Jiaqing Chen

Influence of the Bar Shape on the Welding Quality of Friction Hydro Pillar Processing

Traditional underwater arc welding methods, for example, TIG and MIG, are generally expensive and complex to implement under water. Besides, the welding quality decreases significantly with the increase of depth of water. So a new-style solid phase welding method called friction stitch welding (FSW) is introduced, since the welding quality of which is almost insensitive to water. This article studies the influence of the bar shape on the welding quality. In the experiments, three typical kinds of shape combinations are adopted. Argon is used as protecting gas, and the flux of which is 30L/min. The feed speed of the spindle is 0.5 mm/s, the rotation speed is 4000r/min. Through the comparison of the macro features and microstructure of the welded joints, the influence of the bar shape on the welding quality is analyzed, and static stress distribution along with the influence on welding temperature by different shapes are investigated. The results indicate that the welding quality obtained by using straight bars with round head is much better than the other shape combinations, the welding defects are reduced and the welded material is much finer.

Theoretical Modeling and Numerical Simulation of Axial-Vortex Separation Technology Used for Oily Water Treatment

The Voraxial Separator (VAS) has attracted increasing attention in recent years because it can separate large volumes of oily water efficiently within a tubular compact structure. However, there is a lack of systematic research into the working mechanism and validation of the design theory of the separation technology. In this paper, the key factors influencing the separation efficiency of the VAS were analyzed, the theoretical model of this new separation technology was established, and a pilot VAS was designed. The velocity field in the pilot VAS was also analyzed by numerical simulation, which could provide a useful reference for the theoretical research. The results show that the tangential velocity distribution at the swirler end is in accordance with the pattern of Solid Body vortex, and there exists a low pressure region along the central longitudinal flowline which can be proved by the distribution of axial velocity. The maximum separation efficiency of the pilot VAS can achieve is up to 93%, which occurs when the back-flow ratio is 2.9-11.4%.

Research on the all-position pipeline automatic welding carriage

In order to explore deep water oil and gas fields in South China Sea area, an all-position automatic pipeline welding carriage was developed, applied in sub-sea pipeline laying. The welding carriage is specially designed for offshore application, so it is compact and lightweight. The control system of the automatic welding is constructed on the CANOpen bus and Ethernet technologies, so the pipeline welding process can be monitored remotely. A master-slave CAN-bus network control welding system is constructed, which is composed of CAN-bus master and welding power source based on CANopen communication. This system satisfies the requirements of all-position welding process that welding system can weld with mated welding parameters at any position. The accuracy of two-axle synchronous movement and the operation stability of welding bug are ensured by using the current follower arithmetic.

Study on Sub-sea Pipelines Hyperbaric Welding Repair under High Air Pressures

Most Chinese sub-sea pipelines are buried in Bohai Sea less than 60m water depth, where air diving are widely used For the application of offshore pipelines repair, the hyperbaric TIG welding process under high air pressures has been successfully developed. Firstly, the hyperbaric welding test chamber is designed and constructed in laboratory, and the welding machine is manufactured. Then, special welding experiments are carried out based on 16Mn steel plates and pipes under 1-7bar air pressures, and high weld quality is obtained. Lastly, the sea-trial of the welding machine and the welding procedure is carried out in Bohai Sea in China, and a perfect all-position 5G girth weld of 16Mn steel pipe is achieved.