String-wound and meltblown cartridges: an in-depth analysis of structure, performance and application

Abstract

 In the field of industrial filtration,string-wound and meltblown cartridges, as the two mainstream filtration elements, are widely used in different scenarios due to their differentiated performance characteristics. In this paper, a comparative analysis is carried out in 8 dimensions, such as structural design, filtration mechanism, performance parameters, cost-effectiveness, etc. Combined with authoritative data and industry cases, the core differences between the two and the selection logic are systematically elaborated to provide selection reference for the industries of water treatment, chemical industry, and food and beverage.

1. Essential differences in structural design

1.1 String -wound cartridge: gradient density of precision winding

The string -wound cartridge takes the porous skeleton (polypropylene or stainless steel) as the core, and then the textile fibers (e.g., polypropylene, degreased cotton threads) are twisted one by one according to a specific process to form a honeycomb structure that is sparse outside and dense inside. Its filtration precision is controlled by the thickness of the string and winding density, for example, when using 0.1mm fiber with high tension winding, the pore space of the outer layer can be up to 50 μm, and the inner layer can be reduced to 1 μm, so as to realize progressive filtration.

1.2 Meltblown Cartridge: Gradient stacking of molten fibers

Meltblown Cartridge adopts polypropylene (PP) particles melted at high temperature and then sprayed into ultra-fine fibers (1-5μm in diameter) to form a three-dimensional microporous structure through random stacking. Its density distribution is loose on the outside and tight on the inside, for example, the outer fiber gap is 20μm, the inner layer can be compressed to 0.5μm, suitable for intercepting submicron particles.

Structure Comparison Table   

2. Comparison of Filtering Mechanisms and Efficiencies

2.1 String -wound Filter Cartridge: Depth Interception and High-Flow Rate Characteristics

The string  wound cartridge realizes the “deep filtration” by the gradient change of the fiber gaps. “deep filtration”. Experiments show that its interception rate of particles above 10μm can reach 95%, but the efficiency drops to 70% when dealing with 1μm particles. Its advantage lies in low pressure drop (0.02-0.1MPa) and high flow rate (10" cartridge processing capacity up to 2.5m³/h), which is suitable for pretreatment or high flow rate scenarios.

2.2 Meltblown Cartridge: Surface Adsorption and High Precision Interception

The Meltblown Cartridge relies on a dense network formed by ultrafine fibers, and works through a dual mechanism of surface interception and deep adsorption. Data show that its retention rate of 1μm particles is more than 99%, and the pressure drop is high (0.1-0.3MPa), which is suitable for terminal fine filtration. For example, in the pharmaceutical industry, meltblown cartridges ensure a 99.99% bacterial retention rate for water for injection.

3. Comparison of Key Performance Parameters

3.1 Filtration Accuracy and Dirt-holding Capacity

• String -wound cartridge : accuracy range 1-100μm, dirt-holding capacity up to 200g/m² (take 10μm cartridge as an example).
• Meltblown cartridge : precision range 0.5-50μm, dirt-holding capacity up to 500g/m² (2.5 times higher than string -wound with the same precision).

3.2 Chemical Compatibility and Temperature Resistance

4. Initial Cost and Replacement Frequency

4.1 Initial Cost and Replacement Frequency

• String -wound cartridges are priced at $50-100 per unit, with a life span of 3-6 months;
• Meltblown Cartridges are priced at $80-150 per unit, with a life span of 2-4 months.
  Hitimisho : Under the same working conditions, the annual cost of using a string -wound cartridge is 30% lower than that of meltblown.

4.2 Comparison of maintenance cost

Meltblown cartridge is easy to be clogged due to high precision, and needs to be equipped with backwashing system, which increases the equipment investment by 15%-20%.

5. Typical applications of string -wound cartridge

1. Food & Beverage : rough filtration of fruit juice (removing >50μm pulp fibers);
2. Petrochemical industry : pre-filtering of hydraulic oil (capacity >10m³/h);
3. Municipal water supply : interception of rusted particles in pipeline (cost <0.1 RMB/ton).

5.2 Core areas of meltblown cartridge

1. Pharmaceuticals : injection terminal filtration (GMP compliant);
2. Elektroniki : ultrapure water preparation (resistivity>18Mω-cm);
3. Desalination : reverse osmosis membrane pre-protection (extends the life of the membrane by 3 times).

6. Selection Decision Tree

Establish the selection model according to the three elements of flow rate, precision and cost:

if demand precision>10μm → choose string-wound cartridge (cost priority) 
elif demand precision 1-10μm and flow rate<5m³/h → choose meltblown cartridge (efficiency priority) 
else → combination (string-wound pre-filtration+meltblown fine filtration)

7. Authoritative Cases and industry endorsement

1. An Environmental Protection : adopting string -wound cartridge to treat rust-containing cooling water in an oil refinery in Northwest China, saving 1.2 million RMB in annual maintenance cost;
2. A Water Treatment Company : configuring meltblown cartridge system for a branded mineral water plant, the turbidity has been reduced from 5 NTU to 0.1 NTU;
3. Academic research : Williams et al. (2021) confirmed that the meltblown cartridge can be used in high temperature oil filtration, which is the most effective way of filtering high temperature oil. cartridge stability in high temperature oil filtration.

8. Future Technology Trends

1. Composite Filter Element : string -wound + Meltblown multi-layer structure ;
2. Intelligent Monitoring : Embedded with pressure sensors to warn of clogging in real time.

Muhtasari

The essence of the difference between string -wound and meltblown cartridges lies in the trade-off of the   precision-flow-cost triangle . String -wound cartridges are the preferred choice for pre-treatment because of their economy and high flow rate, while meltblown cartridges are the core component of end-of-line filtration because of their high precision. Industrial selection needs to be combined with specific working conditions, if necessary, the use of a combination of solutions to maximize performance. With the development of new materials and intelligent technology, the performance boundaries of the two will be further broadened to promote the filtration industry to efficient and precise.