There’s more to selecting the right wire filtration mesh than its micron retention rating. Filtration designers would love to depend on certain known quantities from which to start a new filter product design. Unfortunately, wire mesh is not one of them. The qualities of wire mesh often defy the typical physical qualities that more compliant materials possess. There are so many weave patterns to choose from, each with its own set of performance qualities; then, there are the inevitable compromises between a desired aperture for optimal flow and the final product’s durability in operating conditions; and finally, forming wire mesh into a fabricated product is nothing like fabricating with solid materials.
If you are looking for more details, kindly visit our website.
To better understand the complexities of mesh selection overall, we will consider a limited example of just a 60-micron filtration rating. By isolating a specific micron rating, we can look at all the other variables that influence filtration mesh selection.
When seeking a 60-micron mesh that also meets the designer’s durability and configuration specifications, in order to recommend the right one, the mesh supplier will have several questions. Some of these are likely more commonly understood than others:
• How much differential pressure will the mesh be subjected to?
• What is the desired volumetric flow rate through the mesh?
• How will the mesh be mounted? Will it need a support structure?
• Will it need to be pleated, punched, or formed?
• Will the edges be welded, crimped, glued, hemmed, or over-molded with plastic?
• How will all this be implemented for manufacturability, accounting for material cost and availability?
After considering responses to these questions, a knowledgeable mesh expert will consider a variety of nominally 60-micron mesh weaves and a few close matches. They’ll think about which one’s unique characteristics would make it the most suitable one for the application.
Table 1 shows nine different types of wire mesh weaves, all of which have close to a 60-micron retention. Comparing these weaves, the first four are what most people think micronic woven filter mesh is: a square weave, like the familiar bug screen, only finer. In fact, square meshes that fine tend to be too fragile for most filtration applications. Research shows that prior to reaching out to a mesh expert, only about 1-in-5 engineers are aware that different mesh weaves other than square weave exist.
A variety of Dutch weave meshes were developed to be more durable than square weaves for filtration. A Dutch weave is one in which the warp wire is larger than the shute wire, and a reverse Dutch weave is one in which the warp wire is smaller than the shute wire. With these weaves, the larger, more widely spaced wires add strength while tightly spaced smaller wires maintain the micron retention. The complexity of these weaves means that predicting how easily fluid passes through the mesh is more complicated than just measuring the open spaces between wires. Instead, flow resistance must be determined by either:
It is clear from Table 2 that although the micron retention rating may meet specification, some of the mesh weaves will not be durable enough to meet the specified pressure, or the lifetime of wear and tear on the filter. When designing a wire mesh filter assembly, these two variables are connected, and the trade from these plays a large part in correct mesh selection.
Mesh filter durability is affected in four different ways: sustained high pressure, repeated pressure fluctuations, corrosion, and operator error when cleaning and servicing the filter.
As particles caught by the micron mesh filter gradually block the screen, the back pressure will increase. In some instances, the operation of the system calls for periodic deblinding before the pressure exceeds a threshold beyond which the mesh suffers damage. Left unattended, this pressure could simply exceed burst pressure, which is a durability catastrophe. Before burst pressure is reached, however, less noticeable system failure can occur, such as exceeding a bypass valve setting, which could allow unfiltered fluid and solids where they are not wanted. Better design can raise the damage threshold of the filter, and better maintenance adherence can prevent the mesh from suffering damaging pressures to begin with.
In a properly designed and maintained filter system, the durability of the micron mesh should not be significantly compromised by normal use and operation. In addition to considering the effects of constant pressure on a mesh filter, the frequency of pressure changes must be considered as well. A mesh that can handle a constant pressure of 100 psi could fail quickly from oscillating between 0 and 50 psi.
Pressure oscillations such as from a diaphragm pump or an automated system repeatedly triggering a backflow cleaning cycle can compromise the mesh by work-hardening the wire far sooner and with less overall pressure differential than a system with a steady pressure.
Over the course of a filtration session the micron mesh is slowly blocked by particles. This reduces the volumetric flow rate through the filter or results in differential pressure building until the same volumetric flow rate is achieved through brute force. The added pressure can cause wear and damage to the mesh. Alternatively, the filter will need more frequent cleaning and maintenance, increasing the opportunities for wear and tear to the mesh through handling (or mishandling). The loss of production time can also have a significant economic impact.
Some of the more robust Dutch weave meshes are too stiff for a pleating machine, whereas others are too thin for a welding machine. One mesh might have a 1% improvement in flow rate but a 500% increase in cost.
If the calculated surface area of the wire mesh required is less than space allotted in the filter housing, it will need to be formed by either rolling, pressing, stamping or pleating the mesh into a shape necessary to increase the surface area for the filtrate to pass through. This means the manufacturability of the weave chosen needs to be considered. Once formed:
Some of the more robust Dutch weave meshes are too stiff for a pleating machine, whereas others are too thin for a welding machine. One mesh might have a 1% improvement in flow rate but a 500% increase in cost.
When considering a specific weave for a filter assembly, Table 2 provides a brief overview of the manufacturability of each weave type. Filter designers must be aware that the practical issues with respect to manufacturability of a specific mesh are often different from the performance suggested in theoretical mesh tables because the manufacturing processes can greatly affect its filtration properties.
Each of these factors and more are why early collaboration with a mesh filtration application engineer is an opportunity to sort the practical from the possible.
Processing – that is, how easy or difficult it will be to turn a roll of woven wire mesh into a filter, and how many steps that will take – is key to filter design and mesh selection. There are innumerable ways that micron wire mesh can be shaped and mounted, so there is no comprehensive list of steps or a flow chart to follow to maximize manufacturability. However, there are a few areas to consider:
When using wire cloth as the filtration media in filters, considering their processability and availability is the easiest path to manufacturing functional, durable, and cost-effective products.
Mesh screen manufacturers publish tables of all the products they are capable of weaving. What these tables do not often indicate, however, is how common those micron meshes are. While many highly respected mesh suppliers carry thousands of standard types in stock, the mesh an engineer specifies may not actually be on the shelf ready to ship. A knowledgeable mesh expert will be able to recommend one with similar properties that is more readily available.
For more information, please visit Shengfa.
With custom weaving, sourcing nearly any mesh is possible, but this comes at a cost. Collaboration with a mesh expert will help the designer source one that is the most suitable and cost effective for the intended application.
There’s nothing easy about designing filters from wire mesh. Perhaps the more experienced wire mesh filter designers know best what they don’t know. Rather than relying on data from tables, they have learned from prior experience that the shortest path to success is consulting with a wire mesh professional they trust to help nail down the difficult variables the material presents.
There are many characteristics to consider when selecting the right Wire Mesh product for your project. One of the primary differences between Woven Wire Mesh and Welded Wire Mesh is how they are constructed, or how the wires intersect. Woven Mesh is formed when cross wires and line wires are crossed over and under each other.
Wire Mesh is classified as Welded Wire Mesh when its wire intersections are melted and cooled together. Nevertheless, the differences and capabilities of these two categories of Mesh go far beyond their methods of construction.
Since the bonds of Welded Mesh are fused together, they are able to provide a certain level of rigidity and strength. Therefore, they maintain their fixed opening shape even under force. It should be noted, however, that if outside pressures put too much stress on Welded Wire Mesh intersections, a “breaking point” exists. This point is where welded bonds can eventually snap.
Woven Mesh does not have fixed bonds, so the product is pliable and does not possess the rigid qualities of its Welded counterpart. However, because they are formed without Welded bonds, the flexibility of Woven items allows the product to yield under outside pressure before springing back. These characteristics provide a unique durability that is useful in applications. Especially where stress applied to Wire Mesh is an important consideration.
It is likely that when deciding which construction type is right for you, the desired opening size (clear space between wires, measured from the inside edge of one wire to the inside edge of the next adjacent wire) will be an important factor. Generally, Woven items are available with smaller opening sizes, while Welded is better suited for applications that call for larger openings.
For Welded, the smaller the desired opening size, the smaller the wire diameter has to be in order to leave enough clear opening for the welding process to occur between the wires. However, if the wire diameter (often referred to as wire gauge) becomes too small, the heat generated from the welding process can melt the wires.
For these reasons, the smallest opening size offered for Welded is typically 4 x 4 Mesh (four openings per lineal inch measured from the center of the wires), although there are a few smaller Mesh sizes available in Stainless Steel and PVC-coated finishes.
It is important to note that woven is often unavailable in some of the larger opening sizes common in welded items. Without Welded bonds to hold them in place, woven wires in larger opening sizes can shift and lose their original shape. If you need a larger opening size but still require a Woven construction, Lock Crimp and Intercrimp weave types provide increased rigidity.
Seeing as Woven items are not bonded at each intersection, it is possible for wires to come apart at pattern ends or where the material is cut. Larger opening sizes and smaller wires will reduce the rigidity of Woven items and, therefore, make them more likely to unravel slightly at the ends once sheared.
Some Woven Meshes come with a selvage, or finished, edge. One common way of producing a selvage edge is by curling the shute (short) wire and weaving it back through the warp (long) wires. These looped ends help prevent the item from unraveling. Other methods of keeping Woven Mesh intact are by framing the material or, for larger openings, by leaving a stub to hold the ends in place (though this practice can be difficult for skew, or diagonal, cuts).
Lock Crimp and Intercrimp weaves are more likely to stay together once sheared; however, they are also not permanently fastened and can come apart. Since Welded Wire Mesh is secured at each wire intersection, it is less likely to come apart once cut.
Wire Mesh is formed in a number of material types and finishes, though there are a few limitations depending on the construction type chosen. For example, Welded Mesh is unavailable in Aluminum because the metal tends to be too soft and, therefore, the wires are susceptible to melting. Additionally, although we offer Woven materials that have been pre-galvanized, Woven materials are generally not hot-dipped galvanized after the wires have been woven together.
This is largely because smaller opening sizes (less than 1/4") can become clogged with the zinc oxide solution involved in the coating process. Furthermore, hot-dipped galvanizing and powder coating are not ideal for Woven items because this process merely coats the wires where they rest together during the dipping process. It is possible that there could be a lack of coverage where wires overlap or intersect, and when Woven wires later shift, the raw or uncoated steel can become exposed to corrosive elements in the environment.
Wire Mesh is available in coil and sheet forms. Typically, Woven Wire Mesh is stored as coils or in rolls. When coiled materials are unrolled to be installed or sheared, it is possible that cut pieces will maintain their coiled shape rather than lying flat. This occurrence is called “coil memory.”
To reverse the coil shape, pieces can be flipped over and laid flat with a heavy object placed on the surface to reduce coil memory. If this type of flattening process is chosen, it is important to use an object that will not crush the wires or weave the pattern.
With Welded Wire Mesh, the fused wire intersections make the material very stiff and, therefore, more difficult to roll tight enough to be stored as a coil. Instead, Welded Wire Mesh is typically stored in the form of a sheet. Due to these reasons and because woven is more frequently constructed from thinner wires than welded, the “coil memory” phenomenon is more common with woven items.
Despite having similar appearances and purposes, there are many different factors in determining whether a Woven or Welded construction type is right for your application. We trust this volume of Hole Stories has illuminated some of the characteristics of these two versatile Mesh types.
If you have questions or would like help determining which Wire Mesh item is right for your project, contact us at 866.252., , or via Live Chat on mcnichols.com.
For more High Flow Weave Wire Meshinformation, please contact us. We will provide professional answers.