Strainers

What is a strainer?

Strainer is an indispensable device on the transmission medium pipeline. It is usually installed at the inlet of pressure reducing valve, pressure relief valve, constant water level valve, square strainer and other equipment. The strainer is composed of cylinder, stainless steel strainer screen, sewage part, transmission device and electrical control part. After the water to be treated passes through the strainer cartridge of the strainer screen, its impurities are blocked. When it needs to be cleaned, just take out the removable strainer cartridge and reinstall it after treatment. Therefore, it is very convenient for use and maintenance.

Classification of strainers

Functional classification of strainers

Strainers are mainly divided into: self-cleaning strainer, full-automatic strainer, stainless steel brush strainer and elastic strainer. The four working principles are different. The following are the working principles of each strainer.
1. Self cleaning strainer
The self-cleaning strainer is a kind of precision equipment that uses the strainer screen to directly intercept impurities in the water, remove suspended solids and particles in the water, reduce turbidity, purify water quality and reduce the generation of system dirt, bacteria, algae and rust, so as to purify water quality and protect the normal operation of other equipment in the system. The main components include: motor, electric control box, control pipeline, main pipe component, strainer element component, 316L stainless steel brush, frame component, transmission shaft, inlet and outlet connecting flange, etc., which overcomes many shortcomings of traditional strainer products, such as small pollution capacity, easy to be blocked by dirt, the strainer part needs to be disassembled and cleaned, and the strainer state cannot be monitored, It has the function of strainering raw water and automatically cleaning and discharging the strainer element. When the self-cleaning strainer is cleaned and discharged, the system provides uninterrupted water supply, which can monitor the working state of the strainer with a high degree of automation. It covers the requirements of various strainering accuracy from 10um to 3000um. It adopts the advanced technology of equipment in the international water treatment industry, which can be installed in any direction and position vertically, horizontally and upside down. It can be used for water filtration in industry, agriculture, municipal power, electronics, medicine, food, printing and dyeing, construction, iron and steel, metallurgy, papermaking and other industries.
2. Automatic strainer
Full automatic strainer is a set of equipment widely used in the filtration industry at present. It overcomes many shortcomings of traditional filtration products, such as small sewage capacity, easy to be blocked by dirt, the filtration part needs to be disassembled and cleaned, and the strainer state cannot be monitored. It has the function of strainering raw water and automatically cleaning and discharging the strainer element.
The full-automatic strainer is composed of shell, multi-element strainer element, backwashing mechanism, electric control box, reducer, electric valve and differential pressure controller. The diaphragm in the shell divides its inner cavity into upper and lower cavities. The upper cavity is equipped with a plurality of strainer elements, which makes full use of the strainering space and significantly reduces the volume of the strainer. A backwashing suction cup is installed in the lower cavity. During operation, the turbid liquid enters the lower chamber of the strainer through the inlet and the inner chamber of the strainer element through the diaphragm hole. Impurities larger than the gap of the strainer element are intercepted, and the purified liquid passes through the gap to the upper chamber and is finally sent out from the outlet.
Advantages: the automatic strainering accuracy of the strainer is 100 microns by default, and can be selected from 100 to 3000 microns. The strainer has large strainering area and high pollution capacity. Users can customize it according to the actual working conditions. The cleaning method is simple, and the cleaning cycle is electronically monitored, which can realize automatic cleaning and sewage discharge. All parameters in the automatic self-cleaning strainer control system can be adjusted.
3. Stainless steel brush strainer
The types of stainless steel brush strainers are: full-automatic stainless steel brush strainers and hand-operated stainless steel brush strainers. Its main function is to remove the suspended solids in the water, reduce the concentration of suspended solids and particles in the water, reduce turbidity, purify water quality, reduce system dirt, bacteria and algae, rust, purify water quality, etc. Picture of stainless steel brush strainer
The stainless steel brush strainer adopts the internal mechanical structure of patented technology to realize the real high-pressure backwashing function, which can easily and completely remove the impurities intercepted by the strainer screen, without dead angle and flux attenuation, so as to ensure the filtration efficiency and long service life.
The stainless steel brush strainer realizes automatic backwashing through its own retrieval and strain functions, which can cope with unstable water quality fluctuations without manual intervention. In the backwashing process of stainless steel brush strainer, each (Group) strainer screen shall be backwashed in turn; Ensure that the strainer screen is cleaned safely and efficiently, while other strainers are not affected, and continue strainering. Stainless steel brush strainer adopts automatic blowdown valve, with short backwashing duration, less backwashing water consumption, environmental protection and economy. Less vulnerable parts, no consumables, low operation and maintenance cost and simple operation and management.
4. Elastic strainer
Elastic strainer is a brand-new product developed by olte COMPANY O, with independent intellectual property rights. It took five years to invest millions of yuan. The biggest advantage is maintenance free and automatic cleaning, which avoids the hidden danger of clogging the strainer element after working for a long time. Product features: maintenance free, automatic cleaning, short cleaning time (3 seconds). When cleaning, the spring opening clearance is equal and can swing. It can replace mesh, barrel, bag and other strainers to reduce the comprehensive cost.
Scope of application: Automobile Industry (processing machinery, cleaning machinery, etc.), machine tool industry (processing coolant, burr processor, etc.), food industry (drainage treatment, recovery of fried residue), filtration of circulating water in swimming pools, baths, hot springs and other large places, high-pressure water cutting machine, stripping device, cooling tower and circulating water filtration (removal of sand, stone, wood chips and foreign matters).

Function classification of strainer

1. Oil suction strainer
The strainer is arranged on the suction pipeline of the pump to strainer the residual pollutants in the oil tank and the pollutants entering through the air hole, which can protect the pump. However, in order to avoid cavitation in the pump, full attention must be paid to the pressure loss. Generally, 100-200 mesh coarse metal mesh or notch metal wire materials are used. Therefore, it is not a strainer to control the pollution concentration of the system.
2. High pressure pipeline strainer (a)
It is set on the outlet pipeline of the pump to protect pollutants from entering the system. Therefore, the pollutant concentration of the system can be controlled. However, because it is a high-pressure main pipeline and is subject to the pulsation and pressure impact of the pump, the material and strength of the strainer element should be carefully considered.
3. High pressure pipeline strainer (b)
In the system, this strainer, also known as terminal strainer, is installed in order to protect hydraulic parts that are particularly sensitive to pollution. Therefore, it is often smaller than other strainers. Therefore, large capacity should be selected when using. In addition, the material and strength of components shall be fully considered as in (a).
4. Return strainer
It is set on the oil return pipeline of the system to capture the pollutants generated or invaded in the system before returning to the oil tank. Therefore, it is the most effective and important strainer to control the pollution concentration of the system. Although it is a low-pressure pipeline, pulsation or pressure impact will also occur according to the operation condition of the transmission device, so the material and strength of the components should be fully considered.

Working principle of strainer

When the strainer works, the water to be strainered enters from the water inlet, flows through the strainer screen, enters the pipeline required by the user through the outlet for process circulation, and the particulate impurities in the water are intercepted in the strainer screen. With such continuous circulation, more and more particles are intercepted and the filtration speed is slower and slower, while the imported sewage still enters continuously, and the strainer hole will be smaller and smaller, resulting in a pressure difference between the inlet and outlet. When the large difference reaches the set value, the differential pressure transmitter transmits the electrical signal to the controller, and the control system starts the drive motor to drive the shaft through the transmission assembly, At the same time, the drain outlet is opened and discharged from the drain outlet. After the strainer screen is cleaned, the differential pressure drops to the minimum, the system returns to the initial filtration state, and the system operates normally. The strainer is composed of shell, multi-element strainer element, backwashing mechanism, differential pressure controller, etc. The diaphragm in the shell divides its inner cavity into upper and lower cavities. The upper cavity is equipped with a plurality of strainer elements, which makes full use of the strainering space and significantly reduces the volume of the strainer. A backwashing suction cup is installed in the lower cavity. During operation, the turbid liquid enters the lower chamber of the strainer through the inlet and the inner chamber of the strainer element through the diaphragm hole. Impurities larger than the strainer element gap are intercepted, and the purified liquid passes through the gap to the upper chamber and is finally sent out from the outlet. The strainer adopts high-strength wedge-shaped strainer screen and automatically cleans the strainer element through differential pressure control and timing control. When the impurities in the strainer accumulate on the surface of the strainer element, causing the inlet and outlet differential pressure to increase to the set value, or the timer reaches the preset time, the electric control box sends a signal to drive the backwash mechanism. When the inlet of the backwashing suction cup is aligned with the inlet of the strainer element, the blowdown valve is opened. At this time, the system releases pressure and discharges water. A negative pressure zone with a relative pressure lower than the water pressure outside the strainer element appears inside the suction cup and the strainer element, forcing part of the net circulating water to flow from the outside of the strainer element into the inside of the strainer element. The impurity particles adsorbed on the inner wall of the strainer element flow into the pan with the water and are discharged from the blowdown valve. The specially designed strainer screen produces a spraying effect inside the strainer element, and any impurities will be washed away from the smooth inner wall. When the pressure difference between the inlet and outlet of the strainer returns to normal or the timer setting time ends, the flow of materials is not cut off in the whole process, and the backwashing water consumption is less, so as to realize continuous and automatic production. Strainers are widely used in metallurgy, chemical industry, petroleum, papermaking, medicine, food, mining, electric power and urban water supply. Such as industrial wastewater, circulating water filtration, emulsion regeneration, waste oil filtration treatment, continuous casting water system and blast furnace water system in metallurgical industry, high-pressure water descaling system for hot rolling. It is an advanced, efficient and easy to operate automatic strainering device.
The water to be treated by the strainer enters the body from the water inlet, and the impurities in the water are deposited on the stainless steel strainer screen, resulting in differential pressure. The pressure difference at the inlet and outlet is monitored through the pressure difference switch. When the pressure difference reaches the set value, the electric controller sends a signal to the hydraulic control valve to drive the motor. After the equipment is installed, the technicians will conduct commissioning, set the filtration time and cleaning conversion time, the water to be treated enters the body from the water inlet, and the strainer begins to work normally. When the preset cleaning time is reached, the electric controller will send signals to the hydraulic control valve and drive the motor, causing the following actions: the motor drives the brush to rotate to clean the strainer element, At the same time, the control valve is opened for blowdown. The whole cleaning process only lasts for tens of seconds. When the cleaning is completed, close the control valve, the motor stops rotating, the system returns to its initial state and starts to enter the next strainering process. The shell of the strainer is mainly composed of coarse strainer screen, fine strainer screen, sewage suction pipe, stainless steel brush or stainless steel suction nozzle, sealing ring, anti-corrosion coating, rotating shaft, etc.
A simple strainer is formed by separating the container into upper and lower cavities with strainer media. The suspension is added into the upper chamber and enters the lower chamber through the strainer medium under pressure to become filtrate. The solid particles are intercepted on the surface of the strainer medium to form strainer residue (or strainer cake). During the filtration process, the strainer residue layer on the surface area of the strainer medium is gradually thickened, the resistance of the liquid passing through the strainer residue layer increases, and the filtration speed decreases. When the strainer chamber is full of strainer residue or the filtration speed is too small, stop the filtration, remove the strainer residue and regenerate the strainer medium to complete a filtration cycle.
The liquid must overcome the resistance when passing through the strainer residue layer and the strainer medium, so there must be a pressure difference on both sides of the strainer medium, which is the driving force to realize filtration. Increasing the pressure difference can accelerate the filtration, but the deformed particles are easy to block the pores of the strainer medium when the pressure difference is large, and the filtration slows down.
There are three ways of suspension filtration: slag layer filtration, deep filtration and screen filtration.

• ① Strainer residue layer filtration: at the initial stage of filtration, the strainer medium can only intercept large solid particles, and small particles pass through the strainer medium with the filtrate. After the initial strainer residue layer is formed, the strainer residue layer plays a major role in filtration. At this time, large and small particles are intercepted, such as the filtration of plate and frame strainer press.
• ② Deep filtration: the strainer medium is thick, the suspension contains less solid particles, and the particles are smaller than the pores of the strainer medium. During filtration, the particles are adsorbed in the pore channel after entering, such as filtration of porous plastic pipe strainer and sand strainer.
• ③ Screen filtration: the solid particles retained by filtration are larger than the pores of the strainer medium, and the solid particles are not adsorbed inside the strainer medium. For example, the rotary drum strainer screen strainers out the coarse-grained impurities in the sewage. In the actual strainering process, the three methods often appear at the same time or successively.

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