how do i build a Refrigerant Recovery Unit

[wdrzal]

ahh now i get it so the o2 sits on top of the gas
so a wid guess is the pressure a set value?
or is it like 0 psig making -15 for r134a?
or other random figure
will the same work for all gas or just 134a
on and thanks for the help

First air is not O2 (oxygen) . Air contains about 20.9% oxygen(@ least @ my elevation around 1400' Above sea level.,78% nitrogen .o3% co2 and the rest is rare earth gases.

You need to study and understand pressure/temperature charts for each refrigerant/ gas.
If you know the pressure,you know the temperature,if you know the temperature you know the pressure. This applies to tanks or system that have at least 1% liquid present(the number is actualy lower but 1% is very little liquid and a safe rule of thumb.If no liquid is present the p/t chart is invalid.

you also need to understand the critical pressures and temperatures and triple points of each gas. figures are not random.

air has a specific gravity of 1,some refrigeration vapors(or pure gases) are heavier than air or greater than 1 and some are lighter than air ,less than 1. You need to consult physical properties of each specific refrigerant or gas. most MSDS sheets list these but not all list complete info.