Wilson,
There are more similarities with slurry piping and petrochemical than one might think.
Let me first address the above comment by 11echo regarding centrifugal pumps. PCP’s together with peristaltic pumps are used in slurry application but are very limited. They’re best suited for homogenous, fine particle pastes and slimes respectively. Slurries are, by definition, fluid mediums containing anything from 25mm particles to 25 microns. The Mono pump that reliably handles 2mm particles would really be something to behold. Of the slurry applications 95% utilize centrifugal pumps.
The biggest considerations with slurry are naturally the wear rate, as well as necessary velocity. These are of course mutually exclusive. Wear rate in pipelines increases by the square of the velocity. But for heterogeneous slurries i.e. solids concentrations of less than 30% by volume (rough rule of thumb), the average velocity would need to be large enough and pipe diameter small enough to eliminate settling out of the particles and blockage - in the order of 2.5 to 3 m/s.
Your biggest wear components are your reducers, elbows, pump impeller and pump nozzle. Eccentric reducers for liquids are usually top flat, for slurries bottom flat. A top flat reducer creates an impingement site for the particles concentrated towards the bottom of the pipe. Elbows should be 3D or 5D bends. This is not only from a wear point of view but also to reduce drag. Pump impellers are not like that for water distribution. Clearances are greater and the impellers are hardened chrome for larger particles slurries and rubber lined for finer tailings and slimes. Because of the wear rate, especially for a badly selected pump curve, the piping arrangement for both discharge and suction lines should allow quick turn-around for casing disassembly. Natural rubber lined piping is the norm and really is unrivalled as an economic compensation for wear rates. However, on very large pumps, the churning transmitted by the impeller “swirls†back through the suction line into the sump / tank. These components should have a more exotic lining example ceramic. Polyethylene piping is also a very good alternative. For tight bends and installations many applications utilize reinforced rubber lined, industrial hose – but not of pump suctions.
As for piping arrangements, vertical lines are good. The majority of slurry processes, excepting overland pipelines, try to use gravity feed as much as possible. The philosophy is therefore to use large pumps to pump vertically to a convenient datum and then allow gravitation through the process equipment.
Instead of 90 elbows use two 45’s with a spool piece between
Avoid dead and dog legs
Space flush points every 5m – for high concentration slurries
Avoid branch entry tees – especially for your parallel pumping use lateral tees and y-branches
Avoid butterfly valves – even rubber lined ones, use diaphragm or pinch valves
Make sure the piping engineer specs the pipe for water hammer
Pipeline discharge should ideally be to atmosphere
Pump discharge should be vertical or 45 degrees up or top horizontal discharge. Avoid bottom horizontal discharge as air entrainment in the casing with cause cavitation and de-sliming.
As a research objective try and visit any website that shows pictures of a mineral sands plant. That should give a lot of hints
Centrifugal slurry pumps, also called mud pumps, slurry pumping machine, which are effective dredging machines for slurry or mud extraction and long distance transportation. High-quality centrifugal slurry pumps can achieve a certain depth of slurry extraction, or multiple centrifugal slurry pumps can cooperate to achieve slurry extraction and long distance delivery. In the practical application, What factors you should consider when design and operate the centrifugal slurry pumps system? How will OCEAN Pump help for your centrifugal slurry pumps solution? The key factors are analyzed and summarized below.
1. What is slurry
1.1 Two types of slurry
In order to simplify the classification, the conveyed slurry is usually divided into two types.
1.1.1 Non-settling slurry（Uniform media）,
Non-settling slurry usually looks like a fluid mixture of mud and water. An example is the red mud. The solid particles are small and not easy to settle. The solid concentration at the bottom of the pipeline is usually higher than that at the top in the transportation state, and the mud slurry is distributed like bullets.
The solution for non-settlement mud design is to model the fluid as a non-Newtonian fluid (also known as Bingham plastic). If this liquid is released on the ground, it will not flow like water, but will collapse a little (that is, scattered slightly). The “smaller” the liquid slump, the higher the shear stress and shear rate, the more difficult it is to slurry pump.
1.1.2 settling slurry （non-uniform media）
Sometimes, centrifugal slurry pumps can’t handle uniform slurry. A typical case is the coal tailing conveyed by the deep cone thickener. In this case, the workers can use more expensive positive displacement pumps, or use joint disposal methods, such as setting tailing to the coarse ore on the conveyor belt, and then processing and extracting tailing.
There are larger solids in the mud, and the concentration is higher. The particle size of D50 is usually between 0.02mm and 150mm, which includes gravel. The way to deal with this kind of sedimentation slurry usually draws on years of practical experience. The theoretical method is inconsistent, partly because this method cannot model the effect of turbulence. The empirical method requires a lot of data and depends on the following factors.
D50 particle size. Medium specific gravity. Solid concentration. The ratio of particle size distribution to mud pumps impeller diameter.
1.2 What is mud slurry
In the mud pumps concept, “mud slurry” is a liquid containing solid particles. It may look like thick red mud, or a low concentration medium that contains gravel more than ten centimeters and granular mud lumps. Slurry pumping machine is widely used to transport mud slurry. The initial transportation distance was very short, but now centrifugal slurry pumps can be used for long distance transportation that are tens or even hundreds of kilometers long. OCEAN Brand centrifugal slurry pumps are used in several projects in Zhejiang with a transportation distance of 50-80 kilometers in progress, the construction period is until 2022. Interested customers can go to the work site for inspection and guidance.
Mud slurry transportation is common in the mining industry and as part of the mining, processing and coal washing. The solids can include raw mineral materials, or anything processed to fine tailing. Other applications of mud slurry treatment include power generation, sewage, sand and gravel, and even agricultural engineering.
2. The design origins of centrifugal slurry pumps
In 1930, while working at the Kalgoorlie Gold Mine, a young Australian engineer named Charles Warman invented slurry pump that was more efficient and reliable than previous slurry transportation equipment, and applied for a patent. By the 1970s, the company he established had become a global market leader. Today, most sand slurry pump design principles are from Warman centrifugal slurry pumps. OCEAN Brand centrifugal slurry pumps also refer to some unique design concepts and supporting methods of Warman Pumps, and are improved and recombined to form a relatively mature slurry dredging design and overall solution. The modern centrifugal slurry pump advantages are wear resistance, easy operation and maintenance. Centrifugal slurry pumping machine is usually operated in remote and harsh environments, so they must be reliable and easy to maintain.
Engineers must understand the basic principles of mud slurry treatment. Consequences of mud slurry handling problems may include long downtime and sealed areas leaks. This article describes the key considerations that every engineer needs to understand, including pipeline friction loss, solids settling, and the centrifugal slurry pumps system performance and life.
3. Main points in the centrifugal slurry pumps operation process
There are five factors to consider when dealing with slurry with centrifugal slurry pump, namely centrifugal slurry pumps wear and corrosion, centrifugal slurry pumps seal, slurry pumps performance, pipeline friction loss and pipeline blockage.
3.1 Centrifugal slurry pumps wear and corrosion. The most important issue for sand pump machine is the wear and corrosion of the slurry pumps and pipeline. For some mud pumps materials, the pump casing may be worn through within a few days, which will cause the mud leakage to harm the environment and cause the entire slurry transporting project to stop. The original Warman slurry pumps used thickened overflow castings to extend the life, and added easy-to-replace bushings to reduce downtime.
Goto SHANGLISHI to know more.
Although modern centrifugal slurry pumps still have these functions, great efforts have been made to develop more wear-resistant materials as follows.
a. Rubber and polyurethane. They have excellent corrosion resistance and cavitation resistance, and reduce wear when handling fine particles.
b. Hard metals, such as white iron and high chromium alloy materials, some of which have patent protection. These materials are suitable for hard and sharp particles, such as hard metal mineral processing.
c. Ceramics have been unsuccessful because they are difficult to manufacture and expensive, and they are broken once they have cracks.
In addition, in the range of 70% to 110% of the best efficiency flow rate, the wear of the centrifugal slurry pump is the lowest. In other range, the wear will be faster due to high flow velocity or increased cavitation.
3.2 Seal for the pumps
The slurry pumps sealing is also a problem that engineers need to consider.
3.2.1 packing seal
The cheapest and most effective sealing method is packing seal. However, this requires to inject of clean packing sealing water, which may be difficult to obtain in some cases. An alternative method is to use a centrifugal shaft seal, which eliminates the need for packing seal water.
3.2.2 mechanical seal
The second choice is mechanical seals, which are relatively expensive. In terms of downtime and parts replacement, mechanical seal failure has become a costly task, because the entire mud pumps need to be disassembled during the process of replacing the mechanical seal. Therefore, be careful when choosing a mechanical seal configuration.
3.3 Performance for slurry pump
When designing slurry pumps, OCEAN PUMP will publish the performance curve of each slurry pump, which usually conforms to GB3216. Engineers use these curves to select the most suitable centrifugal slurry pumps type for the projects. Because the performance curve test uses clean water as the carrier, regardless of the type of slurry in use, the delivery pressure and efficiency of the slurry pumps will be reduced compared with clean water. For a constant conveying slurry, these reduction discounts are usually summarized as the total pressure ratio (HR) and efficiency ratio (ER). Engineers often use empirical theory to estimate these values, and some unexpected factors are also referenced in the consideration.
3.4 Pipeline friction loss
Compared with pumped water, pipeline friction loss will increase when pumping mud. For settling slurry, when the pipe flow is laminar rather than turbulent, the maximum increase. For homogeneous slurry, calculation formulas can be used to calculate pipe friction loss. These calculation formulas assume input from the Bingham Plastic model. In this case, the engineer can use the mud rheology test to determine the input value.
3.5 Pipeline blockage
All the sludge transported by the centrifugal slurry pumps, especially the non-settling sludge, will settle into solids in the pipeline. Bottom siltation may occur. Solid particles are attached to and move along the bottom of the pipe. However, if the sedimentation is too much, the water flow rate will slow down, and the pipe will be blocked, requiring shutdown for inspection. In order to prevent pipeline blockage, the slurry flow rate must be increased to reduce the risk of solids settling.
However, because the friction loss is proportional to the square of the pipeline speed, high speed pipeline transportation will cause large friction losses and require large supporting power equipment. The designer must weigh these standards carefully.
Conclusion
This article outlines the main considerations when selecting and operating centrifugal slurry pumps. The OCEAN PUMP engineers will choose the overall solution of the slurry pumps with sufficient power and pressure to transport the mud, and also consider the centrifugal slurry pumps seal, the flow parts wear and the pipeline blockage. Engineers also need to consider the upfront capital cost in construction. At the same time, they need to control the centrifugal slurry pumps and supporting power equipment size and weight, and consider the overall service life. An effective slurry system design requires expert advice. The OCEAN Pump designer has more than 20 years experience in mud transportation, please feel free to contact us for sand pump and sand dredger selection, operation and maintenance. Any questions or problems, please fill the following form, we will answer as soon as possible.
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