Safety instrumented systems, SIL/SIF, ESD, HAZOP/LOPA, interlocks, and relief systems. 79 terms in this topic - each defined in plain English on its own page.
Safety instrumented systems, SIL/SIF, ESD, HAZOP/LOPA, interlocks, and relief systems.
How the one-out-of-two architecture lets either channel trip the process, favoring safety over spurious trips.
Read → GlossaryThe precision resistor that converts a 4-20 mA loop to 1-5 V and gives HART the loop resistance it needs.
Read → GlossaryThe two-channel scheme where both must agree to trip, minimizing spurious trips at the cost of safety availability.
Read → GlossaryHow two-out-of-three majority voting balances safe trips against spurious trips in high-availability SIS design.
Read → GlossaryMachinery trip using alert and danger setpoints, channel voting, and startup trip-multiply, feeding the unit shutdown.
Read → GlossaryDual thrust probes watch rotor float against the bearing with alert and danger setpoints and a highly protective trip.
Read → GlossaryThe absorbance-equals-concentration-times-path-times-absorptivity law behind NDIR, TDLAS and UV analyzers.
Read → GlossaryThresholding an image and measuring connected regions by area, count, and shape to count parts and catch defects.
Read → GlossaryThe barrier model with a top event at the center, threats and prevention barriers left, consequences and mitigation right.
Read → GlossaryThe mandated backflow chain and injection-to-irrigation interlock that a controller enforces and logs for compliance.
Read → GlossaryThe ignition, occupancy, and time-at-risk factors that scale a LOPA scenario, and how they differ from protection layers.
Read → GlossaryThe Arps method for forecasting production and reserves, built on clean, continuous production history.
Read → GlossaryA second pump brought on in parallel to add capacity during high inflow, versus a standby that only runs on failure.
Read → GlossaryThe safety system that brings a facility to a safe state - isolating, de-energizing, and blowing down through hierarchical shutdown levels.
Read → GlossaryRanking assets by consequence and likelihood to decide which get monitored versus run to failure.
Read → GlossaryThe layered shutdown hierarchy from unit trip to total facility shutdown, where each higher level pulls in all the lower ones.
Read → GlossaryThe cause-and-effect trip, first-out latching of the initiating cause, and the permissives required before reset.
Read → GlossaryThe fail-safe, fast-closing isolation valve that acts as the final element of an emergency shutdown, driving a process to a safe state.
Read → GlossaryThe fail-safe valve held open by a normally energized solenoid that springs shut on any loss of power or signal.
Read → GlossaryThe top-down deductive method that traces an undesired top event through AND/OR gates to its root causes.
Read → GlossaryHow to read a flat trend pen - railed low, railed high, flat at last value from comms, or forced mid-scale.
Read → GlossaryThe safety extension of FMEA that produces the failure-rate splits feeding SFF, DC, and PFD.
Read → GlossaryThe discipline, defined by IEC 61508 and 61511, of designing safety functions to detect hazards and act reliably across a full safety lifecycle.
Read → GlossaryThe formal independent judgement, at defined lifecycle stages, that a SIS meets its requirements.
Read → GlossaryA meltable plug or pressurized fire loop that trips the ESD and closes the safety valve in a fire.
Read → GlossaryThe composition and heating value report that drives energy allocation, where sampling cadence quietly governs accuracy.
Read → GlossaryRequiring two or more detectors in a zone to confirm gas before ESD or deluge, so one faulty detector cannot trip a plant.
Read → GlossaryHow No, More, Less, Reverse and the other guide words combine with parameters to generate deviations like reverse flow.
Read → GlossaryHow a P&ID is divided into study nodes with a defined design intent, and why node boundaries make or break a HAZOP.
Read → GlossaryThe team-based process hazard analysis that walks a P&ID node by node to find deviations, causes, and safeguards.
Read → GlossaryThe LSHH trip that automatically closes the inlet or stops the pump above the high alarm to prevent overfill.
Read → GlossaryIntake-mounted detectors close dampers and stop fans so a gas cloud is not pulled into a control room or analyzer house.
Read → GlossaryThe umbrella functional-safety standard for E/E/PE systems, defining SIL, the safety lifecycle, and systematic capability.
Read → GlossaryWhy partial test coverage leaves a residual PFD term that never resets and quietly erodes achieved SIL.
Read → GlossaryTrending as-found deviations across calibrations to predict when an instrument will exceed tolerance.
Read → GlossaryApplying DC with a megohmmeter to trend winding insulation health using PI, DAR, and the one-megohm rule.
Read → GlossaryThe safety and process logic that blocks or forces an action, permissives vs trips, and how interlocks relate to ESD systems.
Read → GlossaryA deliberate, time-limited, annunciated bit that inhibits a protection. A forgotten bypass is a classic incident cause.
Read → GlossaryThe U.S. safety instrumented systems standard, adopting IEC 61511 and carrying regulatory weight for SIF and SIS design.
Read → GlossaryBreaking a job into steps, identifying each step's hazards, and assigning controls before work begins.
Read → GlossaryThe total series resistance a 2-wire transmitter must drive, the max-load spec, and the 250 ohm HART resistor.
Read → GlossaryThe semi-quantitative method that counts protection layers to assign a target SIL between HAZOP and design.
Read → GlossaryAn electrochemical probe that reads a near-instantaneous corrosion rate for fast inhibitor feedback.
Read → GlossaryThe hardwired station that lets an operator force a facility shutdown independent of the logic solver.
Read → GlossaryThe M-out-of-N framework that unifies 1oo1, 2oo2, 1oo2, and 2oo3 and the trade-off behind choosing M and N.
Read → GlossaryFinding a well's operating point where inflow meets outflow to drive tubing, choke, and lift decisions.
Read → GlossaryHow stress changes resistance in silicon, giving DC response for static pressure and powering 4-20 mA transmitters.
Read → GlossaryThe relief valve that uses process pressure through a pilot to seal tighter near set point and pass high flow.
Read → GlossaryThe tank breather valve that vents overpressure and breaks vacuum - set points, emissions, and why it matters - explained.
Read → GlossarySeries stator resistors drop voltage at start then short out as the motor accelerates for a smooth closed transition.
Read → GlossaryThe OSHA PSM hazard-analysis program that HAZOP and What-If studies satisfy, with a five-year revalidation cycle.
Read → GlossaryA permissive gates the start, checked once; an interlock guards the run, checked continuously.
Read → GlossaryThe periodic full-function test that reveals dangerous undetected failures and resets a safety function's accumulated PFD.
Read → GlossaryThe fraction of dangerous failures a proof test actually catches, and how imperfect coverage inflates real PFD.
Read → GlossaryThe lab study of reservoir fluid behavior that underpins every production forecast, allocation calc, and net-oil setting.
Read → GlossaryThe self-acting spring valve that vents overpressure to protect equipment.
Read → GlossaryThe pressure above MAWP a relief device may reach while relieving, the 10, 16, and 21 percent limits, and why they drive capacity.
Read → GlossaryBuilt-up vs superimposed back pressure, how flare-header pressure shifts set pressure, and why bellows valves are used.
Read → GlossaryThe two IEC 61508:2010 methods for meeting architectural constraints, and how each drives redundancy.
Read → GlossaryThe non-reclosing single-use membrane that bursts at a set pressure and pairs with or replaces a relief valve.
Read → GlossaryThe condition a safety function drives the process to, and the de-energize vs energize-to-trip fail-safe choice.
Read → GlossaryOne sensor-to-final-element loop with its own SIL, and how it differs from the SIS it lives inside.
Read → GlossaryAn independent layer of sensors, a safety logic solver, and shutdown valves that drives a process to a safe state under IEC 61511.
Read → GlossaryA SIL 1 to SIL 4 rating that quantifies how reliable a safety function must be, defined by its probability of failure on demand.
Read → GlossaryThe analysis, realization, and operation framework that ties SRS, LOPA, verification, and proof testing together.
Read → GlossaryTwo-way emergency-shutdown link letting the vessel or terminal trip a transfer, closing the arm ESD valve and stopping pumps.
Read → GlossaryThe on/off isolation final element that closes tightly on a trip, distinct from a control valve and a fail-open blowdown valve.
Read → GlossaryThe front-end step that assigns required risk reduction to each safety function to set its target SIL from LOPA.
Read → GlossaryThe loop-level roll-up that proves a sensor, logic solver, and final element together achieve the target SIL.
Read → GlossaryThe small relief valve that protects blocked-in liquid-full lines from thermal expansion overpressure.
Read → GlossaryA measure in mg KOH/g of the acids from oil oxidation, tracked against a condemning limit.
Read → GlossaryPackage-level cause-and-effect table mapping each trip to its outputs and severity class, with run-on and first-out.
Read → GlossaryAir-sampling detection that draws air through a pipe network to catch smoke at the incipient stage in high-airflow rooms.
Read → GlossaryHow a logic solver revotes from 2oo3 to 1oo2 to 1oo1 when diagnostics find a channel fault, keeping protection available.
Read → GlossaryClassifying wear debris by size, shape, and metal to find the failing bearing, gear, or seal.
Read → GlossaryThe scenario-brainstorming PHA technique, the What-If/checklist hybrid, and when it is chosen over HAZOP.
Read → GlossaryRanking a plant's loops by impact so limited engineering time fixes the few that cause most of the variability.
Read → GlossaryHow a swapped span/zero, wrong raw range, or reversed direction produces impossible values with Good quality, and how to back-check the conversion.
Read → GlossaryA scheme where breakers signal each other for fast, selective tripping that lowers arc-flash energy.
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