help? Ultra low refrigeration help?

[Dalem554]

I have a meeting in which I need to understand the use and troubleshooting of ultra low refrigeration..I know... problem is I have no experience with it.. can someone point me in the right direction or a quick break down of operation?

[Paulajayne]

Hi

http://www.fridgesolutions.com/basics.shtmlhttp:


Start with the basics.

Depending upon how low you want to go I would have look at cascade systems.

HTH

Paula

[ultralo1]

It is not something you learn overnight.

The first stage system provides the cooling for the second stage.

The first stage evap acts as the condensor for the second stage. The second stage evap is wraped around the box.

Both systems use flooded evaps.

If the first doesnt get cold enough the second does not come on.

If the first gets to warm the second shuts off.


This should help get you through

[Brian_UK]

I wonder?????

Is this meeting a job interview for a new line of work;)

[The MG Pony]

Well if some low temp kit explodes we'll know.

You do know they explode if repaired wrong dalem? It can take a whole block out! Verry risky, you have to do it 'Just" right or BOOM!

[Dalem554]

No..it's not for a job but, I'll be in the building of a customer that has these systems and the tech that belongs to them is on vacation. I just need to know enough to answer some casual questions if the topic is brought up while I'm pitching a proposal.

[ultralo1]

I'm pitching a proposal

Just what are you pitching?

Working on Ultralows can get you in alot of trouble with the customer, if you "think" you know what you are doing.

I have seen more than one persons reputation get killed and not be allowed back in the building.

[Samarjit Sen]

Hi Dalem 554,

It appears that you have not earlier worked on a Cascade system ( Ultra Low Temperature Units). The stages of cascading shall depend on the final temperature that you would like to attain. Upto - 60oC you can operate with double stage single compressor. Then down to - 80oC you will have to use two seperate compressors. The first one is to cool the condenser of the second one, and the second one will bring down the temperature of the unit. Then you have the three stage system where the temperature would be about down to - 120 to -150oC. All the compressors shall have different refrigernts depending on the boiling point of the refrigerants.

The refrigeration controls are specifically manufactured and designed for such low temperature applications. You must rember that any metal will change its mettalurgy at a very low temperature.

All the stages are interconnected. Unless you attain the desired temperature in the first stage, which is generally - 30oC the second stage would not start. You got to have a cascade condensers. These could be good quality PHEs.

It is a very interesting line, but you must have suffecient experience before even thinking of touching one.

Further the refrigerants that are used are 404A in the first stage, R 23 0r R 508 B in the second and third stage.

I wish you all the best for your meeting and hope that with the informations provided in this forum you will be able to make your point.

[The MG Pony]

Forgeting about autocascades too! They be an odd beast

[Dalem554]

Don't worry Untralo1..I'm not there to troubleshoot anything. I just needed a little info for the slight chance someone in the meeting brings it up and that I am aware of it's normal operation temps and operation to a point where a technician would take over.

[The MG Pony]

Just politely say you are not qualified on it to comment and leave it at that, they will spot the fact you have no idea what your talking about and that leaves a bad impression.

Best to just say "I'm not sure but our tech sure does!" then to try and parrot some info of which you can't expand on if they ask for it.

[ultralo1]

Just politely say you are not qualified on it to comment and leave it at that, they will spot the fact you have no idea what your talking about and that leaves a bad impression.



Amen, brother. This will get you alot of respect.

If it is a research facility that you are dealing with, they think that their babies are in those freezers. They do have their lifes work in there. My researchers have samples dating back to 1975 in some of these freezer.