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WorksheetsFWG:
Total questions: 15
Worksheet time: 8mins
In a low-pressure FWG, vacuum creation mainly allows:
Faster boiling
Lower-temp evaporation
Air removal
Stable feed flow
When distillate salinity rises, the salinity cell triggers:
Heat cut-off
Discharge bypass
Vacuum boost
Feed increase
Partly clogged ejector nozzle leads to:
Stronger vacuum
Weak vacuum
Constant output
Stable pressure
Condensation in FWG happens as vapor:
Cools on surface
Mixes with seawater
Compresses
Chills by refrigerant
FWG operation can best be described as:
Atmospheric boiling
Vacuum evaporation with waste heat
Vapor compression
Centrifugal desalting
During FWG operation, the distillate salinity alarm activates. Jacket water temperature and vacuum are normal. The most likely cause is:
Leaking condenser tubes
Low ejector suction
Faulty salinity cell
Cold feed flow
A gradual loss of vacuum in the FWG while temperature remains steady indicates:
Air leak at ejector line
Scale in condenser
Overheated brine
Faulty thermostat
Distillate flow is steady but salinity slowly increases. This suggests:
Minor condenser leak
Excess feed flow
High jacket temp
Weak vacuum
If the FWG ejector fails to maintain vacuum after overhaul, the likely overlooked step is:
Priming the ejector
Replacing salinity probe
Bleeding the condenser
Reducing feed rate
During routine monitoring, the operator notes gradual rise in distillate temperature. This is a sign of:
Scaling in condenser
Air leak in ejector
High brine discharge
Overcooled feed
Why is the distillate first routed through a salinometer before reaching the storage tank?
To remove air bubbles that could cause corrosion
To allow automatic rejection of impure water
To measure temperature for vacuum correction
To stabilize flow rate to prevent surges
Which operational adjustment best prevents long-term scaling in the FWG?
Run under deeper vacuum
Raise feed temperature
Regulate brine discharge rate
Boost jacket water flow
The FWG operates under vacuum primarily to:
Minimize scale on heating surfaces
Lower boiling point for waste-heat use
Accelerate vapor condensation
Stabilize feed level control
The FWG yields less distillate in tropical waters mainly because:
High salinity lowers heat flow
Warm seawater limits condensation
Humid air increases vapor loss
Cooler jacket water reduces heating
When seawater salinity rises, the FWG operator should:
Reduce feed pressure
Raise feed pressure
Adjust brine flow upward
Limit membrane surface
