Advise about pipe connection for air cooler

[dolce]

Hello my friends
Please Advise about pipe connection for air cooler. when i checked R22 plant this problem Drew attention the air cooler connection i know there are cooler top feed type and other bottom feed . this air cooler use in freezing system -25C by over feed pumped liquid. here in attach pic. see top feed but i prefere to modifiy to change to bottom feed FYI the top header is 3 inch and low header is 2 1/2 inch.
thank for all
http://www.refrigeration-engineer.com/forums/asset.php?fid=13282&uid=9992&d=1548571079

[chemi-cool]

what material is the pipe made of?

[dolce]

what material is the pipe made of?
Coil of cooler material is galvanize and connection pipes steel

[chemi-cool]

What pressure and temp at the connection point? Are there any vibrations at any of the sides?

[dolce]

What pressure and temp at the connection point? Are there any vibrations at any of the sides?
the pressure and temp. are not available at these point but I think that when the coil is completely full with pumped liquid the gas resulting from evaporation and goes up against the liquid hole happening decrease in ΔP. this make liquid stop and when the ΔP increase again liquid flow will start again IS MY THINKING OK OR NO ?

[RANGER1]

the pressure and temp. are not available at these point but I think that when the coil is completely full with pumped liquid the gas resulting from evaporation and goes up against the liquid hole happening decrease in ΔP. this make liquid stop and when the ΔP increase again liquid flow will start again IS MY THINKING OK OR NO ?

If hand expansion valve open to much, or if has suction riser full of liquid unit will not work as well in either situation, top or bottom feed.
Why do you think you have to change it?
What type of defrost method do you have, hot gas, water?

[dolce]

If hand expansion valve open to much, or if has suction riser full of liquid unit will not work as well in either situation, top or bottom feed.
Why do you think you have to change it?
What type of defrost method do you have, hot gas, water?
Dear RANGER
the suction line without riser and oil trap. this cooler is feeded by overfeed method and hot gas method as mentioned below 15333

[Josip]

Hi, dolce..


Hello my friends
Please Advise about pipe connection for air cooler. when i checked R22 plant this problem Drew attention the air cooler connection i know there are cooler top feed type and other bottom feed . this air cooler use in freezing system -25C by over feed pumped liquid. here in attach pic. see top feed but i prefere to modifiy to change to bottom feed FYI the top header is 3 inch and low header is 2 1/2 inch.
thank for all
http://www.refrigeration-engineer.com/forums/asset.php?fid=13282&uid=9992&d=1548571079

According to attached photo your evaporator is designed for bottom feeding (header is 2 1/2") and top one is 3" .. I do not see any problem to connect evaporator as you mentioned ... Seems your defrosting cycle will be completely manual ... or maybe attached scheme is not complete because there are lot of valves missing, but if all is new you have a lot of possibilities how to solve complete connection of the evaporator to the system.

Best regards, Josip

[dolce]

Hi, dolce..



According to attached photo your evaporator is designed for bottom feeding (header is 2 1/2") and top one is 3" .. I do not see any problem to connect evaporator as you mentioned ... Seems your defrosting cycle will be completely manual ... or maybe attached scheme is not complete because there are lot of valves missing, but if all is new you have a lot of possibilities how to solve complete connection of the evaporator to the system.

Best regards, Josip
Thank you
please find attach file and please help me to choose the best15334

[RANGER1]

dolce,
Sometimes headers have orifice in each circuit of inlet header, so if changing pipework need to check first.

Top picture is way to go as suction lines independent & free flowing.

In my first post I asked if something wrong, as your pipework could be totally flooded if regulating valve is open to much causing poor temperatures.

If inlet & outlet mixed up, of course problems also.

Pump liquid line also need non return valve after solenoid valve for hot gas defrost, as not shown in schematic.

Is there enough load on plant other than this to generate enough hot gas to defrost both units at once?

[Josip]

Hi, dolce ...


Thank you
please find attach file and please help me to choose the best15334

I agree with RANGER1 suggestion and questions ... we do not know anything about your plant and your idea ... so it is not easy to give you the best advice ...
instead check attached drawing ... how we did things 20+ years ago ...

for sure it is not bad idea to use liquid feed regulating valve in front of each cooler ... more expensive, but for sure less headache after ... of course you can use other types of solenoid valves i.e. available to you ...



15335

HG - hot gas
PL - liquid delivery line
R - return line - suction
HGR - hot gas return - defrost liquid and gas return

Hope this will be of some help to you ... anyhow we are here for any further help ...

Best regards, Josip

[dolce]

Hi, dolce ...



I agree with RANGER1 suggestion and questions ... we do not know anything about your plant and your idea ... so it is not easy to give you the best advice ...
instead check attached drawing ... how we did things 20+ years ago ...

for sure it is not bad idea to use liquid feed regulating valve in front of each cooler ... more expensive, but for sure less headache after ... of course you can use other types of solenoid valves i.e. available to you ...



15335

HG - hot gas
PL - liquid delivery line
R - return line - suction
HGR - hot gas return - defrost liquid and gas return

Hope this will be of some help to you ... anyhow we are here for any further help ...

Best regards, Josip
many thanks and appreciate your reply and help
i asked only about i think i have problem in connection because this cooler is overfeed type and bottom feed , work by R22 the owner of the plant called me to check the many of problems . i asked the technicians did you charge oil say yes i asked How many oil drums you charge in 6 months answer 6 drums about 1200 Kg i asked did you drain oil out say No and one of wrong thing the cooler was designed to bottom feed and there is not oil riser or oil trap .in defrost process oil can not return .for these i want to modify the connection bottom feed and return oil from small size to main suction line is my idea Ok or not wait your advise .
yes i completely agree with you in your drawing it is the original design . yes i will modify as your advise
many thank you

[Tycho]

This is the way I would have done it:
https://i.ibb.co/LQzdxpS/aircooler.jpg (https://ibb.co/WDWvkKn)

-starting on top with the hotgas, I like to have a bleed valve 1/2 the size of the main line to prevent any hydraulic shock when the defrost starts, usually let it bleed 1 minute before the main defrost opens.

-Liquid line, you need a non return valve AFTER the liquid solenoid
I also use an overflow valve (danfoss OFV25) adjusted to open at 5 bar during defrost, sending the liquid back into the main suction line. since you have isolating valves betore and after the suction solenoid valve I elected to connect it between the suction solenoid and the isolating valve for ease of service.

-Suction line, the bleed valve needs to be across the suction solenoid to bleed the pressure down, unless you want your suction line to do this: https://i.ibb.co/m5d7vtj/Scholarly-Caring-Gecko-max-1mb.gif after every defrost.

I'm guessing that the two valves on the liquid line closest to the coolers are reg valves used to balance the liquid feed.

[Tycho]

many thanks and appreciate your reply and help
i asked only about i think i have problem in connection because this cooler is overfeed type and bottom feed , work by R22 the owner of the plant called me to check the many of problems . i asked the technicians did you charge oil say yes i asked How many oil drums you charge in 6 months answer 6 drums about 1200 Kg i asked did you drain oil out say No and one of wrong thing the cooler was designed to bottom feed and there is not oil riser or oil trap .in defrost process oil can not return .for these i want to modify the connection bottom feed and return oil from small size to main suction line is my idea Ok or not wait your advise .
many thank you

An easier way to remove oil from the coolers, is if you connect the OFV line to the bottom line on the cooler and the outlet of the OFV to the highest point on the suction/return line.

If I remember correctly, you can have 20% of oil mixed in the ***** charge before it starts becomming a problem.


Is there any type of oil return from the LP receiver to the compressors?

I would start looking there before I started rebuilding anything

[dolce]

An easier way to remove oil from the coolers, is if you connect the OFV line to the bottom line on the cooler and the outlet of the OFV to the highest point on the suction/return line.

If I remember correctly, you can have 20% of oil mixed in the ***** charge before it starts becomming a problem.



Is there any type of oil return from the LP receiver to the compressors?

I would start looking there before I started rebuilding anything
Yes Tycho this good idea for me thanks what about for useing Mobile arctic 300 oil with R22?

[RANGER1]

Dolce,
As you & Tycho mention, system appears heavily oil logged.
Evaporator full of oil is symptom of oil return from liquid recirculated vessel not returning oil to common still that should be in system.
If compressors throwing over a lot of oil it may also not be able to keep up with oil return system.
Can you show how oil return works on pump vessel?
It sounds so full of oil, best to pump system or components down & drain oil out of system if drain points available.

Oil probably ok, but seems more suitable for higher temperature applications above -25 deg C

[dolce]

Dolce,
As you & Tycho mention, system appears heavily oil logged.
Evaporator full of oil is symptom of oil return from liquid recirculated vessel not returning oil to common still that should be in system.
If compressors throwing over a lot of oil it may also not be able to keep up with oil return system.
Can you show how oil return works on pump vessel?
It sounds so full of oil, best to pump system or components down & drain oil out of system if drain points available.

Oil probably ok, but seems more suitable for higher temperature applications above -25 deg C
Ok 15336 oil return from taking a small amount of pumped liquid to HP receiver in internal coil making separation and evaporate the liquid , go together to compressor suction as shown mentioned

[RANGER1]

Ok 15336 oil return from taking a small amount of pumped liquid to HP receiver in internal coil making separation and evaporate the liquid , go together to compressor suction as shown mentioned

It looks good, is it working, can you have a sight glass or something to monitor oil return so oil & gas, not liquid returning to compressor which can cause compressor to use oil especially reciprocating compressor.
What type & how many compressors?
Are they throwing over excess oil, if so has oil separator oil return working, do they have coalescing filters, have they been replaced, is compressor getting flood backs?
High pressure liquid receiver would also have to have correct level to warm oil return line. Liquid flood back to compressors could also contribute to oil consumption of compressor.

[mbc]

Hi
As you know the density of oil is a less than R22
So the oil will stay on top of R22
to remove that in wet Evaporator system is not easy
you have to feed hot gas from suction side and let goes to return pipe suction line or if you got own line for returning liquid line during defrost system
give more time for defrost to push R 22 and oil goes for return pipe and it become a little warm
your system has separator and feed by pump

All oil goes back to separator and you have to remove it with RECTIFIER VESSEL system

You need a rectifier vessel with either an electric heater or hot gas

[Tycho]

It looks good, is it working, can you have a sight glass or something to monitor oil return so oil & gas, not liquid returning to compressor which can cause compressor to use oil especially reciprocating compressor.
What type & how many compressors?
Are they throwing over excess oil, if so has oil separator oil return working, do they have coalescing filters, have they been replaced, is compressor getting flood backs?
High pressure liquid receiver would also have to have correct level to warm oil return line. Liquid flood back to compressors could also contribute to oil consumption of compressor.

This, we use a TX valve on the liquid line to measure across the heat exchanger, also a reg valve and a sight glass before compressor suction

[Tycho]

Some crude drawings of oil rectifier designs, I'm getting pretty good at MS Paint :)

15337
This is by far the easiest one to install and adjust.
One side is fed from the refrigerant pump discharge, through a solenoid (not on drawing) solenoid opens when 1 of the compressors start, liquid is fed through a TX valve into the heat exchanger, on the outlet I always put a Reg valve to adjust the flow during start up (it may be a bit exessive until the TX valve catches up), during normal operation there will be a nice and slow trickle of almost refrigerant free oil.

Warm side is fed by warm liquid from the HP receiver, doesn't matter if the liquid valve to the LP receiver is on/off or stepless.

15338

This one is still fed by the refrigerant pumps, but can be a pain to adjust properly.
Liquid is fed from the refrigerant pump discharge through a Reg/needle valve (usually 1/2" pipe) into a balancing pipe the balancing pipe drains back to the bottom of the LP receiver.
The important part is to fill the rectifier to no more than 80%.
When warm liquid enters on the other side of the tubes, it will cause boiling on the cold side that in turn lifts the "oil rich" refrigerant up to the pipe feeding the compressor suction.

Reg valve and sight glass on the line to compressor suction is an absolute must

15339

Same as the previous one, except this one does not have a balance pipe, the cold side is connected to the LP drum.

Main issue with this type is that you have to have a pretty stable level in the LP receiver, this type is almost exclusively used on Chillers where you have a very stable/fixed level.


My favourite is the fist one, because it's easiest to comission, and "it just works"

[RANGER1]

Nice drawings & explanations Tycho