What's the difference between these two pneumatic valve symbols?

[Nick_bobo]

Hello,

I have a schematics of a pneumatic system with various type of actuating valves. There are two different types of symbols for solenoid valves that I don't understand what is the difference. Both of these are two-port/two-position valves, actuated electrically, but the symbols are a little different.

In picture 1, it has a regular solenoid actuator that open/close the valve.

In picture 2, it also has electrical actuation but I am not sure about the downward triangle in the box, which is usually used for pilot (air) actuation.

Well, the only connections to actuator of the second valve are electrical and no pilot line is there. So, what that actually means?

Thank you for your help

 

[1503-44]

It appears to be actuated by the electric signal only, but I'm guessing. Maybe someone else knows better than I.

A black swan to a turkey is a white swan to the butcher ... and to Boeing.

 

[Compositepro]

One thing to consider is that the source of the pilot pressure maybe internal or external to the valve. If the pressure that the valve controls can be variable or low, then an external source of pilot pressure is required.

 

[Nick_bobo]

Thank you @1503 and @Compositepro.

To my understanding the arrow on the actuator of the first valve means the signal is variable and actuation is continuous between min and max, but the straight line on the second one means it's an on-off actuator. The second valve is a part of an ABS system that should be able to open/close very fast. Definitely there is no external pilot pressure, but not sure about the internal pilot.