i still deal with r-13 as well as r-23 , if you have liquid nitrogen and a portable j/c with a solenoid valve you can make a coffin insulate it an pump that into that with the container inside usual go to -130 that's 0 psi for 13. use that about once a month. never had a problem. open up the low side the refrigerant just walks out the compressor into the bottle.