Part 1: Custody transfer of fuel products demands sophisticated Flow analysis beyond volume readings. Product characteristics can be dynamicCONTROL ENGINEERING China版权所有, requiring monitoring at the same time.
　　The need to measure large-volume flow (how much gas or liquid has moved from point A to B over a specific period of time) with precision advanced many years ago when energy purchasers (e.g., oil, gasolinewww.cechina.cn, natural gas) started questioning seller’s invoices. This led engineers to develop mechanical flowmeters using

paddlewheel and propeller techniques in the pipeline to “count” the amount of flowing material. Unfortunately, these systems weren’t always very accurate and were prone to mechanical breakdown, but at least the buyer and seller had some basis for agreement.
　　As technology advanced, custody transfer applications expanded to include more accurate and reliable techniques such as magnetic field, positive displacement, and ultrasound. However true flow calculation needed to consider other measurements and conditions: temperature, pressureCONTROL ENGINEERING China版权所有, pipe diameter, and material purity all matter. Because these attributes are dynamic and can change frequently over time控制工程网版权所有, a way to measure these variables continuously and then calculate flow was required. The concept of a flow computer evolved precisely for this purpose.
　　Flow computers monitor data from flowmeters while simultaneously collecting information from other sensors such as temperature, pressureCONTROL ENGINEERING China版权所有, density and chemical analyzers. Computers process the data using standard based algorithms to calculate mass or volume flow. Often flow computers are installed in remote areas where LACT (leased automated custody transfer) units are located such as offshore oil rigs, pipelines, tank farms and compressor stations. The resulting flow information can be displayed locally or transmitted into a computer system.
　　As energy systems grew and telecommunications advanced, DCSs (distributed control systems) became more practical. This required the colle