Liquid Hydrocarbon Cross Country Pipeline Network Custody Transfer "Measurement System" for
Custody Transfer "Measurement System" for Liquid Hydrocarbon Cross Country Pipeline Network

Reduction in capital expenditure and operating expenses can result from a well-designed skided metering facility, elaborates Trilochan Gupta.

 

Introduction
LPG is a popular domestic fuel, moved in bottles. Generally, the majority of LPG is not bottled in cylinders in the premises where it is produced, instead moved by road or rail in bulk form to the LPG bottling plants. The road or rail movement is not only expensive, but also uses other hydrocarbon fuels like diesel while posing environmental hazard. Also, the movement by railways is constrained by the availability of rolling stock and the track capacity. Thus, the popular mandate is to reduce the percentage of such road transport. The LPG movement by a pipeline is preffered due to its distinct advantages. As, the movement of LPG through pipelines is more reliable, safer, environmentally friendly and the most economical mode of transportation, it reduces road traffic congestion and the need for inventories and LPG storages in either spheres or cavern at several places, creating an efficient “energy network”. In a perfect world, the ideal pipeline system would be a continuously running, constant rate pipeline with one input and output point; connected through a short, straight, continuous diameter pipe located on a flat horizontal plane. The physical properties (viscosity, temperature, pressure and specific gravity) of a single phase constant flow liquid passing through such pipeline would remain constant and measured through identical measurement systems at input and output. Such networks are complex system, operating on a fine line between profit and compliance and do not fit the simplified model of the “Ideal Pipeline”. A matter of concern for LPG is its vapour pressure, which could lead the product vapourisation within the line, during the flow. During the design stage simulations are required to be done to avoid this kind of occurrence, assuring the presence of liquid phase at all times. These pipeline systems have a high turndown rate LPG flow across long distances with multiple flow outlet and inlet feeders. LPG flows in varying diameters of pressurised pipes, with changing line pack, varying physical pipeline parameters and changing dynamic fluid characteristics and withdrawal rates. For the complete custody transfer metering in a LPG pipeline system performance, high-pressure Coriolis flow meters are best suited. Coriolis flow meters are selected for their direct mass measurement ability, wide turndown and no moving parts. Measurement of LPG in and out of the transmission system is carried out at all the metering sites, with each designed as either a single meter run site with 100% hot back up capacity or as a 3 x 50% stream configuration. These meters are then in-situ calibrated (API MPMS 5.6) in the field on a “mass basis”. The field verification is accomplished by using a mobile density integrated small volume compact prover – “Mass Prover”. The local regulatory authorities and weights and measures official routinely witness the performance of the metering system and verify in-situ proving and also the measurement integrity of the mobile “Mass Prover” which is of the greatest hierarchical precision in this custody transfer chain.

cont....

To Read Further Subscribe Your PRINT COPY Today.