250+ TOP MCQs on Pipes, Valves and Fittings and Answers

Dairy Engineering Multiple Choice Questions on “Pipes, Valves and Fittings”.

1. What is the aim of pipes system in the dairy industry?
a) Facilitate product flow
b) Pasteurization
c) Fouling
d) Storage
Answer: a
Clarification: The product flows between the components of the plant in the pipe system. A dairy also has conduit systems for other media such as water, steam, cleaning solutions, coolant and compressed air.

2. Which material is used for pipes which are in contact with milk or product?
a) Stainless steel
b) Copper
c) Ceramic
d) Plastic
Answer: a
Clarification: All components in contact with the product are made of stainless steel. Stainless steel is easy to clean and non corrosive.

3. Which material is used for pipes which conduct water and air?
a) Stainless steel
b) Copper
c) Ceramic
d) Plastic
Answer: b
Clarification: Plastic is used for water and air lines. Plastic also provides transparency.

4. Which material is used for pipes which conduct waste?
a) Stainless steel
b) Copper
c) Ceramic
d) Plastic
Answer: c
Clarification: Various materials are used in the other systems, e.g. cast iron, steel, copper and aluminum. Plastic is used for water and air lines, and ceramic for drainage and sewage pipes.

5. Which grade of stainless steel is known as acid proof steel?
a) AISI 304
b) AISI 316
c) SIS 2333
d) SIS 2359
Answer: b
Clarification: For hygienic reasons, all product-wetted parts of dairy equipment are made of stainless steel. Two main grades are used, AISI 304 and AISI 316. The latter grade is often called acid proof steel.

6. Which of the following are installed in order to collect product samples hygienically for quality analysis?
a) Bends
b) Reducers
c) Sampling device
d) Tees
Answer: c
Clarification: Sampling devices need to be installed at strategic points in the plant to collect product samples for analysis. For quality control, such as determining the fat content of milk and the pH value of cultured products, the samples can be collected from a sampling cock.

7. Which among the following is not a permanent wielding connection?
a) Bends
b) Reducers
c) Sampling device
d) Tees
Answer: c
Clarification: Some examples of fittings for permanent welding are Tees, reducers and bends. This union allows disconnection without disturbing other pipe work. This type of joint is hence used to connect process equipment, instruments, etc. that need to be removed for cleaning, repair or replacement.

8. What are the reasons causing pressure drop in hydraulic systems?
i. Long length of pipe
ii. Friction
iii. Type of fluid
iv. Losses in valves and bends
a) i and iv
b) Only i
c) ii and iii
d) i, ii, iii and iv
Answer: d
Clarification: Pressure drop is the difference in the pressure of liquid entering the hydraulic system and pressure of liquid leaving the system. Long length of pipe, friction, fluid type and losses in valves and bends are all reasons behind pressure drop in hydraulic system.

9. Calculate area of a pipe if, flow rate is 20 l/min and flow velocity is 5 cm/s.
a) 66.66 cm2
b) 60 cm2
c) 62 cm2
d) 64 cm2
Answer: a
Clarification: Flow rate = 20 litre/min
= 200000 cm3/60s
= 333.33 cm3/s
Flow Rate = Velocity x Area
333.33cm3/s = 5cm/s x Area
Area = 333.33cm3/s / 5 cm/s
= 66.66 cm2.

10. Which formula is used to calculate head loss in valves?
a) K2 (v/2 g)
b) K (v/2 g)
c) K (v2/2 g)
d) K3 (v2/2 g)
Answer: c
Clarification: K (v2/2 g) calculates head loss for Newtonian fluid. When fluid flows inside a pipeline, friction occurs between the moving fluid and the stationary pipe wall. The friction converts some of the fluid’s hydraulic energy into thermal energy. The thermal energy cannot be converted back to hydraulic energy, so the fluid experiences a drop in pressure. This conversion and loss of energy is known as head loss.

11. Which among the following is shut-off and change over valve?
a) Seat valve
b) Butterfly valve
c) Seat valve and butterfly valve
d) Bend
Answer: c
Clarification: There are many places in a piping system where it must be possible to stop the flow or divert it to another line. These functions are performed by valves. Seat valves, manually or pneumatically controlled, or butterfly valves, are used for this purpose.

12. To prevent the product flow in the wrong direction which of the following valve is used?
a) Seat valve
b) Butterfly valve
c) Seat valve and butterfly valve
d) Check valve
Answer: d
Clarification: A check valve is fitted when it is necessary to prevent the product from flowing in the wrong direction. The valve is kept open by the liquid flow in the correct direction. If the flow stops, the valve plug is forced against its seat by the spring. The valve then closes against reversal of the flow.

13. Which of the following valves is used to maintain pressure in the system?
a) Pressure relief valve
b) Check valve
c) Manual control valve with variable flow plug
d) Pneumatic control valve with variable-flow plug
Answer: a
Clarification: A pressure relief valve maintains the pressure in the system. If the pressure is low, the spring holds the plug against the seat. When the pressure has reached a certain value, the force on the plug overcomes the spring force and the valve opens.

14. The pipes will expand considerably when the product temperatures are high and during cleaning.
a) True
b) False
Answer: a
Clarification: Pipes must be firmly supported. On the other hand the pipes should not be so restrained that movement is prevented. The pipes will expand considerably when the product temperatures are high and during cleaning. The resulting increase in length and tensional forces in bends and equipment must be absorbed.

15. Valves with constant outlet pressure are used after which of the following machines?
a) Separator
b) Pasteurizer
c) Homogenizer
d) Filling machine
Answer: d
Clarification: Valves for constant inlet pressure are often used after separators and pasteurizers. Those for constant outlet pressure are used before filling machines.

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