Vibration Analysis of Large-Diameter Wedge Gate Valves During Closing

Abstract: Large-diameter wedge gate valves play a critical role in ensuring the safe and stable operation of petrochemical pipeline systems. During operation, these valves are subjected to combined fluid pressure and thermal loads, which can lead to several problems:

Increased structural deformation: Valve deformation intensifies, increasing friction and wear between the valve stem and bonnet and significantly shortening the valve's service life.

Flow-induced vibration: Severe flow disturbances can induce vibration and, in extreme cases, cause serious failures such as valve stem fracture.

For example, a DN1200 gate valve installed on a major oil pipeline experienced valve stem fracture during operation, resulting in production shutdowns and substantial economic losses. To address these issues, this study investigates the vibration characteristics of large-diameter wedge gate valves during closure. The analysis integrates process discretization, numerical simulation using ANSYS, Fourier signal analysis, modal analysis, and harmonic response analysis. The findings are intended to provide a theoretical basis and technical guidance for optimizing the design of large-diameter wedge gate valves.

Large-diameter wedge gate valves are critical components of petrochemical pipeline systems and are often subjected to combined fluid-dynamic and thermal loads. These loads can exacerbate structural deformation, increase friction and wear between the valve stem and bonnet, and disturb the internal flow field. Under certain conditions, the resulting flow-induced vibration may lead to severe failures, including valve stem fracture. This study investigates the vibration characteristics of a DN1200 large-diameter wedge gate valve during closure. First, process discretization is used to divide the closing stroke into discrete valve positions. ANSYS-based numerical simulations are then conducted to characterize the internal flow field, while Fourier analysis is used to examine pressure pulsations. Finally, modal and harmonic response analyses are performed to investigate the dynamic behavior of the coupled valve–pipe–fluid system and identify potential resonance characteristics of the valve stem–gate assembly at different stages of closure. The results show that at small valve openings, flow disturbance caused by the gate generates pronounced Kármán vortex streets and flow recirculation downstream of the valve. These disturbances intensify pressure pulsations and flow instability, potentially inducing large-amplitude vibrations near resonance in the coupled valve–pipe–fluid system and ultimately contributing to valve stem fracture.

To mitigate these effects, a downstream pipe expansion section is proposed. The results indicate that this design effectively suppresses downstream vortices and flow recirculation, reduces pressure pulsations, and mitigates flow-induced resonance. The effects of the expansion section dimensions on pressure pulsation attenuation and resonant amplitude reduction are also evaluated qualitatively and quantitatively. Comparative analysis identifies an expansion section with a diameter 1.3 times the pipe diameter (1,560 mm) and a length equal to the pipe diameter (1,200 mm) as the configuration that provides the greatest vibration reduction. These findings provide a theoretical basis and technical guidance for optimizing the design of large-diameter wedge gate valves.

A three-dimensional model of a DN1200 large-diameter wedge gate valve was developed using SolidWorks, taking into account key structural features, including the gate geometry and sealing configuration. The model was then imported into ICEM-CFD for unstructured mesh generation. To improve computational accuracy, local mesh refinement was applied to critical regions, particularly the sealing interfaces between the gate and valve seats and the narrow flow passages. After iterative mesh refinement and optimization, a mesh containing [X] elements was generated to meet the accuracy requirements of the subsequent numerical simulations.

Figure 1. Schematic of the structure of a large-diameter wedge gate valve

1. Actuator
2. Yoke
3. Valve stem
4. Bonnet
5. Gate
6. Valve seat
7. Valve body

Boundary conditions were specified in ANSYS based on the actual operating conditions. An inlet velocity of [V] m/s was prescribed at the inlet, while the outlet pressure was specified in Pa. A no-slip boundary condition was applied to the solid walls of the valve. The pressure-based solver was adopted, and turbulence was modeled using the standard k–ε model. To improve computational accuracy, a second-order upwind scheme was adopted. The convergence residual was set to 10-5, ensuring both accuracy and convergence.

The steady-state flow fields of the wedge gate valve were calculated at different opening positions. When the valve was nearly fully open, the fluid flowed through the valve relatively smoothly, with a comparatively uniform velocity distribution and regular streamlines. The pressure contours also showed a relatively stable pressure distribution. As the valve closed, the descending gate progressively restricted the flow passage. At smaller openings, the gate significantly obstructed the flow, causing fluid accumulation and low-velocity regions upstream of the gate. The resulting flow deflection and local acceleration produced a more complex downstream flow field, characterized by low-pressure regions, pronounced vortices, and flow recirculation. Comparisons of the velocity vector plots and pressure contour plots at different valve openings revealed the evolution of the internal flow field, providing a basis for subsequent transient flow simulations and vibration analysis.

Building on the steady-state flow-field calculations, the transient flow field was solved. To better capture the dynamic changes in fluid behavior during valve closure, the time step was set to [Δ t] s. Pressure monitoring points were located upstream and downstream of the valve to record transient pressure data. Fast Fourier transform (FFT) analysis was then performed to characterize the frequency-domain features of pressure pulsations at different valve openings. The results show that pressure pulsations are concentrated primarily at frequencies below 50 Hz. As the valve closes and its opening decreases, the pulsation amplitude gradually increases. At small openings, the amplitude rises sharply, indicating increased flow instability and a greater potential for flow-induced valve vibration.

Thermal-fluid–structure interaction (TFSI) involves the coupled effects of fluid mechanics, structural mechanics, and heat transfer. During the closure of a large-diameter wedge gate valve, the fluid exerts pressure and shear forces on the valve body and gate, while heat is transferred between the fluid and the valve components. The combined effects of fluid pressure and thermal loading cause structural deformation and may induce vibration in the valve components. This coupled behavior can be described by the following governing equations:

Fluid Dynamics Equations: The Navier–Stokes equations govern fluid motion, accounting for viscous effects, mass conservation, and momentum transport within the flow domain.

Solid Mechanics Equations: The structural response of the valve body and gate is described by the equations of elasticity, which relate stress and strain to material properties and external loads.

Heat Transfer Equations: The heat transfer equations describe thermal energy exchange between the fluid and solid components through convection and conduction, with radiation included where relevant.

For the numerical simulation, an iterative coupling approach is adopted. First, the flow and temperature fields in the fluid domain are calculated. The resulting fluid pressure and thermal loads are then transferred to the solid domain to determine the structural response. The resulting structural deformation is subsequently fed back into the fluid domain to update the flow boundaries. These calculations are repeated until the coupled solution converges.

A fluid–structure interaction analysis of the wedge gate valve was performed using ANSYS. The flow-field results were used as input for the thermal analysis, which calculated heat transfer between the fluid and solid domains. To reflect actual operating conditions, the ambient temperature and convective heat transfer coefficient were specified accordingly. In the structural analysis, the material properties of the valve components, including Young's modulus, Poisson's ratio, and density, were defined. The thermal loads obtained from the thermal analysis and the pressure loads derived from the flow-field calculations were then applied simultaneously to the structural model to evaluate the combined effects of thermal and mechanical loading. Through iterative calculations, the stress and strain distributions and vibration responses of the valve at different opening positions were determined.

The stress and strain distributions of the wedge gate valve under coupled thermal and fluid loading were analyzed. The results reveal distinct distribution patterns at different valve openings. Stress concentrations occur primarily at the contact interfaces between the gate and valve seats due to fluid pressure and contact forces. However, the calculated stresses remain within the allowable limits of the valve material and satisfy the applicable strength requirements. Comparison of the stress and strain contour plots at different valve openings shows that the peak stress and strain increase as the opening decreases, although both remain within acceptable limits. These results indicate that the valve body and gate, designed using empirical formulas, meet the structural strength requirements under the analyzed operating conditions.

Modal analysis was performed to determine the natural frequencies of the wedge gate valve. The results revealed multiple natural frequencies of the valve stem–gate assembly, some of which were close to the dominant frequencies of the pressure pulsations. The resonance characteristics of the valve at small openings were then investigated using harmonic response analysis. The results show that pronounced resonance occurs at small openings when the excitation frequency approaches a natural frequency of the valve stem–gate assembly. For example, within a specific range of valve openings, an excitation frequency of [f] Hz produces a peak vibration amplitude of [A_max] mm. These findings indicate that the valve is more susceptible to resonance at small openings, which can intensify valve stem vibration and potentially lead to stem fracture. To verify the simulation results, the resonant frequency was also estimated using empirical formulas. The calculated values were in close agreement with the natural frequencies obtained from the modal analysis.

To reduce excessive vibration amplitudes caused by resonance when large-diameter wedge gate valves operate at small openings, a vibration mitigation scheme involving the installation of a pipe expansion section downstream of the valve is proposed. The expansion section increases the flow area, reducing the average fluid velocity downstream and weakening the interaction between the flow and downstream piping components.

In addition, the expansion section modifies the downstream flow pattern, helping to suppress vortices and flow recirculation, improve flow stability, and reduce pressure pulsations. Its geometry may also alter the dynamic response of the fluid system, potentially reducing flow-induced vibration. By optimizing the diameter and length of the expansion section, the flow characteristics and vibration response can be improved to achieve effective vibration mitigation.

Three expansion-section configurations with different diameters and lengths were designed and compared:

Configuration 1: An expansion diameter of 1,320 mm (1.1 times the original pipe diameter) and a length of 960 mm (0.8 times the original pipe diameter).

Configuration 2: An expansion diameter of 1,560 mm and a length of 1,200 mm (equal to the original pipe diameter).

Configuration 3: An expansion diameter of 1,800 mm (1.5 times the original pipe diameter) and a length of 1,440 mm (1.2 times the original pipe diameter).

The flow fields and vibration characteristics of the wedge gate valve were analyzed for each configuration to evaluate the effects of expansion-section diameter and length on vibration mitigation. The velocity vector fields and pressure contours obtained with and without the downstream expansion section were compared. The results show that the expansion section effectively suppresses downstream vortices and flow recirculation, produces a more uniform velocity distribution, and significantly reduces pressure pulsation amplitudes. Modal and harmonic response analyses were also conducted to evaluate the effects of the expansion-section dimensions on the natural frequencies and resonant amplitudes of the valve stem–gate assembly. The results indicate that incorporating an expansion section into the valve–piping system significantly reduces the resonant vibration amplitude. Comparison of the three configurations shows that the optimal design has an expansion diameter of 1.3 times the original pipe diameter and a length equal to the original pipe diameter (1D), providing the greatest reduction in vibration amplitude among the configurations evaluated.

(a) Configuration 1 (b) Configuration 2 (c) Configuration 3

Figure 2. Three downstream pipe expansion configurations

Considering both flow-field improvement and vibration reduction, the optimal configuration was determined to be a downstream expansion section with a diameter of 1.3 times the original pipe diameter (1,560 mm) and a length equal to the original pipe diameter (1,200 mm). The effectiveness of the optimized design was evaluated through numerical simulations and experimental tests. For the numerical analysis, a refined mesh and a detailed computational model were used to investigate the flow field and vibration characteristics of the optimized wedge gate valve. The results show that the expansion section improves the downstream flow field and effectively reduces vibration within the valve cavity.

For experimental validation, a full-scale (1:1) test model of the wedge gate valve incorporating the optimized expansion section was constructed. Flow-field and vibration parameters were measured during valve closure on a test rig designed to reproduce the actual operating conditions. The experimental results showed good agreement with the numerical predictions, supporting the validity of the simulation model and the effectiveness of the proposed optimization method.

This study investigated the vibration characteristics of a DN1200 large-diameter wedge gate valve during closure using process discretization, ANSYS numerical simulation, Fourier analysis, modal analysis, and harmonic response analysis. The results show that as the valve opening decreases, the gate increasingly restricts the flow passage, resulting in upstream flow accumulation and downstream vortices and flow recirculation. Pressure pulsations are concentrated primarily below 50 Hz, with their amplitudes increasing significantly at small openings, indicating increased flow instability.

Thermal–structural analysis showed that the valve satisfies the applicable stress requirements under the analyzed operating conditions. However, modal and harmonic response analyses indicated that the valve stem–gate assembly is susceptible to high-amplitude resonance at small openings. To mitigate flow-induced vibration, a downstream pipe expansion section was proposed and evaluated. Comparative analysis showed that an expansion diameter of 1,560 mm (1.3 times the original pipe diameter of 1,200 mm) and a length of 1,200 mm provided the greatest reduction in pressure pulsations and resonant vibration amplitude among the configurations evaluated. Full-scale experimental tests further supported the effectiveness of the optimized design. The findings provide a theoretical basis and practical guidance for vibration mitigation in large-diameter wedge gate valves. Future work will investigate valve vibration under a wider range of operating conditions and evaluate additional vibration mitigation measures to further improve the design methodology.