Test 4 Flashcards
What material is wrapped around the metallic core of the solenoid?
Helical coil of wire of steel or iron
T/F A solenoid valve is a combination of two basic functional units: a solenoid and a valve.
True
How is the flow controlled through a solenoid valve?
The solenoid is energized and de-energized utilizing the electromagnetic coil to control the flow of fluid through its valve, offering rapid and precise on/off control
Label the parts of the solenoid valve shown below. A
Coil solenoid
Label the parts of the solenoid valve shown below. B
Solenoid Spring
Label the parts of the solenoid valve shown below. C
Lead Wires
Label the parts of the solenoid valve shown below. D
Piston
Label the parts of the solenoid valve shown below. E
Outlet Port
Label the parts of the solenoid valve shown below. F
Orifice
Label the parts of the solenoid valve shown below. G
Valve Body
Label the parts of the solenoid valve shown below. H
Inlet Port
Label the parts of the solenoid valve shown below. I
Coil Windage
This part of the solenoid valve moves either upward or downward to regulate the flow of fluid through the valve.
Plunger/Piston/Core
This part enables the passage of electrical current from a power supply to the solenoid valve.
Lead Wires
This part isolates the solenoid from the fluid media.
Diaphragm
This part prevents the fluid flow when the solenoid valve is in the closed position.
Disc
A 3/2 solenoid valve has ___ ports (orifices).
3
A 3/2 solenoid valve has ____ switching states.
2
The standard of symbols for fluid power were developed by this organization.
ISO International Organization of Standardization in collaboration what the IEC International Electrotechnical Commission
In a fluid power diagram, each state of the valve is indicated by a _________.
Square
The symbol represents what type of actuation?
Electrical Actuation-Coil
The symbol represents what type of actuation?
Manual Actuation-Spring
Closed ports on a solenoid valve drawing are represented by a(n) ______.
“T”
For the solenoid valve drawing below answer the following questions This valve is a normally ________ valve.
Closed
For the solenoid valve drawing below answer the following questions This valve is a ____ way (state) valve.
Two
For the solenoid valve drawing below answer the following questions In the normal state, this valve ________ allow flow.
does not
For the solenoid valve drawing below answer the following questions The square on the ______ shows the valve in non-energized (normal) position
right
The designation of an “E” of a port on a 3-way valve indicates _________.
Exhaust
The designation of an “P” of a port on a 3-way valve indicates _________.
Pressure
The designation of an “C” of a port on a 3-way valve indicates _________.
Cylinder
The three3-way solenoid valve shown is a normally ______ valve.
Open
Three way solenoid valves are used primarily on ___________ actuators.
Spring Return
A three-way solenoid valve has______ pressure inlet port.
One
How many exhaust ports does a three-way valve have?
One
A four-way solenoid valve has ____ port(s) for the cylinder (actuator).
2
Four-way solenoid valve are used with _______ acting actuators.
Double
Actuators that use a four-way solenoid valve with fail ________.
last position
Name the type of valve represented by the P&ID symbols
Two-way on/off solenoid valve
Name the type of valve represented by the P&ID symbols
Three-way on/off solenoid valve
External solenoid valve leakage is attributed to issues with ________.
O-ring seals
Name two advantages of using a solenoid valve
Can be remotely operated and have a fast response time
Name a disadvantage of using a solenoid valve.
Are sensitive to any fluctuations in input voltage and compared to other types of valves, solenoid valves cannot handle high flow rates
T/F Valve accessories are typically mounted directly to the valve.
True
What function does the filter, regulator and relief valve provide to the actuator?
They condition, maintain pressure, and protect the actuator from being overpressured.
Where are filters typically installed?
Between the source of the power supply and the actuator or positioner most often located immediately upstream of the accessory they are protecting
T/F Some actuators cannot operate at the outlet supply pressure provided by the compressed air system.
True
What equipment does the relief valve protect from damage?
The outlet body of the regulator and the actuator
T/F Limit switches are mounted directly to the actuator or case and connect with the moving stem or shaft.
True
Name the two styles of limit switches.
Single pole double throw switch and a double pole throw switch
What is a pole?
A component of the switch that is moved by the switch to make or break an electrical connection
What is a throw?
The total number of possible electrical connections that can be made by a given pole
What is SPDT an acronym for?
Single Pole Double Throw switch
A SPDT has ___ set of normally open and ____ set of normally closed contacts
1,1
T/F Most limit switches share a “common” terminal between the Normally Closed and Normally Open contacts.
True
T/F Limit switches are often coupled to a visual indicator that will locally indicate valve position to operators
True
T/F A proximity switch contacts the valve stem or shaft.
False
Proximity switches are ____ sensitive to dust, moisture, and oil than limit switches.
less
T/F A position transmitter provides a continuous signal of valve position.
True
The signal provided by the position transmitter is a(n) ________ signal
analog
T/F Valve positioners can transmit actual valve position.
True
T/F A valve positioner provides feedback to the controller.
True
A(n) _______ loop system provides feedback back to the controller.
Closed
Where are valve positioners normally mounted?
On the yolk or top casing of the pneumatic actuator for linear control valves or near the end of the shaft for rotary valves
Name the four capabilities that a positioner can provide.
- Ability to have fine control over a precise process.
- Increase the speed of response to change in process, allowing for faster loading and venting.
- Allow for split ranging (one controller for two valves.)
- Overcome seating friction in rotary valves.
T/F The difference between upstream pipeline pressure and downstream pipeline pressure is known as pressure drop or pressure differential.
True
The highest velocity and lowest pressure occur immediately downstream of the narrowest restriction and is called the ________.
vena contracta
Frictional losses as the fluid passes through the valve or restriction cause the downstream pressure to be less than the upstream pressure and is known as _______.
pressure recovery
Cavitation and flashing occur when the liquid pressure decreases below the _______ pressure.
vapor
With cavitation, the pressure recovers to a point _____ the vapor pressure.
above
In _____ flow, additional increases in pressure drop across the valve do not result in additional flow.
choked
T/F The liquid/vapor mixture created by flashing is highly erosive to metal.
True
T/F Flashing will first occur at the vena contracta pressure.
True
Describe the appearance of metal erosion caused by flashing.
Washed out sections of the plug
Gas flow ____ cavitate.
Cannot
Identify the following terms on the graph: A
Valve Inlet Pressure P1
Identify the following terms on the graph: B
Recovery Region
Identify the following terms on the graph: C
Pressure Loss ▲
Identify the following terms on the graph: D
Valve Outlet Pressure P2
Identify the following terms on the graph: E
Pressure Recovery
Identify the following terms on the graph: F
Vena Contracta Pressure
The difference between exit pressure P2 and pressure at the vena contracta is called the ______.
Recovery region
Provide the equation for pressure recovery and a definition of each term.
FL = √[(P1-P2) / (P1-Pvc)] FL = Pressure Recovery Factor (unitless)
P1 = Absolute fluid pressure upstream of the valve
P2 = Absolute fluid pressure downstream of the valve
Pvc = Absolute fluid pressure at the vena contracta (point of minimum fluid pressure within the valve
T/F The style of valve is influential on the pressure recovery factor.
True
Describe the sound of cavitation in a pipeline.
A ringing sound
Cavitation is a ______ phase occurrence.
Three
Describe the appearance of cavitation damage on valve parts and piping.
Erosion and pitting
Describe the sound of flashing in a valve
A ‘hissing” sound similar of what sand might sound like if it were flowing through the valve
Name the three levels of cavitation.
Incipient, constant and choked
This state of cavitation has a steady rumbling sound associated with start of possible valve damage.
Constant
As the cavitation index value, σ, ________, the cavitation damage is increasing.
decreases
Name a recommendation to eliminate or minimize cavitation.
Flow resistance can be added downstream of the control valve
T/F Some valves (i.e. globe) can be equipped with anti-cavitation design features that include special cages that perform pressure drop staging.
True
T/F Cavitation can cause damage to equipment in the pipeline system near the valve.
True
What impact does high flow velocities cause in gas applications?
Creates turbulence and vibration in liquid applications and high noise levels in gas applications
Water hammer is a result of a _______.
pressure surge
Name a cause for water hammer.
Open valve suddenly closing
Name two long term effects of water hammer.
Pump and flow system damage and ruptured pipes
Name a mechanism to reduce the effect of water hammer.
Spring assisted check valves
Name the two types of valve leakage.
Fugitive emissions and leakage remaining in the piping systems
Name two causes of valve leakage.
Corrosion and wear of valve parts
T/F Vapor pressure is not dependent on temperature
False
T/F When gas or steam flows through a control valve, noise is generated.
True
T/F Noise from a control valve may be loud enough to cause hearing damage to those who are nearby.
True
When gas flows past a restriction in the control valve, the velocity _______.
Increases
T/F If the pressure drop across the control valve is high enough, the turbulence will generate sound waves which will move down the pipe with some coming through the pipe wall.
True
Name the two strategies for reducing control valve noise.
Source control and Path control
Define “pressure drop staging” noise reduction.
Instead of taking the entire pressure drop in one step, the pressure drop is divided up into two or more steps
Doing something to the valve to make it less noisy is known as ____ control
source
T/F Small reductions in velocity have a small effect on reducing valve noise.
False
Define “flow division” noise reduction.
Instead of having the flow pass through a single opening, the flow is divided up so that it passes through serveral openings in parallel
For the “flow division” noise reduction method, every time you double the number of openings, you reduce the noise by ___dBA.
3
T/F Using the smaller opening associated with “flow division” actually shift the noise to higher frequencies.
True
Globe control valve using flow division with one stage noise trim can achieve noise reduction of ___dBA noise reduction.
10-15 dba
Multiple stage flow dividers can achieve ____ dBA noise reduction.
15-25 dba
Name the three types of path control method that can be used to control noise.
Distance, heavy wall pipe and thermal or acoustic insulation
Thicker pipe walls attenuate ____ noise as it passes through the pipe wall compared to thinner pipe walls.
more
Name a disadvantage of using heavy wall pipe to control noise.
If you rely on heavy wall pipe you must use as far down stream as you want the noise reduction which is a very expensive solution
Name a disadvantage of using acoustic insulation to control noise.
The same issue as heavy wall pipe, you must insulate as far downstream as you want the reduced sound pressure which can be prohibitively expensive
