Similarly, sludge pumps are designed to handle thick, viscous mixtures known as sludge, which often contain a high concentration of solids and can be even more challenging to transport than typical slurries. A standard centrifugal pump is rarely robust enough for pumping slurries, as the abrasive nature tends to wreak havoc on mechanical seals, the pump casing, the pump shaft and even the rotating impeller. To pump slurry effectively, specialized centrifugal pumps are necessary.
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Understanding the nuances of pumping abrasive slurries and sludge is essential for selecting the appropriate equipment and optimizing industrial processes. Slurries are prevalent in mining operations where ore and tailings must be moved, while sludge is commonly encountered in wastewater treatment plants and dredging activities. Both materials require robust, reliable, either centrifugal or positive displacement pumps that withstand harsh conditions and maintain high-performance levels. Also helpful can be flooded suction pumps, which are used often for wastewater treatment, mining and construction. Dredging activities often use submersible pumps for the same activities, as they can provide superior performance.
This comprehensive guide provides an in-depth look at slurry pumps, exploring the different types available, the benefits of different designs, the various slurry pumping applications, and the leading manufacturers in the industry. By delving into the technical aspects and practical considerations, we aim to equip you with the knowledge to make informed decisions when selecting and utilizing slurry pumps in your operations.
A slurry pump is designed specifically to handle abrasive and high-density slurries that contain solid particles mixed with liquids. These pumps are engineered to withstand the harsh conditions and mechanical wear of transporting such mixtures. Slurry pumps play a crucial role in various industrial applications, ensuring that slurries are efficiently moved from one location to another, whether within a processing plant, a mining operation, or dredging activities.
The primary function of a slurry pump is to provide the necessary hydraulic force to transport the slurry through pipelines, channels, or other conduits. They are built to handle the solid particles’ impact and abrasiveness, which would quickly wear out standard pumps. This durability makes slurry pumps indispensable in industries where solid-liquid mixtures are commonplace.
Slurries can be categorized based on their solid content, particle size, and abrasiveness into three main types: light, medium, and heavy-duty.
Light-Duty Slurry:
Light-duty slurries typically contain smaller and less abrasive particles. They are often encountered in applications like paper manufacturing, where the mixture is relatively thin and easy to pump. The primary concern of light-duty slurry pumps is ensuring they can handle the solid content without clogging.
Medium-Duty Slurry:
Medium-duty slurries have a higher concentration of solids and are more abrasive than light-duty slurries. They are commonly found in industries such as chemical processing and wastewater treatment. Pumps handling medium-duty slurries must balance wear resistance with efficiency, ensuring they can operate continuously without excessive maintenance.
Heavy-Duty Slurry:
Heavy-duty slurries are characterized by large, highly abrasive particles and a high solid content. Mining and mineral processing industries frequently deal with heavy-duty slurries, where ore and tailings must be transported over long distances. Heavy-duty slurry pumps are built with robust materials and designs to withstand such applications’ intense wear and tear.
While slurry and sludge pumps may seem similar, they are designed for different purposes and applications, with some key differences:
Composition:
Slurry Pumps: Slurry pumps are designed to handle mixtures of solids and liquids, where the solid particles can range from fine to coarse and from non-abrasive to highly abrasive. The slurry’s liquid component helps maintain the flow, making it less dense than sludge.
Sludge Pumps: Sludge pumps are specifically designed to handle thick, viscous mixtures known as sludge. Sludge typically has a higher concentration of solids, often organic, and is more challenging to pump due to its density and viscosity.
Design and Construction:
Slurry Pumps: Slurry pumps are built with materials resistant to abrasion and corrosion. They often feature larger impellers and thicker casings to withstand the impact of solid particles. They are designed to maintain high efficiency even when handling abrasive slurries.
Sludge Pumps: Sludge pumps are designed to handle high-viscosity fluids with a high solid content. They often have specialized features such as slow-moving components to handle the sludge without clogging or causing excessive wear.
Applications:
Slurry Pumps: These are commonly used in mining, mineral processing, dredging, and other industries where solid-liquid mixtures must be transported. Slurry pump manufacturers design these pumps to handle various slurry types, from light-duty to heavy-duty applications.
Sludge Pumps: These pumps are typically used in wastewater treatment, agricultural applications, and other scenarios where thick, viscous fluids must be moved. Submersible slurry pumps, a subtype of slurry pumps, are also used in dewatering and sump applications, where the pump needs to operate while submerged in the fluid.
Understanding the differences between slurry and sludge pumps and the various types of slurries is crucial for selecting the right equipment for your specific industrial needs. Choosing the appropriate pump ensures efficient and reliable operation, reducing downtime and maintenance costs while maximizing productivity.
Slurry pumps are indispensable in the mining industry. They are used extensively to handle abrasive and high-density slurries containing water and solid particles, such as ore, tailings, and other mining residues.
Applications:
Ore Transport: Slurry pumps transport the mined ore from the excavation site to the processing plant. This involves moving highly abrasive slurries over long distances.
Tailings Management: After the extraction of valuable minerals, the remaining slurry, known as tailings, needs to be transported to disposal sites. Slurry pumps are crucial for efficient and safe tailings handling.
Dewatering: Submersible slurry pumps are employed in dewatering operations to remove excess water from mining pits, ensuring safe and dry working conditions.
Processing: Slurry pumps facilitate the movement of slurries through various stages of mineral processing, including grinding, flotation, and thickening.
Slurry pumps are vital in the construction industry for handling the slurry produced during various construction activities. These pumps ensure that the site remains manageable and that operations continue smoothly.
Applications:
Tunneling: During tunnel construction, slurry pumps remove the slurry generated by boring machines. These pumps handle the mixture of water and excavated materials, ensuring the tunnel remains clear for continuous operation.
Foundation Drilling: Slurry pumps manage the slurry produced during foundation drilling, ensuring the boreholes remain stable and debris-free.
Sediment Removal: In construction sites where sediment and debris accumulate, slurry pumps efficiently remove these materials, maintaining site cleanliness and operational efficiency.
Concrete Mixing: Some slurry pumps are designed to handle the mixing and transport of concrete slurry, ensuring consistent quality and efficient delivery to construction sites.
Dredging is a critical application for slurry pumps, mainly submersible slurry pumps. These pumps remove sediment and debris from the bottom of water bodies, maintaining navigability and environmental health.
Applications:
Harbor and Port Maintenance: Slurry pumps dredge harbors and ports, removing accumulated sediment to maintain clear and safe waterways for ships.
River and Canal Dredging: Slurry pumps remove sediments from rivers and canals to prevent flooding and maintain water flow.
Land Reclamation: In land reclamation projects, slurry pumps transport dredged material to new land areas, creating new land from the sea or other water bodies.
Environmental Dredging: Slurry pumps are used in environmental projects to remove contaminated sediments from water bodies, helping to restore ecosystems and improve water quality.
Slurry pumps are crucial in wastewater treatment plants. They manage the thick, viscous sludges produced during treatment and ensure the efficient handling and processing of wastewater and sludge.
Applications:
Sludge Transport: Slurry pumps move sludge from one stage of the treatment process to another, ensuring continuous and efficient operation.
Thickening and Dewatering: Slurry pumps concentrate sludge in thickening processes and remove excess water in dewatering processes, reducing the volume of sludge that needs to be disposed of.
Aeration: In some treatment plants, slurry pumps mix and aerate the sludge, enhancing the breakdown of organic materials and improving treatment efficiency.
Chemical Dosing: Slurry pumps also handle and dose chemicals needed for treatment, ensuring precise and efficient chemical delivery.
Slurry pumps are used in various industrial applications beyond mining, construction, dredging, and wastewater treatment. Their ability to handle abrasive and viscous mixtures suits them for multiple tasks.
Applications:
Chemical Processing: In the chemical industry, slurry pumps handle corrosive and abrasive slurries, ensuring safe and efficient material transport.
Food and Beverage: Some slurry pumps transport food slurries, such as fruit pulp or other viscous mixtures, ensuring consistent quality and processing efficiency.
Power Generation: Power plants use slurry pumps to transport ash slurry from coal combustion in power plants, ensuring safe and efficient waste management.
Pulp and Paper: In the pulp and paper industry, slurry pumps handle wood chips and pulp slurries, ensuring smooth processing and efficient transport.
Selecting the appropriate slurry pump for your application is critical to ensure efficient and reliable operation. Here are vital factors to consider:
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Slurry Type:
Determine the slurry’s nature, particle size, density, abrasiveness, and viscosity. Different slurries require different types of pumps, such as light-duty, medium-duty, or heavy-duty slurry pumps.
Pump Material:
Choose a pump from materials that can withstand the slurry’s abrasive and corrosive properties. Common materials include high-chrome alloys, rubber linings, and stainless steel, each offering specific benefits for different slurries.
Power Requirements:
Assess the power needed to move the slurry efficiently. This includes considering the pump’s head (the height to which the slurry needs to be lifted) and the flow rate. Ensuring adequate power prevents underperformance and potential damage.
Pump Type:
Based on your operational environment and specific needs, it’s important to understand the differences between types of slurry pumps, such as centrifugal, submersible slurry pumps, or horizontal or vertical pumps.
Matching the pump specifications to your application’s needs is crucial for optimal performance. Incorrect pump selection can lead to:
By ensuring the pump’s specifications align with the application’s requirements, you can achieve better performance, longevity, and cost-effectiveness.
Regular maintenance and timely troubleshooting are essential for keeping slurry pumps, including submersible and sludge pumps, in optimal condition.
Regular Inspections:
Conduct routine inspections to check for signs of wear, corrosion, and leaks. Early detection of issues can prevent major failures.
Proper Lubrication:
Ensure all moving parts are adequately lubricated to reduce friction and wear. Follow the manufacturer’s guidelines for lubrication schedules and types.
Monitor Performance:
Monitor the pump’s performance metrics, such as flow rate and pressure. Any significant deviations can indicate potential problems that need to be addressed.
Replace Worn Parts:
Replace worn parts like impellers, liners, and seals regularly to maintain the pump’s efficiency and prevent breakdowns.
Training and Safety:
Ensure that personnel are trained in pump operation and safety protocols. Proper handling and operation can extend the pump’s lifespan and prevent accidents.
By considering these factors and following best practices for maintenance and troubleshooting, you can ensure that your slurry pump operates efficiently and reliably, providing long-term value and performance.
Choosing the right slurry pump and maintaining it properly are vital steps in optimizing industrial processes. Leading slurry pump manufacturers like DAE Pumps offer a range of high-quality pumps designed to meet the diverse needs of various industries, ensuring you have the best solutions for your specific applications.
From motor size and pump speed to wear life and operating costs, an imposing array of choices face a buyer intent on reaching and maintaining optimum pump performance. Here are some tips from experts.
by russell a. carter, contributing editor
Slurry pumps are essential for moving hard-to-handle, high solids-content fluids and sludge, and annual demand for these pumps reflects just one aspect of the significant space they occupy in several industry sectors. The global market for all types of slurry pumps is estimated at well more than a billion dollars each year, and although those sales represent only a single-digit portion of overall pump sales, slurry pumping costs take up a lot of space in mining’s collective energy budget. Process equipment supplier Metso estimated that slurry pumps account for only about 5% of centrifugal pumps — the most common type used for this purpose — installed throughout the mining industry, yet this small segment represents up to 80% of the industry’s total operational pumping costs.
The space they physically inhabit in a mining operation is typically harsh — at the bottom of a sump, a prep plant or thickener-underflow discharge point, or serving a pipeline carrying abrasive slurry. Their duty cycles range from continuous to sporadic depending on the application, often with highly variable flow rates and particle sizes. Internal wear can be severe in some applications, with as much as 2 mm of material a day disappearing from crucial component surfaces. Due to the increased probability of high wear rates from the materials being transported, pump builders add thicker, heavier components and/or internal liners, making slurry models larger and heavier than their water-pump brethren.
The wide range of pump-performance requirements encountered at thousands of mine, mill and other industrial sites requires an equally wide variety of pump types, sizes and mounting configurations. Two recent product introductions illustrate the range of available choices.
Going Big, Going Mobile
Late last year GIW Industries announced that it had developed the TBC-92 slurry pump specifically for use in oil sands operations. Named for its 92-in.-diam (234 cm) impeller, GIW claims the TBC-92 is the largest and heaviest slurry pump available in the mining industry.
At the other end of the size and portability scale, Gorman-Rupp’s transportable SludgeKat self-priming, positive displacement hydraulic piston pump is designed for convenient pumping of sludges and slurries from clarifying pits, wastewater treatment, mud pumping, environmental cleanup and similar applications.
The SludgeKat has 4-in. (100-mm) suction and discharge ports and is capable of flows up to 226 gpm (14.3 lps) and heads up to 390 ft (118.9 m). Depending on the product being pumped, SludgeKat can pass up to 2.4-in.-diam solids without damaging or clogging the pump. Units are equipped with Kohler Tier IV diesel engines.
Each SludgeKat comes standard with a wheel kit. The pump end frame is mounted to a 52-gallon (197-l) fuel tank base and offers a full-load run time of 25.5 hours. The pump end frame can be detached from the unit and when connected to optional 150-ft (46-m) hoses, provides increased portability around the job site.
In the space between these two very different pump solutions lies an array of conventional horizontal and vertical centrifugal models, submersibles and other types offering a wide range of performance characteristics that can be applied to specific slurry pumping requirements.
Pumps, unsurprisingly, can also fail to perform adequately if specified or installed incorrectly.
Look Beyond the Pump
The industry’s continuous drive to increase production from existing assets makes it important to view pump systems as one part of a much larger picture. In a recent blog post, Metso’s head of pump product management and marketing, Chris Wyper, outlined some important points to consider about pumps when aiming for plant-wide production increases. Among his recommendations:
Ensure motor power availability: “A well-designed plant has enough power allocated to mill pumps. Pumps typically operate on variable speed drives, meaning there are many process variables affecting speed and, finally, the power draw. It is a good idea to look at SCADA data on historical power drawn to better estimate the amount of power that would be available for tonnage increases. Rather than using engineering data sheets that are somewhat oversimplified, it is beneficial to use a point cloud type plot showing flow and pump pressure as a function of time. This information makes it possible to determine the optimal size of all the pumps and cyclones for the plant.”
Consider gearbox cooling at higher power: “As pump duty is increased, it usually also increases the power transmitted through the gearbox. This means that the amount of heat increases as well: a gearbox that is sized marginally for air to air cooling may overheat with higher continuous duty. Consideration must be given to the cooling capacity of the lubrication system, particularly at higher ambient temperatures and altitudes.”
Ensure gland seal water pressure at higher heads: “The pump gland seal water system should be sized so as to be able to deliver a constant flow of gland water under all operational conditions. This applies to the pump duty, including any increase in head due to tonnage increases. It should also be checked that the gland seal water system is adequate when other demands are placed on it, such as hose downs or flushing.”
Take a close look at pipe sizing: “If you double the speed, the rate of material loss increases 16-fold and the rate of abrasive wear on the surface is approximately proportional to the fourth power of velocity. If there is a significant increase in input, it is necessary to consider whether the pipe sizing is optimal. The right size allows friction losses and wear to be minimized. Of course, if there is a large variation in flow, then minimum velocity to prevent settling should be examined.”
Prepare for crash stops by calculating floor sumps: “In the case of a plant crash-stop, prepare for the maximum inflow based on calculations on the live volume of floor sumps. This may include the mill static overflow and any dump valves to empty pipes and sumps. If sump size is increased or the mill volume changed, then the sumps may be undersized. In this case, the existing sumps can be deepened or enlarged, to deal with the volume, or then additional sumps created. Typically, mill sumps should be separated from the other sumps in the plant due to the possibility of mill balls entering the sump.”
Expanding Future Options
As industry-wide figures indicate, slurry pumping can serve as a prime example of purchased capital equipment where operating and maintenance (O&M) costs rapidly eclipse the initial procurement cost. A myopic view of TOC (Total Cost of Ownership) factors when selecting a pump can result in a variety of bad outcomes ranging from the need to prematurely replace an inadequate unit, to sky-high maintenance costs and production losses from unscheduled downtime. Conversely, pump OEMs and aftermarket suppliers are increasingly cognizant that their customers can’t always predict future events and consequently are expanding their product and services portfolios to provide affordable options when mining conditions, maintenance resources or technology changes occur over time.
Manufacturers are also looking at ways to incorporate more performance flexibility into their pump models and ease some of the concerns associated with necessary pump modifications. “For example, we are developing a line of pumps designed with a solid casing with replaceable all-metal, liner-like elements,” said Will Pierce, manager of engineering, Schurco Slurry. The metallurgy for these wear components is a novel enhancement to the proven 27%-28% chrome white iron that the industry has used for decades. We have hard rock customers that started with rubber liners 20 years ago, now they’re in a different ore deposit at the same mine and the material is sharper or has different abrasive characteristics and the rubber isn’t lasting. With the shell we’ve developed, they’re able to convert to a completely metal lined pump without major impact to the overall installation through using backward compatible adapter plates,” Pierce explained.
The new design also offers Shurco’s coal clients notable benefits: “Our coal customers almost always use metal-lined pumps, but the industry is very price-sensitive right now, so this new development doesn’t have the traditional massive ductile iron outer shell and metal liner — instead, it has replaceable metal wear components. There’s no quality compromise on the pump’s internal components, no change in wear or hydraulic performance. It’s just a lower-cost alternative.”
Designing for Durability
A rule of thumb when selecting a slurry pump is to look for the most robust pump, in terms of performance, wear resistance, power and maintainability, that falls within the service class rating for the type of material being pumped. Even that simple process can be complicated when special circumstances arise, such as unusually high mechanical wear experienced in a specific application, or intermittent operation rather than steady running. Pump manufacturers generally have vast knowledge of what works and what doesn’t under many conditions, and they incorporate the features that do work into their latest designs. For example:
FLSmidth Minerals expanded its line of Krebs millMAX slurry pumps with the introduction of the millMAX-e, which features a unique wear-ring design that the company claims solves grinding and recirculation problems within the pump by maintaining clearances between the impeller and the suction side. By maintaining the design performance without increasing the speed, the wear ring extends the life of all wet end parts and reduces power consumption.
The millMAX-e model is unlined and offers a compact, space-saving exterior design aimed at reducing capital and replacement costs as well as motor-power requirements. However, according to the company, millMAX-e’s power frame uses the same bearing and shaft components as the equivalent millMAX power frames and is capable of handling applications requiring high speed and power. The millMAX-e is equipped with the patented Krebs pump belt tensioning system that allows users to quickly change out v-belts without having to realign the sheaves.
Tsurumi Manufacturing’s entries in the mining-class slurry pump market include its GPN and GSD series, rated at motor outputs of 7.5-50 hp (5.5-75 kW) kW and 50-100 hp (37-75 kW), respectively. Both series comprise submersible three-phase, high head and high volume heavy-duty slurry pumps driven by a four-pole motor. They are equipped with high-chromium cast iron agitators that the company said assist in smooth handling of settled materials. Motors are enclosed by a water jacket that assures efficient cooling even when the motor is exposed to air. Pumps in this series incorporate seal pressure relief ports that prevent pumping pressure from affecting the shaft seal.
Finland-based Flowrox’s heavy-duty CF-S horizontal centrifugal pump is the first in a series of centrifugal pumps to be introduced by the company and capable of continuously pumping highly abrasive and dense slurries. The company said the new pump can provide flows from as low as 2.3 m3/h to more than 4,000 m3/h at heads exceeding 76 m. The pump’s split-case design is claimed to provide a good balance between efficiency and wear, and models are available with a range of liner material options. The pump is compatible with Flowrox’s Digital Services platform, a customized IIoT-based process data collection and analysis system.
MBH Pumps unveiled the Ni-Hard series submersible slurry pumps, designed and built to pump slurries containing abrasive solids up to 65% by weight. These heavy-duty pumps, according to the supplier, are equipped with an external agitator that breaks settled or compacted solids, while its adaptive spiral plate technology delivers higher pumping with less energy consumption.
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