South European Pipeline Proving System – Influence on the global performance of the pipeline

SPSE owns and operates 3 pipelines starting in the South of France, 2 ending in Germany, and the third one in the center of France. The pipelines are 24", 34" and 40" in diameter. The longest line is 769km long. SPSE transports 25 Mm3/year for 5 different clients for three countries along the 40" main line. Each client has its own measurement system and tankfarm.

SPSE owns and operates a centralized flowmeter proving facility. The following text summarizes why SPSE created a flow laboratory and the results obtained with that choice. The laboratory allows also SPSE to be aware of technology progress while testing new metering systems for third parties.

TECHNICAL PERFORMANCE
SPSE receives the clients crude oil in a tankfarm in Fos sur Mer. Each Tank is equipped with a radar based
gauging system. Typically, a pipeline performance is based on the volume received by the pipeline company compared with the volume delivered to its clients. That is called Losses.

For SPSE the typical results are :

Typical loss % : 0. 0079 %.
Typical loss m3 : 2 100 m3 lost including 770m3 for Shrinkage

This means that for 1m3 received in the tankfarm, SPSE will deliver 0.999921 m3

The overall performance is also influenced by the water detection.

For comparison, an acceptable figure for pipeline systems is 0.03%. Due mainly to measurement uncertainties.

INFLUENCE OF THE METERING SYSTEM
To achieve such results a high precision metering system is necessary. SPSE could have used the tank gauging of the end client as the measurement basis. But as SPSE had different clients with different standards, quite soon in the company history, it was decided to control the measurement of the deliveries. Moreover, the introduction of a systematic error at one delivery point, would favor one client at the expense of another. It would also introduce a wrong balance for the concerned refinery. Therefore, an efficient measurement for custody transfers was necessary.

As no existing facility fulfilled SPSE needs, it was decided to invest in an adapted flowmeter calibration laboratory. SPSE made the choice of a centralized calibration. More than the clear cost reduction compared with classical prover loop fitted delivery terminals, the centralized calibration guarantees a better metrology performance. All the meters are calibrated with the same tool. If a systematic error exists, it’s the same for every metering bench.

This is true once the difference due to the metering bench geometry is eliminated. For that a flow corrector is used at each delivery terminal. SPSE led different tests with real size copies of its delivery terminals to study the influence of bends installed prior to the metering bench. This study was led mainly on turbine meters. Its aim was to check that with a proper flow corrector installed at 10xDiameter from the meter, the same meter factor was found regardless of the elbows. Private tests with other meter technologies show that these flow correctors are sometimes necessary even with non mechanical meters.

The choice of a centralized proving required the use of reliable meters in terms of repeatability and resistance to wear. Therefore the choice of turbine meters at the time (end 70's). Nowadays, the experience obtained from the calibrations made for meter manufacturers and the improvements made on ultrasonic or coriolis meters would probably lead to other choices in SPSE's application.

The Metering system isn't reduced to a facility. In order to have an efficient tool, the proving facility is considered as an independent unit of SPSE. It has its own quality system and agreement. This guarantees its performance to SPSE's pipeline clients and also to the proving facility direct clients and authorities. The agreements obtained from the French authorities and metrology services are the best incentive to maintain and improve the system performance.

THE PROVING FACILITY

At the time of writing this facility is unique in Europe. It allows calibrations up to 4000m3/h within a range of viscosities from 0.5 to 150cSt on standard (up to 500cSt with specific products).

Reference standards :
Standard for proving station quality insurance : ISO CEI 25
Standard for metrology quality insurance : EN 450001

The proving station is COFRAC accredited since 1998. This means that the process is mastered and the uncertainties guaranteed. It also gives the calibration results a multilateral recognition from other countries certification services. Agreement with UKAS (Great Britain), DKD (Germany), NATA (Australia) etc... Reference equipment is kept and maintained in this facility. These references (temperature, pressure, viscosity) are necessary to obtain a reliable uncertainty of the calibration facility. Calibration is made in compliance with Cofrac requirements, International standards (NF-EN-ISO-7278), and
internal procedures. For calibrations with the prover loop, the double chronometry method is used when required. For calibrations over 3000m3/h, master meters are used. In each case uncertainties are calculated and guaranteed.

The calibration bench includes mainly :

• Prover loop
• Pumping equipment
• Specific crude tanks
• Three 20m test lines (diameter range 6" to 20")

Typical uncertainty :

• Reference volume : +/- 4,9 10-4 or 7.45 litres (total volume 15164.97)
• Meter factor (turbine or other) : +/- 11 10-4