WorksheetsSolenoid Valves and Sensing Switches Quiz
Total questions: 102
Worksheet time: 56mins
A solenoid valve is an electro-mechanical device that, when energized or de-energized, performs which function?
Measures fluid pressure
Shuts off or allows fluid flow
Increases fluid temperature
Compresses instrument air
When an electric current energizes the coil of a solenoid, what is produced?
A magnetic field
High-pressure air
A chemical reaction
A loud alarm
In a de-energized solenoid valve as shown in Figure 2A, what component pushes the valve stem down to keep the valve closed?
The core (armature)
The spring
The electric leads
The inlet port
According to the P&ID in Figure 3, what does 'AO/AFC' stand for?
Actuator Open / Actuator Fails Closed
Air Open / Air Fails Close
Automatic Open / Automatic Fails Close
Always Open / Always Fails Close
In the emergency trip circuit (Figure 3), what happens to the solenoid valve ZV-010 when the temperature switch TS-010 trips at \bm{100^{\circ}C}?
It energizes
It de-energizes
It throttles to 50%
It sends a signal to the controller
When the 3-way solenoid valve ZV-010 de-energizes, it closes the air supply (P) and opens which port to vent the actuator?
Port A (Actuator)
Port P (Pressure)
Port E (Exhaust)
Port D (Drain)
In the circuit shown in Figure 5, what component is energized when the Level Switch LS1 is closed?
The 110 Vdc power supply
Relay R1
Solenoid Valve ZV-1
The 12 Vdc battery
In Figure 5, what action directly causes the solenoid valve ZV-1 to energize?
The level switch LS-1 opening
The 12 Vdc supply turning on
The relay contacts R1-1 closing
The pressure exhausting from port E
What is the condition of the solenoid valve coil during the normal operation of the ESD system shown in Figure 3?
De-energized
Normally closed
Energized
Bypassed
Relays and solenoids are often used together in which type of systems?
Process control loops
Alarm and ESD systems
Power distribution units
Data acquisition systems
A micro-switch is a single-pole, double-throw switch, which is abbreviated as what?
SPST
DPDT
SPDT
DPST
In the dual-switch circuit of Figure 8, at what pressure will the 'H Alarm' activate?
24 psi
100 psi
110 psi
120 psi
In Figure 8, when pressure reaches 110 psi, switch S2 activates, de-energizing the solenoid valve and turning on what?
The 'Normal' green light
The 'H Alarm'
The 'HH Alarm'
The booster pump
Mercury switches are motion-based switches consisting of a sealed glass tube, contacts, and a small amount of what?
Nitrogen
Argon
Liquid mercury
Distilled water
What is a known disadvantage of mercury switches?
They are not very accurate
They cannot handle high voltage
They consume a lot of power
Excessive vibrations can cause false connections
The high-pressure sensing element shown in Figure 13 is made from what two components?
A float and a stem
A piston and spring
A bulb and capillary
A diaphragm and magnet
A medium-range pressure sensing element is typically made from what?
A large diaphragm
A small piston
Large bellows
A capillary tube
A low-range pressure sensing element is made from a (a) .
A temperature sensing element is made from what two primary components?
RTD and thermocouple
Piston and spring
Bulb and capillary
Float and magnet
In a temperature sensing switch, an increase in temperature creates pressure in the bulb and capillary, which then acts on what component to activate the switch?
The diaphragm
The bellows
The float
The magnet
What is the primary purpose of an ESD (Emergency Shutdown) system?
To optimize process efficiency
To protect plants and personnel from injury
To log process variable data
To control the final product quality
ESD systems must be automatic because a process can go out of control faster than what can be taken?
A data backup
A product sample
A pressure reading
Corrective action
During an emergency shutdown, control valves will fail into a safe position. What is the correct description of their action?
All valves will close
All valves will open
Valves may open or close depending on their fail-safe design
All valves will go into manual mode
In the GOSP P&ID (Figure 20), which three process variables are monitored for the ESD system?
Flow, Viscosity, and Density
Pressure, Level, and Temperature
pH, Conductivity, and Turbidity
Vibration, Speed, and Torque
The logic circuit in Figure 21 uses an AND gate. This means the plant will shut down if:
Any one of the input signals is missing (goes to OFF)
All of the input signals are missing
At least two input signals are present (ON)
The output signal is manually overridden
In the wiring diagram of Figure 22, relay R7 will only energize if:
At least one of the relays R1 to R6 is energized
The 110 Vac power supply is on
All six relays (R1 to R6) are energized
Switch S1 is closed
If the shipper pump bearing overheats (Figure 22), switch S4 opens, de-energizing relay R4. What is the immediate effect of R4 de-energizing?
Relay R7 de-energizes because contact R4-1 opens
Only the shipper pump stops
An alarm sounds, but the plant continues to run
Relay R3 energizes
During an ESD initiated by the shipper pump, what is the fail-safe action of PCV-3?
It closes to stop the flow to the flare
It opens to vent gas to the flare
It closes to stop the flow to the gas compression plant
It throttles to control flare pressure
In the ladder diagram (Handout 8.2-1), the low-level switches LS1 and LS2 are what type of switches?
Normally Open
Normally Closed
Single Pole, Single Throw
Double Pole, Double Throw
During a 'Start Up or Empty Tank Condition,' which two indicator lights will be ON?
L3 (High Indicator) and L4 (High High Indicator)
L1 (LL Indicator) and L2 (Low Indicator)
L5 (RUN Indicator) and L6 (STOP Indicator)
L1 (LL Indicator) and L5 (RUN Indicator)
During normal level conditions, what is the state of the Master Trip Relay R3?
It is de-energized
It is energized and latched through contact R3-A
It is bypassed by the Trip Reset Switch
It energizes and de-energizes with the level
What happens when the level drops below the LOW LEVEL set point, causing LS2 to close?
The system shuts down immediately
Relay R1 energizes
The Low Indicator light L2 turns ON
The horn sounds
A system shutdown is initiated when the level drops to the LOW-LOW LEVEL set point because:
R1 energizes, causing contact R1-B to open and de-energize R3
L1 turns on, which is wired to the shutdown circuit
LS1 sends a direct signal to the solenoid valve
R2 energizes, causing contact R2-B to open
A system shutdown is initiated when the level rises to the HIGH-HIGH LEVEL set point because:
A system shutdown is initiated when the level rises to the HIGH-HIGH LEVEL set point because:
LS4 sends a direct signal to the solenoid valve
L4 turns on, which is wired to the shutdown circuit
R2 energizes, causing contact R2-B to open and de-energize R3
R1 energizes, causing contact R1-B to open
What is the purpose of the "Trip Reset Switch"?
To manually shut down the system in an emergency
To test the indicator lights
To bypass the level switches during maintenance
To reset (re-energize) relay R3 after a fault has been cleared
Activating the Bypass switch BP-1 will energize the solenoid valve, bypassing which two components?
The low-level switches (LS1, LS2)
The high-level switches (LS3, LS4)
The level alarms and the master trip relay
The RUN and STOP indicators
During normal operation, the RUN indicator (L5) is ON. Which relay contact keeps it on?
R1-A (Normally Open)
R2-A (Normally Open)
R3-C (Normally Open)
R3-C (Normally Closed)
The STOP indicator (L6) will be ON when:
The system is running normally
The Master Trip Relay R3 is de-energized
The Bypass switch is activated
The level is in a high alarm state
In the GOSP system (Figure 22), if the HPPT pressure switch (S5) opens, what will happen?
Only the HPPT section will shut down
The entire GOSP system will shut down
Only an alarm will sound
The IPPT will take over the process
What is the fundamental principle of this "fail-safe" ESD system?
It requires two separate signals to shut down
Any open circuit in the input permissive chain will shut the plant down
It can only be shut down manually
It automatically restarts after a trip
What type of device is ZV 010 in Figure 3?
A pressure transmitter
A flow control valve
A solenoid control valve
A temperature switch
In Figure 13, the movement of the piston is controlled by the increase and decrease in what?
Temperature
Level
Pressure
Flow
Which of the following is a key point to remember about ESD systems?
They are manual systems
They must operate before damage is done
They are only for protecting equipment
They are only used during startup
In Figure 20, what is the destination for the crude oil after it leaves the Shipper Pump?
To Refinery
To Flare
To Gas Compression Plant
To IPPT
In Figure 21, the inputs to the AND gate are from what kind of devices?
Transmitters
Controllers
Switches
Indicators
What is the power source for the relays R1 through R6 in Figure 22?
110 Vac
24 Vdc
Instrument Air
A backup battery
In the ladder diagram, which relay is referred to as the "LL Relay"?
R1
R2
R3
R7
Which relay is referred to as the "HH Relay"?
R1
R2
R3
R7
What must happen for the Horn (rung I) to activate?
Relay R3 must be energized
Relay R3 must be de-energized
Relay R1 must be energized
Relay R2 must be energized
The logic where a relay contact (R3-A) is used to keep its own coil (R3) energized is called a:
Bypass circuit
Seal-in or latching circuit
Trip circuit
Alarm circuit
If the level is normal, but indicator L2 (Low Indicator) is ON, what is the most likely cause?
Switch LS2 is stuck closed
Switch LS1 has failed open
Relay R3 has failed
The bulb in L2 has burned out
If the level is normal, but the system is shut down and the STOP light (L6) is on, what component should be checked first?
The solenoid valve
The Master Trip Relay (R3) and its control circuit
The Low Level Switch (LS2)
The High Level Switch (LS3)
What is the function of FCV-1 in the GOSP diagram (Figure 20)?
It controls the level in the HPPT
It controls the flow of crude oil into the HPPT
It controls the gas pressure leaving the HPPT
It is a bypass valve for the shipper pump
The core of a solenoid is also referred to as the:
Spring
Coil
Armature
Stem
If pressure is normal in the circuit from Figure 7, the solenoid valve is energized through which contact of the switch?
The NO (Normally Open) contact
The COM (Common) terminal
The NC (Normally Closed) contact
The RET (Return) line
The level sensing element in Figure A uses a float to operate what type of switch?
Micro-switch
Mercury Switch
Pressure Switch
Temperature Switch
An ESD system is designed to perform a shutdown before what happens?
The shift change occurs
The process variable reaches its setpoint
Damage is done to equipment or personnel
The operator can intervene
In Figure 20, what is the purpose of the "MIN. FLOW BYPASS" line?
To flare excess gas
To protect the pumps during low flow conditions
To send crude oil back to the IPPT
To provide a secondary path to the refinery
In the GOSP wiring diagram (Figure 22), all the relay contacts R1-1 through R6-1 must be ________ for the system to run.
Open
Bypassed
Closed
De-energized
In the ladder diagram, a low-low level trip is considered more critical than a low-level alarm because it:
Only activates an indicator light
Sounds a horn
De-energizes the Master Trip Relay and shuts the system down
Requires a manual reset
What component is located at grid reference C,2 in the ladder diagram (Handout 8.2-1)?
L2 Low Indicator
LS2-Low Level switch
R1-A contact
LS3-High Level switch
If the High-High Level Switch (LS4) fails in a closed position, what will happen?
The system will immediately shut down
The system will operate normally
The High-High indicator L4 will be on continuously
The system cannot be started
Which of the following conditions will NOT cause a shutdown in the ladder diagram system?
Level dropping below the LS1 set point
Level rising above the LS4 set point
The Trip Reset Switch failing in the open position
Level rising above the LS3 set point
The symbol for the solenoid valve in the P&ID (Figure 3) and ladder diagram (Handout 8.2-1) indicates it is a(n):
Electrically actuated device
Pneumatically actuated device
Manually actuated device
Hydraulically actuated device
What is the primary safety function of the MOV ZV valve in Figure 20?
To control the pressure in the HPPT
To stop the flow of crude oil into the plant during an ESD
To regulate the flow to the shipper pump
To bypass the IPPT
If a wire breaks in the circuit for the HPPT Level Switch (S1) in Figure 22, what is the result?
An alarm will sound, but the system continues to run
The system will shut down because R1 will de-energize
The system will ignore the signal from S1
Nothing will happen until the level actually reaches 12 feet
The "Trip Reset Switch" in the ladder diagram is a:
Normally Closed push button
Normally Open push button
Toggle switch
Selector switch
For relay R3 to be initially energized during startup, what two actions are required?
be initially energized during startup, what two actions are required?
The level must be normal and the bypass switch must be closed
Contacts R1-B and R2-B must be closed and the Trip Reset button must be pushed
Switches LS1 and LS2 must be open
The horn must be silenced and the RUN button pushed
In the GOSP system, LCV-1 is designed to fail in which position?
Air Open / Air Fails Close (AO/AFC)
Air Close / Air Fails Open (AC/AFO)
Fail in last position
Manual override
What is the set point for the IPPT Pressure Switch in the GOSP ESD system?
120 psi
180 psi
90 psi
12 feet
In the ladder diagram, if relay R2 is energized, what is the status of indicator L4?
It is OFF
It is ON
It is flashing
It depends on the state of R1
The use of a 24 Vdc control circuit (Figure 22) is common in industrial settings because it is:
Higher power than 110 Vac
Less expensive to install
Considered a safer, lower voltage for control logic
The only voltage relays can operate on
If the RUN indicator L5 is ON, what is the state of the solenoid valve?
It is de-energized
It is energized (unless bypassed)
It is closed
It is in manual mode
Which event is considered an "alarm only" and does not directly cause a trip?
A high-high level condition (LS4)
A low-low level condition (LS1)
A low level condition (LS2)
A failure of the Master Trip Relay (R3)
In Figure 20, the Booster Pump and Shipper Pump are configured in:
Parallel
Series
A standby arrangement
A bypass loop
The temperature switches in the GOSP logic (Figure 21) are monitoring the temperature of what?
The crude oil in the HPPT
The gas leaving the IPPT
The bearings in the electric motors
The ambient air temperature
If contact R3-A in the ladder diagram were to fail open, what would be the result?
The system would run normally
The system would shut down and could not be reset
The horn would sound continuously
The bypass switch would not function
The primary function of the IPPT is to:
Receive crude oil directly from the inlet
Separate gas and oil at a lower pressure than the HPPT
Pump crude oil to the refinery
Flare excess gas from the process
In the ladder diagram, the contact R3-C (NC) in rung L serves what purpose?
To turn on the RUN indicator when the system is running
To turn on the STOP indicator when the system is shut down
To energize the solenoid valve
To sound the horn during a trip
A technician finds that relay R1 is energized. This indicates:
A high-high level condition
A normal level condition
A low-low level condition
The system has been manually shut down
In Figure 3, the dashed line around the solenoid valve and its connection to the actuator represents:
An electrical connection
A software or data link
A pneumatic (air) line
A mechanical linkage
During an ESD in the GOSP system, PCV-1 and PCV-2 both close. What is the purpose of this action?
To stop gas from being sent to the flare
To stop feeding the gas compression plant
To increase the pressure in the HPPT and IPPT
To open a bypass around the traps
In the ladder diagram, what would happen if the bulb for the "RUN Indicator" (L5) burned out?
The system would shut down
The solenoid valve would de-energize
The system would continue to run normally, but without the visual indication
The STOP indicator would turn on
The device tagged FCV 010 in Figure 3 is what type of valve?
An on/off motor-operated valve
A pressure control valve
A flow control valve
A level control valve
Why is it necessary for the ESD system to shut off the Booster Pump and Shipper Pump during a trip?
To save electricity
To prevent them from running dry or pumping into a blocked line
To allow them to cool down
To reduce plant noise levels
In the ladder diagram, if the level is between the Low (LS2) and High (LS3) set points, how many indicator lights should be on?
None
One (L5 - RUN)
Two (L5 and L6)
Four (L1, L2, L3, L4)
What is the function of the "PERMISSIVE START UP" logic in Figure 22?
It allows the plant to start even if there is a fault
It ensures all conditions are safe (all switches closed) before allowing the plant to run
It bypasses all alarms during the startup sequence
It is a manual override for the ESD system
If the solenoid valve in the ladder diagram system fails and will not energize, what is the consequence?
The process cannot be shut down
The process cannot be started or run
The level alarms will not function
The system will operate normally
Which component in the ladder diagram acts as the "brain" of the shutdown logic, holding the system in a run state or a trip state?
Relay R1 (LL Relay)
Relay R2 (HH Relay)
Relay R3 (Master Trip Relay)
The Solenoid Valve
The term "actuate" for a switch means to:
Trip and change from its normal state
Return to its normal state after a trip
Fail in its current position
Send a continuous signal
What is the purpose of FCV 4 in Figure 20?
To control crude oil flow into the plant
To control crude oil flow from the shipper pump to the refinery
To bypass the shipper pump
To control flow to the booster pump
The GOSP ESD system uses what voltage for its final shutdown devices like solenoid valves and motor controls?
24 Vdc
12 Vdc
110 Vac
480 Vac
In the ladder diagram, if R1-B and R2-B are both closed, but R3 will not energize when the reset button is pushed, what is a possible cause?
The coil of relay R3 has failed
The level is too high
The level is too low
The horn is disconnected
What is the fail-safe action of FCV 2 in Figure 20?
Air Open / Air Fails Close (AO/AFC)
Air Close / Air Fails Open (AC/AFO)
Fails in last position
Manually closed
If the level is rising, in what order will the switches in the ladder diagram be activated?
LS1, LS2, LS3, LS4
LS2, LS1, LS3, LS4
LS3, LS4
LS2, LS3, LS4
When a process shutdown occurs in the GOSP, the MOV ZV valve is closed by what?
An electric motor
Instrument air pressure
A large spring
A manual handwheel
The contact R2-A in the ladder diagram is a:
Normally Closed contact from relay R2
Normally Open contact from relay R2
Normally Closed contact from relay R3
Normally Open contact from relay R1
The overall purpose of the complex relay logic in Figure 22 is to implement a simple:
OR function
NOT function
XOR function
AND function
During a shutdown in the ladder diagram system, contact R3-C (NO) in rung J opens, which de-energizes what final control element?
The Horn
The RUN indicator
The Solenoid Valve
The STOP indicator
For plant safety, where is the gas from PCV 3 routed during an emergency?
Back to the IPPT
To the Gas Compression Plant
To the Flare
To the Refinery
