Hermetic Compressors

Why is a special sand cloth used on a hermetic compressor system?

You’re never supposed to sand the connections before brazing refrigerant lines.

The question you ask in my opinion is somewhat complicated and may require more information to provide a meaningful response.
The following is my opinion on the possibilities.
I have been in the hvac/r industry for 28 years and have never heard of a special sand cloth for brazing any kind of connection dealing with refrigeration pipe.
Some compressor stubbs are made of steel with a copper flashing. If you sand the stub of this type of connection you may remove the copper flashing and then make brazing the connection impossible by using “silphos” (“silphos” is an alloy of silver and phosfurous) and will not require sanding or flux.
This makes Marc"s statement true that you should never sand a refrigeration joint in this case.

Having said this, you can sand with regular plumbers cloth any full copper joint prior to brazing with “silphos”.

I am new to posting on the message board but have wached it for some time .

Marc’s responses are quite impresive and I am a little leary to contradict him since he has been bang on in the past and very helpfull to me.
Anyway this is what I have to say.

Hope this helps

Correct, the grit will get inside the system and coper to coper doesn’t need to be “sanded” when “silver soldering” anyway.