fwg troubleshooting

8/18/2019 FWG Troubleshooting

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Certificate of Competency - 5G e n e r a l E n g i n e e r i n g K n o w l e d g e

FRESH WATER GENERATOR TROUBLESHOOTING

Problem Cause Consequence Action

Drop in productiondue to lower

boiling temperature

and lower t over

evaporator

Partially blockedfead water orifice

and / or sludge

deposits on hot

water side

scaling of heatexchanger plates

on vapor side

Dismantleevaporator

section and clean

evaporator and

orifice

Drop in production

due to higher

boiling temperature

and lower t overcondenser

sludge on the heat

exchanger plates on

the sea water side

Dismantle

condenser section

and then clean

Production drop

due to lower boiling

temperature and

higher t over

evaporator /

condenser

Inlet channel

in evaporator /

condenser plate

stack blogged, eg:

with rust scales,

gasket, fragments

etc

Dismantle

evaporator,

condenser section

and clean

Production drop

due to low vacuum

(normal vacuum

above 90%)

Too low ejector

pump pressure

Not sufficient

flow to condenser

section and

ejector

See instructions

for low flow ejector

pump, below

Leakages Low vacuum Carry out a pressure

test at max. 150

kPa(1.5 kp / cm2)

(21.8 PSI)

Foreign bodies in

ejector nozzles

Blocking Inspect nozzles,

and clean, replace

nozzles, if damaged.


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Too high back

pressure downsteam

of ejector. Max 60

KPa (0.5 kp / cm2)(8.7 PSI)

Product ion drop Check overboard

pipe and valves for

blocking / function

ability

Non return valve in

air extraction pipe

defect

Replace non-return

valve


Production due

to high boiling

temperature

Too low ejectorpump pressure

Not sufficientflow to condenser

section and ejector

See “Sea coolingwater flow”

Air in condenser Production drop vent condenser

Too high back

pressure downsteam

of ejector max

60kPa(0.6,kp/ cm2)

(8.7 PSI)

Product ion drop Check overboard

pipe and valves for

blocking/function

ability

Leakages Low vacuum Carry out a pressure

test at max. 150

kPa(1.5 kp/cm2)

(21.8 PSI)

Foreign bodies in

ejected nozzles

Blocking Inspect nozzles,

and clean. Replace

nozzles, if damaged

Too low ejector

pump pressure.

Minimum pressure

300 kPa(2.0 kp/

cm2) (43.5 PSI)

Pressure gauge

defect

Clean or replace

power gauge


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Suston strainer

blocked

No sufficient

pressure and

flow to condenser

section and ejector

Clean suction

strainer

Valves on suction or

pressure pipe defect

see above Examine and

overhaul defective

valves

Leakages from

suction pipe to pump

see above Repair

Impeller/seal ring

defective

see above Check pump

maximum clearanceis 1.0mm

Pump rotating in

wrong direction

see above Interchange phases

Too low fresh

water production

due to incorrect

temperature on the

circulated heating

water

Warm or incorrect

injector nozzle

Replace nozzle

Air pockets in steam

arrangement

Discrete steam

arrangement andevaporator section

steam pressure

Incorrect

See “technical

specification” and

adjust pressure

accordingly

Incorrect back

pressure in

condensate

discharge pipe

Check whether

actual back pressure

on condensate line

corresponds with

max back pressure

on installation

(PI) diagram. See

“technical drawings”


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Sight glass overflow.

Suction pipe

leakage.

produced

freshwater

escapes

overboard through

ejector

Check suction pipe

especially unions

and connections,

repair.

Mechanical seal in

freshwater pump

defect

see above Replace mechanical

seal

Impeller / seal

ring in fresh waterextraction pipe

defect

see above Check pump. Max

clearance 0.9mm.

Pump rotating in

wrong direction

see above Interchange phases

Valves to freshwater

tank closed

Check all valves

Inlet filter for waterclock blocked

see above Clean filter

Production drop

according to water

clock. In spite of

normal pressure and

temperature and

no visible overflow

in sight glass andvacuum pipe

Defective water

clock

Examine water

clock. Let the

produced water flow

through water clock

into a 10

and check

production with astop watch


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Salinity too high

(more than 2.0

ppm).

Demister not fitted

correctly

Dumping of

produced

freshwater

Check the demister

is fitted against

baffle and front

cover

Front cover gasket

defect or not fitted

correctly

Replace front cover

gasket

Insufficient brine

extraction

High brine level

(normal level 10 –

20 mm).

See separate

instructions for

insufficient, brine

extraction, below.

electrode unit

defective or dirty

Examine electrode

unit for cracks.

Check that is fitted

correctly. Clean if

necessary.

leakage in

condenser section

Open distiller

and pressure test

condenser. Max.600kPa (6.0 kp/ cm2)

(87 PSI). If there is

a defective plate,

remove together

with adjacent plate

assemble plate stack

according to new

plate number with

reduced assembly

measurements.

Check plate gaskets

and replace, if

necessary.


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Insufficient brine

extraction-brine

level in sight glasshigher than 20 mm.

Ejector pump

pressure too low

High boiling

temperature, low

vacuum. Salinity

higher than 2.00

ppm

See special

instructions for too

low ejector pump

pressure, above.

Foreign bodies in

ejector nozzles

see above Check nozzles,

and clean. Replace

damaged nozzles

Too high back

pressure downstream

of ejector

see above Examine overboard

pipe and valves

Wrong dimension of

feedwater orifice

see above Examine office

dimension-

check technical

specification

Non-return valve in

brine suction pipe of

ejector defect

see above Examine valve and

repair, or replace

Frequent refit

of freshwater

expansion tank due

to lose of hot water

Leakage in

evaporator section

Open distiller

and pressure test

condenser. Max. 600

kPa (6.0 kp/ cm2)

(87 PSI). If there

is defective plate,

remove together

with adjacent platesassemble plate

stack according to

new plate number with

reduced assembly

measurements. Check

plate gaskets and

replace, if necessary.


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Abnormal amperage

consumption of

ejector pump motor

Ejector nozzles

defective

High boiling

temperature, low

vacuum

Replace nozzles

Wrong dimension

of feedwater inlet

orifice

Check dimensions

on spare parts list.

Bearings in motor

defective

High temperature

in motor ends,

and exercise

noise

Examine with

stethoscope, and

replace bearings, if

defective

Contractor defective Frequent motorstops

Examine andreplace contactor

set, if defective

Breaking of phases See above Max. 5% difference

in amperage

between phases

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