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Question 1 (20 pts)
Spring design
You need to design the compression spring in a pressure release valve for a pneumatic air
compressor system that releases air when the pressure rises above 150 psa. The valve head is a
flat piston with a 1 in diameter. The outer diameter of the spring must be within 0.75 to 1 in to fit
inside the valve body. The unstretched length of the spring should be between 3-3.5 in. The
spring should be able to handle a load of at least 80 lbf. To minimize cost, the spring should be
unpeened and made from the most common spring material, music wire. When the air pressure
in the system rises above 150 psi and the release valve allows air to flow through it, the valve
piston is expected to be pressed down with an additional force of 30 lbs above the spring preload
force, which could occur at a frequency of up to 2 Hz. You must select the least expensive stock
spring from your preferred spring manufacturer, Century Spring, that will meet the specifications
for the pressure release valve with an appropriate factor of safety for infinite fatigue life. You
should also check the critical frequency of the spring to make sure it meets the design
specifications.
Note: the images shown below are for a similar valve called a check valve used in oil pipelines,
but the release valve you are designing has a different scale, dimensions, and application
Closed valve.
Open valve.
