At present, the number of offshore oil platforms that China has invested in has reached 200, and the annual oil and gas volume can reach 54 million tons. The offshore oil platform has made tremendous contributions to China's petroleum industry. The author has a simple understanding of it and conducted a simple analysis of the instrument fittings used in it.
1 Overview of the instrument connector and how it works
In China's offshore oil platform, the types of instrument fittings used are very complicated. Different types of instrument fittings have different advantages and disadvantages, and also play different roles in the construction of offshore oil platforms.
1.1 ferrule threaded fitting
In China's offshore oil platform, the most common instrument pipe fitting used is the ferrule threaded fitting. Its main advantages are: reliable sealing performance, convenient installation and operation, compact structure, well-made and repeatable operation. Since the tube fittings are not welded, the effect of pipe impurities on system performance is reduced.
Therefore, the ferrule type pipe fitting is increasingly widely used in the hydraulic and pneumatic equipment pipelines with oil, gas and medium, and is especially suitable for occasions with burning hazard, high-altitude operation and frequent assembly and disassembly.
1.2 ferrule threaded fitting common thread type
Common thread is divided into two categories: sealed thread and non-sealed thread. The sealing thread: NPT and BSPT thread, sealed by thread sealant or raw tape; sealed thread: BSPP and SAE unified thread, these two threads are mainly through O A ring or other gasket is used to achieve the seal. In China's offshore oil platforms, the most common taper thread used is the NPT thread.
2 Instrument pipe fitting production materials and corresponding production process
When China's offshore oil platform is constructed, it will formulate corresponding construction projects according to the environment of the construction site. The construction site of the offshore oil platform is all in the ocean. The surrounding environment is very humid, and the salt content in the air is very high. It will cause certain corrosion to the structure and connection part of the offshore oil platform. In order to ensure that the offshore oil platform can operate normally, ensure the personal safety of the relevant staff, and ensure that the fittings of the offshore oil platform do not corrode, the material of the instrument pipe fitting needs to be selected. It is very important to choose the corresponding pipe fittings with high corrosion resistance and high quality processing technology. The instrument pipe fitting making materials and the corresponding manufacturing process will be analyzed below.
2.1 Instrument fittings and instrumentation tube materials
From the actual situation of the application of instrument pipe fittings in China's offshore oil platform, the surface of most instrumentation is very clean and tidy, there is no corrosion, and the salt content of the instrument surface is not high, it will not cause serious corrosion. Such instrument fittings are relatively safe to make and have a very low probability of damage. Most of the materials used in the instrument pipe fittings used in China's offshore oil platforms are 316SS. In the pipe connection of the instrument, 316 stainless steel seamless pipes are used. This will ensure its corrosion resistance and save a lot of money. Due to the advancement of China's smelting technology, the cost of this material has been declining, and its comprehensive performance is excellent, and it is widely used in China's offshore oil platform.
2.2 Casing fitting processing technology
In China's offshore oil platform, the material used for the instrument tube is generally selected 316SS. In order to ensure the reliability and fit of the fittings in the offshore oil platform, the same raw materials must be used in the production. Instrumented pipe fittings made of different raw materials may cause thermal expansion and contraction of the pipe fittings due to changes in sea surface temperature. Due to the different melting points of different materials, the degree of thermal expansion and contraction is also different, which may cause leakage of the instrument pipe fittings, which seriously threatens the personal safety of the relevant personnel. The 316SS material is essentially austenitic stainless steel and has good corrosion resistance at sea. In order to improve the safety and reliability of its use, it is necessary to go through the corresponding processing technology before it can be used. Generally, the ferrule is treated by low-temperature carburizing technology to improve the hardness of the ferrule and enhance its corrosion resistance.
3 Installation and inspection of instrument fittings
In China's offshore oil platform, when installing the instrument pipe fittings, the installers need to be familiar with the correct installation method and testing method of the ferrule fittings to ensure the installation is qualified before they can be applied to the offshore oil platform. At the time of installation of the instrument pipe fittings applied in China's offshore oil platform, a seamless instrument Tubing tube is required. Tubing tube hardness is less than instrument tube fittings.
3.1 Installation of pipe fittings
When installing the instrument fittings used in offshore oil platforms, first cut the Tubing tube of the required length with a pipe cutter and then use a deburring knife to remove the burrs on both ends of the Tubing tube. Insert the tube into the bottom fitting body, tighten the nut by hand, and then mark the initial position with a marker line; fix the fitting body and then rotate the nut 1/4 turn at the same time to complete the installation.
In addition, it should be noted that for some small-sized pipe fittings, it is only necessary to rotate 3/4 turns from the hand tightening. For details, please refer to the manufacturer's product installation instructions.
3.2 Detection of pipe fittings
In general, the detection of pipe fittings includes installation inspection and leak detection. Installation testing is to ensure the quality of the installation and to avoid potential hazards due to tight rotation. Usually, the inspection gauge is inserted between the pipe fitting body and the nut. If the inspection gauge can be placed between the nut and the hex head of the body, it means that the nut is not tightened enough to meet the installation requirements.
4 Conclusion
In summary, the author explained the materials, precautions and installation steps of the instrument pipe fittings used in China's offshore oil platform. The installation of instrument pipe fittings has a great impact on the overall quality and safety of China's offshore oil platform. It is hoped that relevant inspection and management departments will strengthen the management of the installation of instrument pipe fittings.
