In year 2013, PowerQ performed validation of custody transfer gas metering system for a 6mpta LNG terminal. This is an onshore LNG import/export terminal comprising of facilities for LNG unloading/reloading, LNG storage, Boil-off Gas (BOG) Handling, LNG send-out, LNG re-gasification and natural gas metering and regulation.
LNG is imported from LNG tanker, offloaded through unloading arm and pumped at LP to storage of half million cubic meter capacity. From storage tanks, the LNG was pumped at HP to bulk consumers at pressure in excess of 500 psi.
The export system is equipped with specialized Gas Metering Systems that support the Gas metering and Gas Quality Monitoring. The metering stream configuration for each metering skid is configured with pay and check meters of 2 x 100% (i.e. one active and one standby).
This validation plan addresses the following sub-systems of the Gas metering system:
PowerQ performed validation exercises in four phases as follows:
The validation was performed under the available gas flow rate (approximately 60K cu.m/hr) and the condition of the gas. It was noted that the gas flow rate was within the design range but was not the expected design flow rate.
The gas metering system was validated based on hourly flow rate accuracy of ±1% as per specification and as per gas code. However, the metering accuracy varies according to flow rate.
PowerQ final analysis report recommended that calibration program of periodic calibration of critical instruments shall be implemented according to an approved schedule and approved calibration procedures. It is recommended for periodic test and calibration of meter installations as guided by codes.
In conclusion, the design, installation, operational and performance validation conducted by PowerQ validated that the pay and check metering system performed with reasonable accuracy. It is within tolerance limit of the overall inaccuracy of the system, and is acceptable and eligible for custody transfer.