MET230: Hydraulics and Pneumatics

Unit 3 Review Assignment

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Problem 1

A compressor delivers 180 scfm of air through a 3/4-in schedule 40 pipe at a receiver pressure of 85 psig. Find the pressure loss for a 170-ft length of pipe

*Hint: Use the table shown if needed.*

Tabulated values of d and d5.31 for schedule 40 common pipe

Problem 2

A compressor delivers 2000 cfm of air through a pipe at a receiver pressure of 140 psig. What minimum size schedule 40 pipe should be used if the pressure loss is to be limited to 0.10 psi per foot of pipe length?

*Hint: use the table of Problem 1 if needed.*

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Problem 3

For the circuit shown, cylinder 1 will not hold against a load while cylinder 2 is retracting. Modify this circuit by adding a pilot check valve and appropriate piping so that cylinder 1 will hold while cylinder 2 is retracting. Show the modified circuit schematic.

Figure for Problem 3

Problem 4

The pneumatic system shown contains a double-rod cylinder controlled by two three-way, two-position directional control valves. In each of the following cases, what is the behavior of the cylinder?

1. Only V1 is actuate

2. Only V2 is actuate

3. Both V1 and V2 actuated Figure for Problem 4

4. Both V1 and V2 not actuated

Problem 5

How heavy an object can be lifted with a suction cup having a lip with a 8-in outside diameter and a 6.5-in inside diameter if the vacuum pressure is

a. -5 psig

b. A perfect vacuum

Assume a factor of safety of 2.5

Problem 6

A pneumatic vacuum lift system has a total volume of 15 ft3 inside the cup and associated pipeline leading to the vacuum pump. The vacuum pump produces a flow rate of 3 scfm when turned on. The desired suction pressure is 5 psia and atmospheric pressure is 29.5 in Hg abs. Determine the time required to achieve the desired suction pressure.

(*Hint: 30 inHg = 14.7 psia*)