1. What is a Centrifugal Slurry Pump?
Centrifugal slurry pumps, also called as mud pumps and slurry pumping machines, are effective dredging machines for mud or slurry extraction and long distance transporting. High-quality centrifugal slurry pumps can achieve a certain depth of slurry extraction, while multiple centrifugal slurry pumps combined can achieve slurry extraction and long distance delivery.
In the practical application, What factors should be considered in the design and operation of centrifugal slurry pumps system? How can OCEAN Pump help with your centrifugal slurry pump solutions? The key factors are analyzed and summarized below.
2. What is Mud or Slurry?
In the context of mud pumps, “mud” refers to a liquid containing solid particles, which can appear as thick red sludge or a low-concentration mixture with gravel and granular sediment exceeding ten centimeters in size. Slurry pumps are extensively utilized for slurry transportation, initially over short distances but now capable of covering tens or even hundreds of kilometers through centrifugal force. OCEAN brand centrifugal slurry pumps have been employed in various projects in Zhejiang, facilitating transport distances ranging from 50-80 km. These projects are currently underway and expected to be completed by 2022. Interested customers are welcomed to visit the construction site for guidance.
Mud transfer is commonly practiced within the mining industry during mining operations, processing procedures, and coal washing activities. The solids involved can include mineral raw materials or any substances processed into fine tailings. Other applications for mud treatment encompass power generation, sewage management, sand and gravel handling, as well as agricultural engineering.
In order to simplify the classification, the conveyed slurry is usually divided into two types.
2.1 Non-settling slurry（Uniform media）
Non-settling slurry usually looks like a liquid mixture of mud and water. Red mud is an example, in which solid particles are small and not easy to settle. In the conveying state, the solid phase concentration at the bottom of the pipeline is usually higher than that at the top, and the slurry is distributed in a bullet-like manner.
The solution to non-settling mud design is to model the fluid as a non-Newtonian fluid (also known as Bingham plastic fluid). If this liquid is released on the ground, it will not flow like water, but will collapse slightly (that is, disperse slightly). The smaller the slump of the liquid, the higher the shear stress and shear rate, the more difficult the mud pumping.
2.2 settling slurry （non-uniform media）
Sometimes, the centrifugal slurry pump is not capable of handling uniform slurry effectively. A typical example is the transportation of coal gangue tailings by a deep cone thickener. In such cases, workers can opt for a more expensive positive displacement pump or employ a combined treatment method, such as conveying the tailings onto a coarse mine on a conveyor belt and subsequently treating and extracting them.
The solids in this slurry are larger and more concentrated, with particle sizes ranging from 0.02mm to 150mm, including gravel. Treating this type of slurry typically relies on extensive practical experience due to inconsistencies in theoretical approaches that fail to account for turbulence effects. Empirical methods necessitate substantial data and depend on various factors as followed.
D50 particle size.
Medium specific gravity.
Solid concentration.
The ratio of particle size distribution to mud pumps impeller diameter.
3. What is the Design Origins of Centrifugal Slurry Pumps?
In 1930, Charles Warman, a young Australian engineer working at the Kalgoorlie Gold mine, invented and patented a mud pump that exhibited superior efficiency and reliability compared to previous mud transfer equipment. By the 1970s, his company had established itself as a global market leader. Today, most mortar pumps are designed based on the principles derived from Warman centrifugal slurry pumps. OCEAN Pump centrifugal mud pump also incorporates unique design concepts and supporting methods from the Warman pump while undergoing improvements and restructuring to develop a more advanced mud dredging design and comprehensive solution. The modern centrifugal slurry pump offers advantages such as wear-resistance, ease of operation, and maintenance.
Pump engineers must possess a comprehensive understanding of the fundamental principles governing mud treatment. The repercussions stemming from mishandling mud can encompass prolonged operational downtime and potential breaches in hermetically sealed areas. This article elucidates pivotal considerations that every engineer should be cognizant of, encompassing pipe friction losses, solid sedimentation, as well as the performance and longevity of centrifugal slurry pump systems.
4. What are the main points in the operation of the centrifugal slurry pump?
Five factors should be considered when treating the slurry with the centrifugal slurry pump, namely the wear and corrosion of the centrifugal slurry pump, the sealing of the centrifugal slurry pump, the performance of the slurry pump, the friction loss of the pipeline and the blockage of the pipeline.
4.1 Wear and corrosion of centrifugal slurry pump.
The most important issue for sand pump machine is the wear and corrosion of the slurry pumps and pipes. For some mud pumps materials, the pump casing may may wear out within a few days, causing mud leakage and endangering the environment, causing the entire mud transfer project to stop. The original Warman mud pumps used thickened overflow castings to extend life and added easy-to-replace bushings to reduce downtime.
Although modern centrifugal slurry pumps still have these functions, efforts have been made to develop the following more wear-resistant materials.
- Rubber and polyurethane. They have excellent corrosion and cavitation resistance and reduce wear when handling fine particles.
- Hard metals, such as ferrous and high-chromium alloy materials, some of which are protected by patents. These materials are suitable for the processing of hard, sharp particles, such as hard metal minerals.
- Ceramics have been unsuccessful because they are difficult to make, expensive, and break when cracks appear.
In addition, the wear of the centrifugal slurry pump is lowest in the range of 70% to 110% of the optimal efficiency flow rate. In other ranges, wear will be faster due to high flow rates or increased cavitation.
4.2 Seal of pumps
The sealing of the mud pump is also an issue that engineers need to consider.
4.2.1 packing seal
The cheapest and most effective sealing method is a packing seal. However, this requires the injection of clean filler sealing water, which may be difficult to obtain in some cases. An alternative is to use a centrifugal shaft seal, which eliminates the need for packing to seal water.
4.2.2 mechanical seal
The second option is a mechanical seal, which is relatively expensive. Mechanical seal failure has become a costly task in terms of downtime and part replacement, as the entire mud pump needs to be disassembled during the process of replacing the mechanical seal. Therefore, be careful when choosing a mechanical seal configuration.
4.3 slurry pump Performance
When designing slurry pumps, OCEAN PUMP publishes a performance curve for each pump, typically conforming to GB3216. Engineers use these curves to select the most appropriate type of centrifugal slurry pump for the project. Because the performance curve test uses clean water as the carrier, no matter what type of slurry is used, the conveying pressure and efficiency of the slurry pump will be lower than that of clean water. For a constant feed stock, these reductions are generally summarized as total pressure ratio (HR) and efficiency ratio (ER). Engineers often use empirical theory to estimate these values, and also consider some unexpected factors when considering them.
4.4 Pipeline friction loss
Compared with pumping water, pumping mud increases pipe friction losses. For settling slurry, the increase is greatest when the pipeline flow is laminar rather than turbulent. For homogeneous slurry, the pipeline friction loss can be calculated by calculating formula. These formulas assume that the inputs come from the Bingham plastic model. In this case, engineers can use mud rheological tests to determine the input value.
4.5 Pipeline blockage
All the sludge transported by the centrifugal slurry pump, especially the unprecipitated sludge, will precipitate into solid in the pipeline. Silting may occur at the bottom. Solid particles adhere to the bottom of the pipe and move along it. However, if there is too much precipitation, the water flow rate will slow down, the pipe will be blocked, and it needs to be stopped for inspection. In order to prevent pipe clogging, the slurry flow rate must be increased to reduce the risk of solid settlement.
However, because the friction loss is proportional to the square of the pipeline speed, high-speed pipeline transportation will cause greater friction loss and require larger supporting power equipment. Designers must weigh these criteria carefully.
5. Conclusion
This article summarizes the main considerations when selecting and operating centrifugal slurry pumps. OCEAN PUMP engineers will select a total solution of mud pumps with sufficient power and pressure to transport mud, while also considering centrifugal mud pump seals, wear of flowing parts and pipe clogging. Engineers also need to consider the upfront capital costs of construction. At the same time, they need to control the size and weight of the centrifugal slurry pump and the accompanying power equipment, and consider the overall service life. An effective sizing system design requires expert advice.
OCEAN Pump designers have more than 20 years of mud transfer experience, please feel free to contact us for the selection, operation and maintenance of sand pumps and dredging vessels. If you have any questions or problems, please fill out the form below and we will answer them as soon as possible.
