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Aux Systems, Part II > Fresh Water Makers > Flashcards

Fresh Water Makers Flashcards

1
Q 
Which of the following desalination plants will always require a sterilizer when providing water to a potable water system?
A	Titanium plate type unit
B	Multi-stage flash type unit
C	Submerged tube type unit
D	Reverse osmosis type unit
A

D Reverse osmosis type unit

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2
Q

In order for a reverse osmosis fresh water generator to be able to overcome the osmotic pressure without damaging the spiral-wound membrane modules, the pressure must be controlled. What is the location of the pressure regulator?

A

Brine outlet from the membrane modules.

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3
Q 
Which of the following fresh water generators has an operating principle that evaporates pre-heated sea water by causing it to undergo a pressure drop into a vacuum?
A	Submerged tube unit
B	Flash type unit
C	Titanium plate unit
D	Reverse osmosis unit
A

B Flash type unit

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4
Q

A high reading is only indicated at the salinity cells labeled “W” and “6” shown in the illustration. This would be the probable result of __________. GS-0053

A

a faulty cell at location “6” and a tube leak in item “I”

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5
Q

If a reverse-osmosis freshwater generating unit has a high salinity alarm associated with the freshwater outlet, what should be done?

A

The membrane modules should be flushed and cleaned.

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6
Q

What is the BEST indication that the pre-treatment filter (or filters) of a reverse- osmosis freshwater generator must be serviced by cleaning or replacement?

A

An excessive pressure drop across the pre-treatment filter.

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7
Q

What is the BEST indication that the membrane module is damaged and is no longer semi-permeable and allowing the solute to pass through?

A

High freshwater outlet salinity.

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8
Q

A high reading at a salinity cell located in the loop seal between two stages of a flash type evaporator would indicate __________.

A

carryover in the first-stage

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9
Q

A high reading is indicated at the salinity cells labeled “Y”, “Q”, and “6” shown in the illustration. This would be the probable result of __________. GS-0053

A

carryover from “III”

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10
Q

The quantity and density of brine discharged from the last effect of a flash type evaporator should be kept at a constant value so as to __________.

A

ensure distillate quality and distilling plant efficiency

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11
Q 
Which of the listed problems could produce a high absolute pressure within a flash type evaporator?
A	seawater feed temperature below 165*F
B	a cracked distillate pump vent line
C	production of high salinity distillate
D	a leak in the first stage demister
A

B a cracked distillate pump vent line

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12
Q

If the demister used in the device shown in the illustration is improperly installed, which of the following will occur? See Illustration MO-0110

A

There will be an increase of chlorides measured at the distillate pump salinity cell.

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13
Q

Which of the following conditions can cause high salinity of the distillate due to sea water leakage in the illustrated device. MO-0110

A

Failure to properly tighten the bolts of the condenser heat exchanger.

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14
Q

Which of the conditions listed would indicate a large condenser tube leak within the distiller shown in the illustration? See Illustration MO-0111

A

The activation of the salinity monitoring equipment’s annunciator circuit.

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15
Q

A salinity indicator is used to determine the __________.

A

location of salt water contamination

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16
Q

A salinity indicating system functions on the basic principle of measuring the __________.

A

electrical conductivity of water

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17
Q

In a flash-type evaporator, an electrical salinity cell would be installed in the __________.
A distillate outlet from the distillate cooler
B distillate inlet to the distillate cooler
C condensate drains from the distiller feed water heater
D all of the above

A

D all of the above

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18
Q

Which of the following statements represents the basic principle of operation of an electrical salinity indicator?
A Measures the hydrogen ion concentration.
B Measures the voltage of the chloride ions.
C Measures the electrical resistance of the water.
D Determines the conductivity of the dissolved oxygen.

A

C Measures the electrical resistance of the water.

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19
Q

A salinity indicator system such as that used to measure the salt content of potable water systems and boiler feed and condensate systems uses what technology?

A

a salinity cell that senses the electrical conductivity of water

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20
Q

If the salinity indicator periodically registers high salinity in the main hot well, the cause may be __________.

A

a contaminated distilled water tank

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21
Q

Indicated high salinity of the distillate discharged from a flash-type distilling plant will be a result of __________.

A

leaks in the demister baffles

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22
Q

Regarding a freshwater generator of the reverse-osmosis type, what statement is true?
A The solute is salt and the solvent is fresh water.
B The solute is fresh water and the solvent is salt.
C The solute is saltwater and the solvent is salt.
D The solute is salt and the solvent is saltwater.

A

A The solute is salt and the solvent is fresh water.

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23
Q

reverse-osmosis freshwater generators usually feature multiple membrane modules, typically of the spiral-wound membrane type. How are these multiple membrane modules piped?

A

The multiple membranes may be connected in series, parallel, or in some combination of series and parallel.

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24
Q

Regarding a reverse-osmosis type freshwater generator using multiple spiral-wound membrane modules, what statement is true?
A Modules may be piped in series to increase the freshwater throughput.
B Modules may be piped in series to increase the freshwater purity.
C Modules may be piped in parallel to increase the freshwater purity.
D Modules may be piped in series to decrease the likelihood of fouling.

A

B Modules may be piped in series to increase the freshwater purity.

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25
Q

To ensure potable water of drinking quality, chemical treatment is required for reverse- osmosis freshwater generators. What is the purpose of chemical pre-treatment?

A

Chemical pre-treatment sterilizes the sea water entering the unit to prevent bacteria from becoming resident in the reverse-osmosis unit filters and membrane modules.

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26
Q

Regarding the operating principle of a reverse-osmosis type freshwater generator, what statement is true?

A

External pressure is applied to the side of strong concentration forcing freshwater through the semi-permeable membrane to the side of weak concentration.

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27
Q

Regarding the high-pressure pump of a reverse-osmosis freshwater generator, what statement is true?

A

The high-pressure pump is typically a multiple-cylinder reciprocating pump, but may be a multi-stage centrifugal pump.

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28
Q

For the successful operation of a reverse-osmosis freshwater generator, why is the high pressure pump required to operate in the 750 to 1200 psig range for a discharge pressure?

A

To overcome the osmotic pressure generated by the difference in solution concentrations.

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29
Q

For the successful operation of a reverse-osmosis freshwater generator, the setting of the brine back pressure regulator is critical. What statement regarding the set point of this regulator is true?

A

If the regulator setting is set too high, the membrane modules may be damaged. If the regulator setting is too low, the freshwater production will be too low.

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30
Q

What component of a reverse-osmosis freshwater generator could be isolated and replaced with the unit remaining in service?

A

A parallel-connected membrane module.

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31
Q

Under what conditions would the pre-treatment capabilities of a reverse-osmosis freshwater generator MOST likely be overloaded, and as a result, these conditions should generally be avoided?

A

Entering harbors.

32
Q

When a reverse-osmosis freshwater generator is shutdown, what must be accomplished?

A

The unit must be flushed with freshwater and treated with an anti-bacterial growth inhibitor.

33
Q 
Which of the freshwater generators listed below is operated without a source of heat?
A	Titanium plate type
B	Flash type
C	reverse-osmosis type
D	Submerged tube type
A

C reverse-osmosis type

34
Q 
Which of the following freshwater generators has an operating principle that requires it to run under a substantially positive pressure?
A	Submerged tube unit
B	Titanium plate unit
C	reverse-osmosis unit
D	Flash type unit
A

C reverse-osmosis unit

35
Q 
In which of the following freshwater generators would an air ejector be unnecessary?
A	reverse-osmosis unit
B	Submerged tube unit
C	Titanium plate unit
D	Flash type unit
A

A reverse-osmosis unit

36
Q 
Which of the freshwater generators listed below requires a source of heat and evaporates sea water at a location other than a heat exchanger surface?
A	Submerged tube type
B	reverse-osmosis type
C	Titanium plate type
D	Flash type
A

D Flash type

37
Q

If a reverse-osmosis freshwater generator has fouled membrane modules, what statement is true?

A

The freshwater production rate would be lower than normal, and the feed pressure would be higher than normal.

38
Q 
In a two-stage flash evaporator, the sea water feed temperature is increased as it passes through the \_\_\_\_\_\_\_\_\_\_.
A	first-stage distilling condenser
B	second-stage distilling condenser
C	salt water feed heater
D	all of the above
A

D all of the above

39
Q

In a flash evaporator, heated water under pressure is converted into vapor by suddenly __________.

A

decreasing its pressure

40
Q

If the orifice in the loop seal of a flash evaporator were to become significantly enlarged through erosion, the __________.

A

evaporator absolute pressure could eventually equalize in both stages to that of the second stage

41
Q

Other than taking a scale thickness through a zinc plug opening of the water box of a feed water heater of a flash evaporator, what would be the BEST indication for a need to remove scale build-up?

A

A rise in the feed water heater shell temperature and a rise in the feed water heater shell absolute pressure (decrease in vacuum).

42
Q

What procedure can be used to reduce the rate of scale formation on the heating surfaces of a flash evaporator while still maintaining the desired rate of distillate production?

A

Chemically treating the incoming feed water.

43
Q

Where a two-stage air ejector set is used in a two-stage flash evaporator, the first-stage air ejector takes suction from the second stage of the evaporator, and the second stage air ejector __________.

A

takes suction from the first stage ejector discharge

44
Q

A fixed orifice plate is generally installed in the live steam supply to a flash evaporator. One of the functions of this orifice is to control the quantity of the supplied steam. A second function is to __________.

A

reduce pressure fluctuations of the steam supply in the salt water feed heater

45
Q

The thickest deposit of scale in a flash evaporator is most likely to occur in the tubes of the __________.

A

saltwater feed heater

46
Q

In a flash evaporator, scale as a result of higher than normal temperatures is most likely to occur in the __________.

A

saltwater feed heater

47
Q

If a higher than normal water level is observed through the inspection port of a flash evaporator, you should suspect __________.

A

a malfunctioning brine pump

48
Q

Irregular feeding or surging of the feed water supply to a flash evaporator may be attributed to __________.

A

a dirty strainer in the salt water feed pump suction line

49
Q

A multistage flash evaporator will be unable to produce consistently pure distillate if the __________ .

A

vacuum is fluctuating

50
Q

An excessively high brine level in a flash evaporator can be caused by __________ .

A

failure of the brine pump

51
Q

In a two stage flash evaporator, heated feed water is vaporized in the __________ .

A

first and second stage flash chambers

52
Q 
In which of the areas listed would you expect to find the highest salt concentration in a flash evaporator?
A	Distiller air ejector cooling medium
B	Saltwater heater discharge
C	First-stage internal feed box
D	Second-stage internal feed box
A

D Second-stage internal feed box

53
Q 
In which of the following types of evaporators is the control of brine density least important?
A	Solo shell evaporators
B	flash evaporators
C	Submerged tube evaporators
D	Basket evaporators
A

B flash evaporators

54
Q

Irregular feeding or surging of the feedwater supply to a flash evaporator may be attributed to __________ .

A

a dirty strainer in the saltwater feed pump suction line

55
Q

Less scale formation occurs in a flash evaporator than in a submerged tube evaporator because __________ .

A

no boiling occurs on heat transfer surfaces

56
Q

One distinct advantage of flash type evaporators, as compared to most other evaporators, is that in a flash evaporator shell __________ .

A

scale formation is not a severe problem

57
Q

The condensers located in the various stages of a flash evaporator are cooled by __________ .

A

seawater

58
Q

The distillate produced by a flash evaporator has a salinity of 0.21 grains per gallon, with a feed water temperature entering the first-stage of the evaporator at 170°F. Under these conditions the three-way solenoid valve will __________.

A

direct distillate to the freshwater tanks

59
Q

The first stage feedwater temperature and shell absolute pressure in a multistage flash evaporator is __________ .

A

higher than the second stage feedwater temperature and shell absolute pressure

60
Q

Tube leaks in the distillate cooler of a two stage flash evaporator will result in __________ .

A

contamination of the distillate

61
Q

Vapor is produced in a flash evaporator by introducing __________.

A

heated water into a low pressure area

62
Q

What is the main reason that live auxiliary steam is normally attemporated before entering the feed heater of a flash evaporator?

A

To reduce the rate of scale formation on heating surfaces.

63
Q

When a flash evaporator is being operated in extremely cold water, you may need to throttle the seawater supply to __________.

A

maintain the feedwater temperature above the required minimum input temperature

64
Q

Which of the listed conditions will cause the feed water, that has not flashed to vapor in the first-stage of a flash evaporator, to flow into the second-stage?

A

Higher vacuum in the second-stage

65
Q

While in operation, the function of the orifice in the flash evaporator loop seal is to __________ .

A

maintain the absolute pressure difference between the first and second stages

66
Q

Small droplets of water entrained in the flashed vapor produced in a flash-type evaporator are removed by the __________.

A

demisters

67
Q

In order to prevent salt water contamination of the distillate in a flash-type evaporator, it is important to provide a positive seal around the __________ .

A

demisters

68
Q

The demisters installed in a flash-type evaporator serve to __________.

A

remove small water droplets entrained in the flashed vapor

69
Q

The process of boiling seawater in order to separate it into freshwater vapor and brine is usually defined as __________.

A

evaporation

70
Q

Which of the following statements is correct relative to distillation plant operation?

A

Distillation is the process of boiling seawater to produce vapor which is condensed into fresh water.

71
Q

The efficiency of a flash type evaporator can be increased by __________.

A

decreasing the absolute pressure of each stage

72
Q

Diesel engine jacket water is used in the fresh water distillation process as the __________.

A

means of heating the feed water

73
Q

The brine level in the second-stage of a flash-type evaporator is determined in part by the feed rate, the rate of evaporation in both stages, and the __________.

A

throughput of the brine overboard pump

74
Q

What is the BEST indication that the membrane module is damaged and is no longer semi-permeable and allowing the solute to pass through?

A

High freshwater outlet salinity.

75
Q

In a two-stage flash-type distilling plant, the mesh-type vapor separators function to __________ .

A

improve distillate purity

76
Q

The vapor separators installed in some distilling plants consist of several rows of vertical hooked vanes which remove entrained moisture from the vapor by __________ .

A

abruptly changing the direction of vapor flow

Aux Systems, Part II (5 decks)

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