HelplineGas Flow Facilities
The Gas Laboratory, shown in the picture on the right, has four test rigs undertaking research and development, calibration and testing on flowmeters. These are the Gravimetric Test Rig, the High Pressure Gas Re-circulating Loop (HPGRL), the 7-bar line and the Fan lines.
Modernization of the Gravimetric Gas Flow National Standard Facility
The new high-pressure gravimetric gas flow standard facility is due to start commissioning trials after September 2008.
Key aspects for the modernization include:
- A new control and data acquisition system utilising digital AS-I bus and Profi-bus communications.
- The use of lightweight multiple composite cylinders to form the pressure vessel (1,700 litres capacity) to hold the gas during weighing. The advantage of this approach is the much reduced dead weight and hence greater resolution and accuracy of the gas being weighed.
- A new weighing platform with a capacity of 2500 kg is installed in a dedicated weighing room. The sensitive weighing system has a resolution of 1 gm to weigh pressurised gas volumes up to 60kg.
- A multiple sonic nozzle assembly containing eight sonic nozzles reference meters in parallel that are permanently fixed in position. Each nozzle has single bodied double block and bleed isolation ball valve and these are used to direct the flow of gas through selected nozzles.
The modernized facility will represent state-of-the-art in air flow measurement and will be re-accredited by UKAS for gas flow calibrations. The design operating parameters are given below.
| Fluid | Dry compressed air |
| Temperature Range | -20 to 25 °C |
| Flow Range (no diversion) | 0 to 4 Kg/s |
| Normal Flow Range | 0 to 2.5 Kg/s |
| Uncertainty | Target 0.15% |
| Working Pressure Range | 0.25 to 70 Bar |
| Pressure Vessel | 1,700 litres (60 Kg gas) |
| Test Line Size | 25 to 150 mm |
| Flange Connections | Class 600 RF |
High Pressure Gas Re-circulating Loop
The High Pressure Gas Re-circulating Loop (HPGRL) is a closed system capable of performing dry- and wet-gas tests and calibrations. For safety, nitrogen is used as the test gas together with a kerosene substitute for the liquid phase. The facility comprises a 150 mm closed loop within which the gas is circulated by a high-pressure blower. Liquid injection is accomplished with a multi-stage pump. At the end of the test section, the two phases are separated in a separator vessel, the lower half of which acts as the reservoir for the liquid injection pump. The temperatures of gas and liquid in the loop are controlled by water-cooled heat exchangers. Liquid content of up to 5% by volume can be achieved, depending on chosen pressure and flowrate.
The HPGRL has an ultrasonic meter as the reference meter, and operates at pressures in the range 15 - 62 bar. The maximum flow has recently been increased to 1400m³/h. The uncertainty associated with the measurement of volume flow is 0.25 %.
7 Bar and Fan Lines
The 7-bar lines are used for lower flowrates and use sonic nozzles as the reference. Flowrates of up to 10,000 l/min can be measured in these lines. The uncertainty associated with the measurement of mass flow is 0.3 %.
The fan lines operate at atmospheric pressure and, depending on pressure drops in the system, can handle flows from 50 l/s up to 4000 l/s (14,400 m³/hr). These lines normally operate with pipework in the range 200 - 300 mm, although other sizes can be accommodated on request The uncertainty associated with the measurement of volume flow on the fan lines is 0.5 %.
Other facilities are available for low gas flow measurement and include a Califlow piston prover. These facilities can be used to measure flowrates from as low as 0.02 l/min up to 30 l/min with uncertainties between 0.15% and 0.25%.
In addition to these facilities the laboratory has the flexibility to allow test rigs to be built to test pipeline components and undertake scale-model testing to meet any research or calibration requirement.
| Facility | Capacity | Uncertainty of reference measurements |
|---|---|---|
| Gas * | 0.3ml/s-16,000 m³/hr. pressures between 0 to 62 barg | 0.15 - 0.5% |
* Facility accredited by UKAS to ISO 17025