Chilled water and water production Flashcards
what is chilled water used to provided cooling for?
- Weapons Systems
- Radars
- Ships Computer Systems
- Air Treatment Units (ATUs)
What is the major difference between the components of the refrigeration plant and the chilled water plant?
The chilled water plant has a chiller in place of the evaporator
What provides cooling water for the condenser and the motors?
Sea water pump
what colour are fresh water hoses
Blue
what are the uses of fresh water
Drinking
washing
cooking
cleaning
what other services are provided by the fresh water system
Laundry
galley
showers and skinks
water heaters
medical use
bridge window washing
fresh water hose reals
machinery cooling
What is osmoisis
osmosis is the transfer of pure water through a semi permeable membrane into pure water
what is reverse osmosis
reverse osmosis is the transfer from salt water goes through a semi permeable membrane into pure water
what are the measurements of water purity?
the measurement is TDS Total dissolved solids
the TDS of sea water is approximately 34,000ppm
the TDS of the water after desalination is between 250 to 300 ppm
approximately 80% of the supplied salt water is ejected
after the water has been desalinated water is called permeate or made water
the waste water after desalination is called concentrate
what are the two stages of filtration in the reverse osmosis plant?
Bag filter which filters the water down to 60 microns
Two cartridge filters which filters down to 10 microns
what kind of pump does the reverse osmosis plant have?
3 piston positive displacement pump at high pressure providing 65 bar.
what do the cushion membranes have?
ultrasonically welded edges for salt water to pass through
what does the anti scalant dosing unit prevent
this prevents the precipitation of calcium salts forming directly onto the membrane surfaces.
what is added to the anti scalant dosing untit?
hypersperce and anti-scalant at the rate of 5ppm
what is the CCV
concentration control valve
what does the CCV do?
the CCV controls the back pressure of the sea water acting on the membrane cushions, by closing the valve the back pressure is increased and the amount of the permeate is increased therefor opening the valve reduces the back pressure and the amount of permeate is reduced.
what chemical must the reverse osmosis plant not contain and why?
it must not contain chlorine as this can cause irreversible damage to the membranes.
why is chlorine added after the water has passed through the membranes?
to kill off any harmful bacteria
what level should the chlorine to water be and when should this be checked?
the chlorine should be at 0.2ppm and is checked daily and before embarkation.
when should desalination not be done?
when the water is most likely contaminated such as harbours and estuaries.
what are the 3 fresh water tests
- CHEMets test kit (glass tube colour comparison and will show you how much chlorine is in the water.
- Visual
- Taste
what hot water systems are used on board
Calorifiers are used to heat water on-board ship.
why is an air eliminator important?
One symptom of air in the fresh water system is known as “water hammer” which is a loud and repetitive banging noise inside the pipes.
