A pipe handles a flow rate of 35 gpm. Find the minimum inside diameter that will provide an average fluid velocity not the exceed 20 ft/s.
- Clearly present:
- The given data
- The unknowns
- The formulas needed, and
- Sketches, where applicable
- Use consistent units (Do not switch or convert between USCS and SI)
- Round off final answers to proper degree of precision or accuracy (Use 3 decimal points or 3 significant digits for all your calculations and answers)
- Underline your final answer with proper unit
MET230: Hydraulics and Pneumatics
Week 4 Review Assignment
Problem 1
A pipe handles a flow rate of 35 gpm. Find the minimum inside diameter that will provide an average fluid velocity not the exceed 20 ft/s.
Problem 2
A steel tubing has a 1.5-in outside diameter and a 1.210-in inside diameter. It is made of AISI 1020 annealed steel having a tensile strength of 57,000 psi. What would be the safe working pressure for this tube assuming a factor of safety of 8?
Problem 3
Select the proper-sized steel tube for a flowrate of 25 gpm and an operating pressure of 1,000 psi. The maximum recommended velocity is 20 ft/s and the factor of safety 8. The tube is made out of SAE 1010 with a tensile strength of 55,000 psi.
Figure 10-7. Common tube sizes
Problem 4
Oil at 24 gpm and 1200 psi enters the low-pressure inlet of a 4:1 Racine pressure intensifier. Find the discharge flow rate and pressure.
Problem 5
Oil at 155oF and 2250 psi is flowing through a pressure relief valve at 25 gpm. What is the downstream oil temperature?
Note
· 1 hp = 42.4 Btu/min.
Also, for oil under consideration,
· Specific heat = 0.42 Btu/lb/oF
· 1 gpm = 7.42 lb/min
Problem 6
A hydraulic pump operates at 150 bars and delivers oil at 0.0015 m3/s to a hydraulic actuator. Oil discharges through the pressure relieve valve (PRV) during 50% of cycle time. The pump has an overall efficiency of 87%, and 15% of power is lost due to frictional pressure losses in the hydraulic lines. What heat –exchanger rating is required to dissipate all the generated heat?
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MET230: Hydraulics and Pneumatics
Week 4 Study Guide 1
Question 1
Which of the following statements is NOT true about hydraulic distribution systems?
A. A primary purpose of a fluid distribution system is to carry the fluid from the reservoir through operating components and back to the reservoir
B. The flow velocity generally recommended for the discharge side of a pump is 25 ft/s
C. The flow velocity generally recommended for the inlet side of a pump is 4 ft/s
D. Conductors and fittings should not be made out of copper
E. None of the above
Answer B. “The flow velocity generally recommended for the discharge side of a pump is 25 ft/s”
Justification: The recommended velocity is 20 ft/s.
Question 2
Which of the following statements is NOT true about hydraulic distribution systems?
A. Zinc, magnesium and cadmium cannot be used conductors or fittings
B. Malleable iron cannot be used for hydraulic fitting
C. Hydraulic shock raises the system pressure up to 4 times of the steady state value
D. Conductors should always have greater strength than the required system working pressure
E. None of the above
Answer: B. “Malleable iron cannot be used for hydraulic fitting”
Justification: Malleable iron can be used for hydraulic fittings for low-pressure lines such as inlet, return and drain lines.
Question 3
Which of the following metals CANNOT be used with water-glycol hydraulic fluids?
A. Zinc
B. Magnesium
C. Cadmium
D. A, B, and C
E. None of the above
Answer D. “A, B, and C”
Question 4
Which of the following variables determine the wall thickness and factor of safety of a conductor for a particular operating pressure?
A. Tensile strength of conductor material
B. Conductor outside diameter
C. Operating pressure levels
D. A, B, and C
E. None of the above
Answer D. “A, B, and C”
Question 5
Which of the following is NOT one of the four primary types of hydraulic conductors?
A. Steel pipe
B. Steel tubing
C. Plastic tubing
D. Flexible hose
E. None of the above
Answer: E. “None of the above”
Question 6
Which of the following is one of the four criteria by which the size of a hydraulic reservoir is determined?
A. It must make allowance for dirt and chips to settle and air to escape
B. It must hold all the oil that might drain form the system
C. It must maintain oil level high enough to prevent a whirlpool effect at the pump inlet
D. It must have a surface area large enough to dissipate heat
E. All of the above
Answer: E. “All of the above”
Question 7
Which of the following is NOT one of the three common reservoir design?
A. U-shaped design
B. Flat top design
C. L-shaped design
D. Overhead stack design
E. None of the above
Answer: A. “U-shaped design”
Question 8
Which of the following accumulators creates a constant fluid pressure throughout the full volume output of the unit regardless of the rate and quantity of output?
A. Weight loaded accumulator
B. Spring loaded accumulator
C. Gas loaded accumulator
D. No accumulator create a constant pressure
E. None of the above
Answer: A. “Weight loaded accumulator”
Question 9
Which of the following is NOT a major separator-type gas-loaded accumulators?
A. Piston accumulator
B. Diaphragm accumulator
C. Bladder accumulator
D. Gravity loaded accumulator
E. None of the above
Answer: D. “Gravity loaded accumulator”
Question 10
Which of the following is the main advantage of the bladder type accumulator over other gas type accumulators?
A. Its ability to handle very high or low temperature system fluids
B. Its small weight-to-volume ratio
C. A positive sealing between the gas and oil chambers
D. Its exclusive use of nitrogen
E. None of the above
Answer: C. “A positive sealing between the gas and oil chambers”
Question 11
Which of the following materials is used for hydraulic seals?
A. Leather
B. Buna-N
C. Silicone
D. Neoprene
E. All of the above
Answer E. “All of the above”
Question 12
Which of the following is one of important factors to consider when selecting a heat exchanger?
A. Heat generation rate
B. Oil flow rate
C. Allowable oil temperature
D. A, B, and C
E. None of the above
Answer D. “A, B, and C”
Question 13
Which of the following is a flow-measuring device?
A. Rotameter
B. Durometer
C. Bourdon gage.
D. Schrader gage
E. None of the above
Answer: A. “Rotameter”
Question 14
Which of the following is a pressure-measuring device?
A. Rotameter
B. Turbine flow meter.
C. Durometer
D. Schrader gage
E. None of the above
Answer: D. “Schrader gage”
Problem 1
A pipe handles a flow rate of 25 gpm. Find the minimum inside diameter that will provide an average fluid velocity not the exceed 20 ft/s.
( Hint: 1 ft3/s = 449 gpm)
Solution
Known Data
Pipe flow rate Q = 25 gpm = 0.05568 ft3/s
Maximum average velocity v = 20 ft/s
Unknown (s)
Minimum inside diameter D?
Needed
Pipe flow area A?
Formula (s)
Detailed Calculation
First, we convert the flow rate into units of ft3/s
Next, we solve for the minimum required pipe flow area
Finally, the pipe diameter is found from
Problem 2
A steel tubing has a 1.25-in outside diameter and a 1.120-in inside diameter. It is made of AISI 4140 annealed steel having a tensile strength of 95,000 psi. What would be the safe working pressure for this tube assuming a factor of safety of 8?
Solution
Known Data
Outside diameter Do = 1.250 in
Inside diameter Di = 1.120 in
Tensile strength S = 95,000 psi
Factor of safety FS = 8
Unknown (s)
Working pressure WP?
Needed
Wall thickness t?
Burst pressure BP?
Formula (s)
Detailed Calculation
First, calculate the wall thickness of the tubing:
Next, find the burst pressure for the tubing
Finally, calculate the working pressure
Problem 3
Select the proper-sized steel tube for a flow rate of 35 gpm and an operating pressure of 1,000 psi. The maximum recommended velocity is 20 ft/s and the factor of safety 8. The tube is made out of AISI 4130 steel with a tensile strength of 75,000 psi
Figure 10-7. Common tube sizes
Solution
Known Data
Flow rate Q = 35 gpm = 0.07795 ft3/s
Operating pressure p = 1000 psi
Maximum average velocity v = 20 ft/s
Tensile strength S = 75,000 psi
Factor of safety FS = 8
Unknown (s)
Working pressure WP?
Needed
Pipe flow area A?
Inside diameter D?
Burst pressure BP?
Formula (s)
Detailed Calculation
First, we convert the flow rate into units of ft3/s
Next, we solve for the minimum required pipe flow area
Finally, the pipe diameter is found to be
From Figure 10-7 above, the smallest acceptable tube size based on flow rate requirements is:
1 in. OD, 0.065 in. wall thickness, 0.870in. ID
The burst pressure and working pressure for the above tubing for the AISI 4130 material are
This working pressure is adequate since it is greater than the operating pressure of 1000 psi.
So,
Use 1 in. OD, 0.065 in. wall thickness, 0.870 in. ID
Problem 4
Oil at 25 gpm and 1000 psi enters the low-pressure inlet of a 5:1 Racine pressure intensifier. Find the discharge flow rate and pressure.
Solution
Known Data
High inlet flow rate Q = 25 gpm
Low inlet pressure p = 1000 psi
High pressure/Low pressure = 5/1
Unknown (s)
Discharge pressure?
Needed
Pipe flow area A?
Formula (s)
Detailed Calculation
Problem 5
Oil at 135oF and 2010 psi is flowing through a pressure relief valve at 18 gpm. What is the downstream oil temperature?
Note
· 1 hp = 42.4 Btu/min.
Also, for oil under consideration,
· Specific heat = 0.42 Btu/lb/oF
· 1 gpm = 7.42 lb/min
Solution
Known Data
Upstream Temperature = 135 oF
Inlet pressure p = 2010 psi
Flow rate Q = 18 gpm = 133.56 lb/min
Specific heat = 0.42 Btu/lb/oF
Unknown (s)
Downstream Temperature?
Needed
Power loss?
Formula (s)
Detailed Calculation
First, calculate the horsepower lost and convert into heat generation rate in units of BTU/min.
Next, convert the oil flow rate in units of lb/min .
The temperature increase can therefore be calculated as
The downstream temperature is then found to be
Problem 6
A hydraulic pump operates at 2050 psi and delivers oil at 12 gpm to a hydraulic actuator. Oil discharges through the pressure relieve valve (PRV) during 65% of cycle time. The pump has an overall efficiency of 80%, and 16% of power is lost due to frictional pressure losses in the hydraulic lines. What heat –exchanger rating is required to dissipate all the generated heat?
( Hint. 1 hp = 42.4 Btu/min = 2544 Btu/hr)
Solution
Known Data
Pump pressure p = 2050 psi
Flow rate Q = 12 gpm
Duty cycle = 65% = 0.65
Pump overall efficiency ηo = 80% = 0.8
Lines frictional losses = 16% = 0.16
Unknown (s)
Downstream Temperature =?
Needed
Power loss?
Formula (s)
Detailed Calculation
Let’s express the total loss into units of Btu/hr
Problem 7
A hydraulic pump operates at 150 bars and delivers oil at 0.0015 m3/s to a hydraulic actuator. Oil discharges through the pressure relieve valve (PRV) during 55% of cycle time. The pump has an overall efficiency of 85%, and 10% of power is lost due to frictional pressure losses in the hydraulic lines. What heat –exchanger rating is required to dissipate all the generated heat?
Solution
Known Data
Pump pressure p = 150 bars = 15000000 Pa
Flow rate Q = 0.0015 m3/s
Duty cycle = 55 % = 0.55
Pump overall efficiency ηo = 85 % = 0.85
Lines frictional losses = 10 % = 0.1
Unknown (s)
Downstream Temperature?
Needed
Power loss?
Formula (s)
Detailed Calculation
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