Fresh Water Production Flashcards
What are the four uses of fresh water?
Drinking
Washing
Cooking
Cleaning
What 8 services are provided by the fresh water system?
The Laundry
The galley
Showers and sinks
Water heaters
Medical use
Bridge window washers
Fresh water hose reels
Machinery cooling
What is the definition of reverse osmosis?
Transfer of water from salt water through a semi permeable membrane into pure fresh water.
What does TDS stand for?
Total Disolved Solids
What is the TDS of salt water before and after desalination?
Before: 34,000ppm
After: 250 - 300ppm
What percentage of supplied sea water is ejected overboard?
80%
What is the name of the desalinated water?
Permeate
What is the name of waste water after desalination and what is the concentration of salt in this solution?
‘Concentrate’
56,000ppm
Describe the two stages of filtration in an RO plant
Bag filter - filters down to 60 microns
Bank of two cartridge filters - filters down to 10 microns.
Describe the HP pump on an RO system
3 piston positive displacement pump. Pressure up to 65 bar.
What part of the RO plant does reverse osmosis take place?
In the cushion membranes
What is the purpose of the anti-scalant dosing unit?
Prevents precipitation of calcium salts directly forming on the membrane surfaces.
What is the name of the anti-scalant used?
Hypersperse
What does CCV stand for?
Concentration Control Valve
What is the purpose of the CVV?
Controls the back pressure of sea water acting on the Membrane Cushions. This forces more or less water through the membranes, which controls the total TDS of made water.
How often is the chlorine content checked?
Daily and before embarkation
What level is the chlorine content maintained at?
0.2ppm
What colour are the hoses used to embark fresh water, and what are the two things that must be done prior to embarking?
Hoses are blue.
Must be flushed through before use and tests must be carried out on the fresh water.
What are the three tests carried out on fresh water?
Visual test
CHEMets test
Taste test
How is hot water provided?
By the use of calorifiers
What is the “water hammer” effect and how is it removed?
A loud, repetitive banging noise inside the pipes which is a symptom of trapped air. Removed using an air eliminator.
How often are fresh water levels checked? How are they checked?
Checked hourly with dip tape
What are the three parts of the cushion membrane?
Membrane
Fleece sheet
Ultrasonically welded edges
