PROJECTEnquire ↗Technical glossary
Concise explanations to help specify equipment, measurement, documentation and acceptance requirements. The actual scope and parameters are determined by the project conditions.
DN is a standardised size designation for a piping component, consisting of the letters DN and a number. That number is not an exact inside or outside diameter in millimetres. Actual dimensions depend on the product standard, material and wall thickness; connection details must also match.
Specify the dimensional standard, wall thickness and required connection alongside DN.
PN identifies a standardised pressure designation for piping components. Its number does not establish the permitted operating pressure at every temperature. Applicable limits depend on material, construction, the relevant standard and the product pressure–temperature rating; seals and connected components can impose additional restrictions.
State operating and design pressures, temperatures and fluid so the complete assembly can be checked.
Kv and Cv describe a valve’s flow capacity under defined reference conditions, using different unit conventions. Their numerical values are therefore not interchangeable. The required coefficient depends on fluid properties, flow and pressure conditions; a rated coefficient alone does not describe performance across the full control range.
Provide minimum, normal and maximum flow together with upstream and downstream pressures for valve sizing.
Absolute pressure uses an ideal vacuum as its reference rather than the surrounding atmosphere. This reference matters when describing vacuum conditions or calculating gas properties. The same numerical value of absolute and gauge pressure represents different physical conditions, so the pressure reference must always be clearly identified.
Identify absolute pressure explicitly for each range and preserve that designation in the control system.
Gauge pressure describes pressure relative to a reference, normally the surrounding atmosphere in a vented sensor. Positive values indicate pressure above that reference and negative values indicate pressure below it. A sealed-reference instrument behaves differently and must be assessed against the manufacturer’s specification.
State the positive or negative gauge range and the required pressure reference arrangement.
Differential pressure is the pressure difference between two measurement points. It can indicate filter loading, support flow measurement across a primary element or measure level. A small difference may occur within a highly pressurised system, so differential range and permitted static pressure require separate consideration.
Specify the differential range, pressure on both sides and possible one-sided overload during operating changes.
An analogue current loop represents a measured quantity as electrical current. With conventional linear scaling, 4 mA corresponds to the lower range value and 20 mA to the upper value. The live zero helps identify certain faults, but actual fault signalling depends on instrument configuration and receiving equipment.
Specify the measurement range, loop power arrangement, input type and required fault response.
HART enables digital communication with field instruments. In conventional HART over a current loop, digital data supplements the 4–20 mA signal with parameters, diagnostics and additional values. Access to that information also depends on compatible input cards, communication devices and instrument management tools.
State whether the project needs only the current signal or also remote HART configuration and ongoing diagnostics.
An RTD measures temperature through changes in the electrical resistance of its sensing element; a platinum Pt100 is a common example. Lead wiring, measuring current, probe construction and contact with the process influence the result. The element designation alone does not establish the installed system’s accuracy or response time.
Specify range, required uncertainty, cable length, wiring arrangement and the required measurement response.
In TDR level measurement, an electromagnetic pulse travels along a probe and is partly reflected by the medium’s surface. The instrument derives distance from the return time. Probe selection and signal evaluation depend on medium properties, deposits, vessel geometry and whether level or interface measurement is required.
Describe the medium, possible deposits, vessel internals and any requirement to measure an interface.
A P&ID shows functional relationships between equipment, piping, valves and instrumentation using symbols and identifiers. It aligns process, control and operating requirements. It is not a dimensionally accurate layout: lengths, installation positions and access clearances belong in other documents, which should use consistent equipment identifiers.
Provide the current P&ID revision and identify both the supply boundaries and requested changes.
I/O identifies the interfaces through which a control system receives information and sends commands. These include digital or analogue channels and data carried over industrial networks. A point count alone is insufficient: each signal needs an assigned function, electrical characteristics, address, diagnostics and any special requirements.
Provide a signal list covering type, location, function and the required allowance for future expansion.
A PLC is an industrial controller that evaluates inputs and operates machine or process outputs according to a program. Its behaviour depends on software, hardware configuration and connected communications. Ordinary process control and safety functions have different requirements and must be explicitly distinguished during design.
Identify the existing platform, required functions, interfaces, access to the source program and the scope of changes.
An HMI gives operators access to equipment status, permitted commands, settings and messages. It may be a local panel or a software application. A clear screen does not itself define control logic or user permissions; those relationships must be designed together with alarms, operating modes and fault responses.
Describe operator roles, required languages, operating modes and the information needed during normal operation and faults.
SCADA supports supervision of a plant through data collection, visualisation, alarms and usually historical records. It brings together information from controllers and measurement points. Archiving, remote access and control functions are designed for the operation; the label SCADA does not establish a particular availability or security level.
Define the areas monitored, required history, user roles, integrations and rules for remote access.
A FAT checks agreed equipment or system characteristics before dispatch, usually at the supplier’s premises. Testing follows an approved plan and acceptance criteria, sometimes using simulated signals or operating conditions. The report records results, deviations and outstanding items; its meaning is limited to the scope actually tested.
Agree the functions tested, acceptance criteria, customer attendance and the process for closing deviations before ordering.
A SAT checks agreed characteristics of a supplied system after installation at its place of use. It can cover connections, communications, functions and interfaces with surrounding equipment under available conditions. Its scope follows the project acceptance plan; a successful FAT does not automatically verify the installed system’s local interfaces.
Define site readiness, available utilities, participants’ responsibilities and the conditions for accepting the installed supply.
A WPS describes how a weld is to be made, including essential conditions such as process, materials, joint preparation and welding parameters. It provides working instructions for repeatable execution. Its applicability depends on the procedure’s scope and qualification route; it does not itself qualify an individual welder.
Specify materials, thicknesses, joint types, required quality and the rules governing the welding work.
A WPQR records trial welding conditions and the inspection and test results used to demonstrate a procedure’s capability within a defined range. It supports a corresponding WPS. Applicable rules determine the qualification range; a successful test on one joint does not qualify every material or thickness.
Link procedure qualification requirements to the actual materials, thickness ranges, processes and construction rules.
NDT comprises methods used to examine selected properties or discontinuities in materials and joints without making them unfit for further use. Examples include visual, penetrant, magnetic particle, ultrasonic and radiographic examination. Each method has its own sensitivity and limitations; no indication is not universal proof of defect-free material.
Define the areas examined, relevant discontinuity types, examination extent and project acceptance criteria.
An EN 10204 Type 3.1 document states the manufacturer’s conformity with the order and reports results of specific inspection. An authorised manufacturer’s representative, independent of the manufacturing department, validates it. This is not automatically third-party certification, and the document must be traceably connected to the material or product supplied.
State the document type, material standard, required tests and delivery identification method in the purchase order.
Calibration establishes, under stated conditions, a relationship between reference values and instrument indications, including their associated uncertainties. It enables interpretation of a measurement result. Calibration does not itself adjust an instrument or automatically establish suitability for a particular process; any adjustment and subsequent verification must be distinguished clearly.
Specify the range, calibration points, required uncertainty and whether results are needed before and after any adjustment.
Metrological traceability is a property of a measurement result that can be related to a stated reference through a documented, unbroken chain of calibrations, each contributing uncertainty. It is more than an instrument label. A traceable result may still have uncertainty too large for the intended decision or tolerance.
Request evidence of the reference and uncertainty sufficient to assess the result against its intended use.
WLL identifies the maximum working load assigned to lifting equipment under stated conditions of use. It must not be confused with breaking load or proof load. Usable capacity depends on the particular equipment, lifting arrangement, sling angles, temperature and other conditions specified by its manufacturer.
Provide the load mass and centre of gravity, lifting points and the intended handling arrangement.
Cavitation occurs when local pressure in a flowing liquid falls below its vapour pressure and the resulting vapour bubbles collapse as pressure recovers. In a valve, it can cause noise, vibration and surface damage. Risk depends on the liquid, temperature, pressure conditions and flow path design.
Provide operating temperature, upstream and downstream pressures and the full flow range for assessment.
Flashing occurs when a liquid experiences a pressure reduction that leaves a persistent vapour phase downstream of a restriction. Unlike cavitation, pressure does not recover sufficiently for the vapour to collapse. The resulting two-phase flow can substantially change velocities, capacity and erosion exposure in the valve and downstream piping.
Specify fluid composition, temperature and downstream pressure so the design can assess possible two-phase flow.
A thermowell provides a mechanical and pressure barrier between a temperature sensor and the process. Its dimensions, material and mounting affect strength and measurement response. Flow can induce vibration, so the design may require assessment of mechanical loading and vortex excitation as well as the temperature range.
Provide fluid, flow velocity, pressure, temperature, pipe dimensions and the required insertion length.
Measurement uncertainty characterises the spread of values attributable to a measured quantity using the available information. It is not the same as measurement error or display resolution. Contributions can arise from the instrument, method and conditions; comparison with a tolerance requires understanding how uncertainty was evaluated and expressed.
Specify the requirement for the complete measurement result and the decision rule used when comparing it with a tolerance.
Your next project
Send your drawings, operating parameters or a short description of the change you need. We will review the technical interfaces and propose the next steps towards a quotation, clarifying any missing information with you.
Discuss your requirements ↗Prepare a technical brief →+420 731 771 147info@emkoproject.cz