Removal of migrated oil in dimple plate milk vat

[Cary]

Can any one suggest a more efficient way of removing logged oil in a mutiple feed dimple plate milk vat.
It is a 5000lt horizontal vat with three circuts fed off on TX .
The sysyem employes a Terry PJS open drive compressor running on R22 and mineral 4GS running through an oil seperator.
The previous compress ran completly dry of oil and stuffed the seal ,this of course happened on Christmas Eve in rural Queensland Australia where seals for eldery compressors are not all that abundant.
After informing the customer that I thought the likelyhood of effective repair was slim I was told to give it a go.
A bit of a drive and some horse trading and part swapping had it put back together before Santa Arrived.
On commissioning the unit I was a bit shocked by the horrible noises emminating from deep in the compressor but even more shocked by the owners comment that it was running much quieter than it use to.
Any way back to the present as I predicted the unit was not long for this word and began to leak at the seal again.This time it was decided to go for a remanafacture unit, still a 50+ year old design but at least not worn internaly(I hope).The oil seperator was also replaced and upon removal was found to be bone dry the old compressor was also found to be severly oil challanged.
So I figure at least the Primary oil charge plus the refit from christmas must add to about 4 or 5 lt on flushing the entire system I was only able to recover about 1lt from the evaporator plate of the vat and that only after I replaced the TX(without any restriction the N only blew over the oil and did not push it ) valve and blew back nitrogen via the inch and a quater suction line.To my figering there is still a shirt load of oil sitting around somewhere Short of blowing a tanker of nitrogen throught it or drilling a drain in the bottom of the plate ,can any one suggest a good was of removing it.
Or should I just leave it there

[chemi-cool]

hi cary,

working with these milk tanks for many years and I belive I've seen it all.

first, there are two basic construtions of the dimpled evaporators.

first one (I'm sure is the one you're on about) have the evaporator at the bottom of the tank along the vessel, up to 4 circuits are used TEV's connected at the bottom back side, suction, adove it.

the second type and much better cooling results have the evaporator across the tank and these are cooling up to the middle of the tank, connections are the same.

cleaning of milk tanks used to be by entering from the top manhole and doing the job by hand, (I think in your case, this is the way)

later, a set of sprinklers was developed and acid was used.

today, the modern ones are using 95C hot water with no detergents at all.

a solenoid valve should be used in all systems and operates as pumpdown.

sometimes when " smart designers" use too large condensers without dicharge presure control, towards the end of the cooling cycle, suction temp is dropping and so discharge temp does, refrigerant flow speed decreases and oil does not return to oil sump.
bare in mind that oil separators do not seperate all the oil.

too big orifice in the TEV will result too much liquid passing and pulling more oil in.

resently I have seen a 30000L which had an " explosion" from oil of six compressors!!! fanny but condenser was too large, no head presure control and the orifice in the TEV was one size too big!

the easiest way to push the oil out is by disconnecting the liquid and suction lines from the tank, braze a smaller pipe with any connection you use to the suction side of the tank, get some R141 to clean the sistem and push it out into a container with OFN.

this method leaves the dimples shine like a miror, inside.

did that unit was working on R12 at the beggining?
by the way, 4GS is too thick for this application, 3GS will be better.

hope that help you and next time you travel in the outback and seeing all those old units, please take some pictures for me.

need more help? you can contact me through my email.

chemi

[RogGoetsch]

I, too, assume this was not originally an R-22 system. If so, how long after the conversion to R-22 did the original compressor dry up?

I suspect you may need to use a different refrigerant, especially if the compressor requires 4GS oil, otherwise the problem will repeat.

Rog

[Cary]

Thanks for the tips and sorry for the reply delay
you are right about the vat evaporator on the bottom 3 circuts and built before automatic wash and what I would consider a way oversized condensor . As far as I can tell the unit was moved there 10 years agoand weather the vat and condensor were ever ment to be together is another question.
The system was proberly originaly on R12 during the phasing out period the was a lot of change the TX valve bang on a oil seperator and bingo R22system.
During the last check visit I did a compressor sump oil change to remove as much of the 4GS oil I put in the seperator changing it back with 3GS I assume I will mave to do this a few times.
I am in the situation where the owner is refitting the milk room moving the troublesome vat another smaller vat and introducing a medium vat. As the troublesome vat is to be totaly relocated (vat compressor and remot condensing unit)I thought this would be a prime time to change the TX valve orrifice no prob.and install high side pressure regulation ,more of a problem .
In sunny Queensland our normal problem is keeping head pressures down and on the few units that are tropical designed a condensor fan speed regulatornormally suffices (the problem vat employs 3 fans one on head pressure control).
What is the best valve to use and where is it best situated.
These are the reading required for the remanafactured compressor warrenty
Refrigerant R22
Ambient temp 28
Vat temp 2.5
suction pressure 290kpa
suction line temp@ compressor 17 (14 return through cement)
Discharge gas temp 80
Discharge pressure 1240
Crankcase temp below oil 35

Liquid line temp 34
Liquid line pressure 1220

Thanks once more for your reply

Cary

[chemi-cool]

hi cary,

dont go away, I'm going to take some pitcures for you and give you all the instructions.

chemi

[chemi-cool]

hi cary,

when changing any unit from R12 to 22, capacity will remain the same, therefore the most simple thing to do is to check the TEV size.

in milk tanks the thumb rule is 1.1 sq/m= 1 ton.

generally, changing compressor to a smaller one will do.

it is very difficult to design condensing units for these tanks cause the temp inside changes dramaticly from 35C milk entering temp to 3C cooling end temp.

there era a few common methods of condensing but the best is 3 to 4 fans to control the high condensig temp.
for example, a unit I was working on today had head pressure of 340psi. ambient 36C.
two hours later, it went down to 240psi which is normal.
this unit had only two condenser fans.

I attach some pictures of a 40000 L milk tank with 7 condensing units made by maneurop. I have built it 3 years ago.

sorry, my files are too big and I can not take smaller pictures(camera too good)
if you want, send me an email and I will send them direct.



chemi

[Dan]

sorry, my files are too big and I can not take smaller pictures(camera too good)

Shucks. Just when I was getting interested. There are handy programs to reduce your pix.

http://www.imageresizer.com/

[chemi-cool]

thanks dan,

I will give it a try, no need to suck yet

chemi

[chemi-cool]

ok,

lets give it a try,

this picture shows the liquid separators and suction filters.

they have been installed out of the main frame so that condensed water will not drip on the steel work

chemi

[chemi-cool]

some more pictures showing the SV arrangment and the isolating switches.

computer interface for monitoring milk tanks ( in a different language, of course)

chemi

[chemi-cool]

and the las one shows the condensing units behind the steel net (sefety)

chemi

p.s.

very good little piece of software dan.