Research On The Sealing Performance Of The Flat Valve Stem Of The Tree In The Offshore Platform Of Bohai Sea

Offshore platform tree is the wellhead to control and regulate the production of oil and gas, and the flat valve is one of its key components. Once the sealing ring of the flat valve stem broken, it will cause the leakage of the tree, which will not only cause big waste of oil and gas resources but also pollute the environment, sometimes even cause accidents such as poisoning, fire, and explosion etc. At present, the international research of the sealing ring focuses on the O and Y types based on the finite element simulation method, there is no systematic and comprehensive study of the performance of the V-shaped flat valve sealing ring, which was widely used in the flat valve. Therefore, this paper adopts the finite element simulation method, combining with the single factor analysis method and the orthogonal test design in to make the study of V-shaped sealing ring performance. The detailed research contents and results are as follows:(1) The analysis of the breakdown of the offshore platform trees in the bohai sea region shows that:the most frequent breakdown part is the flat valve, for which the outside leakage of the flat valve is the most serious one. In addition,84.85% of the outside leakage of the flat valve is related to the break of the sealing ring which is caused by its structure and performance.(2) By using numerical simulation method, this paper carries out performance study and comparative analysis of three kinds of flat valve sealing rings-type O, Y and V. The performance of these three kinds of sealing ring from high to low are:Type V, Y and O. Besides, the most suitable sealing ring for the flat valve stem is V-shaped sealing ring.(3) This paper builds a finite element model of flat valve’s V-shaped sealing ring, and uses the single factor analysis method to investigate the regularity of the influence on the performance of V-shaped sealing ring from lip inclination, posterior labial angle, anterior labial angle, interference amount, we got the result of the trend of V type sealing ring’s maximum Mises stress, contact force and contact zone width while the four parameters above is changing.(4) Adopting the method combining finite element simulation with orthogonal experiment design, this paper analyzes the main factor of V type sealing ring and gets the result that the main influencing factors of V type sealing ring’s maximum Mises stress is posterior labial angle, followed by anterior labial angle and lip inclination and the optimum structure parameters is when the lip inclination is 4°, posterior labial angle is 100° and the anterior labial angle is 95°. The main influencing factors on the average contact stress are posterior labial angle, followed by lip inclination and anterior labial angle. The optimum structure parameters is when the lip inclination is 4°,posterior labial angle is 100° and anterior labial angle is 95°.