Hydraulics dumb question; Help me understand

[beppington]

Something that may be so simple, but I don't understand ... When I move my FEL lever, what exactly happens? Is a port or valve opening?

I don't understand why the tractor goes from fairly quiet where I'm hearing only the diesel engine running to a hydraulic pump also running when I operate the FEL control lever or the 3PH lever.

It sounds like the pump knows that I've opened a port or valve, & therefore kicks itself into gear aka starts pumping. Is there an electrical switch involved?

Of course, if I very gently move the FEL control, the hydraulic pump sound is proportionally quieter.

Maybe there's a hydraulics primer thread on here, but I haven't found it yet.

 

[kennyd]

No switches/electrics involved here (on your machine anyway).

The pump is always pumping if the engine is running, there is just very little pressure if all the valves are in neutral since the fluid is just circulating from the reservoir, into the pump (suction side), then out of the pump (pressure side) to all the valve in the system and then finally back to the reservoir.

When a valve is activated, fluid is diverted (via the "spool") from that free-flowing stream in the body of the valve and directed to the "work port(s)" that ultimately is connected to a cylinder. When the cylinder encounters resistance to movement, then the pressure in the system builds to overcome this resistance.

Here is another explanation: How Do Hydraulic Spool Valves Work? | eHow.com

And this is a great resource also: Army Hydraulics Manual


Clear as mud?:laughing:

 

[J_J]

The sounds you hear are related to the velocity and pressure as the hyd fluid moves through the cavities and orifices in the hyd system, mainly the pump and valves.. If you move the FEL lever a little, you are only letting a small amount of fluid to do work.

You may or may not hear any sound from the system at rest. Put a load on the hyd system, and you will hear various sounds. Learn these sounds, and it will help you determine what is good and not so good.

A hyd gage will also help you to monitor and trouble shoot the hyd system.

Hyd machinery make lots of sounds, but the whine is the most common.

 

[beppington]

Thanks for the replies!

Now I gotta figure out how a spool works.

Looks like it's the unit to direct the fluid from one direction to another?

 

[beppington]

Is a tractor's spool just like the spool explained in this video?

Spool Valves - YouTube

 

[J_J]

Yes, basic idea.