https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&feed=atom&action=history
Process controls - Revision history
2024-03-28T21:51:03Z
Revision history for this page on the wiki
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https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4626&oldid=prev
Kathleenzhou at 23:14, 21 February 2016
2016-02-21T23:14:15Z
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Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4624&oldid=prev
Kathleenzhou: /* Sensors By Measured Variable */
2016-02-21T23:12:48Z
<p><span dir="auto"><span class="autocomment">Sensors By Measured Variable</span></span></p>
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Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4614&oldid=prev
Kathleenzhou: /* References */
2016-02-21T23:00:50Z
<p><span dir="auto"><span class="autocomment">References</span></span></p>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4598&oldid=prev
Kathleenzhou: /* Process Safety and Process Control */
2016-02-21T22:30:33Z
<p><span dir="auto"><span class="autocomment">Process Safety and Process Control</span></span></p>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>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. </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>One way of looking at process safety is a “layers of protection” model.<ins style="font-weight: bold; text-decoration: none;"><sup> [4] </sup></ins> 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. </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File: KZ_SafetyLayers.PNG|400px|thumb|right|Layers of process safety pictured <sup> [<ins style="font-weight: bold; text-decoration: none;">4</ins>] </sup>]]</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Process Interlocks===</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Process Interlocks===</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>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. </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>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. <ins style="font-weight: bold; text-decoration: none;"><sup> [4] </sup></ins></div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Alarms and Safety Trips====</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Alarms and Safety Trips====</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>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.<ins style="font-weight: bold; text-decoration: none;"><sup> [4] </sup></ins></div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[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> [<del style="font-weight: bold; text-decoration: none;">5</del>] </sup>]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[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> [<ins style="font-weight: bold; text-decoration: none;">4</ins>] </sup>]]</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Safety Instrument System (SIS)====</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Safety Instrument System (SIS)====</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>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.<ins style="font-weight: bold; text-decoration: none;"><sup> [4] </sup></ins></div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
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Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4597&oldid=prev
Kathleenzhou: /* Case Study */
2016-02-21T22:29:12Z
<p><span dir="auto"><span class="autocomment">Case Study</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 17:29, 21 February 2016</td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Let us examine the following case of a <del style="font-weight: bold; text-decoration: none;">level-controlled</del> <del style="font-weight: bold; text-decoration: none;">surge</del> <del style="font-weight: bold; text-decoration: none;">tank</del> <del style="font-weight: bold; text-decoration: none;">with</del> <del style="font-weight: bold; text-decoration: none;">water</del> <del style="font-weight: bold; text-decoration: none;">flowing</del> <del style="font-weight: bold; text-decoration: none;">in</del> and <del style="font-weight: bold; text-decoration: none;">out</del>:</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_2_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_4_0_rhs"></a>[[File:<ins style="font-weight: bold; text-decoration: none;">Mixer</ins>.PNG]]</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-left" title="Paragraph was moved. Click to jump to new location." href="#movedpara_8_0_rhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_5_0_lhs"></a>#Specify control objectives - Maintain h at set point h<sub>sp</sub></div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-left" title="Paragraph was moved. Click to jump to new location." href="#movedpara_10_0_rhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_7_0_lhs"></a>#Identify input variables in the system - F<sub>1</sub>,F<sub>2</sub> are input variables (variables that impact the process)</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_5_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_8_0_rhs"></a>#Specify control objectives - Maintain h at set point h<sub><ins style="font-weight: bold; text-decoration: none;">sp</sub>, maintain c<sub>3A</sub> at set point c<sub>3-</ins>sp</sub></div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_9_0_lhs"></a>#Identify output variables in the system - h <del style="font-weight: bold; text-decoration: none;">is</del> <del style="font-weight: bold; text-decoration: none;">an</del> output <del style="font-weight: bold; text-decoration: none;">variable</del> (a variable that is measured which we desire to control)</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_10_0_rhs"></a>#Identify input variables in the system - F<sub>1</sub>,F<sub>2<ins style="font-weight: bold; text-decoration: none;"></sub>, and F<sub>3</ins></sub> are input variables (variables that impact the process)</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_9_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_10_1_rhs"></a>#Identify output variables in the system - h <ins style="font-weight: bold; text-decoration: none;">and</ins> <ins style="font-weight: bold; text-decoration: none;">c<sub>3A</sub>are</ins> output <ins style="font-weight: bold; text-decoration: none;">variables</ins> (a variable that is measured which we desire to control)</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Identify any constraints for the system </div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#*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</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>#*Soft constraint:<del style="font-weight: bold; text-decoration: none;"> 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</del> c<sub><del style="font-weight: bold; text-decoration: none;">2</del></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<del style="font-weight: bold; text-decoration: none;">.</del> </div></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#*Soft constraint: c<sub><ins style="font-weight: bold; text-decoration: none;">3A</ins></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 </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>#Specify operating mode - In this case, this is a continuous operation</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#Specify operating mode - In this case, this is a continuous<ins style="font-weight: bold; text-decoration: none;">, not batch,</ins> operation</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Identify safety, environmental, or economic needs </div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Identify safety, environmental, or economic needs </div></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#*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</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#*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</div></td>
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</table>
Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4412&oldid=prev
Kathleenzhou: /* Formulating a Control Strategy */
2016-02-21T07:35:24Z
<p><span dir="auto"><span class="autocomment">Formulating a Control Strategy</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 02:35, 21 February 2016</td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>===Considerations===</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>There are a number of <del style="font-weight: bold; text-decoration: none;">steps</del> that should be taken <del style="font-weight: bold; text-decoration: none;">in</del> formulating a control strategy. These include <sup> [4] </sup>:</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>There are a number of <ins style="font-weight: bold; text-decoration: none;">considerations</ins> that should be taken <ins style="font-weight: bold; text-decoration: none;">into account when</ins> formulating a control strategy. These include <sup> [4] </sup>:</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Specify control objectives - For example, maintaining a process variable at a setpoint</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Specify control objectives - For example, maintaining a process variable at a setpoint</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Specify operating mode as batch or continuous</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Specify operating mode as batch or continuous</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Identify safety, environmental, or economic needs</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#Identify safety, environmental, or economic needs</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>===Case Study===</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Let us examine the following case of a level-controlled surge tank with water flowing in and out:</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File: SurgeTank.PNG]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#Specify control objectives - Maintain h at set point h<sub>sp</sub></div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#Identify input variables in the system - F<sub>1</sub>,F<sub>2</sub> are input variables (variables that impact the process)</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#Identify output variables in the system - h is an output variable (a variable that is measured which we desire to control)</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#Identify any constraints for the system </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#*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</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#*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. </div></td>
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<td colspan="2" class="diff-empty diff-side-deleted"></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#Specify operating mode - In this case, this is a continuous operation</div></td>
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<td colspan="2" class="diff-empty diff-side-deleted"></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#Identify safety, environmental, or economic needs </div></td>
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<td colspan="2" class="diff-empty diff-side-deleted"></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#*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</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Instrumentation==</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Instrumentation==</div></td>
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Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4374&oldid=prev
Kathleenzhou: /* Process Safety and Process Control */
2016-02-21T05:01:19Z
<p><span dir="auto"><span class="autocomment">Process Safety and Process Control</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 00:01, 21 February 2016</td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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. </div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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. </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[File: KZ_SafetyLayers.PNG]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File: KZ_SafetyLayers.PNG<ins style="font-weight: bold; text-decoration: none;">|400px|thumb|right|Layers of process safety pictured <sup> [5] </sup></ins>]]</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[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>]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[File: AlarmBlockDiagram.PNG]]</div></td>
<td colspan="2" class="diff-empty diff-side-added"></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Safety Instrument System (SIS)====</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Safety Instrument System (SIS)====</div></td>
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</table>
Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4373&oldid=prev
Kathleenzhou: /* Process Safety and Process Control */
2016-02-21T04:43:38Z
<p><span dir="auto"><span class="autocomment">Process Safety and Process Control</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 23:43, 20 February 2016</td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Process Safety and Process Control==</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Process Safety and Process Control==</div></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker" data-marker="−"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>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] </div></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>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]<ins style="font-weight: bold; text-decoration: none;">.</ins> <ins style="font-weight: bold; text-decoration: none;">The role controls play in process safety is of particular note.</ins> </div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File: KZ_SafetyLayers.PNG]]</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-left" title="Paragraph was moved. Click to jump to new location." href="#movedpara_7_1_rhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_4_0_lhs"></a>===Interlocks===</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-left" title="Paragraph was moved. Click to jump to new location." href="#movedpara_7_2_rhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_6_0_lhs"></a>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. </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_4_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_7_1_rhs"></a>===<ins style="font-weight: bold; text-decoration: none;">Process </ins>Interlocks===</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_6_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_7_2_rhs"></a>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. <ins style="font-weight: bold; text-decoration: none;"> 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.</ins> </div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Alarms and Safety Trips====</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Alarms and Safety Trips====</div></td>
</tr>
<tr>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[File: <del style="font-weight: bold; text-decoration: none;">KZ_SafetyLayers</del>.PNG]]</div></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File: <ins style="font-weight: bold; text-decoration: none;">AlarmBlockDiagram</ins>.PNG]]</div></td>
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<td colspan="2" class="diff-empty diff-side-deleted"></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td colspan="2" class="diff-empty diff-side-deleted"></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>====Safety Instrument System (SIS)====</div></td>
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<tr>
<td colspan="2" class="diff-empty diff-side-deleted"></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
</tr>
</table>
Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4371&oldid=prev
Kathleenzhou: /* Safety and Process Control */
2016-02-21T04:38:58Z
<p><span dir="auto"><span class="autocomment">Safety and Process Control</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 23:38, 20 February 2016</td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>==Safety and Process Control==</div></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==<ins style="font-weight: bold; text-decoration: none;">Process </ins>Safety and Process Control==</div></td>
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<td colspan="2" class="diff-empty diff-side-deleted"></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>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] </div></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Interlocks===</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Interlocks===</div></td>
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</table>
Kathleenzhou
https://processdesign.mccormick.northwestern.edu/index.php?title=Process_controls&diff=4370&oldid=prev
Kathleenzhou: /* Safety and Process Control */
2016-02-21T04:37:00Z
<p><span dir="auto"><span class="autocomment">Safety and Process Control</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 23:37, 20 February 2016</td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====Alarms and Safety Trips====</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
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Kathleenzhou