Valve Pre Assessment

Select one answer which mostly fit the statement. 1) Tendency of a ball valve to tightly seal a liquid across, is increased with lubricant injection due to □

Increased surface tension between the liquid and the leakage capillaries between the ball and seat.

□

Easy movement between the ball and the seat.

□

Filling of scratches on the ball and seat, getting close contact between them.

2) leakage criterion expresses □

Volume of fluid to pass through the leakage capillaries in given time.

□

Volume of fluid reained inside valve body

□

time taken for a given volume of fluid to pass through the leakage capillaries.

3) Stem seals sealing action is □

due to their ability to

interact with product and swollen to fill the gap between the stuffing box walls and the stem.

□

expand laterally against stem and stuffing box walls when stressed by tightening the gland.

□

Exert pressure normally against gland and stuffing box bottom when stressed by tightening the gland.

4) Flow coefficient Cv, states the flow capacity of a valve at a specific opening position in □

Cubic meter per hour of water at atemperature between 5 and 40 C that will flow with pressure loss of one bar

□

U.S. GPM of water at a temperature of 60 Fthat will flow with pressure loss of one PSI

□

Leter per minute of of water at atemperature between 5 and 40 C that will flow with pressure loss of one KPa

5) Waterhammer from valve operation occurs when □

a shaking of the pipe and hammering sound due to valve closure or opening

□

A product leakage is observed through valve closure elements

□

A product leakage is observed from valve stem

6) Ball, plug and butterfly valves are mostly fit the service of □

Diverting flow

□

Stopping and starting flow

□

controlling flow rate.

7) Valve rating refers to □

Maximum pressure at which the valve may be operated.

□

Maximum temperature at which the valve may be operated.

□

Pressure temperature relationship within which the valve may be operated.

8) in stuffing box, a lantern ring serves for □

increase the depth of packing column

□

resist the flow of product from inside the valve.

□

support the packing from bottom.

9) Antistatic device is a provision which serves to □

fix the stem position.

□

guarantee electrical continuity betweeen the plug, stem and valvle body.

□

create a static electricity charge between the plub and stem.

10)Reduced bore ball valves are used to obtain □

low temperature drop across the valve.

□

less flow rate through the valve

□

less pressure drop across the valve

11) Fire safe construction of ball valves provides for stem and seat seals being □

fire resistant

□

equiped with secondary seals that is fire resistant.

□

all metal seals

12)When handling dry gases, one of seating faces may be faced with stellite which is known to provide resistance to □

wide range of corrosives

□

erosion

□

galling

13)check valves are utilized in piping systems to □

stopping and starting flow

□

regulate flow

□

prevent flow reversal

14)Lift check valves are distinguished with closure member □

travels in direction normal to the plane of the seat

□

swings about a hinge

□

consists of diaphragm

15)Pressure releif valves are designed to protect pressure system □

against ecessive flow rate

□

against excessive pressure

□

against supersonic flow

16) The differential pressure across the rupture discat which

the disc bursts at a given temperature is called □

burst pressure

□

burst tolerence

□

performance pressure

17)Burning that takes place at a flame speed below the velocity of sound in the medium is called □

Detonation

□

Deflagaration

□

Explosion

18)An equipment used to introduce the pig into the pipeline comprising a apipe barrel, a clsure door and various nozzles is □

Interlock system

□

Receiver

□

Launcher