Shijun Wu

A Novel Mechanical Gas-Tight Sampler for Hydrothermal Fluids

A new mechanical gas-tight sampler has been designed to collect hydrothermal fluids at the seafloor. A key feature of the sampler is the novel sample valve which is pressure balanced under deep sea, and actuated by the ram on a submersibles manipulator. The sampler is designed to be deployed at the seafloor 3000 m underwater and can be used to sample hydrothermal fluid with temperature up to 400degC. Compressed gas is used to compensate for pressure reduction of sample fluids. Simulation of the flow system was conducted to estimate the fill rate. The sampler has been tested successfully in the first Sino-American Cooperative Deep Submergence Project from August 13 to September 3, 2005.

A New Hydraulically Actuated Titanium Sampling Valve for Deep-Sea Hydrothermal Fluid Samplers

Collecting gas-tight fluid samples from deep-sea hydrothermal vents is challenging due to the high pressure, temperature, and corrosiveness of hydrothermal fluids. The most critical part of a gas-tight sampler is the sampling valve because it must have reliable bidirectional sealing capability under such harsh conditions. A new titanium sampling valve has been designed to address these issues. Key features of the new sampling valve include the application of a titanium metal-to-metal seating to achieve high temperature and corrosion resistance, a novel self-tightening design that makes the valve a more reliable closure under high pressure, and a hydraulic actuating mechanism which enhances the convenience and reliability of valves operation under deep sea. Currently, the sampling valve can be used for vent fluids at depths of 6000 m and temperatures up to 400°C. The new sampling valve has been applied on a gas-tight sampler and tested at the hydrothermal vent sites along the Mid-Atlantic Ridge during the cruise KNOX18RR in 2008. Fluid samples were collected from hydrothermal vents with the depths from 744 to 3622 m and temperatures from 94°C to 370°C. Results of the field tests indicated the usefulness of the new sampling valve to collect deep-sea hydrothermal fluids.

A Study of the Sealing Performance of a New High-Pressure Cone Valve for Deep-Sea Gas-Tight Water Samplers

The cone valve plays an important role in high-pressure sealing applications. In this paper, a new high-pressure cone valve, based on the titanium alloy poppet-to-polyetheretherketone seat sealing structure, is proposed for deep-sea gas-tight water samplers. In order to study the sealing performance of the new valve, both the conforming poppet-seat contact model and the nonconforming poppet-seat contact model were evaluated. Finite element analysis based on the two models was performed and validated by experiments. The results indicate that the nonconforming poppet-seat contact model has a better sealing performance than the conforming poppet-seat contact model. The new cone valve also was applied in a gas-tight hydrothermal fluid sampler and successfully tested in a sea trial during the KNOX18RR cruise from 9 July to 12 August 2008.

Optimizing Preloading Pressure of Pre-charged gas for Isobaric Gas-tight Hydrothermal Samplers

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.