Operation of pneumatic 5/3 valve with double solenoids? 1

[mvpieper]

I will be implementing a pneumatic 5/3 valve to control a double-acting cylinder. The valve has two solenoids(for this post I will designate them as S1&S2). I assume that when..
S1=ON & S2=OFF, this will be Position1
S1=OFF & S2=OFF, this will be Position2 (center)
S1=OFF & S2=ON, this will be Position3

however, what will result if...
S1=ON & S2=ON, Is the result unexpected (or unstable)?

Should the solenoids be electrically-interlocked so that only one solenoid may be energized at a time?

 

[budt]

Most manufacturers of 5-Way 3 Position valves mark the solenoids 12 and 14 and the ports are numbered

1= Inlet
2= Cylinder Outlet (Actuator Outlet)
3= Exhaust for Port 2 thru Port 3
4= Cylinder Outlet (Actuator Outlet)
5= Exhaust for Port 4 thru Port 5

Solenoid 12 shifts the valve to give flow from Port 1 to Port 2 and Exhaust's Port 4 thru Port 5

Solenoid 14 shifts the valve to give flow from Port 1 to Port 4 and exhausts Port 2 thru Port 3

Knowing the Port number connections allows the electrical programmer to energize the correct Solenoid to make an actuator perform the designated function.

I always draw the schematic so S12 makes a Cylinder extend or a Rotary Actuator turn Clockwise and S14 to make a Cylinder retract or make a Rotary Actuator turn Counter Clockwise.

With a Direct Solenoid Operated valve, energizing both solenoids at the same time will not change the valves position since that normally gives equal forces from the solenoids and equals no shifting will happen. However, most solenoids will overheat due to high Inrush Current and burn up quickly in this condition. The other possibility is the valve will shift since one coil acts faster and an actuator may operate but the opposing coil will fry due to high inrush current.

To protect the Solenoids always electrically interlock the signals so only one solenoid can be energized.

With Solenoid Pilot Operated valves equal Pilot Pressure to both sides of the valve keep it centered since fores are equal. However the Solenoids that shift the Pilot Section are not mechanically opposed so they operate normally without any damage.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING, INC.

http://www.fluidpower1.us

 

[gerhardl]

Exellent answer from budt. The only thing I can think to add is following:

There would be on the solenoid itself or in following instruction a diagram with numbers on ports and solenoid to illustrate the function. Solenoids (with pilots) each side, nearest square to solenoid to explain corresponding function. Square in middle to illustrate function when both solenids off ('normal' or rest position.)

For a 5/3 solenoid the 'normal' function (both solenoids without current) could (after the solenoid valves constructional type) be either all ports locked, both sides of sylinder/actuator fed with pressure at the same time, or both sides evacuated. All three types do exist, but the first is the most commen.

When you are selecting for a 5/3, you are actually selecting to get one of the 'normal' rest functions for a 5/3 described above, on the reason that this will be essential for the equipment/process function.

A 5/2 would be cheaper, and in most cases suffcient for all safety purposes.

A 5/3 would be more seldom needed. (Special case :For hand operated presses, according to country/area rules, special designed solenoid (cross locked) valves must be used, normal 5/2 and 5/3 may not be accepted.)

 

[mvpieper]

Thank you Bud & gerhardl.

Bud, I appreciate...
I always draw the schematic so S12 makes a Cylinder extend or a Rotary Actuator turn Clockwise and S14 to make a Cylinder retract or make a Rotary Actuator turn Counter Clockwise.

Gerhadl, My application uses the "center position open", which exhausts both sides of cylinder, so that the gate can be easily moved on loss of electrical signals.

Again, thanks. Especially for the quick reply.

 

[budt]

Another interesting note on 5-Way valves:

All 4-Way Spool Design valve, air or hydraulic, are actually 5-Way and are made 4-Way by internally connecting the two Outer Pors together so they will not have to be connected externally. Look at a Cutaway of any Hydraulic 4-Way to see the cross connection of the Tank Ports.

If you can find an old Olmstead company catalog you can see some of their 4" and 5" hydraulic valves with the 5 ports. The manifold they mounted on had the cross tank connections.

Some catalogs list there 5-Way air valves as 5 Ported 4-Ways. In air service the extra exhaust is not a problem since atmosphere is an air systems Tank.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING