Help with college homework, Please.

[buddybeagle]

How would you dehydrate a 20kw water cooled package unit flooded internally.

my answer

After recovering all of the contaminated refrigerant, I would then pressure test with Oxygen free Nitrogen. Then triple vacuum test the system, leaving it for 12 hours on the third vacuum. I would then release the vacuum, replace the filter dryer, then vacuum test again, the recover new refrigerant.

Plese comment. Have I missed something.

[slingblade]

yes you have. you would need to change the oil. also its not just a case of vacuum for 12 hours, it needs to be drawn down to an acceptable level.

[buddybeagle]

Change the oil in the compressure ? and draw it down to 20mbar

[frank]

How would you dehydrate a 20kw water cooled package unit flooded internally.

Hi Buddy

my answer

After recovering all of the contaminated refrigerant

If the unit is flooded internally then you have already lost the refrigerant.

I would then pressure test with Oxygen free Nitrogen.

What about fixing the leak between the refrigerant pipework and water circuit in the heat exchanger first?

Then triple vacuum test the system, leaving it for 12 hours on the third vacuum.

It would be better to pressure test first to verify your repair. Vacuuming the system will not easily remove the moisture following a flood. I would recommend that you leave the system open in a hot area, i.e. in front of a warm air heater or if this is not possible then apply heat to the unit possibly with a portable propane blower (floor standing room heater type).
You can then verify that all the moisture is out of the system by applying a vacuum. If you fail to achieve a good vacuum that holds a steady gauge reading with the circuit isolated then you probably still have moisture present. Use a good drier before your vac pump.

I would then release the vacuum, replace the filter dryer,

It would be good practice to replace the drier when you feel confident that you have achieved a good dry system before your final vacuum. Never release your vacuum, always break it with dry nitrogen - or if you are finally charging the system then break it with refrigerant. Remember, what you are trying to do is keep out all that nasty contaminated atmosphere

the recover new refrigerant.

I think you mean charge with new refrigerant

[slingblade]

if i was called to a burst chiller:-

1. find hole. 9/10 burst evap.
2. recover any gas.
3. remove as much water as possible by blowing with ofn (this may involve breaking open components cond. oil sep. etc)
4. repair hole (new evap.)
5. drian comp oil and remove drier.
6. pressure test
7. evac to say 50 micron (system size dependant) break with ofn.
8. new oil and drier.
9. evac. as before.
10. charge and commission.
11. very large invoice.
12 pub.


hope this helps.

[buddybeagle]

Cool thanks for that,

[buddybeagle]

Thanks the quesion fr my homework was "How would you dehydrate a 20kw water cooled package unit flooded internally"

So my answer would be


Find when it has caused the flood and make suitable repairs. Open system and leave if possible open in a heated area to allow mositure to evporate, then blow system with ofn, drian comp oil and remove drier.
,pressure test evac to 50 micron break with ofn.
new oil and drier. evac. as before. charge and commission.

Does these seem ok

[frank]

Better answer but if you want top marks you ought to elaborate a bit on each task, explaining why you need to carry out the tasks i.e. - how to determine if all the moisture has gone.
Also, it would be good practice to change the TEV as this would most probably contaminated internally. What about fitting a moisture indicator?

Think outside of the box

[slingblade]

Also, it would be good practice to change the TEV as this would most probably contaminated internally.

With what? the level of vacuum achieved combined with the new drier (fitted in the liquid line before the txv i think?) will eliminate the need for this. the customer is facing a big enough bill allready, from me anyway.

[Tycho]

With what? the level of vacuum achieved combined with the new drier (fitted in the liquid line before the txv i think?) will eliminate the need for this. the customer is facing a big enough bill allready, from me anyway.

Corrosion from being submerged if it's a sea water cooler, or dirt if it's freshwater.

if he's allready facing a large bill, why save $40 by not changing a part, when it might cost him another pretty penny to have an engineer come out to do the job a few days later


Also, remove the filter drier before vacuuming... why leave a filter saturated in water... it'll only take longer to dry out the plant.

[slingblade]

Corrosion from being submerged if it's a sea water cooler, or dirt if it's freshwater.

Then by the same token we need to replace all parts subjected to potential contamination. such as evap., cond., tev, suction, liquid line, compressor, if i think of any more ill let you know. £££££.

[Tycho]

Then by the same token we need to replace all parts subjected to potential contamination. such as evap., cond., tev, suction, liquid line, compressor, if i think of any more ill let you know. £££££.

well, ok, maybe not replace, lets call it inspect and test.

The Tev has moving parts, is located in connection with both the chiller and condenser, and in case of a leak in either of those two large enough to get water into the system the tev will be effected.

Of course if the system was completely flooded with water (I've had those) I would remove and service all valves, inspect the compressor for damage and if necessary serviced it (combine accident with xxxx hour service).

usually something like a complete waterflood of a plant will be noticed in short time so internal corrosion on the chiller tube shell and condenser (wall thickness of 15-25mm, special alloy in the tubes) will be minimal once you have dried out the plant and recharged *****, no oxygen, no corrosion.



********edit********

I don't know about you, but I'm in this job to make money for my company so they can pay me

I will not lie to a customer to make more money, I will tell him what I think is best and then it's up to him to consult others or let me do what I think is best.

in the end, I'm gonna be the one to blame (in his eyes) if his plant isnt as good (or better ) as it was before the accident.

[Andy]

Hi

Nobody has recommended heating the evaporator to aid moisture removal. Add heat anywhere you can, compressor, receiver, evaporator and condenser. Only realy way to remove the moisture.

Don't forget the compressor oil, drain it prior to vaccuming and add some after the main vac, giving it a quick vac after adding the new oil. Don't add the oil before the moisture has been removed.

Kind Regards. Andy

[frank]

Nobody has recommended heating the evaporator to aid moisture removal.

Come on Andy That was my first reply

I would recommend that you leave the system open in a hot area, i.e. in front of a warm air heater or if this is not possible then apply heat to the unit possibly with a portable propane blower (floor standing room heater type).

[US Iceman]

I don't know about you, but I'm in this job to make money for my company so they can pay me.

I will not lie to a customer to make more money, I will tell him what I think is best and then it's up to him to consult others or let me do what I think is best.

in the end, I'm gonna be the one to blame (in his eyes) if his plant isnt as good (or better ) as it was before the accident.

An excellent quote. I like that.

[slingblade]

Come on Andy That was my first reply

true.

Don't forget the compressor oil, drain it prior to vaccuming and add some after the main vac, giving it a quick vac after adding the new oil. Don't add the oil before the moisture has been removed.

and i said that twice.

[Andy]

true.



and i said that twice.

Well why didn,t you say so

[Andy]

Come on Andy That was my first reply

Didn't pick up on that

Never thought of leaving it open whilst heating

I usually use an old vacumn pump for the early stage, changing the oil regularly (when it goes emulified), braeking the vac often with OFN. When the vacumn stops dropping I then bring out the new pump to finish the job off

Kind Regards. Andy