Pump knowledge --
Slurry pump
concept and applications


1.Concept of pump: all machines that are used to lift liquid, transport liquid, and increase the pressure of liquid can be called “PUMP”


2.
Slurry pump
: the pump that transports mixture of water and solids particles which contains dross. Speaking from their principle, Slurry pumps produced in Shijiazhuang China are centrifugal vane pumps.



3. Applications of Slurry Pumps:


1) This type of slurry pump is mainly used for slurry transportation in converter dust removal water system, blast furnace gas washing water system, continuous casting turbid water system and steel rolling turbid water system in iron and steel plants.


2) In the power industry, it is used for flue gas desulfurization systems and ash removal systems. Moreover, larger slurry pumps have been well used to act as the desulfurization main circulation pumps, for which, along with the dredging pumps mentioned later, the discharge diameters have been achieved 1 meter in China, and they all work well.


3) Slurry pumps are also widely used for the transportation of pump which contains abrasive solids in mining, metallurgy, coal, and environmental protection industries, such as the slurry pumping work in Metallurgical Concentrator, coal sludge and heavy medium transportation in coal washing plants, and river dredging etc..


4) In the chemical industry, some corrosive slurries containing crystals can also be transported. At present, about 80% of the applications of small and medium slurry pumps are used in concentrators in the mining industry.


5) In the field of seawater sand selection industry, the application of slurry pumps have also been well-known and recognized by the customers. Due to the habit of some industries, slurry pumps are called sand pumps in the seawater sand selection industry, and dredging pumps in the the river dredging industry, where there are super-large slurry pumps in use, which are used on super-large dredgers.


But in terms of the structural characteristics and the slurry transported by the pump, they can all be called slurry pumps.

When purchasing a slurry pump, the
Slurry Pump Supplier
will learn from the customer about the operating environment of the pump and the slurry pumped, etc., so as to recommend the most suitable pump type to the customer to ensure the The pump can last longer in its post. This is what we often call
slurry pump selection
. The following will introduce you to what aspects are related to the choice of slurry pump:



1. First determine which slurry pump to choose according to the working conditions


The working conditions mentioned here are understood as application industries, such as: mineral processing, coal processing, sand pumping, etc. (This step is very important, and it is also a prerequisite for selection)



2. Flow and head are the two most basic parameters for pump selection:


a: Preliminarily determine the general situation of the pump through the working conditions, such as which series model or whether to consider the material, etc.


b: After determining the series model of the pump, read the performance curve through the flow and head to determine the specific model and size of the pump.


c: Read the curve, calculate the power: The parameters that must be known in the calculation of the shaft power of the pump include flow rate, head, efficiency, and slurry specific gravity; efficiency (η) is determined by the flow rate and head, which can be read out by reading the performance curve; What cannot be provided is only through experience points. Generally (between 1-2), an estimated value will be given to calculate the power during technical calculation.


d: Calculated shaft power P=m*g*h/η Its derivation formula: P=ρ*Q*H/102η (pay attention to the use of safety factor in actual calculation)


e: motor power, the motor power which is the nearest and larger than the shaft power is taken as the final motor power by the shaft power.


More parameters: working condition flow head. Slag specific gravity. Specific gravity of solids. concentration. Ph temperature.


According to the basic process of A, except that in step C, the specific gravity parameter of the slurry is directly provided by the customer, or the specific gravity of the slurry is calculated by the specific gravity and concentration of the solid.


The weight concentration generally mainly considers the degree of abrasiveness of the slurry. For a certain kind of slurry, the higher the concentration, the higher the abrasiveness will be, and the higher the specific gravity of the slurry. Therefore, we have the concept of
Heavy-Duty Slurry Pumps
, neutral, and light-duty slurry pumps, which is based on the content of the slurry. There is no strict limit.


Ph value is one of the material factors that we judge to select the overcurrent parts of the pump (generally, the pH value of 5-12 considers the range of metal overcurrent parts, and the rest of the range considers rubber or other special materials. Here is also the theoretical numerical range that cannot be dead. set, to be flexibly applied);


Temperature is also one of the factors to determine whether the material can be used. Generally, temperature is a factor that is rarely considered in most cases, but sometimes there are special conditions that require temperature.


3. Detailed parameters


Working conditions, flow, lift, specific gravity of slurry, specific gravity of solids, concentration of pH, temperature, D50, D80, pipeline (pipeline, elbow, valve, taper (contraction, expansion), viscosity, etc.


It is still the basic process according to the first, but in this kind of detailed parameters, it is generally the bidding project, or the client is very special, so that so many detailed parameters can be provided. In general, the parameters that can be provided to two are already detailed. For some large projects and large bids, special design units or departments will provide customers with a detailed data, so it is possible to provide three levels of detail. In fact, this detailed parameter is mainly to increase the parameters of the pipeline, and the pipeline is the parameter of calculation (dynamic lift). Generally, many customers cannot provide detailed pipeline conditions, or the pipeline is simple, so they are ignored and directly provide a The head is only the head, so we don't need to forget it, but once the detailed pipeline is provided, we need to calculate the dynamic head by ourselves. The specific calculation of the dynamic head is relatively complicated, but there are ready-made formulas to apply.


For slurry pump selection, please contact CNSME - a
Slurry Pump Manufacturer
from China. welcome letter

[email protected]

!

This situation is generally due to the slurry pump suction pipe, or the instrument appears the phenomenon of air leakage, or may be due to the bottom of the slurry pump valve, not open the reason caused by. When encountering this kind of failure, the technical personnel should first check where the leakage position is, and give plugging in time. Secondly, the bottom valve of the slurry pump is repaired and replaced.

1. The cavitation phenomenon of the pump:


When the liquid is at a certain temperature and the pressure is reduced to the vaporization pressure at that temperature, the liquid will produce bubbles. This phenomenon of generating bubbles is called cavitation. When the bubbles generated during cavitation flow to a high pressure place, their volume decreases so that they burst. This phenomenon of bubbles disappearing in a liquid due to pressure rise is called cavitation collapse.


When the pump is in operation, if the absolute pressure of the pumped liquid is reduced to the vaporization pressure of the liquid at the current temperature in the local area of the flow-through part (usually somewhere behind the inlet of the impeller blade) for some reason, the liquid will be here. When the liquid containing a large number of bubbles passes through the high-pressure zone in the impeller, the high-pressure liquid around the bubbles will cause the bubbles to shrink sharply and burst. While the bubbles condense and burst, the liquid particles fill the voids at a high speed, and at this moment a strong water hammer effect is generated, and the metal surface is hit at a high punching frequency, and the impact stress can reach hundreds to thousands Atmospheric pressure will break down the wall thickness in severe cases.


The process of generating air bubbles and bursting of air bubbles in the water pump to damage the flow-through part is the cavitation process in the water pump. After the pump cavitation occurs, in addition to damaging the flow-passing parts, it will also generate vibration and noise, and cause the original performance of the pump to decline. In severe cases, the liquid in the pump will be interrupted and cannot work normally.



Second, the basic relationship between pump cavitation


The conditions for pump cavitation are determined by the pump itself and the suction device. Therefore, to study the conditions of cavitation, both the pump itself and the suction device should be considered. The basic relationship of the pump is:NPSHc≤NPSHr≤[NPSH]≤NPSHa


NPSHa=NPSH(NPSHc)－－－－－－－－—The pump starts cavitation


NPSHa＞NPSHr（NPSHc）－－－－－－The pump has no cavitation


In the formula, NPSHa - the NPSH of the device is also called the effective NPSH, the larger the NPSH, the less likely it is to erode;


NPSHr———Pump NPSH, also known as necessary NPSH or pump inlet pressure drop, the smaller the better the anti-cavitation performance;


NPSHc————critical NPSH, which refers to the NPSH corresponding to a certain value of pump performance decline;


[NPSH]－－－－Permissible NPSH is used to determine the operating conditions of the pump, usually [NPSH]=(1.1～1.5)NPSHc.


3. Measures to prevent cavitation:


In order to prevent cavitation, NPSHa must be increased to make NPSHa>NPSHr. The measures to prevent cavitation are as follows:


1. Reduce the geometric suction height hg (or increase the geometric backflow height);


2. To reduce the suction loss hc, try to increase the diameter of the pipe, and minimize the length of the pipe, elbows and accessories;


3. Prevent working under large flow for a long time;


4. Under the same speed and flow rate, the double suction pump is adopted, and the pump is not prone to cavitation due to the reduced inlet flow rate;


5. When cavitation occurs in the pump, the flow should be reduced as much as possible to reduce the power and speed;


6. The condition of the pump suction pool has an important impact on pump cavitation;


7. For pumps operating under harsh conditions, in order to avoid cavitation damage, cavitation-resistant materials can be used.

CNSME is a professional slurry pump manufacturer and supplier offering all types of slurry pumps. Every time the customer sees the production and assembly of the slurry pump, today we look at how the slurry pump is installed.