Understanding Pump Capacity
Pumps are classified into three types: reciprocating, diaphragm, and centrifugal. Because of their durability and performance, centrifugal pumps are used in many slurry systems. A centrifugal pump moves slurry through the system by rotating an impeller.
Two parameters primarily define pump capacity: head pressure and flow rate. Manufacturers provide each pump with a pump curve that plots pressure and flow against each other. This curve determines whether a pump is appropriate for our application.
The more complex the application, the more critical it is to have expert assistance in determining the pump design characteristics required. However, some fundamental steps can be taken in any situation. Read below to understand the flow and slurry pump calculations.
Choosing a Slurry Pump: What You Need to Consider?
Calculate the flow rate
We must first calculate the flow rate before sizing and selecting a pump. In an industrial environment, the flow rate is frequently determined by the plant’s production stage. It may be as simple as calculating that 100 gpm (6.3 L/s) is required to fill a tank in a suitable or even the total volume may be affected by some procedure contact that must be thoroughly investigated.
Calculate the static head
The height between the vacuum container liquid level and the outflow pipe end height, or the height between the dispersal tank liquid level and the drainage pipe end height, must be monitored.
Calculate the friction head
The fluid velocity, pipe size, and pipe length determine the pressure head. The role of the friction head is essential as it serves the main pipe.
Determine or Calculate the total head
The compression power results from the flow rate (which can either be positive or negative) and the interfacial head.
Selecting the pump
Pump selection is based on total head and flow requirements and application suitability.
Slurry Pump Determination and Slurry Pump Calculations
When calculating a slurry pump, the process measures must be calculated.
Particle size and distribution
Particle size d50 (d85) is a proportion of fragments in a slurry that is a given size or smaller.
The value is calculated by sifting the solids through various mesh screens and measuring each portion. The percentage of particles of different sizes can then be read by drawing a sieve curve. d85= 3 mm, for example, indicates that 85% of the particles have a diameter of 3 mm or less.
Small particle mass fraction
The proportion of particles is less than 75 m in size. The percentage of small particles in the slurry must be determined. Particles smaller than 75 m in diameter can help to move larger particles. If the fraction of particles smaller than 75 m approaches 50%, the slurry’s character shifts to non-settling.
The particle concentration in the slurry can be expressed as a volume percentage, Cv, or a weight percentage, Cm.
What is the Density / Specific Gravity?
The Specific Gravity of a solid denotes its density. This value, SGs, is calculated by dividing the solid’s density by the density of water.
Water has a density of 1000 kg/m3. At 20°C, the SG of water is 1. The price varies slightly depending on the temperature.
A nomograph can be used to determine the specific gravity of the slurry.
The form of the granules is significant for the pumping behavior of the slurry as well as the wear on the pump and pipeline structure. The form factor shows the divergence of the slurry particles from a perfect sphere. It is essential to know these details.
Characteristics of Slurry
Slurries are classified as either settling or non-settling.
A mixture in which the contents do not collapse to the bottom but rather persist in the environment for an extended period. A non-settling slurry has a homogenous, viscous behavior, yet its properties are non-Newtonian.
Size of particles: less than 60-100 m.
A homogeneous mixture is what a non-settling slurry is.
A mixture of solids and liquids in which the solids are evenly distributed.
This type of slurry clears up quickly during the processing time but can be kept suspended by volatility. Particle diameter: more than 100 m
A going-to-settle slurry is a pseudo-homogeneous or heterogeneous mixture that can be fully or partially stratified.
A mixture in which all molecules are suspended, but the accumulation is higher at the bottom.
A solid-liquid combination in which the particles are not distributed evenly and tend to accumulate more at the bottom of the pipe or containment vessel (compared to settling slurry).
Except for density, the viscosity of a liquid determines its properties.
As soon as pressure is given to a liquid, it will deform indefinitely. It is said that they flow. When a fluid liquid flows, it is opposed by internal friction caused by the togetherness of the molecules. This internal friction is a liquid feature known as viscosity.
The viscosity of liquids decreases fast as temperature rises.
Shearing stress in Newtonian liquids is linear and related to the velocity gradient or shearing rate. Water and most liquids are Newtonian.
Liquids with non-Newtonian properties
Some liquids, such as water-based slurries containing fine particles, do not follow the straightforward relationship between shearing stress and shearing rate. They are also known as liquids that aren’t Newtonian.
Some non-Newtonian liquids have the unusual trait of refusing to flow unless a specific minimum shear stress is applied.
The effectiveness of a centrifugal pump pumping slurry varies from the efficacy of a centrifugal pump pumping necessity depending on the slurry’s liquid/solid content
This difference is determined by the slurry’s properties (particle size, density, and shape, as previously described) in the preceding chapter). Power (P), head (H), and efficiency () are the factors that are affected. The following graphs depict the differences between slurry and water.
Energy and Heads of flowing Liquids
In a stable equilibrium, water and other liquids find their balance. Water in a structure high on a hill offers promise. It has the ability to do work or, to put it another way, it has energy. On the way down to the lower grounds, Potential energy is converted to kinetic energy, which is used to perform actual work, such as driving a turbine-generator set or a motor.
Float a barge or a water mill down a river. Put another way, as in a waterfall, all this energy can be wasted.
Dams store water for various reasons, including hydroelectric and electric power generation.
generation, in irrigation schemes, crop cultivation, in municipal water distribution systems, as one of the
essential components of life, as well as river flood mitigation schemes Water, must only be used in hydroelectric schemes.
be kept at high altitudes, where there is a lot of convertible potential energy Water circulation and irrigation
Pumps are used in systems to impart kinetic energy to water so that it can be circulated through pipes and/or elevated to higher land.
Fluid flow is always from the highest energy point to the lowest. Energy is the ability to perform work.
The static pressure is the lateral gap in quality between the slurry source’s surface and the discharge point.
Losses due to friction
Friction occurs when the liquid flows through the discharge line and valves. When pumping slurry, friction damages suffered by pipe diameter bends and valves differ from the standard heavy water pumping losses.
Head of total discharge
This worth is used in pump estimations and is made up of the static head plus friction losses caused by pipes and valves, all transformed into meters of water.
In general, the flow velocity in the pipes must be maintained above a certain threshold. Friction losses increase as flow velocity increases. This may also lead to increased wear in the pipe system. Low flow rates cause sedimentation in the pipes and, as a result, significant losses.
- The water pump curve
- The slurry reduced curve
- The slurry duty point is where the pump system curve and the performance curve intersect.
Other Factors to Consider
When using pumps, the pump’s inlet pressure must exceed the vapor pressure of the liquid inside the pump. The stated required inlet pressure for the pump, NPSH req, must not be less than the available value in the pump system, NPSH.
The available value is affected by the ambient air pressure (height above sea level), the liquid’s vapor pressure, the slurry’s density, and the sump’s level.
Pumping a water-based slurry at 1000 meters above sea level, for example. The liquid temperature is 40°C, and the fluid level is 2 meters above the pump inlet.
NPSHa = air pressure – vapor pressure + sump inlet level.
NPSHa = 9,2 – 0,4 + 2 = 10,8
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