homework

Homework 5 - LabVIEW

1. Pneumatically controlled valves are operated by changing the air pressure applied to a diaphragm, as illustrated in figure below. The pressure, acting on the area of the diaphragm, generates a force that attempts to move the valve stem.

F=PA (pressure x Area)

That force is countered by a spring that pushes on the diaphragm in the other direction.

Fspring=kspringx

Where:

kspring is the spring constant

x is the extension of the spring

Control valves typically use air pressures ranging between 3 psi (lbf/in2) and 15 psi. The change in applied force because of the pressure change causes the valve stem to move approximately 1 inch.

Determine:

a. The force applied to a 10-inch diameter diaphragm by 3 psi air.

b. The force applied to a 10-inch diameter diaphragm by 15 psi air.

c. The change in applied force (ΔF) as the air pressure increases from 3 to 15 psi.

d. The spring constant required to cause the valve stem to move 1 inch in response to the calculated change in force.

Note: The difference version of the spring equation may be helpful: Fspring=kspringx

For each solution (a-d) please print a front panel with the calculated values.