Process controls - Revision history

Kathleenzhou at 23:14, 21 February 2016

2016-02-21T23:14:15Z

← Older revision		Revision as of 23:14, 21 February 2016
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	<br>		<br>

	Author: Samson Fong <sup> [2015] and Kathleen Zhou <sup> [2016] </sup>		Author: Samson Fong <sup> [2015] </sup> and Kathleen Zhou <sup> [2016] </sup>

	Stewards: Jian Gong and Fengqi You		Stewards: Jian Gong and Fengqi You

Kathleenzhou: /* Sensors By Measured Variable */

2016-02-21T23:12:48Z

Sensors By Measured Variable

← Older revision		Revision as of 23:12, 21 February 2016
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	The following is a nonexhaustive list of instruments used to measure certain variables.		The following is a nonexhaustive list of instruments used to measure certain variables.

			[[File: DPCell.PNG\|300px\|thumb\|right\|A differential pressure cell, which can be used for absolute pressure, differential pressure, level, and interface level determination <sup> [8] </sup>]]


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	\|}		\|}

			[[File: Thermocouple.PNG\|350px\|thumb\|left\|A thermocouple, which can be used as a sensor for temperature<sup> [9] </sup>]]
			[[File: CoriolisMeter.PNG\|300px\|thumb\|right\|A Coriolis meter, which can be used as a sensor for mass flow <sup> [11] </sup>]]
			[[File: VenturiMeter.PNG\|300px\|thumb\|center\|A Venturi meter, which can be used as a sensor for volumetric flow rate<sup> [10] </sup>]]

	===Signal Transmission===		===Signal Transmission===

Kathleenzhou: /* References */

2016-02-21T23:00:50Z

References

← Older revision		Revision as of 23:00, 21 February 2016
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	7. Instrumentation Basics: 4-20 mA and 3-15 psi Control Signals. Learning Instrumentation and Controls Engineering Web Site. http://www.instrumentationtoolbox.com/2011/01/instrumentation-basics-control-signals.html#axzz40cpPcnm6. Accessed February 16, 2016.		7. Instrumentation Basics: 4-20 mA and 3-15 psi Control Signals. Learning Instrumentation and Controls Engineering Web Site. http://www.instrumentationtoolbox.com/2011/01/instrumentation-basics-control-signals.html#axzz40cpPcnm6. Accessed February 16, 2016.

			8. Differential Pressure Transmitters. Vega Controls Web Site. http://www.vegacontrols.co.uk/product_details.asp?productID=312&fixedRangeID=11. Accessed February 21, 2016.

			9. Rugged Pipe Plug Thermocouple Probe with 1/4 or 1/8NPT Fitting. Omega Web Site. http://www.omega.com/pptst/TC-NPT.html. Accessed February 21, 2016.

			10. Venturi Meter. Chegg Web Site. http://www.chegg.com/homework-help/questions-and-answers/venturi-meter-used-measure-flow-speed-fluid-pipe-meter-connected-two-sections-pipe-fig-14--q1236560. Accessed February 21, 2016.

			11. The Basics of Flow Measurement with Coriolis Meters. The Current Flow Solutions Web Site. http://www.micromotionblog.com/the-basics-of-flow-measurement-with-coriolis-meters-part-2/. Accessed February 15, 2016.

Kathleenzhou: /* Process Safety and Process Control */

2016-02-21T22:30:33Z

Process Safety and Process Control

← Older revision		Revision as of 22:30, 21 February 2016
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	==Process Safety and Process Control==		==Process Safety and Process Control==

	One way of looking at process safety is a “layers of protection” model. Ideally, any issues or deviations from the norm are handled at the lowest layer possible for safe operation of the process. These layers are described here in the [https://processdesign.mccormick.northwestern.edu/index.php/Process_safety#Layers_of_Plant_Safety Process Safety page]. The role controls play in process safety is of particular note.		One way of looking at process safety is a “layers of protection” model.<sup> [4] </sup> Ideally, any issues or deviations from the norm are handled at the lowest layer possible for safe operation of the process. These layers are described here in the [https://processdesign.mccormick.northwestern.edu/index.php/Process_safety#Layers_of_Plant_Safety Process Safety page]. The role controls play in process safety is of particular note.

	[[File: KZ_SafetyLayers.PNG\|400px\|thumb\|right\|Layers of process safety pictured <sup> [5] </sup>]]		[[File: KZ_SafetyLayers.PNG\|400px\|thumb\|right\|Layers of process safety pictured <sup> [4] </sup>]]


	===Process Interlocks===		===Process Interlocks===
	Interlocks prevent operators from departing from the set procedure. These interlocks may be pneumatic, electric, mechanical, or programmed. For example, interlocks prevent operators from entering values higher or lower than a set, reasonable value. For example, interlocks may prevent an operator for entering a value for reactor temperature beyond the capabilities of the associated heating unit or beyond safe operating limits for the reactor.		Interlocks prevent operators from departing from the set procedure. These interlocks may be pneumatic, electric, mechanical, or programmed. For example, interlocks prevent operators from entering values higher or lower than a set, reasonable value. For example, interlocks may prevent an operator for entering a value for reactor temperature beyond the capabilities of the associated heating unit or beyond safe operating limits for the reactor. <sup> [4] </sup>

	====Alarms and Safety Trips====		====Alarms and Safety Trips====
	Alarms are intended to alert operators to deviations in process conditions that have the potential to severely impact product quality or safety. Alarms can create audio or visual cues to alert the operator to the situation. Alternatively, sometimes, alarm systems are programmed as automatic trip systems that do not need operator input, especially in situations where lack of response from the operator could lead to serious issues. An automatic trip system is composed of a sensor, some link that transfers the signal from the sensor to an actuator, and an actuator to perform the desired action.		Alarms are intended to alert operators to deviations in process conditions that have the potential to severely impact product quality or safety. Alarms can create audio or visual cues to alert the operator to the situation. Alternatively, sometimes, alarm systems are programmed as automatic trip systems that do not need operator input, especially in situations where lack of response from the operator could lead to serious issues. An automatic trip system is composed of a sensor, some link that transfers the signal from the sensor to an actuator, and an actuator to perform the desired action.<sup> [4] </sup>

	[[File: AlarmBlockDiagram.PNG\|400px\|thumb\|right\|General block diagram for alarm systems, depicting the branching between activating annunciators (alerts to operators) and final control elements (directly changing components of the process) <sup> [5] </sup>]]		[[File: AlarmBlockDiagram.PNG\|400px\|thumb\|right\|General block diagram for alarm systems, depicting the branching between activating annunciators (alerts to operators) and final control elements (directly changing components of the process) <sup> [4] </sup>]]

	====Safety Instrument System (SIS)====		====Safety Instrument System (SIS)====
	SIS is initiated when a critical process variable exceeds allowable limits to try to get the process back to a safe condition. The SIS involves extreme action such as starting or stopping a pump or completely shutting down a process unit. Because such actions may have a significant negative impact on the process equipment and/or the product quality, the SIS is used as a last resort for safety. In order for the SIS to effectively serve as a back up to BPCS, it must be able to function independently of the BPCS. Thus, it is recommended that the SIS have separate sensors and actuators. This is essential in a case such as a power outage, which would take out the BPCS entirely. Because the SIS involves more drastic measures, there tends to be redundant instrumentation to prevent an errant signal from kicking in the SIS.		SIS is initiated when a critical process variable exceeds allowable limits to try to get the process back to a safe condition. The SIS involves extreme action such as starting or stopping a pump or completely shutting down a process unit. Because such actions may have a significant negative impact on the process equipment and/or the product quality, the SIS is used as a last resort for safety. In order for the SIS to effectively serve as a back up to BPCS, it must be able to function independently of the BPCS. Thus, it is recommended that the SIS have separate sensors and actuators. This is essential in a case such as a power outage, which would take out the BPCS entirely. Because the SIS involves more drastic measures, there tends to be redundant instrumentation to prevent an errant signal from kicking in the SIS.<sup> [4] </sup>

	==References==		==References==

Kathleenzhou: /* Case Study */

2016-02-21T22:29:12Z

Case Study

← Older revision		Revision as of 22:29, 21 February 2016
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	===Case Study===		===Case Study===

	Let us examine the following case of a ~~level-controlled surge tank with~~ water ~~flowing in~~ and ~~out~~:		Let us examine the following case of a mixer combining two streams, one of pure water and one of pure compound A:
	~~[[File: SurgeTank.PNG]]~~

	#Specify control objectives - Maintain h at set point h<sub>sp</sub>		[[File:Mixer.PNG]]
	#Identify input variables in the system - F<sub>1</sub>,F<sub>2</sub> are input variables (variables that impact the process)
	#Identify output variables in the system - h ~~is an~~ output ~~variable~~ (a variable that is measured which we desire to control)		#Specify control objectives - Maintain h at set point h<sub>sp</sub>, maintain c<sub>3A</sub> at set point c<sub>3-sp</sub>
			#Identify input variables in the system - F<sub>1</sub>,F<sub>2</sub>, and F<sub>3</sub> are input variables (variables that impact the process)
			#Identify output variables in the system - h and c<sub>3A</sub>are output variables (a variable that is measured which we desire to control)
	#Identify any constraints for the system		#Identify any constraints for the system
	#*Hard constraint: h < h<sub>UL</sub> where h<sub>UL</sub> describes an upper limit for the liquid level in the tank before it overflows		#*Hard constraint: h < h<sub>UL</sub> where h<sub>UL</sub> describes an upper limit for the liquid level in the tank before it overflows
	#*Soft constraint: ~~Not relevant in this case, however, if there were a reaction in the tank (for example, it were a CSTR), a soft constraint might be that~~ c<sub>2</sub> < c<sub>USL</sub>, where c<sub>USL</sub> represents the upper specification limit for the concentration that can be shipped to the customer.		#*Soft constraint: c<sub>3A</sub> < c<sub>USL</sub>, where c<sub>USL</sub> represents the upper specification limit for the concentration that can be shipped to the customer
	#Specify operating mode - In this case, this is a continuous operation		#Specify operating mode - In this case, this is a continuous, not batch, operation
	#Identify safety, environmental, or economic needs		#Identify safety, environmental, or economic needs
	#*Safety: The valve controlling F<sub>2</sub> should fail open such that in case of a power outage, the tank drains rather than overflows		#*Safety: The valve controlling F<sub>2</sub> should fail open such that in case of a power outage, the tank drains rather than overflows

Kathleenzhou: /* Formulating a Control Strategy */

2016-02-21T07:35:24Z

Formulating a Control Strategy

@@ Line 101: / Line 101: @@
 ==Formulating a Control Strategy==
-There are a number of steps that should be taken in formulating a control strategy.  These include <sup> [4] </sup>:
+===Considerations===
 #Specify control objectives - For example, maintaining a process variable at a setpoint
@@ Line 110: / Line 111: @@
 #Specify operating mode as batch or continuous
 #Identify safety, environmental, or economic needs
 ==Instrumentation==

Kathleenzhou: /* Process Safety and Process Control */

2016-02-21T05:01:19Z

Process Safety and Process Control

← Older revision		Revision as of 05:01, 21 February 2016
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	One way of looking at process safety is a “layers of protection” model. Ideally, any issues or deviations from the norm are handled at the lowest layer possible for safe operation of the process. These layers are described here in the [https://processdesign.mccormick.northwestern.edu/index.php/Process_safety#Layers_of_Plant_Safety Process Safety page]. The role controls play in process safety is of particular note.		One way of looking at process safety is a “layers of protection” model. Ideally, any issues or deviations from the norm are handled at the lowest layer possible for safe operation of the process. These layers are described here in the [https://processdesign.mccormick.northwestern.edu/index.php/Process_safety#Layers_of_Plant_Safety Process Safety page]. The role controls play in process safety is of particular note.

	[[File: KZ_SafetyLayers.PNG]]		[[File: KZ_SafetyLayers.PNG\|400px\|thumb\|right\|Layers of process safety pictured <sup> [5] </sup>]]


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	Alarms are intended to alert operators to deviations in process conditions that have the potential to severely impact product quality or safety. Alarms can create audio or visual cues to alert the operator to the situation. Alternatively, sometimes, alarm systems are programmed as automatic trip systems that do not need operator input, especially in situations where lack of response from the operator could lead to serious issues. An automatic trip system is composed of a sensor, some link that transfers the signal from the sensor to an actuator, and an actuator to perform the desired action.		Alarms are intended to alert operators to deviations in process conditions that have the potential to severely impact product quality or safety. Alarms can create audio or visual cues to alert the operator to the situation. Alternatively, sometimes, alarm systems are programmed as automatic trip systems that do not need operator input, especially in situations where lack of response from the operator could lead to serious issues. An automatic trip system is composed of a sensor, some link that transfers the signal from the sensor to an actuator, and an actuator to perform the desired action.

	[[File: AlarmBlockDiagram.PNG]]		[[File: AlarmBlockDiagram.PNG\|400px\|thumb\|right\|General block diagram for alarm systems, depicting the branching between activating annunciators (alerts to operators) and final control elements (directly changing components of the process) <sup> [5] </sup>]]

	====Safety Instrument System (SIS)====		====Safety Instrument System (SIS)====

Kathleenzhou: /* Process Safety and Process Control */

2016-02-21T04:43:38Z

Process Safety and Process Control

← Older revision		Revision as of 04:43, 21 February 2016
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	==Process Safety and Process Control==		==Process Safety and Process Control==

	One way of looking at process safety is a “layers of protection” model. Ideally, any issues or deviations from the norm are handled at the lowest layer possible for safe operation of the process. These layers are described here in the [https://processdesign.mccormick.northwestern.edu/index.php/Process_safety#Layers_of_Plant_Safety Process Safety page]		One way of looking at process safety is a “layers of protection” model. Ideally, any issues or deviations from the norm are handled at the lowest layer possible for safe operation of the process. These layers are described here in the [https://processdesign.mccormick.northwestern.edu/index.php/Process_safety#Layers_of_Plant_Safety Process Safety page]. The role controls play in process safety is of particular note.

	===Interlocks===		[[File: KZ_SafetyLayers.PNG]]
	Interlocks prevent operators from departing from the set procedure. These interlocks may be pneumatic, electric, mechanical, or programmed. For example, interlocks prevent operators from entering values higher or lower than a set, reasonable value.

			===Process Interlocks===
			Interlocks prevent operators from departing from the set procedure. These interlocks may be pneumatic, electric, mechanical, or programmed. For example, interlocks prevent operators from entering values higher or lower than a set, reasonable value. For example, interlocks may prevent an operator for entering a value for reactor temperature beyond the capabilities of the associated heating unit or beyond safe operating limits for the reactor.

	====Alarms and Safety Trips====		====Alarms and Safety Trips====
	Alarms are intended to alert operators to deviations in process conditions that have the potential to severely impact product quality or safety. Alarms can create audio or visual cues to alert the operator to the situation. Alternatively, sometimes, alarm systems are programmed as automatic trip systems that do not need operator input, especially in situations where lack of response from the operator could lead to serious issues. An automatic trip system is composed of a sensor, some link that transfers the signal from the sensor to an actuator, and an actuator to perform the desired action.		Alarms are intended to alert operators to deviations in process conditions that have the potential to severely impact product quality or safety. Alarms can create audio or visual cues to alert the operator to the situation. Alternatively, sometimes, alarm systems are programmed as automatic trip systems that do not need operator input, especially in situations where lack of response from the operator could lead to serious issues. An automatic trip system is composed of a sensor, some link that transfers the signal from the sensor to an actuator, and an actuator to perform the desired action.

	[[File: ~~KZ_SafetyLayers~~.PNG]]		[[File: AlarmBlockDiagram.PNG]]

			====Safety Instrument System (SIS)====
			SIS is initiated when a critical process variable exceeds allowable limits to try to get the process back to a safe condition. The SIS involves extreme action such as starting or stopping a pump or completely shutting down a process unit. Because such actions may have a significant negative impact on the process equipment and/or the product quality, the SIS is used as a last resort for safety. In order for the SIS to effectively serve as a back up to BPCS, it must be able to function independently of the BPCS. Thus, it is recommended that the SIS have separate sensors and actuators. This is essential in a case such as a power outage, which would take out the BPCS entirely. Because the SIS involves more drastic measures, there tends to be redundant instrumentation to prevent an errant signal from kicking in the SIS.

	==References==		==References==

Kathleenzhou: /* Safety and Process Control */

2016-02-21T04:38:58Z

Safety and Process Control

← Older revision		Revision as of 04:38, 21 February 2016
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	==Safety and Process Control==		==Process Safety and Process Control==

			One way of looking at process safety is a “layers of protection” model. Ideally, any issues or deviations from the norm are handled at the lowest layer possible for safe operation of the process. These layers are described here in the [https://processdesign.mccormick.northwestern.edu/index.php/Process_safety#Layers_of_Plant_Safety Process Safety page]

	===Interlocks===		===Interlocks===

Kathleenzhou: /* Safety and Process Control */

2016-02-21T04:37:00Z

Safety and Process Control

← Older revision		Revision as of 04:37, 21 February 2016
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	====Alarms and Safety Trips====		====Alarms and Safety Trips====
	Alarms are intended to alert operators to deviations in process conditions that have the potential to severely impact product quality or safety. Alarms can create audio or visual cues to alert the operator to the situation. Alternatively, sometimes, alarm systems are programmed as automatic trip systems that do not need operator input, especially in situations where lack of response from the operator could lead to serious issues. An automatic trip system is composed of a sensor, some link that transfers the signal from the sensor to an actuator, and an actuator to perform the desired action.		Alarms are intended to alert operators to deviations in process conditions that have the potential to severely impact product quality or safety. Alarms can create audio or visual cues to alert the operator to the situation. Alternatively, sometimes, alarm systems are programmed as automatic trip systems that do not need operator input, especially in situations where lack of response from the operator could lead to serious issues. An automatic trip system is composed of a sensor, some link that transfers the signal from the sensor to an actuator, and an actuator to perform the desired action.

			[[File: KZ_SafetyLayers.PNG]]

	==References==		==References==