Woven Filter Screen Testing

Woven filter mesh testing mainly conducts scientific testing and analysis on opening size, warp and weft wire diameter, mesh count, porosity, breaking strength and elongation, and bursting strength, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Opening size: The opening size is the core indicator for measuring the filtration precision of the woven filter mesh, referring to the minimum distance between two adjacent warp wires or weft wires. It is usually measured with an optical microscope or a dedicated mesh measuring instrument, to ensure that it complies with the design specification, directly affecting the ability of the filter mesh to intercept the target particles.

Warp and weft wire diameter: The warp and weft wire diameter refers to the diameter of the single metal wire or fibre filament constituting the filter mesh. This item directly relates to the strength, porosity and mass per unit area of the filter mesh. It is measured with a high-precision micrometer or laser diameter gauge, ensuring the uniformity of the wire diameter, which is crucial for the mechanical properties and filtration stability of the filter mesh.

Mesh count (or mesh number): The mesh count refers to the number of openings within one inch (25.4 mm) of length, and is a common parameter characterizing the density of the filter mesh. During testing, samples need to be taken at multiple positions, and the number of wires per unit length is counted, to evaluate the uniformity of the weaving and the consistency of the filtration grade of the filter mesh.

Porosity: The porosity refers to the percentage of the total area of all openings in the filter mesh to the total surface area of the filter mesh. It comprehensively reflects the opening size and wire diameter, and is a key parameter for evaluating the permeability and fluid resistance of the filter mesh. It is usually calculated by image analysis software or theoretically based on geometric parameters (mesh count and wire diameter).

Breaking strength and elongation: This item is used to evaluate the mechanical properties of the woven filter mesh under tensile loads. On a universal material testing machine, specimens are respectively taken in the warp and weft directions for tensile tests, and the maximum force at breakage (breaking strength) and the elongation percentage relative to the original gauge length at breakage (elongation) are recorded.

Bursting strength: The bursting strength test simulates the strength of the filter mesh when it is subjected to uniform pressure in the vertical direction until rupture. During the test, the specimen is clamped on a ring-shaped fixture, a load is applied by hydraulic or pneumatic pressure, and the maximum pressure value at the moment of rupture of the specimen is recorded, to evaluate the ability of the filter mesh to withstand pressure differences during the filtration process.

Testing Scope

Metal wire woven filter mesh: The testing scope covers plain, twill or plain Dutch weave filter meshes woven with metal wires such as stainless steel (such as 304 and 316L), brass and Monel alloy. The focus is on its corrosion resistance, high-temperature strength, and dimensional stability and mechanical properties under harsh working conditions.

Synthetic fibre woven filter mesh: Including filter meshes woven with polyester (PET), polypropylene (PP), nylon (PA) and other materials. Testing needs to focus on its chemical compatibility, dimensional changes under different humidity, antistatic performance and creep and aging phenomena in long-term use.

Multi-layer composite filter mesh: For filter media made by combining filter meshes of different mesh counts or materials through sintering, lamination and other processes. Testing needs to evaluate the bonding strength between layers, the overall filtration precision gradient, and the comprehensive influence of the composite structure on the fluid resistance and dust holding capacity.

Filter mesh for industrial filtration: Applied to precision filtration links in industries such as chemicals, petroleum, pharmaceuticals and food and beverages. Testing needs to strictly follow the relevant industry standards (such as GMP and FDA), and focus on verifying its filtration efficiency, cleanliness, absence of shedding materials and biological/chemical inertness.

Filter mesh for sieving and classification: Used for particle classification in the fields of mining, construction and grain processing. The testing core is the absolute precision of the opening size and the abrasion resistance, and wear tests need to be carried out simulating the actual working conditions, to ensure the long-term stability of the sieving efficiency.

Filter mesh for safety protection and shielding: Used in scenarios such as electromagnetic shielding, protective masks and ventilation filter meshes. In addition to basic physical properties, specific functional indicators such as the electromagnetic shielding effectiveness (SE), ventilation resistance and flame retardancy need to be tested.

Testing Methods

Microscopic measurement method: An optical microscope or video microscope with a measuring scale is used to directly observe and measure the opening size and warp and weft wire diameter of the filter mesh. This method is intuitive and accurate, and is the basic method for determining the geometric parameters of the filter mesh, especially suitable for arbitration inspection of high-precision filter meshes.

Image analysis method: A high-resolution CCD camera is used to obtain microscopic images of the filter mesh, and dedicated image processing software automatically identifies the opening boundaries and wire edges, batch calculating the opening size, wire diameter, porosity and shape factor. This method has high efficiency and good repeatability, reducing human errors.

Standard sieve verification method: For sieving filter meshes, standard granular materials with known particle size distributions (such as glass beads and standard sand) are used for pass rate tests. By analyzing the interception and passing conditions of particles of different sizes, the effective filtration opening size and classification precision of the filter mesh are reversely verified.

Tensile test method: In accordance with standards such as GB/T 3923.1 and ISO 13934-1, an electronic universal testing machine is used to carry out uniaxial tension on the filter mesh specimen. Before the test, the specimen needs to be precisely prepared, and the appropriate tensile rate and clamping distance need to be set, to obtain reliable breaking strength and elongation data.

Hydraulic (pneumatic) method for bursting strength: Referring to the bursting strength testing principles of paper and board in ISO 2758 and GB/T 454, a Mullen-type bursting strength tester or similar equipment is used. The specimen is covered on an elastic rubber diaphragm and clamped, and the diaphragm is bulged by hydraulic or pneumatic pressure until the specimen ruptures, recording the maximum pressure value.

Air permeability test method: An air permeability tester (such as the Gurley method or the Schopper method) is used. Under a specified pressure difference, the air flow passing through the filter mesh per unit area per unit time is measured. This method is used to indirectly evaluate the porosity and fluid resistance of the filter mesh, and is an important reference for the filtration performance.

Testing Standards

Domestic Standards:

1. GB/T 3923.1-2013, Textiles — Tensile properties of fabrics — Part 1: Determination of breaking force and elongation at breaking force using the strip method

2. GB/T 1963-2009, Woven wire cloth and perforated plate and screen — Designation and nominal sizes of apertures

3. GB/T 5330-2003, Industrial screens — Woven wire cloth — Dimensions and tolerances of apertures

4. GB/T 454-2020, Paper and board — Determination of bursting strength

5. GB/T 5453-1997, Textiles — Determination of the permeability of fabrics to air

International Standards:

1. ISO 9044, Industrial woven wire cloth — Technical requirements and tests

2. ISO 2758, Paper — Determination of bursting strength

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Optical/video microscope: A microscope equipped with a high-precision moving platform and a micrometer scale is the basic equipment for measuring the micro geometric dimensions of the filter mesh. Modern video microscopes can also be connected to a computer for image acquisition and analysis, realizing the digital storage and processing of data.

Universal material testing machine: Used to carry out various mechanical property tests such as tension, bursting and tearing. The equipment needs to be equipped with pneumatic or mechanical clamping fixtures suitable for fabrics, and have high-resolution force and displacement sensors, to meet the testing requirements of flexible materials such as the filter mesh.

Digital fabric thickness gauge: Used to precisely measure the thickness of the filter mesh under a standard pressure. This is crucial for calculating the volume density of the filter mesh, evaluating the structure of the multi-layer composite filter mesh and ensuring its adaptability within the installation space.

Bursting strength tester: Usually of the hydraulic type, whose main components include a test head, hydraulic system, pressure sensor and display. The test head is divided into upper and lower clamping plates, with an elastic rubber diaphragm in the center of the lower clamping plate. The instrument needs to be regularly calibrated with standard aluminium foil sheets to ensure the accuracy of the pressure readings.

Air permeability tester: According to the different test principles, it is divided into the constant pressure type (measuring the flow) and the constant flow type (measuring the pressure difference). The instrument is composed of a specimen clamping device, gas flow control system, pressure/flow sensors and a calculation unit, and is used to quantify the air permeability of the filter mesh.

Precision balance and oven: Used to determine the mass per unit area (grammage) of the filter mesh. A specimen of a specified area is cut according to the standard, dried in an oven to constant weight, and then weighed with a precision balance. This parameter is the basis for calculating the theoretical porosity and evaluating the material consumption.