Waste Water Engineering Multiple Choice Questions on “Autoclaves”.
1. ________ is a pressure chamber used to carry out processes at high temperature and pressure.
b) Micro clave
d) Hot air oven
Clarification: An autoclave is a pressure chamber used to carry out industrial processes requiring elevated temperature and pressure different from ambient air pressure. Autoclaves are used in medical applications.
2. Autoclaves are used in the medical applications to perform ______
Clarification: Autoclaves are used in medical applications to perform sterilization and in the chemical industry to cure coatings and vulcanize rubber for hydrothermal synthesis. There are other industrial applications also.
3. What is the common temperature used in autoclaves?
Clarification: Many autoclaves are used to sterilize the equipment and supplies by subjecting them to high-pressure saturated steam at 121 °C (249 °F) for around 15–20 minutes depending on the size of the load and the contents.
4. Who invented the autoclave?
b) Charles Chamberland
c) Arnold O. Beckman
d) Antonie van Leeuwenhoek
Clarification: Pasteur invented hot air oven. Charles Chamberland invented autoclave. Arnold O. Beckman invented pH meter. Antonie van Leeuwenhoek is considered as the father of microbiology.
5. All the trapped air is removed from the autoclave before activation.
Clarification: It is very important to ensure that all of the trapped air is removed from the autoclave before activation, as trapped air is a very poor medium for achieving sterility. Sterilization can be achieved in three minutes by steam at 134˚C.
6. A device that uses steam to sterilize equipment and other objects is a medical autoclave.
Clarification: Autoclaves are found in many laboratories, medical fields, institutions and other places that need to ensure the sterility of an object. This means that all bacteria, fungi, viruses and spores are inactivated.
7. What is the inner surface of autoclaves made of?
a) Mild steel
b) Stainless steel
Clarification: There is a horizontal and vertical type of autoclave. In vertical autoclaves, the whole autoclave is made of stainless steel and the outer surface is made of mild steel. Vertical autoclaves are used mainly for the sterilization process.
8. What is the operating temperature for table top steam sterilizer?
a) 110-115 ˚C
Clarification: The sterilization temperature for high pressure sterilizer of a rectangular model is 121˚C. The operating temperature for high pressure sterilizer of rectangular model is 121˚C to 135˚C.
9. The sterilizer of pressure cooker type is made of ________
c) Stainless steel
Clarification: The sterilizer of pressure cooker type is made of aluminium for quick transfer of heat, which generates steam under pressure. The sterilizer is subjected to the saturated steam environment for preset specified time as soon as it reaches the right temperature.
10. Which type of autoclaves is mainly used for bulk research work?
a) Vertical autoclave
b) Horizontal autoclave
c) Sterilization pressure cooker
d) Table top steam sterilizer
Clarification: Horizontal autoclaves are mainly used for institutions or laboratory for doing bulk sterilizing research work. These autoclaves have double walled inside and outside made of stainless steel of 304 quality.
11. Which type of control valve can be used for 90-degree change in direction of flow?
a) Butterfly valve
b) Diaphragm valve
c) Globe valve
d) Gate valve
Clarification: Globe valves are the only ones which can be used for 90 degree change in direction of flow. Specifically angle- globe valves are used for that purpose. Globe valves are not used for controlling pressure.
12. Which of these is a linear motion control valve?
a) Ball valve
b) Butterfly valve
c) Plug valve
d) Diaphragm valve
Clarification: Control valves are classified as linear and rotary motion valves. Diaphragm and Globe valves are classified as linear motion control valve. Whereas Ball, Butterfly and plug valves are classified as rotary motion control valves.
13. Which of the following is not a type of control butterfly valve?
a) Single off-set
c) Triple off-set
d) Concentric centreline
Clarification: Control butterfly valves are of 4 types. Single offset, double offset, triple offset and concentric centreline. There is no type of control butterfly such as concentric.
14. What is inherent flow characteristics?
a) The curve obtained between control valve capacity and valve stem travel
b) The curve obtained between control valve capacity and Cv
c) The curve obtained between Cv and valve stem travel
d) The curve obtained between control valve capacity and pressure drop
Clarification: The curve between control valve capacity and valve stem travel is known as inherent flow characteristics. This curve is obtained at a constant pressure drop. The relationship between control valve capacity and valve stem travel is known as flow characteristic of the control valve.
15. Which type of valve is preferred for sequential operations?
a) Electric actuated control valve
b) Single acting control valve
c) Quick opening valve
d) Double acting control valve
Clarification: Quick opening valves are used for sequential processes. These are used in batch and semi-continuous process. These are self- actuated valves.
16. Which of these control valves has the lowest pressure recovery?
a) Globe valve
b) Ball valve
c) Butterfly valve
d) Plug valve
Clarification: Globe valves have lower pressure recovery than the ball, plug and butterfly valves. The velocity is very high at the vena contracta. As the liquid flows further down due to the increase in an area the velocity decreases and there is an increase in pressure. This phenomenon is known as pressure recovery.
17. Which type of actuator is preferred when high and fast stroking speed is required?
a) Direct acting actuator
b) Reverse acting actuator
c) Electro hydraulic actuator
d) Piston actuator
Clarification: Piston actuators are preferred when high and fast stroking speed is required. This type of actuator utilises air pressure upto 150psig. This eliminates the need for a pressure regulator.
18. Direct acting actuators fall under which category of actuator?
a) Diaphragm actuator
b) Piston actuator
c) Electro hydraulic actuator
d) Manual actuators
Clarification: Direct actuator is a type of Diaphragm actuator. Another type of diaphragm actuator is reverse acting actuator. The size of these actuators depends on the air supply required.
19. The gain of a control valve should never be less than _______
Clarification: The gain of a control valve should never be lesser than 0.5. Gain is defined as the ratio between the differences in flow to the differences in stoke or travel. In case the value is lesser than 0.5 then there would be a problem in controlling the valve.
20. What should be the rangeability of the control valve?
Clarification: Rangeability should be greater than the turndown of a control valve. The ratio of the Cv at which the valve is fully open to the minimum Cv at which it can control is known as rangeability. Turndown is the ratio of the calculated Cv at the maximum condition to that of the Cv calculated at the minimum condition.