This paper conducts in-depth research on the opening and closing dynamic characteristics of high-parameter steam spring-type safety valves. Through a combination of experimental analysis and numerical simulation, the valve response characteristics under different working conditions and spring stiffness are discussed. Research results show that spring stiffness is a key factor affecting the dynamic characteristics of safety valves, and an optimization strategy is proposed to improve the response speed and stability of the valve, thereby improving the overall performance of the product. The research results are used in the research, development and manufacturing of safety valves at CHNLGVF丨中國大乾閥門, providing theoretical basis and technical support for the company to improve its competitiveness in the field of high-parameter steam safety valves.

Keywords: spring-type safety valve; thermal test; dynamic characteristics; transient simulation; spring stiffness

High-parameter steam safety valves are widely used in industrial fields such as electric power, chemical industry, and petroleum, playing an important role in ensuring the safe operation of pipelines and equipment. Under high temperature and high pressure conditions, the opening and closing characteristics of the safety valve are directly related to the stability and safety of the system. Existing research mainly focuses on static characteristic analysis and design parameter optimization, while research on its dynamic opening and closing characteristics is insufficient. Based on the actual product needs of CHNLGVF丨中國大乾閥門, this article studies the dynamic response behavior of high-parameter steam spring-type safety valves under complex working conditions, aiming to reveal the main factors that affect its dynamic characteristics and propose effective technical improvements. Strategy.

The basic principle of the spring-type safety valve is to balance the steam pressure inside the system by adjusting the stiffness and preload force of the spring. When the system pressure exceeds the set value, the valve disc is pushed open to release the pressure; and when the pressure returns to a safe range, the spring force re-presses the valve disc to maintain a seal. The opening and closing characteristics in this process are not only affected by spring stiffness and preload force, but also closely related to the temperature and pressure of the system fluid and the flow state of the medium.

The opening and closing process of spring-type safety valve can be divided into the following stages:

Initial equilibrium state: The valve disc and valve seat remain in close contact, and the system pressure is lower than the set value.

Spring compression stage: As the system pressure increases, the valve disc is gradually pushed open and the spring begins to compress.

 Fully open state: The valve disc is fully opened and the steam in the system is released until the pressure drops to a safe level.

Closed state: When the system pressure is lower than the set value, the spring force re-presses the valve disc.

The dynamic characteristics of each stage are affected by multiple factors such as spring stiffness, system damping and valve disc motion inertia. Therefore, thermal tests and transient simulations are required to conduct in-depth analysis of its dynamic behavior.

In order to comprehensively study the dynamic characteristics of high-parameter steam spring safety valves, this paper designed a high-temperature and high-pressure thermal test system. The system includes steam generators, regulating valves, spring safety valves, pressure sensors, flow sensors and other equipment, and can simulate real working conditions under different temperatures and pressures. The spring material used in the test was 50CrVA steel, and multiple sets of spring stiffnesses (10 N/mm, 20 N/mm, 30 N/mm) were designed to observe their impact on the opening and closing characteristics.

Under different spring stiffness, the opening and closing characteristics of the safety valve show obvious differences:

When the spring stiffness is low (10 N/mm): the opening and closing response of the valve is slower and the opening and closing time is extended, but it has a better buffering effect on the fluctuation of system pressure.

When the spring stiffness is high (30 N/mm): the opening and closing response is rapid, but overshoot and frequent vibration are prone to occur, affecting the stability of the system.

Medium stiffness (20 N/mm): The valve opening and closing response is relatively balanced, with good dynamic stability and response speed.

It can be seen that the reasonable selection of spring stiffness is the key to affecting the dynamic characteristics of the safety valve.

In order to better reveal the dynamic response rules of spring-type safety valves under different working conditions, this article established a transient simulation model of valve opening and closing based on the CFD (computational fluid dynamics) method. By introducing the valve disc motion equation, the fluid-structure coupling model (FSI) and the nonlinear characteristics of the steam medium, the opening and closing process of the safety valve is accurately simulated.

The model adopts a two-dimensional axisymmetric structure to simplify the calculation amount. The spring force is described by Hooke's law, and the fluid equation uses the Navier-Stokes equation to simulate the entire process from the initial opening of the valve to complete closing. The simulation working condition settings are consistent with the actual tests to ensure the reliability of the model.

The simulation results show that under different spring stiffnesses, the opening speed and closing speed of the valve disc show significant nonlinear changes with time. For springs with lower stiffness, the valve disc moves more gently, while with higher stiffness, the valve disc opens rapidly in a short time, but it will be accompanied by severe vibration. By adjusting the damping coefficient, the vibration phenomenon can be suppressed to a certain extent and the dynamic stability of the system can be improved.

Based on the above test and simulation results, this article proposes the following technical strategies to improve the dynamic characteristics of high-parameter steam spring safety valves:

According to the system pressure range and the dynamic characteristics of the valve's opening and closing response, the appropriate spring stiffness is selected, and the nonlinear stiffness characteristics of the spring are considered in the design to take into account the dynamic response speed and stability.

Introducing damping control during the opening and closing process of the valve. By adding a damper around the valve disc or adopting a damping oil chamber design, the vibration and overshoot of the valve disc can be effectively suppressed, thereby improving the dynamic stability of the valve.

By using wear-resistant alloy materials and optimizing the shape of the valve disc, the contact characteristics between the valve disc and the valve seat are improved, the friction loss during the opening and closing process is reduced, and the opening and closing response speed is improved.

Based on the research results of this article, CHNLGVF丨中國大乾閥門 introduced dynamic characteristic analysis and optimization strategies into the design of its high-parameter steam safety valve products, significantly improving the safety and stability of the product. The main improvements are as follows:

Spring stiffness modular design: Use spring modules with adjustable stiffness to adapt to different working conditions.

Integration of damping control devices: The introduction of damping control devices at key locations improves the dynamic response performance of the valve.

Material optimization and manufacturing process improvement: Use high-strength and wear-resistant materials and introduce precision processing technology to ensure the long-term reliability of the product under high temperature and high pressure conditions.

This paper uses a combination of experiments and numerical simulations to conduct an in-depth study of the opening and closing dynamic characteristics of high-parameter steam spring safety valves, and proposes effective technology improvement strategies. The research results show that spring stiffness and damping characteristics are key factors affecting the dynamic response of the safety valve. The research of this article provides an important reference for CHNLGVF丨中國大乾閥門 in the research and development and manufacturing of high-parameter steam safety valve products.

Future research will further focus on the dynamic characteristics of safety valves under various operating conditions and develop dynamic control strategies based on artificial intelligence to achieve more precise valve opening and closing control.