Metrological assurance for metrology laboratories
We are hands-on metrology engineers. Our approach comes from more than 45 years of custody transfer metering practice: crude oil, petroleum products and gas. We bring together processes, documents and evidence of competence so that your laboratory passes external assessments with confidence and works without time pressure.
Experience with complex facilities lets our engineers work through the technological process beyond oil and gas as well: control and automation systems, energy and other industries. We write algorithms and develop methods, calibration and verification protocols.
We support ISO/IEC 17025 accreditation and scope extension, prepare methods, uncertainty budgets, protocols and traceability routes end-to-end. Metrological accuracy and the legal integrity of documents go together in every solution.
Discuss your taskGas, biogas and biomethane: support for laboratories
Biogas and biomethane measurement stations are being built across the region, and many of them are new for the laboratories that verify them. At the core of each station is a biogas quantity and quality metering system (BQMS): flow, pressure and temperature measurement, gas composition and the flow computer that brings the results together.
To verify such a system, a laboratory needs an approved verification method and specialists who can defend it and apply it on site. This is where we work.
Seminars on biogas metering systems
Structure of biogas and biomethane measurement stations, the metering system inside them and its metrological assurance: the measurement chain, sources of uncertainty and what the verification must confirm. For laboratory engineers and verifiers.
Verification methods and their defence before LATAK
We draft the verification method for a specific metering system or work through the laboratory's own draft, and prepare the technical arguments for the approval discussion with LATAK, the Latvian National Accreditation Bureau.
Audit and review of methods
Independent review of existing methods: scope, measurement chain, uncertainty budget, acceptance criteria and consistency with the standards in force. The result is a written review with recommendations.
Verifier programme
A step-by-step programme for the state verifier or laboratory representative: what to check in the documentation, the configuration and algorithms, and on site during system verification. The verifier leads the verification rather than observing it.
Extending the scope to new measurement types
New measurement types for the laboratory's scope of accreditation: methods, records and evidence of competence, prepared as one package.
Our basis: custody transfer metering practice
The discipline we apply to metering systems for crude oil and petroleum products works in any laboratory. Our practice is documented in the EM Technical Guide series.
- Accuracy and reproducibility
- Full traceability
- Legally sound documents
- Due-date control
- Trained staff
ISO/IEC 17025 accreditation and scope extension
- Electronic working protocols for calibration and verification of measuring equipment.
- Error and uncertainty evaluation with a properly allocated budget.
- Traceability matrix: references, certificates, recall schedules, statuses.
- Staff training: accuracy versus uncertainty, rounding, presentation of results.
- Mock assessment: checklists, record tracing, corrective actions.
Methods and uncertainty budgets
- Applied methods and live uncertainty budgets for temperature, pressure, density, level, volume and flow.
- Measurement method with scope and acceptance criteria.
- Excel templates for error and uncertainty calculation, with explanations and examples, on request.
- Tip-sheet on typical pitfalls: coverage factor, accuracy versus uncertainty, rounding.
- In depth: EM-14 · Accuracy methods
Calibration and verification protocols
- Complete set of conditions and corrections; repeatability and statistics.
- Correct units and rounding rules.
- Tolerance logic with a clear "conforms / does not conform" conclusion.
- Ready for LIMS and for interlaboratory comparisons.
Internal metrological audit and traceability
- Reference chains, certificate validity, calibration and verification statuses.
- Document control: procedure versions, change management, completeness of records.
- Purchasing: requirements for certified reference materials, storage and transport conditions.
- Risks and CAPA: identification, assessment, corrective and preventive actions.
How we work with a laboratory
- Seminar and taskScope, measurement types and objects of the laboratory; what needs a method, a review or training.
- ReviewExisting methods, records and traceability are reviewed, or the method starts from the task.
- Method and verifier programmeMethod draft, uncertainty budget and the programme for system verification.
- Support before LATAKPreparation for approval and assessment; answers to the assessors' technical questions.
What to send us
- Inventory of instruments, standards and methods, with designations and versions. Any rough format works.
- Current protocols and forms, client and assessor requirements.
- Ranges, points, tolerances, uncertainty requirements, schedules.
- Contact of the responsible engineer or QA.
Not everything is ready? Tell us what you have, and we help collect the missing data.
Cooperation formats
- One-off consultation: quick answers and decisions.
- Curator: from the technical specification to the completion acts.
- Method verification and validation.
- Internal metrological pre-audit before accreditation.
- Outsourced metrology under a service contract.
Service contract or framework agreement with work orders; NDA if required.
Standards for laboratories and verification methods
We work to the current editions. The edition in force is checked for every project.
Laboratory competence and uncertainty
- ISO/IEC 17025: competence of testing and calibration laboratories
- JCGM 100 (GUM): expression of uncertainty in measurement
- JCGM 200 (VIM): international vocabulary of metrology
- ISO 5725 series: accuracy (trueness and precision) of measurement methods and results
- ISO 10012: measurement management systems
- ISO 17034: competence of reference material producers
- ISO/IEC 17043: proficiency testing and interlaboratory comparisons
- ILAC P10: policy on traceability of measurement results
- EA-4/02 M: evaluation of the uncertainty of measurement in calibration
- EURACHEM/CITAC QUAM: quantifying uncertainty in analytical measurement
- Documents of the national accreditation body (LATAK in Latvia)
Liquids, gas and biomethane
- OIML R 117: dynamic measuring systems for liquids other than water
- OIML R 137: gas meters
- OIML R 140: measuring systems for gaseous fuel
- EN 1776: gas infrastructure, gas measuring systems, functional requirements
- ISO 6976: natural gas, calculation of calorific values, density and Wobbe index from composition
- EN 16723-1: specifications for biomethane for injection in the natural gas network
Frequently asked questions
1. What is the difference between error and uncertainty?
Correct answer
Error is the deviation of a measuring instrument's indication from the value of the reference standard. Its permissible limits (MPE) are set by OIML R 117 for liquids and by OIML R 137 and R 140 for gas.
Uncertainty is a parameter that characterizes the dispersion of the values that could reasonably be attributed to the measurand (GUM, JCGM 100).
They differ in how the confidence level is evaluated. For uncertainty: k = 2 at a probability of 95 %. For error: for the random component, the Student coefficient; for the non-excluded systematic component, k = 1.1 as established by the method.
2. Can the uncertainty of a metering system be larger than its error?
Correct answer
Yes, if we are talking about the actual error.
3. What are the K-factor and MF (meter factor)? Where are they set and how are they determined?
Correct answer
The K-factor is an instrument coefficient: the ratio of the output signal to the value of the physical quantity, for example pulses/m³, mA/°C, mA/bar. It is set in the measuring instrument at the factory or based on calibration results.
MF is the ratio of the reference instrument's reading to the working instrument's reading: M₀/Mᵢ, V₀/Vᵢ. It is no longer an instrument coefficient. It is obtained from calibration or verification results and shows how closely the working instrument's readings can be brought to the reference.
4. May commission members ask questions or talk to each other during measurements?
Correct answer
No. This is stipulated in the maintenance contract for the system and in the work plan for the measurements.
5. What should commission members do if they find deviations or violations during measurements? Can the measurements be stopped?
Correct answer
Yes, if critical deviations are found. The party that stops the measurements must present its arguments in writing. If the arguments are not substantiated, responsibility lies with the party that failed to provide substantiated arguments. This rule is especially important when the commission is not impartial.
6. What if, before verification, the measuring instrument has no nameplate and is not identified?
Correct answer
Do not start the verification until the instrument is identified.
7. May the software of controllers and flow computers be changed after verification, or boards replaced in a controller? How can this be checked?
Correct answer
No. This is checked by the checksum.
More detail in the modules EM-21 “Metering System Verification”, EM-11 “Error & Uncertainty” and EM-13 “Verification Protocols”: module catalog.
Abbreviations on this page
Standards and bodies
- ISO/IEC 17025 — competence of testing and calibration laboratories
- LATAK — Latvian National Accreditation Bureau
- EA / EA MLA — European co-operation for Accreditation / Multilateral Agreement on mutual recognition
- ILAC / ILAC MRA — International Laboratory Accreditation Cooperation / Mutual Recognition Arrangement
- OIML — International Organization of Legal Metrology
- JCGM — Joint Committee for Guides in Metrology
- GUM — Guide to the expression of uncertainty in measurement (JCGM 100)
- VIM — International vocabulary of metrology (JCGM 200)
Systems, errors and uncertainty
- BQMS — biogas quantity and quality metering system
- MPE — maximum permissible error
- u, uc, U, k — standard uncertainty, combined standard uncertainty, expanded uncertainty, coverage factor
Laboratory quality
- CRM — certified reference material
- PT / ILC — proficiency testing / interlaboratory comparison
- CAPA — corrective and preventive actions
- QA — quality assurance
- LIMS — laboratory information management system
All terms are explained in the free EM-20 Glossary.
EM-8 · Laboratories
The methods on this page are collected in module EM-8 of the EM Technical Guide series. For laboratory managers and quality managers: planning verification and calibration, control of standards and methods, evaluation of uncertainty and traceability of measurement channels, and preparing laboratory results and protocols for internal and external audit.
Public Professional Edition
PDF module, companion glossary and EM catalog. Download right after payment.
NDA Expert Edition
Extended expert edition. On request and after signing an NDA.
Module in development. It can be ordered out of turn, and a set of modules can be ordered for your project: contact us.
Shop page — coming soonRelated modules: EM-11 · EM-12 · EM-13 · EM-14 · EM-21 — module catalog.
Contact
Describe your measurements and your task, and we will propose a plan.
Discuss your taskOr write to info@prometer.pro