{"id":371,"date":"2024-06-01T01:40:00","date_gmt":"2024-06-01T01:40:00","guid":{"rendered":"https:\/\/ehs-hub.contentstudioo.com\/?p=371"},"modified":"2025-01-11T10:27:11","modified_gmt":"2025-01-11T04:57:11","slug":"instrumentation-plant-automation","status":"publish","type":"post","link":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/2024\/06\/01\/instrumentation-plant-automation\/","title":{"rendered":"INSTRUMENTATION &PLANT AUTOMATION"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

INTRODUCTION<\/strong><\/h3>\n\n\n\n

INSTRUMENTS ARE INCORPORATED IN A PROCESS PLANTS TO<\/strong>:\u00a0 <\/p>\n\n\n\n

Measure<\/p>\n\n\n\n

Indicate<\/p>\n\n\n\n

Record<\/p>\n\n\n\n

Control<\/p>\n\n\n\n

various process parameters like temperature, pressure, flow, concentration etc\u2026rendering the smooth & safe as well operation.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Alarms<\/strong><\/h3>\n\n\n\n
\"\"<\/figure>\n\n\n\n

\u2022The fundamental purpose of alarm annunciation is to alert the operator to deviations from normal operating conditions, i.e. abnormal operating situations.<\/p>\n\n\n\n

\u2022The ultimate objective is to prevent, or at least minimize, physical and economic loss through operator intervention in response to the condition that was alarmed.<\/p>\n\n\n\n

\u2022The fundamental purpose of dynamic alarm annunciation is to alert the operator to relevant abnormal operating situations. They include situations that have a necessary or possible operator response to insure:<\/p>\n\n\n\n

\u2022Personnel and Environmental Safety,<\/p>\n\n\n\n

\u2022Equipment Integrity,<\/p>\n\n\n\n

\u2022Product Quality Control.<\/p>\n\n\n\n

\u2022Alarms should be both audible & visible.<\/p>\n\n\n\n

\u2022Some commonly found applications of alarm system are:<\/p>\n\n\n\n

\u2022Alarms for limit of operating parameters like high\/low pressure, temperature, level\u2026<\/p>\n\n\n\n

\u2022Smoke alarms<\/p>\n\n\n\n

\u2022Gas detectors<\/p>\n\n\n\n

\u2022Fire alarms<\/p>\n\n\n\n

Ultimately, alarms give warnings providing opportunity for MITIGATION & does not take actions against abnormality.<\/p>\n\n\n\n

Safety Interlocks<\/strong><\/h3>\n\n\n\n

\u2022Interlock circuits and their components should be designed to actuate the final devices (e.g. control valves) in the direction required to cause the process to fail-safe upon loss of power.<\/p>\n\n\n\n

\u2022A good principle to follow is this: “every system is to fail to its lowest energy state, or to a state away from its critical operating limit”. In other words, each process should be analyzed to determine the major source of energy for operation, e.g. steam to reboiler, exothermic (i.e. heat releasing) reaction.<\/p>\n\n\n\n

\u2022Decreasing the amount of energy reduces the risk of an equipment exceeding the design limits, or at least minimizes the potential damage if the limits are exceeded. For the reboiler example, a fail-safe design would trip the steam supply to the reboiler. In the exothermic reaction example, a fail-safe design would trip the feed to the reactor and\/or the fuel to the reactor heater.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\u2022In a manual trip, the interlock system is manually actuated from a switch or pushbutton, which may be located on a local panel in the field or in the control room. A manual trip allows an operator to trip the system independently of the interlock system in the event of a hazardous situation developing.<\/p>\n\n\n\n

\u2022An automatic trip, as the name implies, is automatically activated when a hazardous situation is detected. A common example is the de-energizing of a solenoid valve that fails a control valve to its safe position.<\/p>\n\n\n\n

BYPASSING INTERLOCKS<\/strong><\/h3>\n\n\n\n

\u2022Interlocks may sometimes required to be bypassed in case of start-up, small anticipated interruptions, faulty feedbacks from instruments.<\/p>\n\n\n\n

\u2022Bypasses may also be necessary in order to test components on-line without tripping protected equipment.<\/p>\n\n\n\n

\u2022A strict protocol<\/strong> should be followed when bypassing of interlock is attempted. Usually only authorized personnel are permitted to bypass any interlock. This can be achieved either using a key or manually operated switch. When a bypass is initiated, an alarm will be triggered.<\/p>\n\n\n\n

Safety Interlocks<\/strong><\/h3>\n\n\n\n

\u2022Safety interlock is a system of sequential operation to trip\/stop:<\/p>\n\n\n\n

\u2022Preventing overflow\/spillage of hazardous chemical<\/p>\n\n\n\n

\u2022To shut down plant safely<\/p>\n\n\n\n

\u2022To release excess pressure<\/p>\n\n\n\n

\u2022To avoid run-away reaction<\/p>\n\n\n\n

\u2022To prevent toxic release\/fire\/explosion<\/p>\n\n\n\n

\u2022To avoid reach of extreme condition leading to severe accidents\/incidents.<\/p>\n\n\n\n

DCS<\/strong><\/h3>\n\n\n\n
\"\"<\/figure>\n\n\n\n

\u2022A distributed control system<\/strong> (DCS) refers to a control system<\/a> usually of a manufacturing system<\/a>, process<\/a> or any kind of dynamic system<\/a>, in which the controller<\/a> elements are not central in location (like the brain) but are distributed throughout the system with each component sub-system controlled by one or more controllers. The entire system of controllers is connected by networks for communication and monitoring.<\/p>\n\n\n\n

\u2022DCSs are connected to sensors and actuators and use setpoint control to control the flow of material through the plant. The most common example is a setpoint control loop<\/a> consisting of a pressure sensor, controller, and control valve<\/a>. Pressure or flow measurements are transmitted to the controller, usually through the aid of a signal conditioning input\/output (I\/O) device. When the measured variable reaches a certain point, the controller instructs a valve or actuation device to open or close until the fluidic flow process reaches the desired setpoint.<\/p>\n\n\n\n

\u2022DCS’s were designed to control processes, not discrete operations.<\/p>\n\n\n\n

\u2022As such, a large number of the inputs and outputs are analog like a 4-20mA signal or 0-10V signal. These signals generally represent temperature, flow, pressure, pH, conductivity or some other process variable.<\/p>\n\n\n\n

\u2022The “distributed” part of the name is indicating that the control functions are spread out among many different hardware parts. Using one big mainframe computer to control a plant was attempted back in the ’60s but it soon became clear that one bug, hang-up, or failure could cause the whole plant to shutdown. Distributed control gives a safety margin!
<\/strong>
PLC<\/strong><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\u2022Small digital logic controller typically utilized to replace hard-wired relay.<\/p>\n\n\n\n

\u2022Especially for discrete control of manufacturing processes.<\/p>\n\n\n\n

\u2022A PLC (i.e. Programmable Logic Controller) is a device that was invented to replace the necessary sequential relay circuits for machine control. The PLC works by looking at its inputs and depending upon their state, turning on\/off its outputs. The user enters a program, usually via software, that gives the desired results.<\/p>\n\n\n\n

\u2022PLCs are installed for sequential operation i.e. interlocks system.<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

INTRODUCTION INSTRUMENTS ARE INCORPORATED IN A PROCESS PLANTS TO:\u00a0 Measure Indicate Record Control various process parameters like temperature, pressure, flow, concentration etc\u2026rendering the smooth & … <\/p>\n","protected":false},"author":2,"featured_media":400,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[129],"tags":[124,21,6,13,8,123,20,19,3],"class_list":["post-371","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-safety-blog","tag-automation","tag-gujaratsafetycouncil","tag-hse","tag-industrial-accident","tag-industrial-safety","tag-interlock","tag-pdis","tag-post-diploma-in-industrial-safety","tag-safety"],"_links":{"self":[{"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/posts\/371","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/comments?post=371"}],"version-history":[{"count":1,"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/posts\/371\/revisions"}],"predecessor-version":[{"id":379,"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/posts\/371\/revisions\/379"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/media\/400"}],"wp:attachment":[{"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/media?parent=371"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/categories?post=371"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ehs-hub.contentstudioo.com\/index.php\/wp-json\/wp\/v2\/tags?post=371"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}