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151/23/007 > RO Plants > Flashcards

RO Plants Flashcards

1
Q

What are the uses of demin water on RN ships?

A

Gas turbine wash
Helicopter engine wash
Medical uses
WE cooling systems
Chilled water systems
Diesel coolant systems

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2
Q

What are the uses of fresh water on RN ships?

A

Drinking/ ice machine
Upper decks wash down
Laundry
Bathrooms/ heads
Galley
Gas turbine wash ( if no demin)
Fuel separators/ LO separators
Mess decks
Weapon magazine space
Technical (demin) water RO plant

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3
Q

Explain the purpose of conductivity meters

A

To give a visual indication of the presence of salt in the sea, potable and technical water of certain engine room machinary

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4
Q

Explain the principle of conductivity meters

A

If two electrodes are placed at a predetermined distance apart in an i contaminated feed water system
Current is applied in series with a lamp
Fresh water being high resistance only allows a minute current to flow
Insufficient to burn indicating lamps
Presence of salt in the water reduces the resistance between the two electrodes allowing an increase in current of sufficient value to burn the lamp

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5
Q

Draw a simple diagram of a conductivity meter

A

Refer to docket

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6
Q

What are the factors determining current flow?

A

Distance between electrodes
Amount of salt in water
Temperature of the water

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7
Q

How are the probe electrodes cleaned?

A

Isolate electrical supply
Disconnect probe
Scrub using nylon brush and 50:50 mix of general purpose detergent and demin water
Rinse throughly and refit

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8
Q

What is the level of chlorination in FW tank?

A

0.5-0.8ppm

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9
Q

What is the level of chlorination at the tap?

A

0.2-0.5ppm

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10
Q

Explain the term Superchlorination and the solution strength used?

A

Uses extremly high dose of chlorine to sterilise the tank
50ppm

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11
Q

When is superchlorination carried out?

A

On commissioning
After cleaning or re-coating internal surface of FW tank
Whenever it is considered necessary to sterilise a FE system or part of the system

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12
Q

What equation is used to determine how much chlorine to add to a system?

A

D=C/1000 x 100/A x V

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13
Q

D=C/1000 x 100/A x V
What does each letter mean?

A

D - quantity of chlorine compound (g)
C - initial concentration of chlorine (mg/L)
A - available % of chlorine in compound
V - volume of water (L)

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14
Q

Describe the potable water chlorine test

A

Fill beaker sample to 25 ml
Glass test tube tip is snapped in water sample beaker
Water filled and mixed with solution
Presence of chlorine will discolour the sample within one minute
It’s colour is compared with a chart to show chlorine content in water

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15
Q

What is the quality of water required by RN?

A

Fresh water - 250-300ppm - all ships
Demin - 2.5-25 ppm - gas ships
- < 0.1 ppm nuclear submarine

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16
Q

What is the chemical compound used for the chlorination of the fresh water supplies?

A

Calcium hypochlorite

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17
Q

What is water purity standards measured in?

A

PPM or TDS ( total dissolved solids)

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18
Q

What water purity is tap water in the UK?

A

200-250 ppm TDS

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19
Q

What level is sea water conductivity?

A

30,000-40,000 ppm
Above 55,000 ppm will include high quantities of pollution, silt, etc

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20
Q

List the steps taken to minimise contamination and stagnation in fresh water systems on board RN ships

A

Tank swapped every 24 hours
Aerator
Injection of chlorine
Non-return valves
Lockable sounding tubes
Leak off lines
Air escape tubes
No dead legs

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21
Q

What is the desired temperature of a calorifier and why?

A

66 degrees C
Prevent scalding

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22
Q

How do you adjust the temperature of a calorifier?

A

Adjust the bimetallic strip deflection using a screwdriver

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23
Q

What would be looked for whilst carrying out a routine inspection of the ships plumbing?

A

Physical damage to systems
Vibration damage to systems
Noise shorts

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24
Q

What are the products after RO has taken place?

A

High purity permeate - 90-99% of of dissolved solids and bacteria have been rejected
Concentrate - remainder of feed water plus rejected dissolved solids and bacteria

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25
Q

What quality does each stage produce?

A

RO1 < 1000 uS/cm
RO2 - 100 uS/cm

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26
Q

What is the principle of Osmosis?

A

A natural process where a solution of a low concentration
Flows through a semi-permeable membrane
To dilute solution of high concentration
Will continue until equilibrium is reached
The level on the high concentration side will rise

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27
Q

What is the principle of Reverse Osmosis?

A

The natural process of osmosis is reversible, if sufficient pressure can be applied to the salt solution to overcome osmotic pressure head.
The level of pure water will increase leaving a greater concentration of salt solution
Process removes 90-99% of total dissolved solids and bacteria
There is a requirement to chlorinate the water made by this process before it is fit for human consumption to ensure the water is bacteria free.

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28
Q

State the location and functions of the following components on the RO including Parameters.

Anti scalant dosing pump

A

Prior to the cartridge filters
Continually injects anti-scalant into oncoming feed water supply
Minimises salt precipitation and scale build up on membranes

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28
Q

State the location and functions of the following components on the RO including Parameters.

Carbon filter

A

Chlorine will attack and destroy membrane materials
5 micron rated filter
1st stage filter is fitted to remove chlorine from flushing, chemical cleaning, preservation and antiscalant water

28
Q

State the location and functions of the following components on the RO including Parameters.

Cartridge filter

A

Fitted after the sand/bag filter
Filter finer suspended particles from the sea water
rated 1 - 10 microns
these are replaced monthly or 1-2 bar

28
Q

State the location and functions of the following components on the RO including Parameters.

Boost Pump

A

Fitted before the prefilters
Supplies water to the HP pump with a min pressure of 1 bar
2.5-4.5bar

28
Q

State the location and functions of the following components on the RO including Parameters.

Relief Valve

A

Fitted to the HP pump discharge from 1st and 2nd stage
Protects the membranes from high pressure
Lifts at 69 bar (1st stage) 41 bar (2nd stage)

28
Q

State the location and functions of the following components on the RO including Parameters.

HP Pump

A

Fitted between the cartridge filters and membrane array
Working pressure of 10-65 bar
Three piston reciprocating or axial piston pumps are fitted to 1st and 2nd stage as required

28
Q

State the location and functions of the following components on the RO including Parameters.

Pulsation dampers (accumulator)

A

Fitted to discharge side of HP Pump
Charged with Nitrogen and reduce the effects of pulsation

28
Q

State the location and functions of the following components on the RO including Parameters.

Sand and bag filters

A

Between boost pump and cartridge filters
1st stage is fitted with >50 micron sand or bag filters
Sand filters backwashed when DP is 1 bar
Bags are replaced when DP is 2 bar

28
Q

State the location and functions of the following components on the RO including Parameters.

Conductivity probe/sensor

A

Transmits the conductivity of permeate to the conductivity meter, is a measure of the chloride level in the water. any increase implies a higher level of salt concentration in the water
Measured in micro-siemens

28
Q

State the location and functions of the following components on the RO including Parameters.

Semi permeable membrane

A

Fitted between the HP Pump and pressure control valve
Spirally wound or cushion type RO membrane filters

28
Q

Draw the diagram of a semi-permeable membrane module

A

refer to docket

28
Q

State the location and functions of the following components on the RO including Parameters.

Reject control valve

A

fitted after the membranes to 1st and 2nd discharge line/control panel
Regulates the feed water pressure through the membranes within the range of 10-65 bar

28
Q

State the location and functions of the following components on the RO including Parameters.

Flow meter

A

Fitted to 1st and 2nd stage units between membranes and water tanks
Provides indication of permeate flow from each stage, can transmit an electrical signal via the magnetic float to the plc which can actuate the control valve to adjust system pressure which will adjust the permeate output

28
Q

State the location and functions of the following components on the RO including Parameters.

Conductivity meter

A

Fitted to the 1st and 2nd stage permeate outlets
Provides a visual indication of conductivity of permeate
Potable water approx 500-1000 uS/cm
Demin water approx 5-100 uS/cm

29
Q

State the location and functions of the following components on the RO including Parameters.

Solenoid diverting valve

A

Governed by the conductivity of the permeate
When the maximum pre-set value is exceeded the permeate is diverted to the bilge

30
Q

State the location and functions of the following components on the RO including Parameters.

Water hardener

A

Fitted on the permeate outlet of the plant before the ready made tank
Used to neutralise the slightly acidic makeup of the water produced
Dolomite calcium rich material is consumed as the permeate flows across it
Checked on a monthly basis

31
Q

State the location and functions of the following components on the RO including Parameters.

Chlorination tank

A

Calcium hypochlorite dosing pump continuously injects chlorine.
Chlorine in tank should be max 0.8 ppm
At the tap should be 0.5 ppm

32
Q

List the control and protection devices fitted to RO plants, stating where they are fitted and their operating parameters

A

Low pressure switches - HP pump suction-1 bar
High pressure switches - HP pump discharge-69 bar
permeate line HP switches - membrane permeate line discharge - 3-4 bar
Concentrate line HP switch - concentrate discharge line - 4-6 bar
Differential pressure switch - across sand and cartridge filter - 1-2 bar
relief valve - HP pump discharge - 69 bar
conductivity sensors and solenoid valve- 1st stage permeate discharge line > 1000uS/cm 2nd stage permeate line > 100uS/cm

33
Q

Why is it prohibited to use ROs in certain locations?

A

due to risk of health by bacteria from human waste or from chemical pollution

34
Q

What are the prohibited locations for using ROs?

A

Estuaries
Harbours
Bays
Narrow Channels
Any location known to or suspected of being contaminated

35
Q

State the main hazards when operating the RO plant and list 3 safety precautions associated with each of those hazards

A

HIGH VOLTAGE ELECTRICAL HAZARD
-plant uses 440V using 2.5-36.7KW single and 3 phase
-ensure supplies to both pump motor and control systems are isolated
-ensure correct LOTO procedure
HIGH PRESSURE HAZARD
-Operate up to 83 bar, don’t work on pressurised systems.
-check security of fixtures and fittings due to vibrations and after maintenance
-on completion of work RO plant must be checked for correct operation
CHEMICAL HAZARD
-ph 1-14 chemicals are used correct PPE must be worn
-avoid spillages and skin contact when mixing chemicals
-Hazard data sheets should be readily available

36
Q

State the rules for mixing acid and water

A

Always add acid to water not water to acid
Never mix acid to salt water or hot water as reaction will occur

37
Q

How is the performance of a plant be assessed?

A

Quality - ability to desalt water measured by rejection ratio
Quantity - ability to produce an acceptable amount of water for ships company

38
Q

With regards to the ROs optimum performance when operating in various areas around the world

How does an increase in sea water temperature affect the rejection ratio?

A

higher output due to membrane becoming softer and pores enlarging
poor rejection ratio hence dirtier made water due to high temperature and the membrane pores stretching, hence more salt particulates entering the product water line.

39
Q

With regards to the ROs optimum performance when operating in various areas around the world

How does an increase in feed water pressure on the membranes affect the rejection ratio?

A

Higher output as more water is forced through the membrane
Better rejection ratio hence the cleaner made water, due to membrane pores being compressed and reduced salt particulates entering the product water line

40
Q

What are the main causes of damage to the Pall DR modules?

A

Torque set incorrectly
Pressure on permeate discharge line
Vacuum in feed or concentrate line

41
Q

What is anti scalant dosing?

A

The continual injection of anti-scalant solution into the feed water of the SSS RO plant

42
Q

What does antiscalant do?

A

Suppresses the precipitation of the insoluble salts in the RO membrane, allowing more efficient operation

43
Q

What are the consequences if anti-scalant dosing is not carried out?

A

Results in membrane failure due to calcium salt precipitation

44
Q

On the Pall plant when is the anti scalant dosing carried out?

A

During sea temp above 15°C
When sea water is showing high silt density index

45
Q

When is chemical cleaning of RO plants carried out?

A

When standardised flux or daily output drops by 10-15%
iaw PMS
When there is a DP of more than 15% across the membranes

46
Q

When cleaning ROs what chemicals are used, what do they clean and when are they used?

A

High pH alkali (RO A) removes organic sand fouling, used 4 weekly
Low pH acid (RO C)for removal of iron and salt scales, used 4 monthly

47
Q

Why is preservation carried out?

A

Prevent biological growth occurring in dark moist membranes

48
Q

When is preservation carried out?

A

When shutting down the RO plants for 2-30 days

49
Q

What solution is used for preservation?

A

Chlorine free made water and 1% sodium metabisulphate

50
Q

What are the consequences for failing to preserve the plant?

A

Irreversible damage to the membranes due to organic growth

51
Q

With reference to the de-acidification/ re-hardener filter on the RO plant

Where is it fitted?

A

On the permeate outlet of the plant

52
Q

With reference to the de-acidification/ re-hardener filter on the RO plant

Why is it required?

A

To neutralise the slightly acidic make up of the water being produced

53
Q

With reference to the de-acidification/ re-hardener filter on the RO plant

What material is inside the filter?

A

Dolomite material

54
Q

With reference to the de-acidification/ re-hardener filter on the RO plant

How often is the contents checked?

A

Checked on a monthly basis and refilled as required

55
Q

With reference to the de-acidification/ re-hardener filter on the RO plant

What is the approx consumption rate?

A

20 grams/ton

56
Q

With reference to the de-acidification/ re-hardener filter on the RO plant

Advantages of using this type of filter

A

Corrosion in pipework, tanks and FW systems are maintained

57
Q

What are the precautions when preparing the chemical make up for the anti scalant dosing?

A

Only use chemical free water as chlorine attacks the membranes

151/23/007 (9 decks)

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