SELECTION OF FLOW METER AT LNG SERVICE

LNG Metering Skid

Natural gas (NG) has become an important part of the energy mix, particularly in electric power generation, where it’s prized as an easily handled, clean-burning liquid. Liquefied Natural Gas (LNG) is a more cost-effective way to bring gas to market across oceans and continents. Construction of many overland pipe-lines is underway, but gas companies are also investing in LNG supply chains, building massive LNG tankers to convey gas from port to port, and terminals to convert gas to its form for easy transport, and back to gas for consumption. In this Paper, we’ll analyze the challenges of Flow measurement at LNG service applications. 

Two different meters can satisfy the previous said requirements.

•  CORIOLIS
•  ULTRASONIC

From field tests conducted at an LNG facility in Alaska, users were able to determine how accurate the meters were by comparing flow measurements to level measurements in the LNG dispensing tanks and onboard a receiving LNG tanker. Under test conditions both meters offered similar accuracy and good repeatability.

WHAT IF A CORIOLIS FLOW METER IS INSTALLED?

Ø      When a coriolis flow meter is installed, typically dual bent-tube designs are used to ensure the highest possible performance, causing pressure to drop and the risk of vaporization resulting multiphase fluid, which makes it difficult to measure and can introduce significant measurement uncertainty.

Ø      Coriolis meters, while immune to changes in flow profile, are only available in diameters up-to 10” sizes.

Ø      While a coriolis meter is a good choice for smaller line sizes and highly accurate in mass measurement several flow meters would be required to maximize throughput.

WHAT IF AN ULTRASONIC FLOW METER IS INSTALLED?

Ø      Untrasonic flow meters on other hand, have a straight flow path and do not obstruct or impede the gas or liquid flow through a pipeline.

Ø      The result is essentially a no pressure drop and reduced risk of vaporization, results in good accuracy of measurement.

Ø      They are also available in larger diameter sizes than coriolis meters, making them a more cost effective alternative for LNG applications, where pressure drop and maximizing throughput are prime considerations.

CONCLUSION

Ultrasonic flow meters offer the right technology and value proposition for custody-transfer applications. The high accuracy and low maintenance profile for capital investment in the oil & gas industry, will propel the ultrasonic flow meter market to double digit growth rates.