Erosion Wear of Non-Planar Tee Pipes Based on CFD Numerical Simulation

Literature Overview

This paper by Mo Li, Liu Qi, and Xu Xianyu, published in Lubrication Engineering (2022, Vol. 47, No. 8, pp. 41-46), investigates the erosion wear behavior of non-planar tee pipes subjected to solid particle-laden fluid flow using a CFD-DPM (Computational Fluid Dynamics - Discrete Phase Model) approach. Funded by the National Key Research and Development Program of China (2019YFC031230), the study systematically examined the effects of flow velocity, particle diameter, sand volume fraction, and tee angle on erosion wear patterns and rates. The research provides valuable insights for the design and protection of tee fittings in erosive service environments such as oil and gas production, slurry transport, and multiphase flow systems.

Core Technical Methodology

The study employed a coupled CFD-DPM approach to simulate the interaction between solid particles and the fluid flow field within non-planar tee geometries:

Simulation Parameters

Erosion Model

The erosion rate was calculated using a semi-empirical erosion model that incorporates:

• Particle impact velocity and angle
• Particle diameter and density
• Material properties of the pipe wall
• Cumulative erosion damage accumulation

Key Technical Findings

Erosion Location Patterns

The simulation identified the primary erosion zones:

• Primary Erosion Zone: The curved surface at the three-pipe junction, specifically the upper wall of the horizontal pipe elbow.
• Secondary Erosion Zone: The downstream wall of the branch pipe where flow impingement occurs.
• Minimal Erosion Zone: The inner wall of the horizontal pipe away from the junction.

The upper wall of the horizontal pipe elbow is most severely damaged because particles following the flow trajectory impact this surface at high velocity and favorable erosion angles.

Effect of Flow Velocity

The maximum erosion rate increases exponentially with flow velocity. This exponential relationship arises because:

• Particle impact velocity increases with flow velocity
• The number of particle-wall collisions increases with flow velocity
• The erosion rate is proportional to a high power of impact velocity

Effect of Sand Volume Fraction

At low velocities, the erosion rate is relatively insensitive to sand concentration because the particle impact energy is below a critical threshold. At high velocities, the erosion rate increases linearly with sand concentration because each additional particle contributes independently to the cumulative erosion damage.

Effect of Tee Angle

Increasing the tee angle from 90° to 150° reduces the erosion rate linearly. This occurs because:

• Larger angles reduce the flow constraint on solid particles
• Particles experience less directional change and lower impact velocities
• The flow pattern becomes more streamlined with reduced turbulence

Effect of Particle Diameter

The maximum erosion rate increases gradually with particle diameter. Larger particles produce more concentrated erosion damage because:

• Individual particle impact energy increases with diameter
• The erosion damage from each particle is more localized
• The spatial distribution of erosion becomes more concentrated

Engineering Practice Implications

Material Selection

The erosion rate data can be used to select appropriate pipe materials for specific service conditions:

• High-velocity, high-sand service requires erosion-resistant materials (e.g., hardened steel, ceramic-lined pipe)
• Lower-velocity service may tolerate standard carbon steel with appropriate wall thickness

Geometry Optimization

The tee angle findings suggest that:

• Larger tee angles (closer to 150°) reduce erosion but may affect system layout
• The optimal angle balances erosion resistance with spatial constraints
• The junction geometry should be designed to minimize flow impingement

Protective Measures

Based on the erosion location patterns, targeted protection measures include:

• Hardfacing or overlay welding at the primary erosion zone
• Sacrificial wear plates at high-erosion locations
• Flow straighteners upstream of the tee to reduce particle turbulence
• Velocity reduction through larger diameter piping upstream

Inspection and Maintenance

The erosion rate predictions enable:

• Establishment of inspection intervals based on predicted erosion rates
• Development of thickness measurement protocols at critical locations
• Proactive replacement planning before failure occurs

Study Insights and Reflections

This study provides a comprehensive quantitative framework for predicting erosion wear in non-planar tee pipes under multiphase flow conditions. The CFD-DPM approach offers a practical tool for evaluating different design parameters and service conditions without extensive and expensive experimental testing. The identification of the primary erosion zone at the upper wall of the horizontal pipe elbow is consistent with field observations and provides a clear target for protective measures. The exponential relationship between erosion rate and flow velocity is particularly important for engineering design, as it means that modest increases in flow velocity can lead to dramatically increased erosion rates. For engineers in the oil and gas, mining, and slurry transport industries, this study provides the technical basis for optimizing tee geometry, selecting protective materials, and establishing inspection and maintenance programs for tee fittings in erosive service. The systematic investigation of multiple parameters simultaneously provides a more complete understanding of the erosion behavior than single-parameter studies, enabling more accurate predictions for real-world service conditions.