Question

What is the difference in construction and action between a poppet valve and a spool valve?

Answer 1

Answer on Question 80265, Engineering - Electrical Engineering

What is the difference in construction and action between a poppet valve and a spool valve?

Answer

The function of the valve is to start/stop/regulate the fluid.

The poppet valve has a push button, inlet P and outlet A, the ball pressed to the hole by spring, the button is connected to the ball with a rod (see the picture). When pushing the button down, the ball goes down and thus let the fluid go through. If there is no on force on the button, the spring pushes the ball up and decreases the fluid flow.

The spool valve has lands 1, 2, 3, 4 with different diameters and the differential area between 1 and 2 (see the picture). When going through the differential area, fluid (with pressure p) causes the differential force $F = p(A_{1} - A_{2})$ which moves the valve left and thus lets the fluid to go through DE channel. The moving force $F = pA_{4}$ can be also created by fluid going to C channel and pushing the area 4. The areas 1 and 3 are equal, so no moving force is created. The spring (or opposite pressure or operator's hand) moves the valve right when the pressure in channels vanishes.