difference between hydraulic & pnuematics

Hydraulic valves redirect hydraulic fluid.

Pneumatic valves redirect air. I hope this helps.

thanks my friend but I want to know about diffrence between symbols. ok

I have used both types for years, and I do not remember any differences in the symbols. You can go to www.grainger.com They sell both, and show their functions on their site. Good luck.

what if we are building a low rider or trying to explain to a class whats the difference between airbags and hydraulic.. and is pnuematics the same as airbags..

Hydraulic is oil driven using an electric oil Pump.

Pneumatic is air driven using an electric compressor.

A direction control valve shows 4 ports for hydraulics and 5 ports for pneumatics.

As stated above, the triangle indicating flow or pilot operation is generally an outline for pneumatics and solid for hydraulics.

The number of ports is guided by the intended use. I have worked both both designs in two port, three port, four port, and five port styles.

I've done a lot of hydraulics, and never used a 5-port direction valve. 5-port pneumatic valves, on the other hand, are the standard 4-way configuration.

TNT rescue tool. Remote dump valve.

1. pressure from the hyd pump.
2. pressure to the tool
3. return from the tool to dump valve
4. return from tool return port to reservoir
5. return from dump valve to reservoir

The extra return line is needed to prevent fluid loss at the tool connectors if changing the tool. The system retains some low pressure in the return line from the tool if not for the extra line. I bought with TNT to eliminate the extra line, but lost. Hope that clears it up some.

And one more quick note : hydro has to have a flow back to the reservoir and pneumatic vents to the atmosphere.