Development of High-pressure Forged Steel Gate Valves for Hydrogenation Equipment (Part One)

Development of High-pressure Forged Steel Gate Valves for Hydrogenation Equipment (Part One)

Feb 25, 2021


Abstract: The design of key components such as the general structure of the valve body, sealing packing system and sealing packing detection system are carried out in view of working conditions, design and development difficulties of high-pressure forged steel gate valves for hydrogenation equipment; key processes such as receiving inspection of raw materials, welding processing and matching design of sealing test equipment are controlled. The results of the pressure test and customer's use indicate that the high-pressure forged steel gate valve for the hydrogenation device developed can adapt to the harsh working conditions. At the same time, the main design parameters, design specifications and pressure tests of high-pressure forged steel gate valves for hydrogenation devices are described.
 
As a device on the pipeline, the gate valve has a wide range of applications in the water supply and drainage, heating and gas supply systems of petroleum, chemical, electric power, urban construction and industrial enterprises. However, in the high-end petrochemical hydrogenation market of the oil refining industry, because the high-pressure hydrogenation device has the characteristics of high temperature, high pressure, hydrogen and high corrosiveness, most of its matching pipeline valves are currently imported. Therefore, the development of high-pressure forged steel gate valves for the hydrogenation device is of great significance for improving China's petrochemical hydrogenation technology and equipment levels and saving national economic resources.
 
In recent years, some domestic technicians have conducted research on key technologies of valves used in hydrogenation devices, such as valve leakage and material selection, and have made a lot of progress and results. Research on the internal and external leakage control of valves used for hydrogenation devices with pressure of 14 to 20MPa was conducted and it was found that using flexible graphite braided packing and designing the contact surface between the ring gasket and valve bonnet as a variable angle arc transition surface could solve the external leakage of packing and gasket seal; overlayed welding of cemented carbide on the sealing surface can solve internal leakage of the gate valve; the main material selection, valve sealing and other aspects for hydrogenation devices like hydrodesulfurization with pressure of 9MPa to 16MPa were studied and it was found that using stable stainless steel CF8C, F321, F347 and OCr18Ni10Ti with stabilized alloying element T or Nb could reduce the adverse effect of C on the hydrogen corrosion resistance of steel; adopting packing structure with reliable sealing and convenient assembly and medium-size gaskets of internal pressure self-sealing valves can solve the problem of valve external leakage. The above research involves the development of valves for hydrogenation devices with pressure of between 3MPa and 20MPa. At present, a high-pressure forged steel gate valve with pressure of from 15MPa to 76MPa used for the hydrogenation device is hardly reported.
 
Aiming to the working conditions, design and development difficulties of high-pressure forged steel gate valves for hydrogenation equipment, key designs such as valve bodies with generalized structure, sealing packing systems and sealing packing inspection systems are carried out; raw material receiving inspection, welding processing, matching design of sealing test equipment and other key processes are controlled. The high-pressure forged steel gate valve for the hydrogenation device developed can adapt to the harsh working conditions based on the pressure test and  customer's usage.
 
1. Working conditions
The working media of the hydrogenation device are generally hydrogen, hydrogen plus hydrogen sulfide, oil gas and hydrogen and hydrogen sulfide, which are flammable and explosive media. Hydrogen is a medium that can penetrate into metal materials and cause material denaturation (deterioration) at room temperature or high temperature. It can cause denaturation and deterioration of metal materials at room temperature, and can make decarburization for internal and external metal materials at high temperatures. Hydrogen sulfide is also very serious to metal materials. It can cause stress corrosion cracking for many metal materials at room temperature, and result in rapid and uniform corrosion of metal materials at high temperatures. The maximum temperature of the medium during operation is 550℃, and the maximum pressure is 42MPa.
 
2. Design and development difficulties
The hydrogenation device is operated with hydrogen and accompanied by hydrogen sulfide at high temperature and high pressure. All these characteristics have put forward harsh requirements on materials and structure of the high-pressure hydrogenation valve. In the design and development process, the following four difficulties need to be solved:
  • Main body and internal material selection
  • Main part structure design and manufacturing
  • Leak-proof sealing design 
  • Key process control including matching design sealing test equipment
 
3. Main design parameters and design specifications
3.1 Design parameters
Technical parameters: nominal diameter from DN50 to 300 mm, nominal pressure 15MPa to 76MPa
Applicable temperature: -29℃ to +427℃
 
3.2 Design and inspection specifications
The design and manufacture shall comply with API 600-2009 Steel Gate Valves-Flanged, Butt Welded and Bolted Bonnets, ASMEB16.342009 Flanged, Threaded and Welded Valves. When selecting materials, please refer to NACE MRO1752002 Metal Materials with Sulfuration Stress Crack Resistance for Oilfield Equipment, NACE MRO130-2003 Materials with Sulfuration Stress Crack Resistance in Corrosive Petroleum Refining Environments, etc.
 
Inspection and testing shall comply with API 5982009 Inspection and Testing of Valves.
 
4. Material selection of main bodies and internal parts
The corrosion of hydrogenation valve is serious, which is the result of multiple corrosion. Therefore, it is necessary to select materials with good performance with resistance to sulfide stress corrosion cracking (abbreviated as SSC) and hydrogen induced cracking (abbreviated as HIC) according to different media environments such as PH values, HS concentration and temperature.
 
For wet HS medium system environment with temperature not higher than 350℃, general carbon steel such as WCB and A105 or alloy steel such as WC6, F11, WC9 and F22 can be used.
 
For the temperature not lower than 350℃, especially the high temperature H plus HS environment, the corrosion rate of the selected material should not exceed 0.25 mm/a. In addition, the effect of H ions on the decarburization of metal materials should be considered. Stable austenitic stainless steel such as CF8C, F321 and F347 or ultra-low carbon austenitic stainless steel such as CF3 and F304L can be selected.
 
For the safety and reliability of the device and valve, the main body material and internal material should be matched in the design, and the specifications in the Table 1 should be adopted in the design and material selection process.
 

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Next: Development of High-pressure Forged Steel Gate Valves for Hydrogenation Equipment (Part Two)

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