A mechanical seal, also known as an end seal, has a pair of end faces perpendicular to the axis of rotation, the end face under the action of fluid pressure and compensating mechanical external elasticity, relying on the auxiliary seal with the other end to maintain the fit and relative sliding, thus preventing fluid leakage
The mechanical seal itself is a demanding precision part, with high requirements for design, machining, assembly, and quality. In the use of mechanical seals, should analyze the use of mechanical seals of various factors, so that mechanical seals are suitable for a variety of pump technology and the use of media requirements and adequate lubrication conditions, so as to ensure long-term reliable operation of the seal.

 

centrifugal-pump-mechanical-seal

The more common causes of leakage of centrifugal pump mechanical seal 

The proportion of mechanical seal leakage accounts for more than 50 % of all maintenance pumps, the operation of the mechanical seal directly affects the normal operation of the pump, which is summarized and analyzed as follows:

Periodic Leakage

The pump rotor axial runout is large, the auxiliary seal and shaft interference is large, and the dynamic ring can not move flexibly on the shaft. After the pump is turned over and the movable and static rings are worn, no compensation displacement is available
Solution: When assembling the mechanical seal, the axial runout of the shaft should be less than 0.1mm, and the interference between the auxiliary seal and the shaft should be moderate to ensure radial sealing while the dynamic ring is assembled to ensure that it can move flexibly on the shaft (the dynamic ring can spring back freely when pressed against the spring)

Insufficient amount of lubricant on the sealing surface causes dry friction or pulls hair on the sealing end face
Solution: the height of the lubricant surface in the oil chamber should be increased to a level higher than the sealing surface of the moving and static rings.

The rotor vibrates periodically. The reason is that the stator is not aligned with the upper and lower end caps or the impeller and the main shaft are not balanced, cavitation or bearing damage (wear), and this condition will shorten the seal life and produce leakage.  
Solution: the above problems can be corrected according to the maintenance standards.  

Leakage due to pressure

High pressure and pressure wave caused by mechanical seal leakage due to the spring than the pressure and the total pressure ratio design is too large and the pressure in the seal cavity more than 3MPa, will make the seal end face pressure is too large, liquid film is difficult to form, the seal end face wear serious, heat generation increased, resulting in thermal deformation of the seal surface.  
Solution: When assembling the machine seal, the spring compression must be carried out in accordance with the provisions, not allowing too large or too small phenomenon, the mechanical seal under high pressure conditions should take measures. In order to make the end surface force reasonable, minimize deformation, can use carbide, ceramic and other materials with high pressure strength, and strengthen the cooling lubrication measures.

Mechanical seal leakage caused by vacuum state operation pump in the start-up, shutdown process, due to pump inlet blockage, pumping medium containing gas and other reasons, it is possible to make the seal cavity negative pressure, the seal cavity if the negative pressure, will cause the seal end face dry friction, internal mechanical seal will produce gas (water) leakage phenomenon, vacuum seal and positive pressure seal is the difference between the direction of the sealing object, and mechanical seal also There is a certain direction of adaptation.  
Solution: the use of double-end mechanical seal, which helps to improve lubrication conditions, improve sealing performance

Leakage due to media

Most of the submersible pump mechanical seals after disassembly, static ring and dynamic ring auxiliary seals are not flexible, some have rotted, resulting in a large number of leakage of the mechanical seal and even the phenomenon of grinding shaft. Due to high temperature, weak acid and alkali in the sewage on the static ring and moving ring auxiliary rubber seal corrosion, resulting in excessive mechanical leakage, moving, static ring rubber seal material is nitrile-40, not high temperature, not acid and alkali, when the sewage is acidic alkali easy corrosion.  
Solution: for corrosive media, rubber parts should be selected for high-temperature resistance, resistance to weak acids, and weak alkali fluorine rubber.

Solid particles of impurities are caused by mechanical seal leakage. If solid particles into the seal face, will scratch or accelerate the wear of the seal face, the scale and oil in the shaft (sleeve) surface accumulation rate exceeds the wear rate of the friction side, resulting in the dynamic ring can not compensate for wear displacement, hard on hard friction side of the operating life than hard on graphite friction side of the long, because the solid particles will be embedded in the graphite seal ring sealing surface.  
Solution: In the location where solid particles can easily enter the tungsten carbide to tungsten carbide friction sub mechanical seal should be used.

Mechanical seal leakage caused by other problems 

There are also mechanical seals in the design, selection, and installation of other places that are not reasonable enough.  
Spring compression must be carried out in accordance with the provisions, do not allow too large or too small phenomenon, error ± 2mm, too much compression to increase the end surface pressure, too much friction heat, resulting in thermal deformation of the sealing surface and accelerate end wear, too little compression static ring end surface pressure is insufficient, it can not be sealed.  
Install the moving ring seal shaft (or sleeve) end face and install the static ring seal sealing gland (or shell) end face should be chamfered and repair light, so as not to touch the static ring seal during assembly

Vertical centrifugal pipeline pump has very good performance in industrial production, urban water supply, high-rise building water delivery and other fields, and its use has been affirmed by people.

vertical-pipeline-pump

Because of the special nature of its workplace, so the vertical centrifugal pipeline pump may occur when working to prepare solutions in advance, preferably the first time the vertical centrifugal pump failure can have timely processing. The next will analyze several common vertical centrifugal pipeline pump failures and hope that these solutions can provide help for the work of users.

1、Fault phenomenon: the pump can not discharge material

Failure analysis:
a. Rotation in the opposite direction.
b. Inlet or discharge valve closed.
c. No material at the entrance or the pressure is too low.
Solution:
a. Confirm the direction of rotation.
b. Confirm whether the valve is closed.
c. Check the valve and pressure gauge.

2、Fault phenomenon: pump flow is not enough

Failure analysis:
a. Suction or discharge valve closed.
b. low inlet pressure.
c. Export line blockage.
Solution:
a. Confirm that the valve is closed.
b. Check if the valve is open.
c. Confirm that the discharge volume is normal.

3、Fault phenomenon: abnormal sound

Failure analysis:
a. large eccentric coupling or poor lubrication.
b. Motor failure.
c. reducer abnormal.
Solution:
a. correct or fill with grease.
b. Check the motor.
c. Check the bearings and gears.

4、Fault phenomenon: the current is too large

Failure analysis:
a. Export pressure is too high.
b. melt viscosity is too large.
c. poor shaft seal assembly.
Solution:
a. Check downstream equipment and pipeline.
b. Check the viscosity.
c. Check the shaft seal and adjust it appropriately.

5、Fault phenomenon: pump suddenly stop

Failure analysis:
a. Power failure.
b. Motor overload protection.
c. Coupling damage.
d. Export pressure is too high, interlock reaction.
Solution:
a. Check the power supply.
b. Check the motor.
c. Open the safety cover and check the coil.
d. Check the instrument interlocking system.

Through the above analysis, we can find that there may be many reasons for the failure of vertical centrifugal pumps in the process of use, because of the special nature of the use of vertical centrifugal pumps, the workers need to consider more in the face of vertical centrifugal pump failure occurs. Hope the above vertical centrifugal pump failure solutions can provide help for new users.

Today we will discuss what is the difference between a single suction pump and a double suction pump in a centrifugal pump that people often wonder about

Single suction pump

Pipeline Pump
Monoblock Pump

The single suction pump also called end suction pump, the basic parts of single suction pump are high speed rotating impeller and fixed worm-shaped pump casing. The impeller with several (usually 4~12) backward curved vanes is fixed on the pump shaft and driven by the motor to rotate the pump shaft at high speed. The impeller is a direct part of the pump to do work on the liquid in the pump, and is the energy supply device of the centrifugal pump. The suction port in the center of the pump casing is connected to the suction pipe, which is equipped with a one-way bottom valve at the bottom. The discharge outlet on the pump casing side is connected to the discharge pipe with a regulating valve.
The single suction pump has the advantages of smooth operation, simple structure, easy maintenance and repair, convenient installation and less land occupation. Single suction pump has low cost, reasonable price and wide application. Single suction pump flow is smaller, the flow is equal, the volume of single suction pump is smaller, but the axial force is large, the bearing load is large.

Double suction pump

double-suction-pump

Double suction pump actually consists of two back-to-back impellers, the water flowing from the impeller converges into a worm gear equivalent to two single-suction impellers of the same diameter working at the same time, in the case of the same impeller outer diameter, the flow can be doubled; the advantage of double suction pump is that, at the same speed and flow, cavitation is less likely to occur due to the reduction of inlet flow

Difference between single suction and double suction pump

The main difference between double-suction and single suction pumps is the impeller. The single suction impeller is single-sided suction, and the front and back covers of the impeller are asymmetrical. The double suction impeller is sucking water on both sides, and the impeller cover is symmetrical

single-suction-pump-impeller
single suction pump impeller
double-suction-pump-impeller
double suction pump impeller

A single suction pump is one where only one end of the impeller feeds water, a double suction pump is one where both ends of the impeller feed water, with two inlets

Double-suction pump is more suitable for conveying a large flow rate and requires smooth running conditions. When the pump flow requirements are very high, if the pump is a single-suction pump is to have a large pump inlet and outlet caliber, at the same time, the speed can not be too large, need to stabilize at about 1450rmp. If the double-suction pump is used, the size and weight of the pump can be relatively reduced, the rotational speed can also be increased, and the volumetric efficiency increased

Double suction pump has stronger anti-cavitation ability than single suction pump. As the medium is sucked in at both ends of the impeller, it will form hydraulic symmetry, so that the double-suction pump can balance the axial thrust effect better than the single-suction pump and run more smoothly. And the flow rate of the medium is low, the impeller is not easy to produce cavitation phenomenon

The cost of single suction pump is lower than double suction pump, end suction pump is a kind of pump commonly used in agriculture, double suction pump is mainly used in mines, cities, power stations, water supply and drainage of various water conservancy projects. The specific decision should be made according to the actual operating conditions of the user.

What is a "slurry"

The Slurry is a mixture of fluids and fine solid particles often used as a means of transporting solids or separating minerals in mining, steel processing, foundries, power generation, and gravel mining. Depending on the mixture, slurries can be abrasive and corrosive

Slurry pump selection

Many types of pumps are used to pump slurries, but the most common slurry pumps are centrifugal pumps. Choosing a pump designed for these heavy-duty applications is critical from the start, and selecting the right slurry pump for your application should consider the following points

1. Slurry Pump Design

The design of the slurry pump is critical to ensure that the abrasive and corrosive aspects of the slurry do not damage the impeller. To ensure that the pump can withstand abrasive corrosion, the impeller size/design, materials of construction, and discharge configuration must be correctly selected.

2. Slurry pump wet-end parts materials

Choosing the right material for a slurry pump is another key process in determining the right pump to handle the slurry. Common materials include high chrome alloy, and natural rubber, and are selected based on the different abrasiveness and corrosiveness of the slurry.

3. Three forms of slurry pump

Horizontal-slurry-pump
AM Horizontal Slurry Pump
slurry-sump-pump
BP Vertical Slurry Pump
submersible-slurry-pump
QSZ Submersible Slurry Pump

The three main methods of slurry pump deployment are

AM horizontal slurry pump is always installed on the ground. It is the most common type of slurry pump in different applications. Suitable for electric motor or diesel engine drives

BP vertical slurry pump is designed in some half-dry situations like sump and pool, its pump body is always underwater while the engine is above.

QSZ whole submersible slurry pump system work underwater, operating directly in the slurries, with no additional support superstructure

For more information on the selection of centrifugal slurry pumps, please contact our technical team

In the slurry pump market, there are many slurry pump manufacturers, and the price of slurry pumps is also varied, some tens of thousands, some only a few thousand dollars. What leads to such a huge gap, and how can buyers make the right choice? Here, I will briefly explain several factors that affect the price of the slurry pump so that you can better choose the right slurry pump supplier

Slurry pump selection

Under the same industrial and mining conditions, design and selection engineers from different slurry pump suppliers will choose different slurry pump models. Different models and different manufacturers have different materials, processes, and weights of slurry pumps, which leads to different prices of slurry pumps.

Material of slurry pump overflow parts

The most expensive parts of a slurry pump are the wear (end wet) parts, namely: the housing, frame and backplate, and the impeller. Usually, slurry pumps are made of Cr27, a high chromium wear-resistant alloy, and as long as this material is chosen, the basic price will not fluctuate too much because the cost is fixed, but many manufacturers have reduced the elemental content of the bill of materials to Cr20 or lower, with little or no nickel content

The weight of slurry pump parts

The design weight of the wearing parts (casing, frame and rear guard, impeller) in the slurry pump parts is determined according to the comprehensive consideration of the use cycle and so on. Many small factories will deliberately reduce the size of the mold in order to reduce costs. The original 150kg becomes 130kg or even lower. The cost of slurry pump parts is calculated based on material weight and processing cost. If the weight is reduced, the price can be much lower, and the whole pump price can be reduced even more, but the service life is shortened a lot, and many problems will occur in the operation of the project, which will lead to an increase in the whole operation cost

Heat Treatment

In order to make the slurry pump parts more flexible and wear-resistant corrosion-resistant need to be heat-treated twice, but for many manufacturers in order to reduce costs to reduce the process, the price will be reduced by a lot

Heat Treatment

Processing technology and assembly technology of slurry pump parts

Slurry pump parts are a relatively high precision process, and many manufacturers are unable to meet the precision requirements of the fittings due to manufacturing equipment or other reasons. Although it does not affect the appearance, it may have problems in use. In addition, the assembly and commissioning of the slurry pump are also very critical. The dynamic balance and static balance test of slurry pump accessories, as well as the assembly and test of slurry pump, require a large number of technicians and tools to achieve a qualified product

There are too many factors that determine the price of a slurry pump, it is impossible to list them all. I just hope that buyers will not blindly consider manufacturers from the perspective of price. They must know the principle of getting what you pay for

Finally, I would like to say, choose An Pump Machinery, we will not let you down, An Pump Machinery professional slurry pump manufacturer designed to help you maximize efficiency and lower operating costs,

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