The FWG consist of evaporator, separator shell and condenser. And combine brain/non-condensed gases ejector, SW ejector pump, distillate pump, salinity indicator/alarm (salinometer), deflector, wire mesh demister, solenoid valve, and distillate flow meter.

General view of of FWG plant with shall-and-tube type of heat exchangers SASAKURA KM 30 presented in next figure.

General view of FWG plant with shall-and-tube type of heat exchangers SASAKURA KM 30

Since the FWG utilizes the waste heat in the circulating cooling water from diesel engine. In case of damage to the fresh cooler, it may be possible to use the freshwater generator only as cooler during the repair of the freshwater cooler.

Part of the engine cooling water is led to the heat exchanger in the FWG where it circulates on the outside of the heating tubes, giving off heat to the feed water (sea water) passing through the inside of tubes (see figure beloow).

The feed water then evaporates at a comparatively low temperature because the inside of the generator is formed vacuum by the water ejector. The generated vapor in the heat exchanger passes through the deflector and mash separator to the condenser where it is condensed by the cooling sea water.

The brain, concentrated sea water, is constantly taken out from the evaporator shell and discharged overboard.

The ejector pump supplies sea water to water ejector. The distillate pumps extract the freshwater produced from the condenser of the FWG and transfer it to the freshwater tank.

Part of cooling sea water heated by condenser is used as feed water and flow into the bottom cover of the heat exchanger after heated by the preheater and passing through the feed water orifice.

Produced FW is always registered by a salinity alarm (salinity indicator). When the salinity is up to the prescribed value (normally 10 ppm, adjustable to the other value), the solenoid valve on the improper freshwater line opens which leads improper freshwater into the evaporator automatically. Fresh water with high purity flows into the freshwater tank.

Working principle of the vacuum FWG plant with shall-and-tube type of heat exchangers

The figure below shows components of the FWG plant with shall-and-tube type of heat exchangers SASAKURA KM type.

The components of the FWG plant with shall-and-tube type of heat exchangers SASAKURA KM type

 

1 – distillate pump, 2 – salinity sensor, 3 – sight glass, 4 – solenoid valve, 5 – condenser, 6 – salinity indicator, 7 – evaporator, 8 – name plate, 9 – vacuum gage, 10 – heater, 11 – distillate flowmeter, 12 – heater air outlet valve, 13 – feed water adjust valve, 14 – bottom blow valve, 15 – thermometer, 16 – vacuum breaker valve, 17 – condenser air outlet valve, 18 – top cover, 19 – lifting hole, 20 – relief valve, 21 – anti-oscillation plate, 22 – vacuum adjust valve, 23 – water ejector, 24 – corrosion bar, 25 – sight glass, 26 – ejector pump

 

The components functions are next:

Distillate pump – discharges product freshwater

Salinity sensor is a sensor for measuring the salinity of the generated distillate

Sight glass – allows the inside process of the evaporator to be viewed

Solenoid valve – returns back to FWG high salinity distillate

Condenser – condenses generated vapor into distillate

Salinity indicator – indicates distillate salinity

Evaporator – evaporates the feed water at a lower temperature due to vacuum

Name plate – shows the work No., type, etc

Vacuum gage – indicates the degree of vacuum in the evaporator

Heater is a heat exchanger that heats the feed sea water to generate vapor

Distillate flowmeter – indicates the quantity of the produced distillate

Heater air outlet valve – release air from the heater (in case of water filling)

Feed water adjust valve uses for adjusting feeding water quantity to the heater

Bottom blow valve is used to drain off the feed water from the FWG

Thermometer – indicates the evaporating temperature

Vacuum breaker valve used to break the vacuum in the Evaporator and restore the internal pressure to atmospheric pressure

Condenser air outlet valve – release air from the condenser

Top cover is opened up for a maintenance procedure within the evaporator

Lifting hole (4 pcs) – used for transport FWG and lift the top cover

Relief valve – protects the inside components of the FWG against possible damage

Anti-oscillation plate

Vacuum adjust valve – increase the evaporating temperature during operations in a low temperature sea water area

Water ejector – maintains vacuum in the evaporator and discharging brine and cooling seawater overboard

Corrosion bar is a sacrifice anode material that protects the pipes and other corrosive parts of the FWG by utilizing the electric potential difference

Sight glass – allows the product distillate water to be visually checked 

Ejector pump is a pump that feeds the driving water to the water ejector in the FWG


Last modified: Wednesday, 22 March 2023, 4:20 PM