Process Description
Pressure Process Description
Pressure Process Operating Principles
The Pressure Process (Unit 1) uses pumped water from Tank #3, 1-T-3, to increase the pressure of air trapped in Tank #2, 1-T-2. The air pocket’s volume is changed by changing the level of water in the tank. Thus, the water in the Tank #2 acts much like a piston in a reciprocating compressor or an automobile engine. The level of water required to achieve a particular pressure will directly depend on the mass of air trapped in Tank #2. A higher mass of trapped air will increase its pressure more quickly as water fills the tank. A lower mass of trapped air will require more water to reduce the volume occupied by the air in order to raise its pressure. It is possible to adjust the mass of trapped air using valve 1-V-7. The water from Tank #2 is normally continuously returned to Tank #3 using valve 1-V-21.
Tank #3 (1-T-3)
Tank #3 is a vertical cylindrical tank open to atmosphere that can hold a maximum of 44 gallons of water. It supplies Pump #2, 1-P-2, from the base of the tank. Three lines return water from Tank #2, 1-T-2 at the top of Tank #3.
Pump #2 (1-P-2)
Pump #2 is a motor-driven centrifugal pump that moves water from Tank #3 to Tank #2. The normal flow is 5 GPM. Flow from the discharge of Pump #2 normally passes through control valve 1-CV-3 and is sent to Tank #2. A bypass line outfitted with a hand valve, 1-V-17, and a solenoid valve, 1-SV-4, is provided around 1-CV-3 to introduce flow disturbances for studying the process and control responses.
Tank #2 (1-T-2)
Tank #2 is a fully enclosed, vertically oriented cylindrical vessel with a capacity of 10 gallons. It normally operates with an air pocket and is mostly filled with water. It receives water from Pump #2 at the top. It normally operates at 15 PSIG. Tank #2 is located above Tank #3 so it can be drained by gravity when the process is shut down.
Pressure safety valve 1-PSV-2 is connected at the top of Tank #2 and is set to relieve at 30 PSIG. The safety valve returns relieved flow back to Tank #3.
A water drain line is connected from the bottom of Tank #2 back to Tank #3. Hand valve 1-V-21 is used to adjust the flow rate of water through this line. 1-V-21 is normally 20% open and passes 5 GPM of water back to Tank #3.
A line is connected to the upper side of Tank #2 and returns to Tank #3. The flow through this line is controlled with hand valve 1-V-7. This hand valve is primarily used to vent air from Tank #2 when it is initially being filled. It can also be used admit air from Tank #3 to prevent a vacuum from being formed when draining Tank #2 back to tank #3 by gravity with valve 1-V-21. This valve is normally closed.
Level Process Description
Level Process Operating Principles
The Level Process (Unit 2) uses pumped water from Tank #3, 2-T-3, to fill Tank #1, 2-T-1. Water from Tank #1 to Tank #3 is returned by gravity flow. The level of water will change depending on the difference between the pumped water flow and the gravity return flow.
Tank #3 (2-T-3)
Tank #3 is a vertical cylindrical tank open to atmosphere that can hold a maximum of 44 gallons of water. It supplies Pump #2, 2-P-2, from the base of the tank. Two lines return water from Tank #1, 2-T-1 at the top of Tank #3.
Pump #2 (2-P-2)
Pump #2 is a motor-driven centrifugal pump that moves water from Tank #3 to Tank #1. The normal flow is 5 GPM. Flow from the discharge of Pump #2 normally passes through a rotameter 2-FG-2 and control valve 2-CV-1 and is sent to Tank #1. A bypass line outfitted with a hand valve, 2-V-4, and a solenoid valve, 2-SV-1, is provided around 2-CV-1 to introduce flow disturbances for studying the process and control responses.
Pump #2’s motor is outfitted with a variable frequency drive (VFD) which allows the pump’s speed to be continuously controlled. The pump is normally operated connected to the power utility line voltage and runs at full speed.
Tank #1 (2-T-1)
Tank #1 is a vertical cylindrical vessel open to atmosphere with a capacity of 15 gallons. It receives flow from Pump #2. It normally operates at 50% full. Tank #1 is located above Tank #3 so it can be drained by gravity during normal operation and when the process is shut down.
A water drain line is connected from the bottom of Tank #1 back to Tank #3. The drain line splits into two lines. Hand valve 2-V-14 on one line is normally used to adjust the flow rate of water back to Tank #3. 2-V-14 is normally 70% open and passes 5 GPM of water back to Tank #3. On the other line, solenoid 2-SV-3 can be used to provide a process disturbance or can be employed to demonstrate on-off level control of Tank #1. Both drain lines return flow back to Tank #3.
Flow Process Description
Flow Process Operating Principles
The Flow Process (Unit 3) demonstrates how liquid flow rate can be controlled using either a control valve on the discharge line of a pump or by a variable frequency drive (VFD) to control the pump speed. The process pumps water from Tank #3, 3- T-3, through a control valve and then returns the water back to Tank #3.
Tank #3 (3-T-3)
Tank #3 is a vertical cylindrical tank open to atmosphere that can hold a maximum of 44 gallons of water. It supplies Pump #2, 3-P-2, from the base of the tank. One line receives return water from Pump #2.
Pump #2 (3-P-2)
Pump #2 is a motor-driven centrifugal pump that moves water from Tank #3 through control valve 3-CV-3, through rotameter 3-FG-2 and back to Tank #3. The normal flow is 5 GPM. A bypass line outfitted with a hand valve, 3-V-17, and a solenoid valve, 3-SV-4, is provided around 3-CV-3 to introduce flow disturbances for studying the process and control responses.
Pump #2’s motor is outfitted with a variable frequency drive (VFD) which allows the pump’s speed to be continuously controlled. The pump is normally operated connected to the power utility line voltage and runs at full speed.
Temperature Process Description
Temperature Process Operating Principles
The Temperature Process (Unit 4) demonstrates heat transfer between a hot fluid stream and a cold fluid stream using a heat exchanger. A hot fluid is produced by pumping water from Tank #3, 4-T-3, through an electrical heater, 4-H-1. The hot fluid the Heater is fed to a heat exchanger, 4-E-1, and is cooled by circulating cooling water. The cooled water from Cooler, 4-E-1, is returned to the supply tank and recirculated.
Tank #3 (4-T-3)
Tank #3 is a vertical cylindrical tank open to atmosphere that can hold a maximum of 44 gallons of water. It supplies Pump #2, 4-P-2, from the base of the tank. One line receives cooled return water from Cooler, 4-E-1.
Pump #2 (4-P-2)
Pump #2 is a motor-driven centrifugal pump that moves water from Tank #3 through control valve 4-CV-3, through rotameter 4-FG-2 and to Heater, 4-H1. The normal flow is 2 GPM. A bypass line outfitted with a hand valve, 4-V-17, and a solenoid valve, 4-SV-4, is provided around 4-CV-3 to introduce flow disturbances for studying the process and control responses.
Heater (4-H-1)
The Heater is an electrical heater that heats the water from Pump #2 from 75 DEG F to about 92 DEG F. The rating of 4-H-1 is 5 kW. A protective circuit will trip out the electric power if the temperature of 4-H-1 exceeds 140 DEG F. The trip circuit will automatically reset when the temperature gets below 100 DEG F.
Cooler (4-E-1)
The Cooler is a shell and tube heat exchanger. Hot circulating water from the Heater passes through the shell side and is cooled from 92 DEG F to 75 DEG F. The cooled circulating water is returned to Tank #3.
Cooling water at 70 DEG F from battery limits passes through control valve 4-CV-2, through rotameter 4-FG-1 and flows through the tubes of 4-E-1. The normal flow rate of cooling water is 1.8 GPM. The cooling water heats up to about 90 DEG F in 4- E-1 by exchanging heat with the hot circulating water. The warmed cooling water is sent to battery limits.
Instrumentation
Pressure Process
This section describes the controls and instruments of the Pressure Process.
Tank #3 (1-T-3)
Level gauge 1-LG-3 indicate the liquid level in Tank #3.
Pump #2 (1-P-2)
Switch 1-P-2 controls the state of the motor for Pump #2. The flow through Pump #2 can be regulated by either flow controller 1-FIC-3 or by pressure controller 1- PIC-2 on Tank #2. Selector switch 1-HS-3 determines which controller’s output is routed to control valve 1-CV-3. When the switch is in the PIC state, 1-PIC-2 will adjust the position of 1-CV-3. When the switch is in the FIC state, 1-FIC-3 will adjust the position of 1-CV-3. The unselected controller is locked in manual mode and its output tracks that of the selected controller. This permits bumpless control when changing the position of 1-HS-3. Normally, 1-HS-3 is in the PIC state.
The position of 1-CV-3 is indicated on 1-VI-3.
The position of bypass valve 1-V-17 is adjusted by a hand controller of the same tag name. The position of solenoid valve 1-SV-4 is adjusted by a switch of the same tag name.
Tank #2 (1-T-2)
The pressure controller 1-PIC-2 will normally control the pressure of Tank #2 by controlling control valve 1-CV-3. The level of Tank #2 based on a DP cell with transmitter is indicated on 1-LI-2. An independent indication of the level of Tank #2 is shown on level gauge 1-LG-2.
The position of Tank #2 to Tank #3 drain valve 1-V-21 is adjusted using a hand controller of the same tag name.
The position of hand valve 1-V-7 is adjusted using a hand controller of the same tag name.
Level Process
This section describes the controls and instruments of the Level Process.
Tank #3 (2-T-3)
Level gauge 2-LG-3 indicate the liquid level in Tank #3.
Pump #2 (2-P-2)
Switch 2-P-2 controls the state of the motor for Pump #2. The power source for the motor of 2-P-2 can be changed using switch 2-HS-2. When 2-HS-2 is in the LINE position, the motor will be connected directly to the incoming power line and the pump will run at full speed. When 2-HS-2 is in the VFD position, the VFD will be connected to the pump’s motor and its speed will be determined by the output of Tank #1 level controller 2-LIC-1. At 0% output, the speed of Pump #2 will be 30% of full speed. At 100% output the pump will run at full speed. Normally, 2-HS-2 is in the LINE state. If the state of 2-HS-2 is changed, 2-LIC-1 will be placed into manual mode on a one-shot basis. Indicator 2-SI-2 indicates the pump speed.
The flow through Pump #2 has two independent indications. The first is rotameter 2-FG 2. The second is flow controller 2-FIC-1.
The position of control valve 2-CV-1 is selected from either the output of 2-LIC-1 or 2-FIC-1 using selector switch 2-HS-1. Normally, 2-HS-1 is in the LIC state and 2- LIC-1 adjusts the position of 2-CV-1 to regulate the level of Tank #1. When 2-HS-1 is in the FIC state, the output of 2-FIC-1 will set the position of 2-CV-1. If the state of 2-HS-1 is changed, 2-LIC-1 will be placed into manual mode on a one-shot basis. Note that selector switch 2-HS-1 will be locked in the FIC state while 2-HS-2 is in the VFD position.
When 2-HS-1 is in the LIC state, 2-FIC-1 is locked in manual mode and its output tracks the output of 2-LIC-1. The setpoint of 2-FIC-1 can be cascaded to the output of 2-LIC-1 only when 2-HS-1 is in the FIC state.
The position of 2-CV-1 is indicated on indicator 2-VI-1.
The position of bypass valve 2-V-4 is adjusted by a hand controller of the same tag name. The position of solenoid valve 2-SV-1 is adjusted by a switch of the same tag name.
Tank #1 (2-T-1)
The level of Tank #1 based on a DP cell with transmitter is indicated on 2-LIC-1. An independent indication of the level of Tank #1 is shown on level gauge 2-LG-1. Level controller 2-LIC-1 normally adjusts the position of control valve 2-CV-1. 2-LIC-1 can also control the flow through Pump #2 via the VFD for its motor. In this control configuration, switch 2-HS-2 will be in the VFD state and switch 2-HS-1 will therefore be locked in the FIC state. The position of control valve 2-CV-1 can be manually adjusted using 2-FIC-1.
An alternate level control strategy for Tank #1 is to use on/off control to open and close the solenoid valve 2-SV-3 on the drain line of Tank #1. This is done by placing on/off level control switch 2-LSC-1 in the AUTO state. In this state, solenoid valve 2-SV-3 will be switched to the OPEN state if the level of indicator 2-LAHL-1 goes above 70%. The solenoid valve will be closed if 2-LAHL-1 goes below 30%. The PV of 2-LAHL-1 is the same as that of 2-LIC-1. Note that when 2-LSC-1 is in the AUTO state, level controller 2-LIC-1 will be locked in manual mode.
The position of hand valve 2-V-14 is adjusted using a hand controller of the same tag name.
Flow Process
Tank #3 (3-T-3)
Level gauge 3-LG-3 indicate the liquid level in Tank #3.
Pump #2 (3-P-2)
Switch 3-P-2 controls the state of the motor for Pump #2. The power source for the motor of 3-P-2 can be changed using switch 3-HS-2. When 3-HS-2 is in the LINE position, the motor will be connected directly to the incoming power line and the pump will run at full speed. When 3-HS-2 is in the VFD position, the VFD will be connected to the pump’s motor and its speed will be determined by the output of pump flow controller 3-FIC-3. At 0% output, the speed of Pump #2 will be 30% of full speed. At 100% output the pump will run at full speed. Normally, 3-HS-2 is in the LINE state. Indicator 3-SI-2 indicates the pump speed.
The flow through Pump #2 has two independent indications. The first is rotameter 3-FG-2. The second is flow controller 3-FIC-3.
The position of control valve 3-CV-3 is selected from either the output of 3-FIC-3 or 100% using selector switch 3-HS-3. Normally, 3-HS-3 is in the VALVE state and 3- FIC-3 adjusts the position of 3-CV-3 to regulate the pump flow. When 3-HS-3 is in the VFD state, the output of the signal selector will be set to 100% to fully open 3-CV-3.
Note that selector switch 3-HS-3 will be locked in the VFD state while 3-HS-2 is in the VFD position.
The position of 3-CV-3 is indicated on indicator 3-VI-3.
The position of bypass valve 3-V-17 is adjusted by a hand controller of the same tag name. The position of solenoid valve 3-SV-4 is adjusted by a switch of the same tag name.
Temperature Process
Tank #3 (4-T-3)
Level gauge 4-LG-3 indicate the liquid level in Tank #3.
Pump #2 (4-P-2)
Switch 4-P-2 controls the state of the motor for Pump #2. The flow through Pump #2 is regulated by flow controller 4-FIC-3 which adjusts the position of 4-CV-3. The position of 4-CV-3 is indicated on 4-VI-3.
The position of bypass valve 4-V-17 is adjusted by a hand controller of the same tag name. The position of solenoid valve 4-SV-4 is adjusted by a switch of the same tag name.
The flow through Pump #2 is also indicated on rotameter 4-FG-2.
Heater (4-H-1)
Switch 4-HS-1 turns the power to the Heater on and off. A protective circuit will internally trip out the electric power if the temperature of 4-H-1 exceeds 140 DEG F. The trip circuit will automatically reset when the temperature gets below 100 DEG F. 4-HS-1 is not affected by this protective circuit.
The outlet temperature of circulating water from the Heater is indicated on 4-TI-2.
Cooler (4-E-1)
The cooling water flow through the Cooler is indicated on both flow controller 4-FIC2 and rotameter 4-FG-1. The cooling water flow can be regulated by either flow controller 4-FIC-2 or by temperature controller 4-TIC-1 on the outlet of the Cooler. Selector switch 4-HS-2 determines which controller’s output is routed to control valve 4-CV-2. When the switch is in the TIC state, 4-TIC-1 will adjust the position of 4-CV-2. When the switch is in the FIC state, 4-FIC-2 will adjust the position of 4-CV2.
Normally, 4-HS-2 is in the TIC state. When 4-HS-2 is in the TIC state, 4-FIC-2 is locked in manual mode and its output tracks that of 4-TIC-1. This permits bumpless control when changing the position of 4-HS-2 from the TIC to the FIC state. When 4-HS-2 is in the FIC state, the output of 4-TIC-1 will track the setpoint of 4-FIC-2 if 4- FIC-2 is in either manual or automatic mode. Whenever the state of 4-HS-2 is changed, 4-TIC-1 will be placed into manual mode on a one-shot basis. When the state of 4-HS-2 is switched from the FIC to the TIC state, the output of 4-TIC-1 will be initialized to match the output of 4-FIC-2 on a one-shot basis.
The position of 4-CV-2 is indicated on 4-VI-2. Note that 4-CV-2 is an air-open valve and its indicated position is 100% minus the selected controller’s output.
The position of bypass valve 4-V-8 is adjusted by a hand controller of the same tag name. The position of solenoid valve 4-SV-2 is adjusted by a switch of the same tag name.
Note that 4-FIC-2 can have its setpoint cascaded from 4-TIC-1’s output. This can be done when 4-HS-2 is in the FIC state. When this is done, the control action of 4-TIC1 must be changed from REVERSE to DIRECT in order to work properly. This adjustment is performed from the DETAIL page of PID controller 4-TIC-1. Refer to the DSS-100 User’s Guide for details on controller configuration changes.