Study Unit 5 Flashcards
A
1st: Analyser
2nd: Alarm
C
2nd: Controller
F
1st: Flow rate
G
1st: (User’s choice)
H
2nd: High (alarm)
I
1st: Current
2nd: Indicator
J
1st: Power
L
1st: Level
2nd: Low (alarm)
LL
1st: Liquid level
P
1st: Pressure
Q
1st: Heat (energy) flow
R
Recorder
S
1st: Speed
2nd: Switch
T
1st: Temperature
2nd: Transmitter
What is a process unit?
Process equipment where mass and heat transfer is physically taking place
Input and output of process units?
Input: Feed streams
Output: Product streams
Input and output of process?
Single input: Manipulated stream (variable)(MV)
Output: Measurable variables (Process variables)(PV)
Any other inputs: Disturbances
How does an open loop control system function?
Manually
How does a closed loop control system function?
Automatically
Why is process control necessary?
Safety Product specifications Environmental regulations Operational constraints Economics
Surge tank level control system
Level transmitter (LT)
Liquid level controller (LLC)
Control valve
LLC
Liquid level controller
Compares level reading from LT with desired level/set point (SP) and then transmits this information on to the control valve
Control valve
Final control element
Valve percent opening is adjusted to correct for any deviations from the set point
Six elements of process control
- Process
- Transmitter/Sensor
- Transducers (not shown in I/O block diagram)
- Transmission lines
- Controller
- Final control element
Transducer
Electronic equipment that converts the pressure/temperature/flow signal from the sensor into an electrical signal or vice versa.
For industrial process control elements what current loops are used for analog signaling?
Analog 4-20 mA current loops
0-10 bar
Dead-zero
0 mA
Indicative of a loop failure
Live-zero
4 mA
Corresponds to the minimum value of 0 bar
Full scale value of analog current loop
20 mA
10 bar
Transmission lines
Communication lines and equipment used to channel information to the necessary equipment
Controller
Controllers are used to determine the size of the corrective action that should be taken to achieve the required outcome
Types of control systems
Distributed Control System (DCS)
Programmable Logic Controller (PLC)
Supervisory Control and Data Acquisition (SCADA)
DCS
Distributed Control System
PLC
Programmable Logic Controller
SCADA
Supervisory Control and Data Acquisition
Final control element
Execute the actions determine by the controller
What is included in a PFD?
Flow of chemical materials Equipment used in process - Utilities (process piping) - Major equipment without showing details - Major process control loops
FA
Flow Alarm
Indicating flow alarm
FC
Flow Controller
Flow control
FE
Flow Element
Flow sensor
FI
Flow Indicator
Flow indication
FIC
Flow Indicating Control
Controling and indicating of flow
FR
Flow Recorder
Recording of flow
FT
Flow Transmitter
Transmitting flow signal
Why is a P&ID so important?
Shows information to design and build plant
Forms the basis for process safety studies
Forms the basis for semi-definite cost estimates of what the plant will cost
HAZOP
Hazard and operability study
What does a P&ID contain?
- Process piping, sizes and identification (indicates to pipe designers the material requirements)
- Valves
- Vents, drains, special fittings, sampling lines, reducers
- Flow direction
- ## Mechanical equipment
Piping class
Defines the type of material, Flange ratings, pipe wall thickness and what fittings to use
