Gas Metrology Services

DESFA features a fully equipped pressure laboratory, accredited according to ELOT EN ISO / IEC 17025:2005 by the National Accreditation Organization (ESYD) SA (Certificate No. 758).
The pressure laboratory of DESFA undertakes calibrations of analog & digital instruments, on absolute & relative pressure up to 100 bar, direct reading, using air medium (digital controllers, transmitters, manometers etc.).
The laboratory has high precision standard equipment such as pressure controllers, as well as an automatic pressure balance.

The laboratory implements one of the best metering accuracies in Greece. Specifically, the calibration & measurement capability, using the pressure balance, is better than 43 ppm. Detailed information and the best calibration & measurement capability, per range of measurement, are depicted on the official Scope of Accreditation (SoA) of the laboratory and the ESYD’s website.

The laboratory is staffed by qualified and experienced personnel for calibrating & regulating equipment from various manufacturers.
On-site calibration, where the equipment is located, can also be provided.

On the certificates of calibration that are issued by DESFA’s pressure laboratory, a combined ILAC – ESYD logo is used, which provides international recognition. Certificates are both issued in Greek and English.

This service, provided by DESFA, involves the inspection of all the metering systems of a metering station – of any capacity – and includes:

• Calibration of the pressure transmitters, using a standard pneumatic pressure controller. Inspection of at least five (5) points in the scale range of the instrument is made, at an ascending and a descending pressure value sequence. Adjustment of the transmitter is performed, if necessary.
• Calibration of temperature transmitters, using a standard digital temperature instrument and a standardized type PT100 sensor. Inspection of at least three (3) points in the scale range of the instrument is made, in an ascending temperature value sequence. Adjustment of the transmitter is performed, if necessary.
• Inspection of the flow meters (ultrasonic or turbine or orifice or rotary). These inspections include, according to each case:
  • Visual inspection of the meter.
  • Diagnostic tests of the ultrasonic meter.
  • Inspection and dimensional measurements of the orifice meter.
  • Check of the pulses of the turbine meter.
  • Serial test of the meters (as long as the installation allows for it).
• Inspection of the flow computer, or flow corrector (PTZ), regarding  the default values, the reference conditions, the reference values, the alarm limits, the calculation algorithm for the compressibility factor Z, the volume and energy of gas.
• Spot test in the flow computer for calculating the volume conversion factor (CFV), the volume and energy of gas, at a given operating pressure and temperature of the metering line and comparison with a standard software of DESFA.
• Inspection of the gas chromatograph regarding the repeatability of response factors and the concentrations of the components, in successive analysis using standard gas. Inspection of the gas chromatograph’s computer system regarding the parameters for calculating the gas calorific value, the standard composition used and operating parameters. Check the transmission of composition data from the chromatograph to the flow computer. The inspections are performed using a standard gas mixture from an accredited by ISO / IEC 17025:2005 laboratory, which is provided by DESFA (as long as an appropriate gas mixture bottle is not available at the installation). After the checks, a calibration of the chromatograph can be made.

For all the aforementioned checks – verifications – calibrations a certificate is issued by DESFA, accompanied by detailed reporting of measurements and calculations.

The certificate can be issued in Greek or English.

This service is provided also during the commissioning of metering systems or during their initial verification.

DESFA SA undertakes the Uncertainty estimation of the entire metering system of gas stations. The method used is based on international standards. Initially, the uncertainties of the individual components of the metering system (pressure, temperature, flow, gas composition etc.) are identified. From the individual uncertainties, the overall uncertainty of the metering system is calculated. The calculations give a statistical estimation of the range within which the real gas volume flow rate and energy, measured at the station, is expected to be. The Uncertainty Study includes the methodology and detailed tables of calculations. The results of the study are required during the inspection of the metering systems of the gas stations. The Uncertainty Study can be written in Greek or English.

DESFA SA undertakes drafting an Operation Agreement between the parties involved at the gas delivery/reception at custody transfer metering stations. The Operation Agreement outlines the technical characteristics of the metering station and the procedures to be followed by the parties for inspection and acceptance of the gas quantity and quality measurements. The Operation Agreement text can be written in Greek or English.

DESFA SA provides consultative services for drafting Specifications and the Technical Evaluation of gas metering systems studies.

DESFA SA has a fully equipped chemical laboratory, which is accredited by the ELOT EN ISO / IEC 17025:2005, for analyzing natural gas samples. DESFA’s chemical laboratory undertakes the analysis of natural gas or LNG samples, to certify their composition and physical properties.

The analyses are performed on a laboratory chromatograph ABB NGC-8206, according to the international standard ISO 6974-1:2012.

The calculations of the natural gas physical properties are in accordance with the international standard ISO 6976:1995.

Sampling of gas for the analyses can be performed by DESFA in consultation with the concerned party.

DESFA SA undertakes the certification of gas analysis chromatographs, according to the standard ISO / IEC 10723:2012. The certification regards any type of gas chromatograph. A certificate is provided which evaluates the performance characteristics of the chromatograph and defines the errors and uncertainties of the gas composition and gas physical properties measurements (e.g. calorific value, carbon dioxide emission factor etc.).

The results of the certification are used to demonstrate the chromatograph’s capability at given gas energy accuracy requirements. The accuracy requirements may be included at gas trade agreements, tender specifications etc.

Particularly, the aforementioned chromatograph certification is necessary for the participation of large gas consumers (e.g. power producers) in the gas emissions trading system (EU / ETS).

DESFA SA undertakes to organize educational seminars in specialized topics of gas metrology (quantity and quality measurement).

The seminars are addressed to technical personnel involved in the design, equipment selection, operation and maintenance of gas metering systems, and the management of measurements.

The seminars include a theoretical and a practical part. The topics can be adapted to the specific requirements of the audience. The seminars can be organized at DESFA’s, or the clients’ premises.

Certifications:

• ACCREDITATION CERTIFICATE of the chemical analysis testing laboratory and the pressure and chemical analysis calibration laboratories.
• Scope of accreditation of the pressure and chemical analysis calibration laboratories.
• Scope of accreditation of the chemical analysis testing laboratory.