Yes, liquid slugging of a compressor will damage it. Usually it will bend the reed valves so they no longer seat properly. Even a small overcharge on an orifice regulated system can reduce the system superheat to the point where a small amount of liquid enters the compressor crankcase and washes the lubrication from the bearings and rings. Compressors are pretty robust but they aren't bullet proof. I have seen several cases where liquid slugging actually broke the connecting rod in the compressors. You'd think it would make the compressor run very noisily but these were 2 cylinder compressors and instead it causes a telltale vibration like no other. They actually all continued to work albeit at reduced capacity. These we factory mistakes that didn't have the accumulator that should have been installed in their particular application.
As for improper evacuation, some of the supposed service techs have told me they don't need a micron gauge since they can tell by looking at their charging manifold gauge, that shows pounds per square inch, when the vacuum is pulled deep enough. That's sort of amusing since an absolute pressure reading that would support a 100 microns column of mercury would be shown as 0.0019336777871316 psi on their gauge. They must have exceptional eyesight and even better powers of perception than I do.
Any oxygen or moisture left in a system will be like poison and will kill the compressor prematurely. We used to pump the refrigerant R-11 in liquid form through burnouts but with the advent of better suction line filters and tougher restrictions on dumping any refrigerant into the environment, the suction filter is now used almost exclusively to clean up a particulate contaminated system. A good quality SLF can also trap the acids that are produced in the system that caused the compressor to fail in the first place. Those acids were created due to improper evacuation. For example, take some oil vapor (which has sulphur in it), add some water vapor and expose it to oxygen at the high temperatures, such as at the discharge of the compressor, and you can produce sulphuric acid.
Now we have been full circle and arrived back at the jack-leg who dummied up, either at the factory or when doing a repair from failure due to other reasons. His work methods sometimes make another premature failure almost assured.
I watched a service tech replace the unit on my neighbor's heat pump a couple years ago. I wanted to manually apply some Darwinian action to him and rid the world of such ignorance. I engaged him in small talk, nothing about refrigeration, yet he broached the subject and succeeded in outlining how technical his line of work was and how it took special training to be able to do it. He said there was good money in it if you're good at it. I think that last part is the only aspect of refrigeration work that he actually knew well. :wink2:
So to make a really long answer short (too late now) the second failure is often the repairman's fault. Vet them and ask if they plan on using a micron gauge. Then watch them to see that they do.
