Library

Every term the atlas uses and every source behind its content.

Acetylene converter (selective hydrogenation): A fixed-bed catalytic reactor that turns the traces of acetylene in the C2 cut into ethylene with hydrogen, because even parts per million of acetylene harm polymerisation catalysts. A tail-end converter sits after the deethaniser and gets hydrogen and CO added separately; a front-end converter treats the whole cracked gas before the cold section and has fewer handles.; Too much hydrogen also hydrogenates ethylene and can make the bed temperature run away, so the hydrogen-to-acetylene ratio is kept as low as the outlet specification allows.
Address space and browsing: The address space is the set of nodes — objects, variables, methods, types and the references between them — that an OPC UA server exposes. Browsing is the client walking this graph to discover what data exists, instead of needing a tag list in advance.; An edge collector browses a DCS OPC UA server from the Objects folder down to Area 200, finds 3,400 variables of the analog-input type and offers them to the engineer for selection.
Advanced process controlAPC: A software layer above the DCS that moves the setpoints of existing regulatory loops so that the plant runs closer to its constraints and economic optimum. It does not replace the DCS and is never part of the safety function.; On a crude unit, APC raises feed until the furnace firing or a column flooding limit becomes active, while it holds product cut points on target.
Advisory (open-loop) mode: The controller runs every cycle and shows its predicted moves and targets to the operator, but writes nothing to the DCS. It is used during commissioning, for operator training and where a site does not yet trust closed loop.
AI management systemAIMS: The organisation-level policies, roles, risk and impact assessments, controls and monitoring with which a company governs how it develops, provides or uses AI systems, as specified by ISO/IEC 42001. Like an ISMS it is certified for an organisation and scope, not for a single model.
Alarm flood: A burst of alarms faster than an operator can handle; ISA-18.2 treats more than 10 alarms in 10 minutes for one operator as a flood, typically during upsets and trips.; After a compressor trip, 250 alarms in five minutes bury the one alarm that tells the operator what to do first.
Anode (copper refining): A cast plate of fire-refined copper (about 99%) that is dissolved in the electrorefining cell; its impurities stay in solution or fall to the cell bottom as anode slime.
Asset model (templates and instances): A structured description of equipment as types (templates) with attributes, calculations and events, instantiated once per real unit and bound to its tags. Defining a pump template once and creating 400 pump instances is what lets analytics scale across units and sites.
Automatic gauge controlAGC: The fast Level-1 loop of a rolling mill that adjusts the hydraulic roll gap of each stand within milliseconds to keep the strip thickness on target, using the stand's roll force and an X-ray thickness gauge after the mill.
Basic oxygen furnaceBOF: A converter in which pure oxygen is blown onto liquid hot metal from the blast furnace to burn out carbon and other elements, turning it into steel without external energy.
Basic process control systemBPCS: The system — usually a DCS or PLCs — that controls the process during normal operation through loops, sequences and process interlocks. Safety standards distinguish it from the SIS, and limit how much risk reduction it can be credited with.
Breakout and breakout prediction: A breakout is a tear in the thin solid shell below a caster mould that lets liquid steel pour out, stopping the caster and damaging equipment; breakout prediction watches rows of mould thermocouples for the temperature pattern of a sticking shell and slows the caster before the shell tears.
Burn-through pointBTP: The position along a traveling grate (or sinter strand) where the heat front reaches the bottom of the bed, seen as the sharp rise in windbox gas temperature. Holding it at the right place ensures every pellet is fired without wasting fuel or overheating the grate.; If the BTP drifts towards the discharge end, the APC slows the grate or raises the firing temperatures.
Bustle gas: The hot reducing gas, rich in hydrogen and carbon monoxide, that enters a MIDREX shaft furnace through a ring-shaped pipe (the bustle) around the furnace; its temperature and quality decide how fast the pellets are reduced.
Cascade control: Two loops in series in which the outer (primary) controller sets the setpoint of the inner (secondary) controller; the fast inner loop rejects local disturbances before they reach the slow outer variable.; A column tray-temperature controller sets the setpoint of the steam-flow controller on the reboiler.
Casting sequence: A series of heats cast one after another through the same tundish without stopping the caster; planning groups heats of compatible grades into sequences, and a longer sequence means fewer restarts and less yield loss.
Catalytic reforming: A process that rearranges low-octane naphtha molecules over a platinum catalyst into high-octane aromatics and branched paraffins, releasing hydrogen. The reactions absorb heat, so heaters sit between the reactors.; Raising reactor inlet temperatures increases reformate octane but also coke on catalyst.
Certification body: An independent organisation, itself accredited by a national accreditation body, that audits and certifies against a standard — for example a product and process certification body accredited to ISO/IEC 17065 for IEC 62443 schemes such as ISASecure or the IECEE CB Scheme, or a management-system registrar for ISO 9001 and ISO/IEC 27001. A certificate is only as credible as the accreditation behind it.; AVEVA's IEC 62443-4-1 certificate was issued by exida, an ISASecure chartered laboratory accredited by ANAB under ISO/IEC 17065.
Closed-loop mode: The controller writes its MV moves to the setpoints of the DCS loops every cycle. It is switched on per MV, only when the DCS loop is in the agreed mode (for example cascade or remote setpoint), and it sheds back to the DCS on any failure.
Coil outlet temperatureCOT: The process temperature at the outlet of a furnace's radiant coil. In a cracking furnace it is the main handle on cracking severity; in a crude or vacuum heater it sets how much of the feed is vaporised.; The furnace controller raises COT by a few degrees to increase ethane conversion, at the cost of faster coking.
Coiling temperature: The temperature of hot-rolled strip as it reaches the coiler, set by laminar water cooling on the run-out table; together with the cooling path it decides the steel's microstructure and strength, so it is controlled by a model plus feedback from a pyrometer before the coiler.
Companion specification: A companion specification is a standard OPC UA information model for one kind of equipment or domain, written jointly by the OPC Foundation and an industry group, so that all vendors expose that equipment with the same structure and names. The OPC Foundation lists more than 150 of them.; Process Automation Device Information Model (PA-DIM) is a companion specification that lets any transmitter report its measured value, status and NE 107 diagnostics in the same OPC UA structure, whichever vendor made it.
Condensed mode: Running a gas-phase polymerisation reactor with part of the cycle gas cooled below its dew point, so liquid comonomer or an added inert hydrocarbon evaporates in the bed and removes much more heat than gas alone, raising reactor output.; The controller watches the dew-point margin, because liquid reaching the wrong part of the reactor can block the gas distributor plate.
Conformity assessment: Any activity that shows a product, process, service or management system meets a standard — a supplier's own declaration (first party), an audit by a customer (second party) or an independent certification (third party). Tenders and regulations say which kind they accept.; Under the EU Cyber Resilience Act most software may use the manufacturer's own conformity assessment, while products listed as important or critical follow stricter routes, up to assessment by a notified body.
Constraint: A limit the plant must respect. Hard constraints (MV high and low limits, MV rate limits) are never violated by the controller; soft constraints (most CV limits) may be violated briefly, with the violation penalised, so the problem always stays solvable.
Contextualisation: Linking raw data to what it means: which equipment a tag belongs to, which product or batch was running, which work order or lab sample relates to it, and which document describes it. Context turns a list of tag names into answers to engineering questions.
Continuous castingCCM: Solidifying liquid steel continuously in a water-cooled mould and spray zone into a strand that is cut into slabs, blooms or billets, with heats cast back-to-back in a sequence.
Continuous catalyst regenerationCCR: A reformer design in which the catalyst moves slowly down through stacked reactors, is lifted to a regenerator that burns off the coke, and returns — so the unit never stops for regeneration and can run at low pressure and high severity. Semi-regenerative units instead stop the whole unit every several months.; The CCR regenerator runs in its own vendor package; the reformer APC only moves the catalyst circulation through the lift ΔP setpoint.
Control horizon: The number of future MV moves the controller plans. It is shorter than the prediction horizon; a shorter control horizon means fewer decision variables and calmer moves.
Controlled variableCV: A process value the controller must keep at a target or inside a range, such as a product impurity, a column delta pressure or a valve opening. Most CVs in industrial MPC are range (zone) variables, not fixed setpoints.
Controller outputOP: The signal a controller sends to its final element, usually expressed as 0–100 % (for example valve opening); in manual mode the operator sets it directly.; A flow loop at 97 % output is close to saturation, so APC should not ask it for more flow.
Coordinated vulnerability disclosureCVD: The agreed process by which a supplier receives vulnerability reports from researchers, customers or national CERTs, fixes the issue and publishes an advisory at a coordinated time, so that users can patch before attackers learn the details. ISO/IEC 29147 covers the outward-facing disclosure and ISO/IEC 30111 the internal handling.
Cracked-gas compressor suction pressure: The pressure at the first stage of the cracked-gas compressor. It sets the back pressure on every cracking furnace, so holding it low improves olefin yield; it is controlled through the steam-turbine speed and must stay above atmospheric pressure even when a furnace trips, or air could be drawn into the gas.; A plant-wide production controller lowers the suction target until the compressor reaches its speed or steam limit, and only then reduces throughput.
Cracking severity: How hard a feed is cracked. For liquid feeds it is usually expressed as the propylene-to-ethylene ratio (sometimes methane-to-propylene), for gas feeds as conversion. It is set by coil outlet temperature, steam ratio and residence time and decides the product slate and the coking rate.; Lower severity on naphtha means more propylene per tonne of ethylene.
Crude assay: A laboratory characterisation of one crude oil: its true-boiling-point distillation curve and the properties (density, sulfur, metals, cold properties …) of each boiling-range cut. Planners use it to value crudes, and engineers use it to predict what the crude unit will produce.; Before a new cargo arrives, its assay is loaded into the refinery LP to decide how much of it to run and which unit targets change.
Cut point: The boiling temperature that divides two neighbouring products of a distillation column. In operation it is held through product specifications such as the 95% distillation point or the flash point, and moving it shifts barrels from one product to the other.; Raising the kerosene draw rate raises the kerosene end point and moves material from diesel into kerosene.
Cycle gas (gas-phase polymerisation): The ethylene, comonomer, hydrogen and nitrogen that a large compressor circulates up through a fluidised-bed polymerisation reactor and back through a cooler. It keeps the bed fluidised and carries away the heat of reaction, and its hydrogen and comonomer ratios, measured by GC, set the polymer grade.; A small vent stream is bled from the cycle gas so inerts and impurities do not build up.
Data catalog: A searchable inventory of every dataset, tag, model and data product with its owner, meaning, unit, quality and access rules. It answers 'does this data exist, can I trust it, and who do I ask?'.
Data diode (unidirectional gateway): A data diode is network hardware that physically allows data to flow in one direction only, usually from the control network out to the business network. Because protocols such as OPC or historian replication need two-way handshakes, unidirectional gateways run software on both sides that replicates servers or files across the one-way link. It removes the remote-attack path into the plant, at the cost of making write-back impossible through it, and is used instead of, or beside, a firewall wherever the risk justifies it — for example between Level 2 and Level 3, so that the controllers stay protected even if the operations network is compromised.; A unidirectional gateway replicates the plant historian to a copy in the enterprise network every second; analysts query the copy, and nothing can be sent back into the control network.
Data lineage: The recorded path of a value from its sources through every calculation, correction and copy to where it is used. Lineage shows which KPIs and models break when a tag is re-ranged or a formula changes.
Data product: A curated, documented dataset that a named team owns and maintains for consumers, with a contract for schema, freshness, quality and access, for example 'daily reconciled unit yields'. It treats data like a product with users, not a by-product of systems.
Data quality: How fit a value is for its use, judged on validity (status Good, Uncertain or Bad from the source), completeness (gaps), timeliness (staleness), plausibility (range, rate of change, frozen or noisy signals) and consistency with balances and other sensors.
Data quality characteristic (dimension): One measurable aspect of how fit data is for its use. ISO/IEC 25012 defines fifteen, some inherent to the data (such as accuracy, completeness, consistency, credibility and currentness) and some that depend on the system holding it (such as availability and recoverability); ISO/IEC 25024 gives the measures.; A flow meter frozen at its last value fails currentness and accuracy even though the historian shows a complete, gap-free record.
Data validation and reconciliation (DVR)DVR: A statistical method that adjusts redundant measurements, within their known uncertainties, so that mass and energy balances close, and flags instruments whose errors are too large to be random. VDI 2048 describes the method; refinery yield accounting and mining metal accounting depend on it.; Three flowmeters around a splitter disagree by 2.1 %; reconciliation spreads the difference by their uncertainties and flags the one that is drifting.
Deadband: A deadband is the minimum change a value must make before it is reported or stored again, set as an absolute amount or a percentage of the range. It cuts network traffic and storage, but a deadband set too wide hides real process movement, which hurts APC model identification and analytics.; With a 0.5 °C absolute deadband, a reactor temperature that drifts from 350.0 to 350.3 °C is not reported, but a move to 350.6 °C is.
Decoking: Taking a cracking furnace off feed and burning the coke out of its coils with a steam–air mixture. Each decoke lasts roughly half a day to two days, and the time between decokes (the run length) is a key furnace KPI.; European crackers spend on average about 3% of furnace run time decoking.
Digital twin: A virtual representation of real equipment or a process, kept in step with it at a defined frequency and fidelity, used to understand the past and present and to simulate likely futures. The data platform feeds the twin with validated, contextualised data; it is not the twin itself.
Direct reduced ironDRI: Porous solid iron made by direct reduction, typically with more than 90% of its iron in metallic form plus some carbon and the original gangue; delivered cold (CDRI), hot (HDRI) or briquetted (HBI).
Direct reductionDR: Removing the oxygen from iron ore in the solid state with a reducing gas (mainly H2 and CO from natural gas) or with coal, below the melting point; the product is DRI. The main gas-based processes are MIDREX and HYL/ENERGIRON.
Disturbance variableDV: A measured input the controller cannot move but whose effect it can predict and counteract early (feedforward), such as feed rate set by an upstream unit, ambient temperature or ore hardness.
Dynamic secondary cooling: Setting the spray water of each cooling zone below a caster mould from a real-time thermal model of the strand, instead of from tables of water against casting speed, so that the strand surface temperature stays on target when the speed changes.
Electric arc furnaceEAF: A steelmaking furnace that melts scrap, DRI and HBI with electric arcs between graphite electrodes and the charge, helped by oxygen and carbon injection; it produces steel in batches called heats.
Electrode regulation: The fast Level-1 control of an arc furnace or ladle furnace that raises and lowers each graphite electrode with hydraulic cylinders, many times a second, to hold the arc impedance or current of its phase at the setpoint chosen by the power program.
ElectrorefiningER: Purifying copper by dissolving impure anodes and plating pure copper (99.99%) on cathodes with direct current in a copper sulfate–sulfuric acid electrolyte.
Emergency depressuring: A safety function that opens a valve from a high-pressure reactor loop to the flare so the pressure falls at a set rate, slowing the reactions and cooling the beds. In a hydrocracker it is the defence against a temperature runaway and must start automatically, because a runaway can develop in minutes.; At Tosco Avon in 1997 the 100 psi/min system started automatically only on a recycle-compressor trip and the 300 psi/min system only by hand; neither was used in time, and a reactor effluent pipe ruptured from the excessive temperature.
Emergency shutdownESD: A safety function, or the safety system that performs it, that brings a unit or whole plant to a safe state, usually by isolating feeds, stopping heat input and depressurising; in process plants it is implemented in the SIS.
Equipment hierarchy (ISA-95 role-based): The tree enterprise, site, area, work centre (process cell, production unit, line, storage zone) and work unit defined by ISA-95, extended by ISA-88 down to units, equipment and control modules. It is the backbone for naming, navigation and access rights.; Company / Bandar Abbas refinery / Crude area / CDU-1 / Atmospheric column C-101.
Event frame: A named period of time with a start, an end, the assets involved and attributes, such as a batch, a heat, a grade transition, a trip or a downtime. Event frames let people search for what happened instead of scrolling through time.; Heat 26-04512 in EAF-2, 08:12 to 09:05, tap weight 148 t, energy 392 kWh/t.
FCC heat balance: The rule that an FCC's regenerator must burn exactly as much coke as the cracking needs in heat. Feed rate, riser temperature, catalyst circulation, air and regenerator temperature are therefore tightly coupled: change one and the others move.; Raising the riser outlet temperature opens the regenerated catalyst slide valve, which circulates more catalyst, makes more coke and raises the regenerator temperature — one reason the FCC suits multivariable control.
Finite impulse response modelFIR: A non-parametric model that stores the response of a CV to an MV as a list of coefficients over time. Easy to identify and the classic form inside DMC-type controllers, but it suits only stable processes and needs many parameters.
Flash smelting: Smelting in which dry concentrate is blown with oxygen-enriched air through a burner into a reaction shaft, where it burns in suspension within seconds; the heat of the burning sulfides does most of the melting, and the melt separates into matte and slag in a settler.; Both Iranian copper smelters, Sarcheshmeh and Khatoonabad, use Outotec flash smelting technology.
Fluid catalytic crackingFCC: A conversion process that breaks heavy gas oil into gasoline, LPG and light cycle oil on a powdered catalyst that flows like a fluid between a riser reactor and a regenerator, where the coke deposited on it is burned off. No hydrogen is added.; The heat released by burning coke in the regenerator supplies the heat that the cracking reactions need — the FCC heat balance.
Foamy slag: Slag in an arc furnace that is made to foam by injecting carbon and oxygen, so that gas bubbles swell it around the arcs; it shields the walls and roof from arc radiation and puts more of the arc energy into the steel.
Fractionation (distillation): Separating a liquid mixture by boiling point in a column where vapour rises and liquid falls across trays or packing; lighter components collect at the top and heavier ones at the bottom.; The crude column fractionates crude oil into naphtha, kerosene, gas oil and residue.
Froth flotation: Separation of minerals in a slurry by making the valuable ones water-repellent with reagents so that air bubbles carry them into a froth that overflows as concentrate.
Froth velocity (mass pull): The speed at which froth flows over the lip of a flotation cell, measured by a camera above the cell; it shows how much concentrate the cell is pulling and is used as a fast control variable long before an assay is available.
Gain matrix: The table of steady-state gains: how much each CV finally moves for a unit change in each MV or DV. It drives the steady-state target calculation, so wrong gains or wrong gain ratios cause wrong targets.
Gain scheduling: Switching or interpolating between several linear models, or scaling model gains, according to the operating point (throughput, grade, ore type), so a linear controller stays accurate over a wider range.
Gas blow-by: High-pressure gas breaking through a letdown valve into a low-pressure vessel when the liquid level in the high-pressure separator is lost. The low-pressure side is not designed for that pressure, so an independent low-low level trip closes the letdown path.; At Grangemouth in 1987 gas broke through into a low-pressure separator after the high-pressure separator's low-low level trip had been disconnected, and the low-pressure separator, whose relief was sized only for fire, exploded.
Grade intermix: The length of strand at a grade change in a casting sequence where the old and new steel mix; a model calculates where it lies so that those slabs can be cut out or downgraded and traced in the genealogy.
Grade transition: Moving a polymer line from one product grade (melt index, density) to another. Until the reactor contents have turned over, the product is off-grade, so the speed and accuracy of the transition decide how much low-value material is made.; A nonlinear MPC changes the hydrogen and comonomer ratios along an optimised path so the new melt index is reached sooner.
Green oil: Oligomers formed as a side reaction in acetylene hydrogenation converters. They build up on the palladium catalyst, lower its activity and selectivity, and are one reason the converter has to be regenerated.; A slow rise in the converter inlet temperature needed to hold outlet acetylene is a sign of green-oil build-up and catalyst ageing.
Heat (steelmaking batch): One batch of steel made in an EAF or BOF and carried in one ladle; the heat number is the main key for all melt-shop data and for the product's genealogy.
High-performance HMI: An approach to operator displays, formalised in the ISA-101 lifecycle, that designs screens around the operator's tasks — muted displays where colour is kept for abnormal conditions, values shown with their normal ranges and trends, and a hierarchy from overview to detail.
Historian compression (deadband and swinging door): Rules that decide which incoming values are worth storing. A deadband (exception) test drops a value that differs from the last reported one by less than a set amount; the swinging-door test keeps only the points needed to redraw the trend within a tolerance. Well-tuned compression saves storage without changing the trend; badly tuned compression destroys information for models.; A flow with a 0.5 % compression deviation may keep one value per minute in steady operation and every value during an upset.
Hot briquetted ironHBI: DRI pressed at 650 °C or more into dense pillow-shaped briquettes (at least 5 g/cm³), which re-oxidise much more slowly and can be shipped like ordinary bulk cargo.
Hydraulic gap controlHGC: The innermost position loop of a rolling stand that sets the gap between the work rolls with hydraulic cylinders; automatic gauge control and the Level-2 setup act through it.
Hydrogen-to-hydrocarbon ratioH2/HC: The moles of recycle hydrogen sent with each mole of feed through a reformer or hydroprocessing reactor. More hydrogen slows coke formation on the catalyst but costs compressor power, so the ratio is held at a minimum that protects the catalyst.; On one reformer the recycle hydrogen-to-naphtha mole ratio wandered between 6.5 and 7.5 before multivariable control held it at its target of 7.
Hydrotreating: Reacting an oil fraction with hydrogen over a catalyst to remove sulfur, nitrogen and metals and to saturate olefins. The sulfur leaves as H2S, which is captured and turned into elemental sulfur.; A diesel hydrotreater raises reactor temperature as its catalyst ages to keep product sulfur on specification.
Ill-conditioning (collinearity): When two or more CVs respond almost identically to the available MVs, the gain matrix has a high condition number and small errors demand huge MV moves. It is a property of the process and must be handled at design time and checked again every cycle for the active sub-process.; Two adjacent tray temperatures in a distillation column cannot be controlled independently.
Induration: The heat treatment that turns soft green pellets into hard fired pellets: drying, preheating, firing and cooling on a traveling grate or in a grate-kiln.
Industrial knowledge graph: A network of plant objects (equipment, tags, documents, work orders, materials, events) connected by typed relations such as 'feeds', 'is measured by' or 'was repaired by'. Unlike a tree, it can follow a stream through a process or find every sensor downstream of a valve.
Inferential (soft sensor): A calculation that estimates a quality that is measured only rarely or slowly, such as a product flash point or a pellet compression strength, from frequent process measurements, so the controller can act every cycle instead of waiting for the lab.
Information model: An information model describes what data means and how it is structured — which objects exist, their properties, units, relations and types — independently of how the bytes travel. OPC UA, IEC 61850, ISA-95, AAS and DEXPI all define information models; Modbus and plain MQTT do not.; In an OPC UA server a pump is an object of type PumpType with child variables for speed, discharge pressure and motor current, each with engineering units, instead of three unrelated tag names.
Information security management systemISMS: An organisation's policies, risk assessment, controls, audits and management reviews for protecting the confidentiality, integrity and availability of information, as required by ISO/IEC 27001. It certifies the organisation and the scope it declares, not a software product.; An ISMS scoped to "development, hosting and remote support of the Data Platform cloud service" covers the people, offices and cloud accounts behind that service.
Interlock: Logic that prevents an action or forces one when certain conditions are or are not met. Process and equipment interlocks live in the BPCS; interlocks that protect against identified hazards with a required integrity belong in the SIS.; A pump cannot be started while its suction valve is closed (BPCS interlock); a furnace trips on low-low fuel pressure (SIS function).
Interpolated versus step values: The rule for the value between two stored points. A continuous measurement such as a temperature is interpolated linearly; a discrete value such as a pump state, a setpoint or a lab result holds its last value until the next one (step). Getting this wrong makes averages and model training data silently wrong.; A lab sulfur result of 8 ppm at 10:00 is a step value; interpolating it toward the 14:00 result invents numbers nobody measured.
ISA-95 levels: The functional hierarchy of ISA-95 (IEC 62264) — Level 0 the physical process, Level 1 sensing and manipulating, Level 2 monitoring and automated control with sub-second responses, Level 3 manufacturing operations management working in days to seconds, and Level 4 business planning and logistics working in months to days.; MES and LIMS are Level 3 systems; ERP is a Level 4 system; DCS and APC perform Level 2 functions.
Kill system (polymerisation): An independent safety function that stops a polymerisation reaction within the reactor by injecting a catalyst poison, such as carbon monoxide or carbon dioxide in a gas-phase polyolefin reactor, when a runaway, loss of cooling or another emergency threatens.; After a kill, the gas is vented and fresh cocatalyst is added so the same bed can be restarted instead of emptied.
Lab bias update: Correcting an inferential with each new lab or analyzer result: the difference between lab value and the prediction at the true sample time is filtered and added as a bias, after checks for outliers and late or duplicate samples.
Ladle furnaceLF: A station where the steel in its ladle is reheated by small electric arcs while alloys are added and argon stirs the melt, to hit the exact chemistry and casting temperature.
Lakehouse: An analytical store that keeps data in open file formats such as Parquet on cheap object storage, adds table features (transactions, schema evolution, time travel) through an open table format such as Apache Iceberg or Delta Lake, and serves both SQL reporting and machine learning from the same copy.
Level 2 (metals industry)L2: In steel and aluminium plants, the process computer above basic automation (Level 1) that runs physical process models, calculates setpoints per heat, slab or coil and tracks material. It is not the same as Purdue Level 2 (supervisory HMI/SCADA); in metals, Level 3 is the MES and Level 4 the ERP.; The hot strip mill's Level 2 calculates the roll gaps and speeds of every stand before each slab arrives.
Looper: A roll on a pivoting arm between two finishing stands that lifts the strip slightly; by controlling the looper angle and torque the mill keeps the strip tension between the stands steady, so the stands neither stretch nor pile up the strip.
LP planning modelLP: A linear-programming model of the whole refinery or complex that chooses feeds, unit operating modes and product slate to maximise margin, using crude assays, unit yields and prices. Its results become monthly plans and targets for scheduling, RTO and APC.; The LP decides that a cheaper, heavier crude pays off because the FCC has spare capacity this month.
Manipulated variableMV: A handle the controller is allowed to move, almost always the setpoint of a regulatory loop in the DCS (a flow, temperature or pressure controller). If that loop is not in the right mode, the MV is unavailable and is treated as a disturbance.
MAPD (methylacetylene and propadiene)MAPD: The two C3 impurities in the cracked propylene stream that poison polypropylene catalysts. A MAPD converter hydrogenates them to propylene, aiming for a small value below a limit of a few ppm while hydrogenating as little propylene to propane as possible.; Because outlet MAPD can jump from zero to ten times its limit in minutes, one plant's MPC controls the propane rise across the bed instead and treats MAPD as a constraint.
Material genealogy: The recorded parent and child relations of material units as they are split, merged and transformed, for example pellet lot to DRI silo to EAF heat to slab to coil, together with the process conditions each unit saw. It lets process data be attached to the product that experienced it, and it is what quality release, root-cause analysis and customer claims rely on.; A customer reports cracks on coil C-88213; the genealogy leads back to slab S-4471, heat 26-04512 and the DRI silo that fed it, with the process data of each step.
Matte: The molten copper–iron sulfide produced by smelting copper concentrate, typically 50–70% copper; converters then remove its iron and sulfur.
Maturity level (IEC 62443-4-1)ML: How rigorously a supplier runs its secure development process, graded 1 to 4 — ML1 Initial (ad hoc, not documented), ML2 Managed (documented and repeatable), ML3 Practiced (followed throughout the organisation, with evidence) and ML4 Improving (measured and continuously improved). It rates the process, not the product.; A first IEC 62443-4-1 assessment of a young company typically targets ML2, because ML3 needs evidence that every practice has been followed on real releases.
Melt indexMI: The grams of molten polymer that flow through a standard capillary in ten minutes at a set temperature and load (ASTM D1238, ISO 1133). A high melt index means a low molecular weight and an easier-flowing polymer; together with density it defines a polyethylene grade.; Because the lab reports melt index only every few hours, the reactor's controller uses a soft sensor that predicts it from bed temperature and the hydrogen-to-ethylene ratio.
Metal accounting: The system that calculates how much metal entered, left and remains in a plant over each period from measured masses and assays, with known measurement uncertainty and reconciliation; the AMIRA P754 code of practice is the industry reference for doing it consistently and auditably.; Concentrator recovery reported to the board must come from the reconciled metal balance, not from the analyzer trend.
Metallization: The share of the total iron in DRI that is present as metallic iron, in percent; the main quality and efficiency figure of a DR plant.; Plants typically run between about 92% and 97% metallization depending on the needs of the melt shop.
Mine-to-mill optimisation: Treating blasting, crushing and grinding as one system, so that blast design and ore blending are chosen for the throughput and energy use of the mill rather than for the mine alone.; Finer blast fragmentation can raise SAG mill throughput, so the mine may blast harder ore more intensively.
MLOpsMLOps: The practices and tooling that take a machine-learning model from experiment to reliable production use: versioned training data, automated retraining and testing, a model registry, controlled deployment (including to the edge) and monitoring for drift. In plants, drift often comes from catalyst ageing, fouling or a new feed.
Model predictive controlMPC: The main APC algorithm. Every cycle it uses a dynamic process model to predict the controlled variables, computes a sequence of future moves for the manipulated variables that respects all limits, sends only the first move, and repeats at the next cycle.
Model-plant mismatchMPM: The gap between the model inside the controller and how the plant really behaves today, caused by revamps, catalyst ageing, fouling, new feed or retuned PID loops. Persistent mismatch degrades control and is the main trigger for re-identification.
Mould level control: The fast loop of a continuous caster that keeps the height of liquid steel in the mould constant by moving the stopper rod or slide gate that meters steel from the tundish; level swings of a few millimetres already cause surface defects.
Move suppression: A tuning weight that penalises large or frequent MV changes. Higher move suppression gives smoother, slower and more robust control; it also lowers the effective condition number of an ill-conditioned problem.
MQTT broker and topic: In MQTT, clients never talk to each other; they connect to a broker. A topic is the hierarchical, slash-separated name a message is published under, and subscribers choose topics, optionally with wildcards (+ for one level, # for all levels below). The topic tree is the de facto data model of an MQTT system, so naming it is a design decision, not a detail.; A subscriber to acme/isfahan/dri/module1/+/temperature receives the temperature of every unit in DRI module 1, but nothing from the pelletizing plant.
MQTT quality of service (QoS)QoS: MQTT defines three delivery guarantees between a client and the broker: QoS 0 at most once (fire and forget), QoS 1 at least once (acknowledged, duplicates possible) and QoS 2 exactly once (four-step handshake). The guarantee applies to each hop, not end to end, and higher QoS costs throughput.; Sparkplug publishes NDATA at QoS 0 for throughput, relying on sequence numbers and birth/death certificates to detect loss, while STATE messages use QoS 1.
Namespace: A namespace is the scheme that makes names unique and meaningful within a system — the OPC UA namespace index of a node, the topic tree of an MQTT broker, or the asset hierarchy of a historian. In a Unified Namespace the term is stretched to mean one shared naming hierarchy for the whole enterprise.; In OPC UA the node ns=3;s=Area200.FIC-101.PV belongs to namespace 3, which the server maps to its own URI; the same text in namespace 2 would be a different node.
Non-interference (with safety functions): The principle that a function without a safety claim — APC, a data platform, an AI optimiser — can never prevent, delay or corrupt a safety instrumented function, whether it works, fails or is attacked. It is achieved by independence and separation (no writes to the SIS, read-only and assessed connections, separate zones), not by testing the non-safety software to a SIL.; APC may read a trip-bypass status through the DCS to stop moving an MV, but it has no path to write anything into the SIS.
Nonlinear model predictive controlNMPC: MPC that uses a nonlinear model (first-principles, neural or hybrid) because gains and dynamics change strongly across the operating range. It is used mainly where linear MPC fails, such as polymer grade transitions, and its applications are typically smaller than linear ones.
On-stream analyzer (OSA)OSA: An analyzer, usually X-ray fluorescence, that takes samples from several slurry streams of a concentrator in turn and reports the metal content of each; because the streams share one instrument, each stream gets a new value only every few minutes.; One XRF analyzer serving 18 streams completes a full cycle in about 16 minutes, so the flotation grade controller acts on values up to that old.
OT DMZDMZ: A separate network between the plant and corporate firewalls where all OT–IT exchanges terminate — replica historian, data relay, jump servers, patch servers — so that no traffic passes directly between the corporate network and the control network.; Engineers in head office read plant trends from a historian copy in the DMZ, never from the historian in the operations zone.
OT versus ITOT: Operational technology monitors and controls physical processes; information technology handles business information. In OT the first concerns are safety, availability and the physical effects of failure, so changes are tested exhaustively, outages are planned weeks ahead and an IT habit such as rebooting a server can be unacceptable.; A security patch that can be installed on office PCs the same day may wait for the next planned shutdown on a DCS server.
Overflash (vacuum column wash bed): The liquid that runs off the bottom of a vacuum column's wash bed: wash oil sprayed onto the bed that was not evaporated again. A minimum overflash proves the bed is wet; a bed that runs dry cokes and ends the run early. It is often not metered and has to be inferred.; Raising the heater outlet temperature lifts more gas oil but evaporates more wash oil, so the vacuum unit APC raises the wash-oil flow to keep overflash above its minimum.
Oxygen coefficient: The volume of oxygen supplied per tonne of concentrate in a flash furnace; it decides how much iron and sulfur are burned and therefore the matte grade, and is the main manipulated variable of smelter control.
Pass balancing: Adjusting the feed, steam and temperature of a furnace's parallel coil passes so they all coke at the same rate and reach their tube-wall temperature limit together on the planned decoke date, instead of one hot pass forcing an early shutdown.; The furnace MPC shifts a little feed from the hotter pass B to pass A until both coil outlet temperatures match.
Pasteurisation section: The few trays at the top of a C2 splitter above the polymer-grade ethylene draw. They strip the last hydrogen and methane out of the ethylene and send them overhead to a small vent, which is why the product is drawn a few trays below the top rather than from the reflux drum.; In one documented splitter the pasteurisation section is the top 9 of 123 trays.
Payload: The payload is the content of a message, as opposed to its envelope (topic, headers, addresses). MQTT allows any payload; Sparkplug fixes it as Protocol Buffers; OPC UA PubSub uses UADP binary or JSON; many projects use their own JSON. Agreeing a payload schema — value, timestamp, quality, units — is as important as choosing the protocol.; {"v": 351.2, "t": "2026-10-08T09:15:00.250Z", "q": "good", "u": "degC"} is a minimal JSON payload that keeps value, source timestamp, quality and unit together.
Peirce-Smith converterPSC: A horizontal, rotating, brick-lined vessel that blows air through a row of tuyeres into molten matte in batches — first a slag blow that removes the iron, then a copper blow that removes the sulfur — to make blister copper.; About 70% of copper smelters still convert in Peirce-Smith converters, and their cyclic off-gas is a main coordination problem for the acid plant.
Pellet (iron ore pellet): A hard ball of about a centimetre made by rolling fine iron ore concentrate with a binder and firing it; pellets are strong and porous enough to be shipped and reduced in a shaft or blast furnace.; A DR plant needs DR-grade pellets with low silica and alumina, because all gangue ends up in the EAF slag.
PID controllerPID: The workhorse feedback algorithm of process control; it moves its output in proportion to the error between setpoint and measurement (P), to the accumulated error (I) and to the rate of change of the measurement (D).; FIC-102 is a PID loop that keeps fuel-gas flow at its setpoint by moving the fuel valve.
Polling versus report by exceptionRBE: With polling, the consumer asks the source for values at a fixed rate whether or not they changed (Modbus, classic SCADA). With report by exception, the source sends a value only when it changes beyond a deadband (OPC UA subscriptions, Sparkplug, DNP3 events). Polling is simple and predictable; report by exception saves bandwidth but needs a way to tell "no change" from "connection lost".; Sparkplug solves the "no change or connection lost?" problem with death certificates; a Modbus poller solves it by marking every value bad when a poll times out.
Power program (EAF): The schedule of transformer taps and current or voltage setpoints that an arc furnace follows through a heat; optimisation software changes it in real time from the state of the melt.
Prediction horizon: How far into the future the controller predicts the CVs, normally at least the longest time to steady state in the model, so that the full effect of every move is seen.
Process variablePV: The measured value of the quantity a loop controls, such as a temperature or flow, together with its quality status.
Production controller (plant-wide MPC): A large multivariable controller above the unit MPCs of an olefins plant. It sets the total feed and shares it among the furnaces, sets the cracked-gas and refrigeration compressor suction pressures, and moves load away from whichever unit reaches a limit, so the plant keeps its throughput; it can run alone or take its targets from the RTO.; When one furnace hits a fuel-valve limit, the production controller lowers that furnace's feed target and raises the others so total feed stays the same.
Protocol conversion: Protocol conversion is translating data from one protocol to another — Modbus to OPC UA, OPC DA to OPC UA, OPC UA to MQTT. Values usually survive; what is often lost is metadata: quality, source timestamps, engineering units, data types and the structure of the information model. Every conversion step should be checked for what it drops.; A gateway that converts Modbus registers to OPC UA must invent the timestamp (the time of the poll) and the quality (good if the poll succeeded), because Modbus carries neither.
Pumparound: A liquid stream drawn from a column, cooled in an exchanger and pumped back a few trays higher. It removes heat from the middle of the column, sets the internal liquid flow, and returns useful heat to the crude preheat train.; Increasing the top pumparound duty lets more heat be recovered into the crude but reduces the reflux above it.
Purdue model: A reference model that stacks plant systems in levels — 0 the physical process and field devices, 1 basic control, 2 supervisory control, 3 site operations, 4 and 5 business and enterprise — with an OT DMZ (often called Level 3.5) added later between Levels 3 and 4. It grew out of the Purdue Enterprise Reference Architecture of the 1990s and is used to organise network segmentation.; A firewall rule set built on the Purdue model stops a Level 4 office PC from talking directly to a Level 1 controller.
Pyrolysis gasolinepygas: The C5+ liquid a steam cracker condenses in its quench, compression and debutaniser sections. It is rich in aromatics but unstable because of its dienes and styrene, so it is hydrotreated before it is used for aromatics extraction or gasoline blending.; Naphtha cracking gives much more pyrolysis gasoline than ethane cracking.
Quality code / status code: A quality or status code travels with every value and says whether it can be trusted: good, uncertain or bad, often with a reason such as sensor failure, communication failure or out of range. OPC DA uses quality flags, OPC UA uses 32-bit StatusCodes, and fieldbuses carry a status with each value. A data platform must store and propagate quality; dropping it turns a failed transmitter into a believable flat line.; When a flow transmitter's loop breaks, the DCS marks FI-205 as Bad (sensor failure); the APC controller stops using it as a controlled variable instead of acting on a frozen value.
Quality giveaway: Product quality delivered beyond what the specification requires — extra octane, lower vapour pressure, less sulfur or a flash point further above the limit. The customer pays the same price, so every unit of giveaway is margin lost; cutting it is one of the main benefits of APC and blend control.; At Shell Deer Park an online octane analyzer feeding the reformer controller cut octane giveaway from 0.7 to 0.2 numbers.
Real-time optimisationRTO: A layer above APC that uses a rigorous steady-state model of the unit or site, usually every one to a few hours when the plant is at steady state, to compute economic targets that it hands down to the MPC controllers.
Redundancy: Duplicating critical components — controllers, power supplies, I/O, networks, servers — so that a standby takes over automatically when the primary fails; it protects against random failures, but not against common causes such as a cyber attack or a configuration error copied to both.
Reflux: Condensed overhead liquid returned to the top of a column. More reflux gives sharper separation and purer products but costs more energy in the reboiler or heater.; A C2 splitter runs at a very high reflux because ethylene and ethane boil close together.
Reformer (MIDREX): A fired heater with catalyst-filled tubes that converts a mix of recycled top gas and natural gas into hot reducing gas rich in H2 and CO for the shaft furnace.
Register map: A register map is the table in a device manual that says what each Modbus address holds — its meaning, data type, scaling, units, byte and word order, and whether it can be written. Modbus itself carries only numbered 16-bit registers, so without the register map the data is meaningless; a data platform should store register maps as reusable device templates.; A power meter's register map states that registers 3027–3028 hold active power in kW as a 32-bit float with the high word first; the same value on another meter model may sit at different addresses in a different order.
Regulatory control (base layer): The base layer of control that holds individual variables at their setpoints with PID loops and simple structures such as cascade, ratio, feed-forward and override, running every second or faster in the DCS or PLC. APC sits on this layer and only moves its setpoints, so if these loops oscillate, sit in manual or have sticky valves, APC cannot perform; auditing and tuning them is the first step of every APC project.; In a survey of about 26,000 PID loops, 36% were in open loop (manual) and only about a third performed well.
Safe park (FCC): An FCC protective state in which both catalyst slide valves close and the feed to the riser stops, so the unit holds its catalyst without cracking. Because air and hydrocarbons sit on either side of the slide valves, a low reactor-to-main-column pressure difference should shut the whole unit down rather than only park it.; The 2015 Torrance explosion happened while the FCC was in safe park: hydrocarbons flowed back through the regenerator side into the electrostatic precipitator, which exploded.
Safety integrity levelSIL: A target level, from SIL 1 to SIL 4, for how reliably a safety instrumented function must act; for low-demand functions each step is roughly ten times more risk reduction (SIL 1 about 10–100, SIL 2 about 100–1,000, SIL 3 about 1,000–10,000). Process plants rarely use SIL 4.
SAG millSAG: A large rotating mill that grinds ore mainly with the ore's own rocks plus a small charge of steel balls; its load, judged from power and bearing pressure, must be kept in a narrow band for maximum throughput.
Secure development lifecycleSDL: The set of practices a product supplier follows so that security is designed, built, tested and maintained into every release — in IEC 62443-4-1 eight practices from security management and requirements through secure design, implementation, verification, issue handling, security updates and security guidelines for users.
Security level (SL-T, SL-C, SL-A)SL: An IEC 62443 measure from 1 to 4 of how strong an attacker a zone or component must withstand — SL 1 casual or coincidental violation, SL 2 intentional violation with simple means, SL 3 with sophisticated means and IACS-specific skills, SL 4 with sophisticated means and extended resources. The asset owner sets a target level (SL-T) per zone, a product is certified for the capability level (SL-C) it can reach when configured correctly, and the level actually reached on site is the achieved level (SL-A).; A site places our edge collector in an SL-T 2 zone; the collector therefore needs an IEC 62443-4-2 SL-C of at least 2, and the site's own configuration decides whether SL-A 2 is reached.
Security support period: The period, stated by the manufacturer at sale, during which it will handle vulnerabilities and ship security updates for a product version. The EU Cyber Resilience Act requires at least five years unless the product is expected to be used for less; plant software usually stays in service much longer, so the period becomes a commercial commitment.
Semantic model / ontology: A shared, machine-readable vocabulary of the things in a plant (equipment classes, materials, measurements, units) and how they may relate. It lets two systems, or a person and an AI model, mean the same thing by 'feed flow of the hydrotreater'.
Service factor: The share of time a controller, or each of its MVs, is actually on and in closed loop. It is the first health KPI of any APC application; a controller that is off or whose limits are clamped earns nothing.; One large survey found up to 30% of MPC controllers inoperative and a similar number made ineffective by clamped limits.
SetpointSP: The desired value of a controlled variable; it can be entered by an operator, written by another controller (cascade or APC) or programmed.; APC raises the reflux-flow setpoint from 120 to 122 m³/h; the flow PID loop then moves the valve to reach it.
Setup model (rolling mill): The Level-2 model that, before each piece enters the mill, calculates the roll gaps, speeds, forces and tensions of every stand from physical models of temperature and deformation, then adapts itself by comparing its predictions with what was measured.
Shedding (fallback to DCS): The DCS-side logic that takes an MV out of APC control and returns the loop to a safe local mode, holding the last good setpoint, when the APC heartbeat stops, a write is rejected or the operator switches the loop.
Soft reduction: Squeezing a continuously cast strand slightly with the segment rolls just where its core is finishing solidifying, to reduce centre segregation and porosity; a Level-2 model calculates where that point is and sets the roll gaps.
Software bill of materialsSBOM: A machine-readable list of every component inside a software release — open-source libraries, their versions, suppliers and licences — so that a new vulnerability in any component can be traced to the affected releases within hours. ISO/IEC 5962 (SPDX) is one standard format, and the EU Cyber Resilience Act requires manufacturers to draw one up.
Solvent extraction – electrowinningSX-EW: The hydrometallurgical route in which copper leached by acid is purified and concentrated by an organic extractant (SX) and then plated as cathode with inert anodes (EW), without smelting.; SX-EW produced about 4.8 Mt of copper in 2024.
Source timestamp versus server timestamp: The source timestamp is the time the value was measured or changed at its origin; the server timestamp is the time a server (or collector) received or last refreshed it. OPC UA carries both. Analytics, sequence-of-events analysis and APC model identification need the source time; using the arrival time after a buffered backlog or a slow network distorts cause and effect.; After a 2-hour network outage an edge buffer releases its backlog; values keep their source timestamps from the outage period, while their server timestamps all show the minute they arrived.
Sparkplug birth and death certificates: A birth certificate (NBIRTH for an edge node, DBIRTH for a device) is the first Sparkplug message after connecting; it lists every metric with its name, data type, metadata and current value. A death certificate (NDEATH, DDEATH) announces that the node or device is offline; NDEATH is registered as the MQTT Will so the broker sends it even if the node dies without warning. Consumers use them to know which data is current and which is stale.; When the edge gateway of a flotation bank loses power, the broker publishes its NDEATH and the SCADA marks all 250 flotation metrics as stale within seconds.
Splitter: A distillation column that separates two components with very close boiling points, such as ethylene from ethane or propylene from propane. Splitters are tall, use high reflux and are among the largest energy users in an olefins plant.; The C2 splitter makes polymer-grade ethylene and sends ethane back to the furnaces.
Statement of applicabilitySoA: The ISO/IEC 27001 document that lists every control of the standard's Annex A, says whether it is applied, and justifies each inclusion and exclusion. Auditors and customers read it to see what a certificate really covers.
Static and dynamic BOF model: The two Level-2 models of a basic oxygen furnace: before the blow, the static model calculates hot metal, scrap, fluxes and total oxygen from mass and heat balances; near the end, the dynamic model uses the sublance measurement and off-gas analysis to calculate the remaining oxygen and coolant so that carbon and temperature are hit at the first turndown.
Steady-state target calculation (LP/QP layer): The part of the MPC that, every cycle, finds the best reachable steady-state operating point from the model gains, the limits and the economic costs, usually with a linear or quadratic program. The dynamic part then moves the plant toward that point.; With crude price high and fuel cheap, the LP prefers more furnace duty and higher distillate recovery until a temperature limit becomes active.
Steam cracking: The main route to ethylene and propylene: a saturated hydrocarbon feed mixed with steam is heated in furnace coils for a fraction of a second until its molecules break into smaller, unsaturated ones, then quenched quickly to stop further reactions.; Cracking ethane gives mostly ethylene; cracking naphtha also gives propylene, butadiene and aromatics.
Steam-to-hydrocarbon ratio (dilution steam ratio): The mass of dilution steam mixed with each unit of hydrocarbon feed before cracking. More steam lowers the hydrocarbon partial pressure, which improves olefin yield and slows coking, but costs energy; liquid feeds use up to about 0.85, ethane less.; The DCS holds the ratio on each coil by moving the dilution-steam flow, and the furnace MPC or optimiser chooses its target.
Step test (plant test): A planned experiment in which each MV is moved in steps or pseudo-random binary signals while the CVs are recorded, to learn how the plant responds. Tests can be manual, automated open-loop, or closed-loop while a controller keeps CVs inside limits.; A classical test steps each MV 8 to 15 times and takes 5 to 15 days around the clock.
Store-and-forward (buffering at the source): Store-and-forward means a collector, edge device or gateway writes data to a local buffer, usually on disk, when the link to the next tier is down, and sends it later, in time order, with the original timestamps and marked as historical (Sparkplug has an is_historical flag for this), so a network outage creates a delay rather than a permanent hole in the history. Buffer size, disk persistence and the order of replay versus live data are the design questions.; An edge collector at a remote mine crusher buffers 3 days of data on its SSD while the satellite link is down and drains the backlog at a capped rate when the link returns; the history shows no gap.
Sublance: A second, automatic lance on a basic oxygen furnace that dips a disposable probe into the bath during or at the end of the blow to measure temperature and carbon and take a sample, giving the dynamic model a real measurement to correct the rest of the blow.
Subscription and monitored item: In OPC UA a client creates a subscription with a publishing interval and adds monitored items to it, each with a sampling interval and an optional filter such as a deadband. The server samples the values and sends only the changes at each publishing interval, so the client does not have to poll.; An APC application subscribes to 120 DCS tags with a 1-second sampling interval and receives a notification only for the tags whose value or status changed in that second.
Superheat: How many degrees the liquid steel in the tundish is above its liquidus temperature, the point where it starts to solidify; it changes how fast the strand solidifies, so it is a key input of the caster's thermal models.
System identification: Building the dynamic model from test data: choosing data slices, fitting model forms (FIR, ARX, state space, transfer functions), checking gains and uncertainty, and assembling the CV × MV model matrix.
Tag (point): A tag is the identifier of an instrument, a loop or a data point. On a P&ID it follows ISA-5.1: the letters say what is measured and what the device does (TIC = temperature indicating controller) and the number names the loop. In a control system, historian or SCADA a tag is a named data item — one measured value, setpoint, output or status, each stored with its value, timestamp and quality — usually named after the instrument or loop tag, such as FIC-101.PV for the measurement and FIC-101.SP for its setpoint. Historians call it a point. Tag names are the most common key for joining data across systems, but they carry little meaning on their own.; The same feed-flow measurement is FIC-101.PV in the DCS, 21FIC101.PV in the historian and "Feed flow, crude unit" in a report — a connector must map all three.
Tap-to-tap time: The time from one tapping of a steelmaking furnace to the next, including charging, melting or blowing, refining and tapping; it sets how many heats the melt shop makes per day.
Time series: A sequence of values of one measurement, each stored with its timestamp and a quality flag, for example a temperature recorded every second. In a plant data platform every tag is a time series, and most questions are asked over a time range.; TI-101 = 352.4 °C, quality Good, at 2026-10-08 08:00:01.
Transfer-line exchangerTLE: The heat exchanger right after a cracking furnace's radiant coils. It cools the cracked gas in a few milliseconds so the secondary reactions stop, and turns the recovered heat into high-pressure steam that later drives the big compressors.; A slowly rising TLE outlet temperature shows coke building up and is one of the signals that the furnace is nearing its decoke.
Tube metal temperatureTMT: The temperature of the radiant-coil tube wall in a cracking furnace, measured with weld-on thermocouples or pyrometer surveys. Coke inside the tube insulates it, so firing must rise and the wall gets hotter over the run; when the hottest tube reaches its metallurgical limit, the furnace must be decoked.; The furnace MPC treats the highest TMT as a constraint and shifts feed between passes so no single tube reaches its limit early.
Tundish: The refractory-lined buffer vessel between the ladle and the casting mould; it keeps steel flowing while ladles are changed and lets inclusions float out.
Unified Namespace (UNS)UNS: An architecture pattern in which every system publishes its current state to one shared, hierarchically named event hub (usually an MQTT broker organised by the ISA-95 hierarchy) and every consumer subscribes there, instead of building point-to-point interfaces. A UNS carries the current state; it is not a historian.; Topic acme/bandar-abbas/crude/cdu-1/c-101/top-temperature, published as a Sparkplug B metric.
Weighted average bed temperatureWABT: The catalyst-weighted average temperature of all beds in a hydrotreater or hydrocracker. It sets the conversion or the desulfurisation, and it creeps up over the run as the catalyst loses activity, so its rate of rise tells how long the catalyst will last.; The hydrocracker's conversion controller sets a WABT target; a lower-level controller then reaches it by moving the heater outlet temperature and the quench hydrogen to each bed.
Weighted average inlet temperatureWAIT: The average of a catalytic reformer's reactor inlet temperatures, each weighted by the share of catalyst in that reactor. It is the main handle on reformate octane: a higher WAIT gives more octane but also more coke on the catalyst and less liquid yield.; When the online octane analyzer reads above target, the reformer APC lowers the heater outlet temperatures a little, which lowers WAIT and stops giving octane away.
Yield accounting: The daily calculation of what went into and came out of each unit and the whole site, from meters, tank gauges and movements, reconciled so that the mass balance closes. It is the basis for performance reporting, loss tracking and the planning model.; Yield accounting shows a 0.5% unexplained loss on the crude unit, which is traced to a drifting flow meter.
Zones and conduits: The IEC 62443 way of segmenting a control system — a zone groups assets that share the same security requirements, and a conduit is a defined communication path between zones with its own protections; only traffic that passes through a conduit is allowed.; A crude-unit control zone, a separate SIS zone and the site operations zone, connected by firewalled conduits that permit only listed protocols.