A NEW ON-LINE LPG VAPOR PRESSURE ANALYZER

摘要

This paper presents an overview of a new on-line instrument for measuring vapor pressure of Liquified Petroleum Gas (LPG) and Natural Gas Liquid (NGL) for Product Pipelines and Gas Processing Plants.Vapor pressure measurements for these products are performed using the ASTM 1267 lab method. This method is time consuming and requires manual labor.Currently, on-line vapor pressure measurements for these products are presented as correlated values using aGas Chromatograph (GC). The correlated values tend to be higher than the physical property lab methodvalues. Gas Chromatographs are also costly to operate.The new instrument described in this paper is an on-line physical property analyzer. The analyzer incorporates a single measuring cell with a pressure transducer. In addition to the measuring cell, there are two solenoid valves that control the filling and emptying of the cell. All timing functions are provided by the microprocessor on the logic board.Analysis results are obtained in approximately 5 minutes. During this time the cell is flushed, zeroed, and the sample filled. After sample equilibration, the final pressure reading is obtained and the LPG vapor pressure value is determined directly, without correction factors. Throughout the cycle, the analyzer performs the self-diagnostics for temperature, sample filling, cell leaking and over-pressure.The simple design makes this new analyzer easy to operate and maintain and offers an excellent alternative to the lab and GC methods.