How can the lifespan of mining pipe fittings be extended?
We understand that in the process of ore beneficiation in mines, pipe fittings play a crucial role as auxiliary equipment for transporting various slurries. To ensure safe transport, these pipe fittings are mostly made of steel or cast iron materials. However, the slurries being transported contain solid particles that can lead to wear and corrosion of the pipe fittings, affecting their lifespan.
So, what are the primary causes of wear in mining pipe fittings?
The main reason for pipe fitting wear is the ore particles. Depending on the particle size of the ore and its distribution within the slurry, we classify slurry into three types: homogeneous, nearly homogeneous, and non-homogeneous. Homogeneous slurry refers to a suspension of solid particles evenly dispersed in a single fluid, typically with particles smaller than 0.25mm, which can mix well with water and adhere to fluid dynamics laws. For particles larger than 0.25mm, in horizontal flow, gravity causes higher particle concentration at the bottom of the pipe, which can lead to sedimentation. Such slurry is considered non-homogeneous and doesn’t fully adhere to fluid dynamics.
In a slurry, ore particle movement can be categorized as suspension, jumping, and displacement. Among these, displacement causes the most significant wear on the pipe wall. The pushing force of ore slurry particles determines their axial speed, and the greater the pushing force, the faster the speed and wear.
What are the other factors contributing to pipe fitting wear?
- Hydraulic Conditions: In the movement of suspended ore particles, the flow rate of the slurry is crucial. Wear is generally proportional to the slurry flow rate raised to the power of 2.7-3.
- Ore Factors: Pipe fitting wear in slurry transport is related to ore particle size, shape, hardness, and slurry concentration. When particle size is less than 0.05mm, wear on the pipeline is minimal. However, as particle size increases between 0.05mm and 0.5mm, wear on the pipeline also increases. For particles larger than 0.5mm, wear on the pipeline becomes significant. Similarly, when the particle concentration in the slurry is less than 1%, the probability of particles colliding with the pipe wall is very low, resulting in minimal wear. But as the particle concentration increases, wear on the pipe also rises. Higher ore hardness leads to faster pipe fitting wear. Additionally, if the ore has a high density, it settles quickly, making it challenging to maintain a uniform suspension and exacerbating wear at the bottom of the pipeline.
- Corrosive Wear: Pipe fittings can experience electrochemical corrosion and pitting. When cast iron and steel rust in the atmosphere, they lose their protective qualities. The presence of sulfides like pyrite and marcasite in the transported slurry can accelerate pipe corrosion. In long pipelines with steep slopes, abrupt changes in pipe height can create localized vacuum and positive pressure when slurry rises and falls, leading to pitting damage to pipe fittings.
Methods to ease pipe wear:
Having analyzed the primary causes of pipe fitting wear, what are some effective ways to mitigate this issue? Based on practical experience, DEF Rubber has compiled some methods. Of course, we are open to your suggestions and eager to discuss further:
- Use Advanced Wear-Resistant Materials: To enhance pipe fitting wear and corrosion resistance, consider using advanced wear-resistant materials such as wear-resistant Rubber Lining, polyurethane, or cast stone. Wear-resistant Rubber Lining, in particular, has proven highly effective. DEF Rubber has developed wear-resistant Rubber Lining with wear indices exceeding 130% and rebound rates exceeding 80%. It finds extensive application in mining machinery and pipe fittings, significantly reducing wear and extending the lifespan of the fittings. Polyurethane materials are more expensive and offer lower wear resistance compared to wear-resistant Rubber Lining. Cast stone is also a popular wear-resistant material for pipe fittings, typically used as an inner lining for steel pipes, protecting the pipe from wear. However, cast stone fittings are more challenging to construct and maintain than wear-resistant Rubber Lining, given their significant weight.
- Increase Slurry Concentration: Maintaining slurry concentration within the “critical concentration” range during transport is essential. The critical concentration is a range, rather than a specific value, as it fluctuates based on factors like slurry volume and solid particle size. In the “reduced drag region” within this range, higher slurry concentration reduces the critical flow rate. This helps prevent coarse, sharp, and hard ore from settling at the pipe bottom, reducing concentrated wear and prolonging pipe fitting lifespan. Moreover, higher slurry concentration conserves water and energy.
- Pre-Separation of Coarse Ore Particles: In tailings transport, a significant portion of the ore particles consists of 0.2-0.5mm particles and some larger than 0.5mm. These particles contribute to higher pipe wear. To reduce wear, consider classifying the slurry before it enters the pipeline to remove larger ore particles, thereby minimizing wear.
- Mitigate Corrosive Wear: To reduce pipe fitting wear due to electrochemical corrosion, consider three main methods: (1) Controlling electrode potential through anodic or cathodic protection. (2) Adding corrosion inhibitors to the slurry. These inhibitors can be anodic, cathodic, or mixed inhibitors, each impacting different aspects of corrosion. (3) Applying protective coatings on the pipe fittings. Non-metallic coatings such as red lead paint and alkyd resin paint can effectively isolate corrosive elements.
- Maintenance: Regularly inspect pipe fitting wear, repair any damaged coatings, and periodically flip or change pipe direction to ensure even wear across the fittings.
Pipe fitting wear and corrosion are complex issues, and the approach to mitigating them may vary for each company. It requires careful and meticulous attention to detail.