Pneumatics, Vacuum, heat exchangers dryer test Flashcards
warmer the air the more moisture it can hold
true
False
True
relative humidity compares the amount of water a sample of air holds to the maximum amount it could hold if fully saturated
true
False
True
if a cubic foot of air has the capacity to hold 11 grains of moisture but has 5 grains of moisture, then it is said to have _______________ % relative humidity
50
45
40
35
45
if the air is cooled past 100 % relative humidty, then condensation will result. this is called the_________
dry air point
specific humidity point
vapour point
dew point
Dew point
water / moisture in a compressed air system needs to be separated and removed by
air receivers
after coolers
dryers
all the above
All of the above
adsorption dryers work on the principle of ________ of molecules in a thin layer onto the desiccant
a chemical bond
vapourization
adheasion
regeneration
Adhesion
the process of removing the accumulation of moisture from the dryer bed is called____________ which uses ________________
regeneration, heat
regeneration, absoption
regeneration, purge gas
both the 1st and 3rd answer are correct
Both first and third
about __________% of dry air is used for regeneration in heater-less dryers
10-15
20-30
40-60
1-2
10-15
the ideal system for adsobtion dryers is a twin tower system with ___________ which reduces the amount of cycle times and compressed air usage
cams and mechanical valves
electronic switches and automatic valves activated by the dew point sensor in the system
electronic switches and automatic valves
none of the above
Electric switches and automatic valves activate by the dewpoint sensor in the system
because desiccant can break down of become contaminated with oil, the air drying system needs to be protected with coalescing filters
true
False
True
in the regeneration cycle, the purge air is _____________ to help reduce compaction and make removal of moisture faster
sped up
deflected
reversed
cooled
Reversed
.a heated adsorption dryer with internal heaters uses about______% of the dryed air.
2
5
10
12
2
the moist gas from the regeneration cycle (purge gas) in not explosive or hazardous, then it can be vented to the atmosphere. otherwise it has to be cooled and ran thru a moisture separator and re-introduced to the dryer inlet gas stream
true
false
True
the rotary drum dryer has 2 separate air flows going thru it. the hot dry gas passes thru____ % of the rotor and the moist gas passes thru ______ % of the rotor
50, 50
75, 25
25, 75
60, 40
25,75
absorption dryers use __________ in the process to dry the air
adheasion
vaporization
chemical bond
all the above
Chemical bond
chemical dryers cannot be regenerated because they dissolve or melt when combined with moisture
true
false
True
in the liquid dehydration process, an absorption agent such as ethylene glycol is sprayed thru nozzles and as the air travels down thru it, it is scrubbed and moisture absorbed
true
False
False
to remove the moisture from the glycol, it is ran thru a ______________where it is heated to 200 C and moisture is evaporated
heat exchanger
vapourizer
steam cleaner
still
Still
refrigeration dryers use the dew point reduction method to remove moisture from the air thru the use of an air circuit and a refrigeration cycle
true
False
True
latent heat is heat that is sensed by a thermometer
true
False
False
in mechanical dryers, water sprayers are added to cool down the air before it strikes the baffles that create a torturous path
true
false
False
colescing filter elements can effectively remove particles down to a size of _________ microns
0.001
0.0001
0.01
0.1
.01
the best way to determine if a dryer is taking out moisture, is to
check the dessicant
watch the cycle times
measure the flow rates
measure the dew point of the air
Measure the dew point
wire drawing is
used to seal flanges
process of air movement thru the dessicant
a fine groove cut in a sealing surface (caused by high pressure gas)
none of the above
A fine groove cut in a sealing surface (caused by high pressure gas)
most dryers that run below 175 degrees C, use a teflon valve seat
true
False
True
in a pneumatic system, the compressor intake should be in a __________ place because the air is denser
wet
cool
hot
Cool
when compressing with a reciprocating compressor, you need a _____________ to help dampen pulsations
after-cooler
minimum of bends in the intake
inter-cooler
receiver
Receiver
the pneumantic piping system that has the compressor close to its point of use is the
grid
decentralized
loop
none of the above
Decentralized
proper sizing of lines in a pneumatic system is important because if the piping is to small, it will
cause moisture in the air supply
cool the air supply
cause a pressure drop in the air supply
create more flow
Cause a pressure drop in the air supply
you must eliminate all leaks in a compressed air system because it will cost more to produce the needed CFM
true
False
True
if an FRL is installed backwards, it would
gum up the regulator with oil
remove lubrication
work normally
the 1st and 2nd answers are correct
Both first and second answers
in an FRL, the filter uses ___________ and the lubricator uses ________ to work properly
centrifugal force, venturi
venturi, centrifugal force
none of the above
regeneration, desiccant
Centrifugal force, venturi
water traps use a _________ to expel moisture automatically from the unit
pressure drop
deflector plate
float valve
hand valve
Float valve
a 5/3 valve has ________ and ____________ positions
3 ways, 5
5 ways, 3
5 ports, 3
both the 2nd and 3rd answers are correct
Both second and third answers are correct
a pressure reducing valve has a normally _____________flow path thru it
closed
open
both open and closed
none of the above
Open
venting regulators will protect the _______________ from over pressure
upstream section
downstream section
does not protect any part of the system
vent to the receiver
Downstream section
a DCV is identified by
of controlled connections
of switching positions
method of activation
all the above
All of the above
external and internal pilot operation, are valves activated
manually
by air
electrically
all the above
by air
you would use a 4/2 valve to activate
a single acting cylinder
double acting cylinder
a center position in the valve
all the above
Double acting Cylinder
you would use a 5/3 valve to
control as cylinder with the valves center position
control a single acting cylinder
control a rotary motor with the valves center position
both the 1st and 3rd answers are correct
Both first and Third Answers are correct
the needle valve is the most accurate flow control valve for metering flow
true
False
True
a quick exhaust valve is used to expel gas at the
directional control valve
cylinder
receiver
compressor
Cylinder
excess flow valves are used on air hoses that are larger than 1/2”, to eliminate hose whipping
true
False
True
double acting cylinders use _____________ to slow down the piston at the end of each stroke
packing
o-rings
stop tubes
cushions
Cusions
when using flow controls to slow down the movement of a cylinder in an circuit, you would _________ the air with the flow control
meter-in
meter-out
Meter out
air logic applications are used in systems that have
an explosive environment
a very wet environment
air gauging
all the above
All of the above
which rotary motor uses a swash plate to control speed of actuation
vane
piston
turbine
gear
Piston
you have a cylinder that is sticking when extending and retracting. what may the problem be
rod packing to tight
pilot pressure is to low to shift spool valve all the way
a bent piston rod
all the above
All of the above
when reassembling and installing parts, you should aways check the component for proper operation
true
false
True
if you have a system that you want to protect an operator from getting their hands caught in an unsafe area, you would have a system that would require the operator to hold both hands on 2 different levers that needs both levers moved at the same time to operate the equipment
true
false
True
when thawing a frozen valve, make sure to apply heat as quick as possible to limit the possibility of a fire
true
false
False
if you have excessive pressure in part of a pneumatic system, you will look for
a flow restriction
leak in the system
pressure regulator set to high
pressure regulator set to low
Pressure regulator set to high
if you have a cylinder moving inconsistently, you will look for
bent piston rod
damaged piston seals
inconsistent air pressure
all the above
All of the above
if a cylinder body seal is leaking, you will look for loose cylinder tie rods
true
false
true
a pneumatic valve is blowing to exhaust when actuated. what is the problem
valve seals are leaking
spool damage
valve to base gasket is faulty
all the above
All of the above
a poppet is chattering in a pneumatic system. the problem is most likely
the air supply pressure is too low
the pilot pressure is too low
air supply pressure is too high
both the first and second answers are correct
Both first and second answers are correct
the actuator cylinder is drifting in a pneumatic system. The problem could be a piston seal is leaking
true
false
True
vacuum systems are limited to ________ of vacuum pressure to work with
14.7 psi
29.92 ‘Hg
29.92 psi
- Kpa
14.7PSI
plumbing size for pipe in a vacuum system must be as small and short as pradtical for static systems
true
False
True
if your vacuum system has back pressure, this will cause the system to be more efficient
true
False
Flase
when hooking up a vacuum system to a cylinder, you would hook the vacuum up to the _________ port to make it extend
rod end
cap end
it works the same way as a pressure system
none of the above
Rod end
if you had an air valve that you are going to use as a vacuum valve, you would hook up the pressure port to atmosphere and the exhaust port to the vacuum source
true
false
True
.you would use a vacuum relief valve for static systems. this would allow the pump to be cooled and lubricated. the system would also use less horsepower
true
false
True
when lifting and holding with suction cups in a vacuum system, you would calculate the area under the cup and times it by the number if inches of Hg (mercury) to find the weight the cup could hold
true
False
False
you want to use _________ seals on your cylinder’s piston for vacuum systems as they produce the least amount of friction
metal
O-ring
leather cup
none of the above
Leather cup
you can use some vacuum systems in combination (as a vacuum system and as a pressure system). the system will produce high pressures ( 100 psi) on the exhuast side of the pump
true
False
False
if you had a 3” suction cup that has a vacuum of 20” Hg pulling on it, how much could you lift?
f = p x a 2’ Hg = 1 psi
31 lbs
51 lbs
61 lbs
71 lbs
71LBS
when replacing gaskets in vacuum pumps, it is important to have the proper thickness for proper sealing inside the pump
true
false
True
heat exchangers have the ability to cool or heat the air and or liquid to a constant temperature
true
False
True
heat exchangers have 3 basic means of heat transfer at work. they are conduction, covection and radiation. the one the uses CONTACT between the fluid and metal surface is
conduction
convection
radiation
Conduction
the rate of heat transfer is influenced by the amount of direct scrubbing action that is present in the fluid flow. this scrubbing action is caused by
laminar flow
forced convection
turbulent flow
forced flow
Turbulant flow
there are many different flow path arrangements. the one that is the most efficient at cooling is the
parallel flow
counter flow
cross flow
mixed flow
Counter flow
in plate heat exchangers. it is important to have the spacing of the plates close together. they should be spaced at _______________ apart
6 to 10 mm
11-15 mm
16-20 mm
2-5 mm
2-5mm
spiral heat exchangers are very efficient because they have a true counter flow and create their owm scrubbing action
true
False
True
cooling towers can be divided into 2 classes. they are forced draft and induced draft
true
False
False
forced draft is when the air flow is pulled out of the cooling tower
true
False
False
double pipe heat exchagers are able to
handle high pressures
only handle low heat duties
be connected in series or in parallel
all the above
All of the above
shell and tube heat exchangers have
large surface areas for heat transfer
the capability of handling only low temperatures and pressures
the capacity of handling high temperatures and pressures
both the 1st and 3rd answers are correct
Both first and third answers are correct
the tubes are commonly expanded into the __________ to form a seal against leakage
shell
tube sheets
baffles
head cover
Tube sheets
an advantage of the u-tube heat exchanger over the fixed tube heat exchanger is
the tubes are cleaned easier
the outside of the tubes are cleaned easier because the tubes can be taken out of the shell
there are inspection doors that let you access the outside of the tubes
it has a higher efficiency
the outside of the tubes are cleaned easier because the tubes can be taken out of the shell
the tube sheet layout that allows for the most tubes for a given size exchanger is the
30 degree style
45 degreee style
the 90 degree style
they all create the same number of tubes
3o degree style
baffles in heat exchagers help
support the tubes to prvent vibration
cause turbulence
prevent dead bypass areas
all the above
All of the above
3 longitudinal baffles will make the heat exchanger a _____________ pass exchanger
1
2
3
4
4
floating head shell and tube exchangers will allow 1 tube sheet to float which allows the exchanger to use fluids of an extremely high temperature differential
true
False
True
the only heat exchanger that is used where it is undisireable to allow the mixing of the tube side and shell side fluids in the exchanger is the
floating head
u-tube
fixed tubesheet shell
double tube sheet
Double tube sheet
heat transfer in a heat exchanger is affected by __________________
fluid flow
temerature differentials
contact time
all the above
All of the above
fluid films are formed next to the tube walls. they decrease the heat transfer. to help increase heat transfer thru the tubes you can increase the
temperature
pressure
velocity
all the above
Velocity
hydrostatic testing is commonly used to check heat exchangers for leaks. the standard pressure used in hydro-testing is
the same pressure as the system
1.5 times system pressure
2 times system pressure
3 times system pressure
1.5 times the system pressure
when first applying the flows of fluid into the heat exchanger, make sure the _____________valve is opened so all air in the exchanger can be purged out
vent
shuttle
butterfly
none of the above
Vent
when purging a dryer or heat exchanger system of toxic gases, you would use
nitrogen
carbon dioxide
steam
all the above
All of the above
