Carrier 30 GX system trouble (dirt/air)

[Andrew1steng]

Good day, Gentlemen. I have joined the ship a week ago. Chiller system on board is suffering from dirt and air which obstructs normal circulation through multiple coils installed in different locations. This is my first experience with chillers. We don\t have buffer tank and expansion tank which is marked on the drawing is also absent. System water is mixed with mono ethylene glycol. Strainers before the coils we have to clean every day and drain the air as well. Pressure in the chilled water line is 3,5 bar. Please advise.

Thanks in advance. Brgds.

1st engineer Andrew.

[Brian_UK]

Hello Andrew and welcome to the forum.

What type/size of ship are you on?

Where is the make up water coming from; is it clean to start with?

Regarding dirt in system I would recommend a full flush with clean water, maybe even a back-flush. Do it section by section until the water runs clear and you are satisfied that all debris has been removed.

Ensure that the chiller tubes are also cleaned properly.

Refill with clean water/glycol mix,vent and start again.

Have fun. ;)

[sedgy]

hi chief,
from the wording of your thread , it seams you have sighned-on , a well worn tramp,
can I take it your chiller is sea-water cooled, glycol- sea water cooler? which is used for a-c throughout the ship?
if some main parts are missing could be its been modified< get proof of this if you can < we dont want anyone DRd do we? brian in the post above is right, it looks like a good blow out is overdue, but is enough fresh water avalable? or is the system salt water resiliant? all the best for now , sedgy.

[Andrew1steng]

Thanks for Your promt reply, Gents! This is a brand new 1 year old ship. Chilled water circuit is topped up with clean water from reverse osmosis unit. But I think that something went wrong from the very beginning...

Where the air is coming from inside the closed system?

Should expansion tank be installed for this system?

Regards!

[Brian_UK]

Expansion Tank: Two options, open feed tank with expansion overflow pipe or sealed system with sealed expansion vessel to accommodate system changes.

Is there, or can you fit, any form or air separator/dirt collector in the system?

Sorry, re-reading your answers.... You say it is a sealed system but doesn't have an expansion vessel.

In that case it is quite likely that air is getting into the system through something like automatic air-vents or leaking valve stems.

When you top up the system the water you use is probably warmer than the system is so has to be cooled down. When the water cools it contracts and will create a partial vacuum compared with outside the pipes.

[Gary]

Good day, Gentlemen. I have joined the ship a week ago. Chiller system on board is suffering from dirt and air which obstructs normal circulation through multiple coils installed in different locations. This is my first experience with chillers. We don\t have buffer tank and expansion tank which is marked on the drawing is also absent. System water is mixed with mono ethylene glycol. Strainers before the coils we have to clean every day and drain the air as well. Pressure in the chilled water line is 3,5 bar. Please advise.

Thanks in advance. Brgds.

1st engineer Andrew.

The minimum pressure (PSI) at the bottom of the system return line should be the height of the system (feet) divided by 2. For example, if the system height is 100 feet, the minimum pressure at the bottom should be 50 PSI. Less than this will result in air problems.

And the system definitely needs an expansion tank. The feedwater PRV, guage and expansion tank should be near the pump suction .

[Gingerair]

Hi Andrew
Has the system always had this sort of problem or is it a recent development ?
Is it definately air in the system, no possibility of an evap leaking refrigerant into the chilled water side ?
Are the chilled water pump shaft seals ok ?
Is there a not a strainer in the pump suction pipework ?

Ginge :)

[Andrew1steng]

Greetings Gentlemen! Thanks for You support and advises! That's brilliant that we can get it here in the middle of the ocean!
Finally we located the expansion tank :)
After two days of continuous air bleeding system works good... Chief Engineer have ordered glycol and when we'll have some time we 'll follow Your advise and perform complete renewing of media.
What is normal proportion for mixing glycol/water?

Thanks! Brgds.

Andrew

[Brian_UK]

Mixtures depend on the temperatures that you want, table and text here...
http://www.engineeringtoolbox.com/ethylene-glycol-d_146.html

[sedgy]

hi andrew,Well done I know its not easy following pipes in engine rooms,
glycol / water mix ask the manufactorers, but the more glycol the less temp, transfer, all the best,
ex- 2nd fridge , nzs co 1969 sedgy

[Gary]

What is the height of the system and the pressure at the bottom of the return pipe? If the minimum pressure is not sufficient, air will enter the system and you will have the same problems again.

[Andrew1steng]

Hi! The height of the system is 20 meters. Return pressure on the circ. pump suction is 0,5 bar.

[Gary]

Hi! The height of the system is 20 meters. Return pressure on the circ. pump suction is 0,5 bar.

Assuming the pump return is at the bottom of that 20 meters, the pressure should be about 2.5 bar. Technically, 2 bar would be the bare minimum, but I like to give it a little extra.

Any less than 2 bar (0.1 bar for each meter height) at the bottom of the return will result in air being sucked into the top of the system.

[brazzy wind]

check Air Vents if they are working properly

[Andrew1steng]

Hello! We've discovered gas leakage from evaporator to chilled water line... That unit is stopped for 2 days already and no more air/gas appearing in the system with unit N2 in service only. Water side of evaporator is opened now. Water pipes are containing a lot of rust. Service engineer will arrive tomorrow. The final question is: from where the RUST is coming from???

[Gingerair]

When your service engineer arrives he should be able to answer most of your questions but in the mean time check the condition of the oil for each compressor..
Also check your chiller water flow switch is operating correctly..
Good luck !!