of the structure, discharges the water to be cooled, as the water drops, air passes up the descending spray removing heat by evaporation. Two types are Natural draft and mechanical draft.

Question 55

Define hyperbolic.

Answer 55

Lines converging from all points to one center. In a hyperbolic cooling tower air is drawn from all directions to converge in the center, exiting out the top.

Question 56

Define traveling screen.

Answer 56

It is used to clean incoming cooling water, a string of baskets joined to form a chain revolves into the bottom of the intake tunnel. Foreign matter is deposited into the baskets and is carried away, on the return trip a spray of water cleans the screens.

Question 57

Define Extraction or Bleeder turbine, Double flow turbine and Semi double flow turbine.

Answer 57

In the extraction type, openings are provided in the turbine casing for extraction of the steam, for heating feed water or other purposes.In the double flow, steam enters the center of the turbine and flows both directions parallel to the shaft, balancing the end thrust. In the Semi double flow, steam enters the turbine passing through one set of blades, then is divided flowing both directions parallel to the shaft, reducing end thrust.

Question 58

What is the difference between a bleeder turbine and a mixed pressure turbine?

Answer 58

The bleeder turbine allows for the extraction of steam at various pressures, from the turbine for other processes. The Mixed pressure turbine admits steam of various pressures into the turbine.

Question 59

What is a reduction gear?

Answer 59

Because turbines run at high shaft speeds, speed reduction gears are sometimes needed to achieve a usable end speed.

Question 60

What do you check on a turbine hourly, monthly, yearly?

Answer 60

Hourly: Oil pressure and temperature, bearings, cooler, steam pressure and temperature, gpm., the load and abnormal noise. Monthly: Check oil for water and sludge, check oil strainer, check governor, over speed trip, vacuum breakers, condensers. Yearly: Dismantle and check for corrosion, wear dirt and scale, oil and steam passages, eroded blading and all valve seats, lubrication system, governor parts, bearings, vacuum pumps, ejector, air leaks.

Question 61

What is the difference between an open feed water heater and a D.A. tank?

Answer 61

The original type open feed water heater operates near atmospheric pressure, simply heating the feed water. The deaerators will operate from 5psi to 15 psi heating the water hotter and has a vent condenser which removes O2 and CO2 from the water.

Question 62

What are the advantages of a feed water heater?

Answer 62

Reduces thermal shock on a boiler, Saves BTU’s, and a D.A. heater will remove O2 and CO2.

Question 63

When installing a steam header what factors must be taken into consideration?

Answer 63

You must consider adequate support for expansion and contraction, operating pressure, velocity and pressure drop, insulation, valve location, trap location, flow of condensate. If you have to connect a common header to the piping listed, what would be the size of the header? 10-1/2” lines, 12-3/4” lines and 2- 4” lines. 10 – ½” lines .5 X .5 X .7854 X 10 = 1.9635 12 – ¾” lines .75 X .75 X .7854 X 12 = 5.3 2 – 4” lines 4 X 4 X .7854 X 2 = 25.133 Added together = 32.397 and √ is 5.692 Next closest size would be 6”

Question 64

Describe a Van Stone pipe joint and where they are used?

Answer 64

The joint is formed by slipping flanges over the pipe then flaring and machining the ends, which are sealed with a gasket when assembled. These joints are used in tight places and easy to put together.

Question 65

Name the methods of joining high pressure steam lines?

Answer 65

Butt welds, or weld flanges.

Question 66

If you have a 100ft. steam line carrying 150 lbs steam pressure in a 70ºF room, how much room is needed for expansion? And what if you had 5 lbs of steam?

Answer 66

Final temp – initial temp X length X inches X coefficiency of expansion/inches/degree for steel. Expansion with 150 lbs steam 366ºF – 70º F X 100 X 12” X .00000734 = 2,607” Final temp – Initial temp X length X inches X coeffic/expan/inch/degree Expansion with 51 lbs of steam 227ºF – 70ºF X 100 X12” X .00000734 = 1.383” Final temp – Initial temp X length X inches X coeff/expan/inch/degree

Question 67

130. How would you operate a vacuum return system with the pump out of service?

Answer 67

Open the condensate line to the drain, increase the makeup to the boiler. Then increase the system pressure if you can to help push the condensate through the system.

Question 68

131. If a boiler HP is equal to 34.5 lbs. of steam per hour and from and at 212ºF, how many BTU’s are equal to a boiler HP?

Answer 68

34.5 X 970.3 BTU’s = 33,475.35 BTU’s/hp

Question 69

133. Define specific heat.

Answer 69

The amount of heat in BTU’s required to raise the temperature of one pound of a substance one degree.

Question 70

134. How hot is steam at 5 pounds gauge and 150 pounds gauge?

Answer 70

5 psig = 227 o F 150 psig = 366 o F

Question 71

135. What is latent heat of one lb. of steam at 0 lbs. gauge and at critical pressure?

Answer 71

At 0 psig, it is 970.3 BTU’s, at critical pressure it is 0 BTU’s