Talk to me about electric air valves

[s410man]

Simple questions really but i can't seem to get my head around it by googling it

Trying to get a pneumatic double acting ram to work via a 12v electric valve

So i think i need a 2 way 5 port valve?

2 way as in open and close then 5 port as in 1 pressure line then a pressure and exhaust port for each side of the ram?

How is a 3 way 5 port valve different?

I need it to hold pressure when the 12v power is disconnected tho so is this closed centre?

Open centre would be more like a float position?

Simple enough but I'm just getting confused if someone could explain it in simple small words would be great!

Cheers

 

[m_c]

5/2 signifies 5 ports, 2 positions.
5/3 is 5 ports, 3 positions.

Key difference is a 5/2 will usually only have one solenoid (or some other way of activating, could be manual, could be air, could be something else, but I'll stick with solenoid as that's what you're wanting). Apply power, valve swaps ports.
3/5 will typically have two solenoids. With neither powered, all ports will typically be closed. Power one solenoid, will connect the Pressure/Vent ports one way to the A+B (outlet/cylinder) ports, power the opposite solenoid and the A+B connections get reversed.

The ISO symbols should help clarify things-

5/2 - Spring holds shuttle to the left. Solenoid pushes the shuttle against the spring.

5/3 the shuttle is held in the centre, and the solenoids push the shuttle against the opposing spring when activated.


*I use typically a lot above, as there are various other specialist valves available, which do things a bit differently. Things like you can get 5/2 valves that aren't spring loaded, but stay in position.

 

[s410man]

So a 5/2 has a default position it reverts to when power is removed whereas a 5/3 will stay in whatever position it's in when power is removed?

I really should spend some time getting my head around those iso drawings!

 

[mtt.tr]

So a 5/2 has a default position it reverts to when power is removed whereas a 5/3 will stay in whatever position it's in when power is removed?

I really should spend some time getting my head around those iso drawings!

Depends on the configuration you have check the drawing or description

 

[Robotstar5]

So a 5/2 has a default position it reverts to when power is removed whereas a 5/3 will stay in whatever position it's in when power is removed?

I really should spend some time getting my head around those iso drawings!

The ones shown above will return to the centre position when power is removed, the zig-zag denotes a spring so when the coil is energised it pull the spool against the spring.

 

[m_c]

ISO symbols aren't that hard to understand, although I just realised I used A&B instead of numbers (hydraulics generally use AB(outputs) P(ressure) T(ank), whereas pneumatics tend to just use numbers)

Taking the top symbol as an example, and adding a bit colour-

The ports remain stationary, and the ISO should show the valve in the default (unpowered/unactuated) position.
In this case, 5 is connected to 4, and 1 is connected to 2.
The wiggly line on the right represents a spring, and the yellow a solenoid (as per previous mentions, the solenoid may be replaced with various other actuators, in which case the exact symbol can change).

When the valve is actuated (via the solenoid in this case), it symbolically* 'pushes' the entire red shuttle section to the right against the spring-

So you now have 1 connected to 4, and 3 connected to 2.
It's worth noting in the case of a 4/2 valve, the main difference is the vent ports are combined into a single port (aka 3 & 5, would just be a single port), but the functionality is the same.

Something to be aware of when designing/connecting valves, is if the pressure and vent/return connections are specified. The valve may work with pressure/vents reversed, but they'll often blow seals out. Things like hydraulic valves will often have the return connection also acting as a case drain to avoid excess pressure building up behind the external seals which are probably only rated to 20-30bar. The valve will work initially, but once the pressure builds high enough, it'll just blow the seals out.

*I say symbolically, as a solenoid typically pulls the valve/shuttle. It's just for ISO symbols, having them symbolically push makes more sense.