When the freon container is almost empty and of course the pressure is too low i have noticed some technicians momentarily tip the container to provide liquid freon to the low pressure line... Is this an approved process.. Is it safe if only a tiny bit is injected at a time... is it necessary to shut down and give the liquid a short time to convert to gas or should the unit continue to run with tiny increments of liquid be injected until the corrrect low and high pressure is reached....

Can the lliquid be more safely injected into the hi pressure line by connecting there?