Hello, What is the purpose of the little air compresor on the hyd. tank of cat excavators? I would think it would drive moisture in there would it not? I have also seen them unhooked..... any reason to do away with them?
i believe they are used to pressurize the hydraulic tanks slightly to help force the hydraulic oil into the pumps to stop any cavitation.
That would be one of a number of benefits kbeen, but the main reason a compressor is actually used on some machines is the tank has no atmospheric vent. Many machines have a vent that allows air to enter the tank as oil level drops when cylinders are extended. Then, when cylinders are retracted, oil level comes up, air drawn into tank is trapped, which pressurizes tank. Some machines, such as Case 9050B, have no vent for tank, instead use an air compressor to pressurize tank. With no vent, and if it had no compressor or means for air to come into tank, when you extend cylinders and oil level dropped, it would collapse tank. Both systems, atmospheric vent as well as air compressor pressure will add a slight bit of moisture to air inside tank, but the non-vented compressor system is less likely to allow dirt/dust into tank as the tank is sealed with no vent.
In the past when most machines had air compressors the pump was mounted at about the middle height of the reservoir. When the fluid level went down the top half of the hydraulic pump was actually below the level of the fluid in the tank, especially when working in adverse terrain for logging machines. Sumitomo machines such as Case and Link-Belts stayed with the compressors for a long time and may still. The compressors added expense and complexity to these machines and I have several horror stories that go with them. In the late 1990's other manufacturers started using turbo charger boost pressure instead of adding the compressors. I didn't care for the idea of putting hot air on top of a hot flammable fluid but it didn't seem to be a big problem. The best systems are the vented tanks with pressure check valves.
Gerat info!! Thanks