Mechanical Piping Objective Questions and Answers - Part 05

Question No. 101
What is Spiral sock valve?
Answer: A valve used to control flow of powders by means of a twistable fabric tube or sock.

Question No. 102
What is Throttling valve?
Answer: Any valve used to closely regulate flow in the just-open position.

Question No. 103
What is Vacuum breaker?
Answer: A special self-acting valve or any valve suitable for vacuum service, operated manually or automatically, installed to admit gas (usually atmospheric air) into a vacuum or low-pressure space. Such valves are installed on high points of piping or vessels to permit draining and sometimes to prevent siphoning.

Question No. 104
What is Quick acting valve?
Answer: Any on/off valve rapidly operable, either by manual lever, spring or by piston, solenoid or lever with heat-fusible link releasing a weight which in falling operates the valve. Quick acting valves are desirable in lines conveying flammable liquids. Unsuitable for water or for liquid service in general without a cushioning device to protect piping from shock.

Question No. 105
What is diverting valve?
Answer: This valve switch flow from one main line to two different outlets. WYE type and pneumatic control type with no moving part.

Question No. 106
What is sampling valve?
Answer: Usually of needle or globe pattern, placed in branch line for the purpose of drawing all samples of process material through the branch.

Question No. 107
What are blow off valve?
Answer: It is a variety of globe valve confirming with boiler code requirements and specially designed for boiler blow-off service. WYE pattern and angle type, used to remove air and other gases from boilers etc.

Question No. 108
What is relief valve?
Answer: Valve to relieve excess pressure in liquids in situations where full flow discharge is not required, when release of small volume of liquid would rapidly lower pressure.

Question No. 109
What is safety valve?
Answer: Rapid opening (popping action) full flow valve for air and other gases.

Question No. 110
What is foot valve?
Answer: Valve used to maintain a head of water on the suction side of sump pump, basically a lift check valve with integrated strainer.

Question No. 111
What is float valve?
Answer: Used to control liquid level in tanks, operated by float, which rises with liquid level and opens the valve to control water level. It can also remove air from system, in which case, air flows out of system in valve open condition, but when water reaches valve, float inside valve raises to close the valve and stop flow of water. Used in drip legs.

Question No. 112
What are flush bottom valves?
Answer: Special type of valves used to drain out the piping, reactors and vessels, attached on pad type nozzles.

Question No. 113
What are types of flush bottom valves?
Answer: Valves with discs opening into the tank and valves with disks into the valve.

Question No. 114
What are the uses of three-way valve?
Answer: Alternate connection of the two supply lines to a common delivery vise versa, isolating one safety valve, division of flow with isolation facility.

Question No. 115
What are uses of four way valve?
Answer: Reversal of pump suction and delivery, By pass of strainer or meter, reversal of flow through filter, heat exchanger or dryer.

Question No. 116
What is metal seated lubricated plug valve?
Answer: A plug valve with no plastic material, where grease is applied to contacting surfaces for easy operation.

Question No. 117
What are three patterns of plug valve design?
Answer: Regular pattern, short pattern and ventury pattern.

Question No. 118
What is regular pattern plug valve?
Answer: Rectangular port, area almost equal to pipe bore, smooth transition from round body to rectangular port, for minimum pressure loss.

Question No. 119
What are short pattern plug valve?
Answer: Valves with face to face dimension of gate valve, as a alternative to gate valve.

Question No. 120
What are ventury pattern plug valve?
Answer: Change of section through the body throat so graded to have ventury effect, minimum pressure loss.

Question No. 121
What are inverted plug design valve?
Answer: Plug valve with taper portion up of plug. For 8” and higher size.

Question No. 122
What is pressure balanced plug valve?
Answer: With holes in port top and bottom connecting two chambers on top and bottom of plug, to reduce turning effort.

Question No. 123
What are Teflon sleeved plug valve?
Answer: PTFE sleeve between plug and body of valve, low turning effort, minimum friction, temperature limitation, anti static design possible.

Question No. 124
What are permasil plug valve?
Answer: Plug valves with Teflon seat instead of sleeves, for on-off applications, can handle clean viscous and corrosive liquids, Graphite seat for high temperature applications. Drip tight shut off not possible.

Question No. 125
What are eccentric plug valve?
Answer: Off center plug, corrosive and abrasive service, on off action, moves into and away from seat eliminating abrasive wear.
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