Optimizing preloading pressure of pre-charged gas for isobaric gas-tight hydrothermal samplers

Abstract

It is required that in-situ pressure of hydrothermal fluids should be maintained before analyzing. For this reason, gas-tight samplers with accumulator attached on the sample chamber have been developed. Pre-charged gas in the accumulator is used for compensating decompression of sample caused by its volume change during withdrawing onboard. Besides the structure of the sampler, pre-charged internal pressure is a critical factor for the pressure-retaining ability of the sampler. In this artical, comprehensive analysis of the pre-charged internal pressure on the sampling efficiency and pressure stability is carried out, based on the ideal gas law and theoretical volume change of chamber under high internal pressure. It is found that pre-charged internal pressure should be set separately in different ranges of depth, Optimizing internal pressure in accumulators for isobaric gas-tight hydrothermal samplers can not only have better sampling performance at different depths, but also can significantly increase the volume of each sample.