Which of the following is a component of a pneumatic system? a. A compressor b. An electric motor c. An actuator d. A valve e. All of the above

MET230 Hydraulics and Dynamics

Unit 1 Study Guide 1

Question 1

Which of the following is a component of a pneumatic system?

a. A compressor

b. An electric motor

c. An actuator

d. A valve

e. All of the above

Answer: e. “All of the above”

Question 2

Which of the following is true about fluid power?

a. A fluid power system uses a liquid to generate, control, and transmit power

b. Fluid power is another term for fluid transport

c. There is no difference between hydraulics or pneumatics fluid power systems

d. Power capacity of fluid systems is limited only by the physical strength of the material used for each component

e. None of the above

Answer: d. “Power capacity of fluid systems is limited only by the physical strength of the material used for each component ”

Problem 1

A hydraulic fluid has a specific weight of 58 lb/ft3. What is its specific gravity SG? What is its density ρ? ( Note: the specific weight of water is γwater = 62.4 lb/ft3, and the acceleration of gravity g = 32.2 ft/s2)

Known data

Fluid specific weight γfluid = 58 lb/ft3

Water specific weight γwater = 62.4 lb/ft3

Acceleration of gravity g = 32.2 ft/s2

Unknown (s)

Specific gravity SG?

Density ρ?

Formula

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MET230: Hydraulics and Pneumatics

Week 1 Review Assignment

Problem 1

A hydraulic fluid has a specific weight of 60 lb/ft3. What is its specific gravity SG? What is its density ρ?

Problem 2

Eleven liters of SAE 30 oil weighs 92 N. Calculate the oil’s

a. Specific weight

b. Density

c. Specific gravity

Problem 3

Convert a -6 kPa (negative 6 kiloPascal) pressure to an absolute pressure in kPa.

Problem 4

A hydraulic cylinder has a 275 mm diameter. How much oil pressure P (kPa) is required to produce 12500 N force at its piston?

Problem 5

An oil (SG = 0.87) has a viscosity of 187 SUS at 120 oF. Find the corresponding viscosity in units of cS (centiStokes) and cP (centiPoise).

Problem 6

In the hydraulic jack shown, a force of 100 N is exerted on the small piston. Determine the upward force on the large piston. The area of the small piston is 65 cm2, and the area of the large piston is 950 cm2. If the small piston moves 12 cm, how far will the large move? Assume the oil to be incompressible.

Problem 7

The pneumatic/hydraulic system shown is use to lift a load. If the inlet air pressure is 450 kPa, determine the maximum load that can be lifted.

Problem 8

What is the theoretical flow rate from a fixed displacement axial piston pump with an eight-bore cylinder operating at 1750 rpm? Each bore has a 1.25-in diameter and the stroke of 0.75 in.

Problem 9

A vane pump is to have a volumetric displacement of 10 in3. It has a rotor diameter of 2in, a cam ring diameter of 4in, and a vane width of 2.5 in. what must be the eccentricity?

Problem 10

Find the offset angle for an axial pump that delivers 50 gpm at 1750 rpm. The volumetric efficiency is 95%. The pump has a nine 0.75 inch diameter pistons arranged on a 6-in piston circle diameter.

Problem 11

A gear pump has a 75-mm outside diameter, a 55-mm inside diameter, and a 30-mm width. If the actual pump flow rate at 2700 rpm and rated pressure is 0.0025 m3/s. What is the volumetric efficiency?

Problem 12

A pump has a displacement volume of 122 cm3. It delivers 0.0027 m3/s of oil at 1720 rpm and 85 bars. If the prime mover input torque is 175 N∙m

a. What is the overall efficiency of the pump?

b. What is the theoretical torque required to operate the pump?

Problem 13

A pump supplies oil at 25 gpm to a in diameter double acting hydraulic cylinder. If the load is 1800 lb (extending and retracting) and the rod diameter in, find the

a. Hydraulic pressure during the extending stroke

b. Piston velocity during the extending stroke

c. Cylinder horsepower during the extending stroke

d. Hydraulic pressure during the retracting stroke

e. Piston velocity during the retracting stroke

f. Cylinder horsepower during the retracting stroke

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MET230 Hydraulics and Dynamics

Unit 1 Study Guide 2

Question 1

Which of the following statements is true about positive displacement pumps?

a. Gear and vane pumps are the only two categories of positive displacement pumps

b. A positive displacement pump cannot be used with a pressure relief valve

c. The motion of a positive displacement pump cannot be reciprocating

d. The output flow rate varies with the system pressure

e. None of the above

Answer: e. “None of the above”

Question 2

Which of the following statements is true about dynamic pumps?

a. Dynamic pumps are self-priming

b. Centrifugal and axial pumps are not classified as dynamic pumps

c. Dynamic pumps are used for low-volume, high pressure applications

d. The flow rate output of dynamic pumps decreases as the circuit resistance increases

e. None of the above

Answer: d. “The flow rate output of dynamic pumps decreases as the circuit resistance increases”

Problem 1

What is the theoretical flow rate from a fixed displacement axial piston pump with a twelve-bore cylinder operating at 750 rpm? Each bore has a 1-in diameter and the stroke of 0.5 in.

Solution

Known data

Number of cylinder Y = 12

Rotational speed N = 750 rpm

Bore diameter D = 1 in

Stroke S = 0.5 in

Using Trigonometry:

Unknown(s)

Theoretical flow rate QT?

Needed

Piston/bore area A?

Displacement volume VD?D

Formula

Detailed Calculation