Ⅰ. Filter element type

There are many types of filter cartridges for liquid filtration, which can be mainly divided into two categories: surface filter cartridge and deep filter cartridge.

1. Surface filter cartridge

Surface filter cartridge captures pollutants through the surface of the cartridge, once the surface is clogged, the cartridge can no longer be used, so the service life is shorter. Although it is believed that the liquid can be mixed with compressed air backwash to reuse the cartridge, but this method is difficult to thoroughly clean the cartridge. Backwashing, rinsing liquid priority through the area of less resistance, resulting in local channels open, all the rinsing liquid from these channels, but other areas of more serious blockage, pore size. If you want to thoroughly clean the cartridge, the method is to use ultrasonic cleaning, pure water as a cleaning fluid, but the cost is higher; can also be used for chemical dissolution method, such as pollutants for the acid soluble, can be used to dilute acid cleaning, but need to pay attention to may cause corrosion of the cartridge aperture with the expansion of the cleaning needs to be rinsed with purified water and inspection after passing before continuing to use. Electroplating solution filtration commonly used cartridges, such as early sintered PVC filter rods, as well as the current polypropylene meltblown cartridges, polypropylene PP filter paper, pure wood pulp filter paper, etc., are surface filtration cartridges.

2. Depth filtration cartridge

Filter element cleaning is cumbersome, to improve the dirt holding capacity of the filter element, to extend the service life of the filter element can reduce the frequency of cleaning, deep filtration filter element is based on this design. Deep filter cartridge in the filtration process, pollutants in the cartridge according to the size of the particles layered retention, so the slag loading capacity is high, long service life, can maintain the nominal filtration accuracy for a long time. It is made of various materials and is suitable for all kinds of liquid and gas filtration. Commonly used in electroplating solution filtration is the wire-wound cartridge made of all polypropylene, commonly known as cotton core, with a small differential pressure, large flow, high filtration precision, long service life, etc., can be in the filtration process to maintain long-term precision.

Ⅱ.Structural characteristics of wire-wound filter element

When the wire-wound cartridge is made, the special roving with fluff is cross-wound on the porous skeleton until it reaches the required diameter. The roving is cross-wound on the skeleton to form a filter layer containing thousands of diamond-shaped holes. The diamond-shaped holes of the filter layer on the cartridge are small near the skeleton, the further out the diamond-shaped holes are, the larger they are, and the outermost diamond-shaped holes are the largest, and the diamond-shaped holes are connected inside and outside to form a channel. In order to increase the flow of liquid in the cartridge, the rhombic pore channel is curved and scattered, and the rhombic holes of each layer are still connected, and the curving extends the channel, which is equivalent to increasing the thickness of the filter layer of the cartridge, improving the filtration effect, and realizing the deep filtration. The yarn is twisted with certain parameters, and the inside of the cartridge forms a diamond-shaped curved filtration channel from the surface to the inside, from big to small. The size of the rhombic hole in the innermost layer of the cartridge is the key to determine the precision of the cartridge, the smaller the rhombic hole, the higher the precision of the cartridge; the larger the rhombic hole, the lower the precision of the cartridge. Regular cartridge manufacturers have a specific cartridge precision and the number of diamond-shaped holes comparison table, different channel number represents different cartridge precision. For example, 8-channel precision of 100μm, 15-channel precision of 20μm, 19-channel precision of 10μm.

Ⅲ.Filtering characteristics of wire-wound cartridge

Another characteristic of wire-wound cartridge is that it can pass large flow rate. Each kind of filtration precision wire-wound cartridge has a fixed number of channels D, filtration precision is determined, the number of channels L according to the length of the cartridge increases or decreases. The formula for calculating the total number of channels is: total number of channels = D x L x 2.

Take the cartridge with a length of 250mm as an example, if the filtration precision is 20μm, the number of channels on the diameter of 15, the length of the longitudinal channel number of 51, the cartridge has a total number of channels of 15 × 51 × 2 = 1530, i.e., 1530 independent channels. If the filtration flow rate of 0.5m³/h (in the case of water), that is, 8.3L/min, the liquid is dispersed into the 1530 independent channel filtration, the flow rate of each channel actually fell to 5.4ml/min.

If the filtration accuracy of 3μm, the number of channels is 27, the length of the longitudinal channel number of 91, the cartridge has a total of 27 × 91 × 2 = 4914 channels. For 3μm precision cartridge, although the filter media (fiber fluff) more dense, but the filter channel to 4914, the channel flow is only 1.7ml/min, this time the flow can be called “siphon flow”.

It can be seen that the wire-wound cartridge filtration can be a large flow through the cartridge, but to disperse the flow of the structure, so that the cartridge in a small differential pressure can still maintain good filtration performance. This structural form of the cartridge is also conducive to filtration of gelatinous or gelatinous substances in the liquid. Wire-wound filter element can filter out particles much smaller than the pore size with a larger pore, so it is often called precision filtration elements.

Ⅳ.Selection of wire-wound filter element

Due to fierce competition, most of the cartridge manufacturers compete to compress the cost, the main methods and adverse effects are as follows: 

Simplify the winding method: although improve production efficiency, but cause a large number of cartridge filtration channel blockage, the formation of blind holes (simplify the way of winding will make the surface layer of rhombic holes by the lower layer of yarn interception, the formation of blind holes), so the wire-wound cartridge degradation into surface filtration type cartridge.

Changing the standard of inner and outer diameters to reduce the thickness of the cartridge: although saving the raw material of yarn, it leads to the thinning of the filtration layer, shortening of the filtration channel, deterioration of the filtration effect, and reduction of stability.

Using inferior raw materials: Although it reduces the cost, it causes corrosion of the filter element.Therefore, when choosing the filter element supplier, we should examine whether it has a complete filter element quality management mechanism and whether it has the ability to ensure the quality of the filter element.

Selection of wire-wound filter element should pay attention to the following issues: Observe the filter element filter holes through: a large number of filter holes blocked into blind holes of the filter element has lost the effect of the wire-wound filter element.

Check the inner and outer diameters of the cartridge: see whether the filtration level has been reduced.

Observe whether the yarn and skeleton of the cartridge are corroded: corrosion will weaken the filtration effect and cause electroplating solution pollution.

Ⅴ.Application areas of wire-wound cartridge 

wire-wound cartridge has the characteristics of large flow rate, low differential pressure, suitable for low-viscosity media, strong corrosion resistance, etc. Therefore, it is widely used in the pre-filtration of high-flow pure water system, water sewage and circulating water treatment of power plants and steel mills, food industry (such as filtration and treatment of slurry such as edible oil, vegetable oil, molasses, chocolate, etc.), chemical industry preparation treatment (such as electroplating solution solution, paints, oil, paint), mechanical oil, cutting oil and other chemicals. (such as electroplating solution, paint, oil, coating, machinery oil, cutting oil, heavy oil, fuel oil, high viscosity resin, grease filtration), pharmaceutical filtration and other fields.

The structure of wire-wound cartridge is wound on the skeleton in a way that prevents fibers from being wound on the skeleton, which has a high capacity to withstand filtration pressure without loss of pressure and a long service life. Polypropylene fiber is non-toxic and harmless, the processing technology is hot melt non-adhesive, very suitable for food and beverage industry. The production of mineral water, syrup, alcohol, edible oil, beverage water, cola drinks and other products, as well as pure water, organic solvents, printed circuit boards, electroplating and other industries and the field of medicine and health, are highly dependent on the wire wound cartridge. Wire-wound cartridge can effectively remove suspended solids and particles in the liquid, with high flow rate, small pressure loss, high slag loading, long service life, and can withstand high filtration pressure. According to the nature of the liquid to be filtered, the filter element has a variety of materials to choose from, to ensure that the filter element and the filtrate have good compatibility.

Ⅵ.The filtration principle of wire-wound cartridge 

wire-wound cartridge filtration in addition to relying on the cartridge roving cross overlap into the aperture grid interception, but also includes the role of the hook of the fibers on the wall of the channel and the deposition of particles in the channel.

1. cartridge channel wall fiber hook role 

liquid from the cartridge outer flow through the narrow and long and curved channel into the inner layer, the channel wall is covered with curled fiber fluff, the liquid particles can be hooked and retained in the channel. 2.

2. The deposition of particles in the cartridge channel 

The cartridge channel is narrow and long and curved, the liquid will repeatedly hit the channel wall when it passes through at a certain flow rate, and the particles in the liquid will gradually be deposited in the channel, just as the sludge is deposited when the river flows through the bends of the river. 3.

3. Filtration Principle 

The liquid to be filtered is pressed in by the inlet of the filter, and is filtered into a clear liquid through the filter layer from the outside to the inside of the filter element, and then discharged through the outlet. Impurities are retained in the deep layer and surface of the filter element to achieve the purpose of filtration. The liquid first enters the lower part of the filter shell by the inlet pipe, and then flows from the outside to the inside of the filter cartridge, the coarser particles immediately precipitate and are discharged by the drain valve, and the smaller particles are intercepted by the filter cartridge. Finally the clean liquid is pooled by the filter element tray and then flows out from the outlet pipe. The liquid to be filtered flows into the wire-wound cartridge, and then shunts inside the cartridge, through the process of filtration, emulsion breaking, water molecules growing up and agglomeration, the filtered liquid flows out from the outlet, the impurities are retained inside the cartridge, and the agglomerated water beads settle down in the precipitation tank, which is discharged through the discharge valve.

4. Maintenance of wire-wound filter element 

Prevent particulate matter from entering the inside of the filter element: when using dust removal filter element (such as PP filter element and wire-wound filter element), it is necessary to prevent particulate matter from entering the inside of the filter element and blocking or jamming the inside of the system.

Regular maintenance and repair: After using for a period of time, the filter element should be maintained and repaired.

Regular cleaning: After a long time of use, the cartridge will deposit a large number of impurities or other pollutants in the system, which need to be cleaned to maximize the effect of the cartridge.

Keep the filter paper moist: to ensure that the filter paper is always in a moist state, can not appear dry, in order to extend the use of time and ensure the accuracy of filtration.

Fiber type filtration method of maintenance: through the fiber type filtration method, dust is easy to enter the dust cartridge in the dust collector, and then through the backblowing peeling off the viscous material on the cartridge, will not affect the cartridge filtration effect, but also better protect the environment, to maximize the extension of its use time.