The significance of fabric air permeability test

Air permeability is a physical index that characterizes the air permeability in the tested sample, mainly for porous materials with large air permeability, such as textiles, sponges, leather, etc. For fabric materials, the air permeability is related to the number and size of the gaps between the warp and weft yarns and the gaps between the fibers, the warp and weft density, the yarn twist, the fiber properties, the yarn structure, the fabric thickness and other factors.Different requirements for fabrics have different air permeability according to their specific uses. For example, the air permeability of fabrics used to make parachutes should be strictly controlled within the specified range. If the air permeability is too large, the parachute cannot be fully inflated. If the air permeability is too small, the stability of the parachute is poor or even damaged. Fabrics used as carpets are required to have relatively high air permeability. Even if they are all fabrics for making clothes, their air permeability should also vary to ensure that the clothes are comfortable to wear. For example, summer clothes should have a large air permeability and good heat dissipation, while winter coats should have a small air permeability to improve the warmth retention effect. Therefore, appropriate air permeability is one of the prerequisites for fabrics to have good performance.

Test principle of fabric air permeability test

According to the specified method and parameters, clamp the sample at the air inlet of the fabric air permeability tester, and then adjust the fan speed to achieve a pressure difference on both sides of the fabric. The air permeability of the breathable fabric is determined based on the nozzle aperture and the size of the pressure difference on both sides. The air permeability refers to: the gas flow rate per unit area of the fabric vertically per unit time under the specified p.

Next, set a specified pressure difference on the tester, which is usually adjusted according to the test standard and fabric characteristics.

Then start the tester and measure the air flow through the fabric under the set pressure difference. The test results are expressed in volume flow units, such as cm's or L/min.

Finally, the tester automatically records the measured data and calculates the air permeability index of the fabric. According to different test standards, air permeability can be expressed as air flow or air permeability.

To ensure the accuracy and comparability of test results, various countries and regions have established multiple air permeability test standards. Common standards include the ASTM D737 standard of the American Society for Testing and Materials, the IS0 9237 standard of the International Organization for Standardization, and the Chinese national standard GBTT5453. These standards have detailed provisions for sample preparation, test conditions, data processing, etc. to ensure the scientificity and consistency of test results.

As a precision testing equipment, the automatic air permeability tester plays a vital role in testing the air permeability of textiles. Through scientific and rigorous testing methods, it can accurately evaluate the air permeability of fabrics and ensure product quality and effect. If you want to know more about this machine, please feel free to consult UTSTESTER.

Email: hello@utstesters.com

Direct: + 86 152 6060 5085

Tel: +86-596-7686689

Web: www.utstesters.com

Introduction

Tearing is one of the most common forms of failure in textiles during actual use. Whether a jacket cuff gets caught on a tree branch, the knee of work pants is struck by a sharp object, or tent fabric is subjected to strong winds—these scenarios can all cause the fabric to tear rapidly along the yarn direction, starting from a localized notch.

Tear strength, as a core indicator for evaluating fabric durability and safety, directly impacts product lifespan and consumer safety. This article provides systematic technical guidance for textile testing laboratories by examining four key dimensions: failure mechanisms, testing methods, influencing factors, and instrument applications.

I. Physical Mechanisms of Tear Failure

1.1 The Nature of Tearing: Sequential Yarn Breakage

Unlike tensile failure, where an entire group of yarns bears the load simultaneously, tear failure exhibits significant stress concentration characteristics. When a notch exists at the fabric edge (e.g., a snag or cut), external force causes the yarns at the tip of the notch to first bear a load far exceeding the average. Once the first yarn breaks, the stress immediately transfers to the next yarn, creating a “domino-effect” chain of failures that ultimately results in rapid crack propagation.

During the tearing process, a characteristic stress triangle (Tearing Triangle) forms within the fabric:

- Vertex: The tip of the notch, where the single yarn currently breaking is located

- Base: The yarn system perpendicular to the tearing direction, which bears the primary load

- Hypotenuse: Adjacent yarns that are gradually drawn into the stress state

1.2 Factors Determining Tear Strength

Based on a mechanical analysis of fabric structure, tear strength primarily depends on the following factors:

1. Yarn tensile strength: Tear strength is directly proportional to the tensile strength of the yarn

2. Yarn elongation: The greater the elongation at break, the larger the area of the stress triangle, and the greater the number of yarns under stress, resulting in higher tear strength

3. Yarn coefficient of friction: Friction resistance between yarns affects stress transfer efficiency and the shape of the stress triangle

4. Fabric density and weave structure: Excessively high density may prevent yarns from sliding, thereby reducing tear strength

II. Testing Methodology and Interpretation of Standards

The most commonly used methods for testing fabric tear strength include the pendulum method (Elmendorf method), the tongue method (trouser method), and the trapezoidal method.

2.1 Pendulum Method (Elmendorf Method) — Dynamic Impact Test

Standards: GB/T 3917.1-2009, ISO 13937-1:2000, ASTM D1424-25

Test Principle: Based on the law of conservation of energy, the pendulum is raised to a predetermined height to acquire potential energy. Upon release, this potential energy is converted into kinetic energy to tear the specimen. By measuring the remaining swing angle of the pendulum after tearing the specimen, the energy consumed is calculated, thereby determining the tear strength.

Specimen Specifications: 63 mm × 100 mm rectangle with a 20 mm slit cut at the center

Scope of Application:

- ✓ Woven fabrics, nonwoven fabrics, laminated fabrics, pile fabrics, airbag fabrics

- ✓ Warp-knitted fabrics tested in the warp direction

- ✗ Weft-knitted fabrics, elastic fabrics, highly anisotropic fabrics

Technical Features:

- Fast testing speed (<1 second per test), simulating sudden tearing scenarios

- Force-time curve exhibits a typical sawtooth pattern, reflecting the process of a single yarn breaking

- Requires a multi-range pendulum (typically 200 gf–6400 gf); the test force should fall within 20%–80% of the range

2.2 Trouser Method (Single-Seam Method) — Constant-Speed Tensile Test

Standards: GB/T 3917.2-2009, ISO 13937-2:2000

Test Principle: A rectangular specimen is cut along the center of the short side to form a “trouser leg” shape. The two legs are clamped in the upper and lower grips of a tensile testing machine, respectively, and stretched at a constant rate (100 mm/min) while recording the force changes during the tearing process.

Data Collection Requirements: Divide the force-displacement curve into four equal segments. Discard the initial quarter and calculate the average of all peak values from the remaining three segments as the final result.

Differences from the Pendulum Method: The mechanisms of the two methods are similar, but the pant leg method involves slow, uniform tearing, whereas the pendulum method involves rapid impact tearing. For the same fabric, results from the pendulum method are typically slightly lower than those from the pant leg method.

2.3 Tongue Method (Double-Slit Method) — Bidirectional Tear Test

Standards: GB/T 3917.4-2009, ISO 13937-4:2000

Test Principle: Two parallel slits are cut into a rectangular specimen to form a tongue-shaped specimen. The tongues are clamped separately to keep the two cut lines parallel, and tensile force is applied along the cut lines to simulate a bidirectional tearing process.

Scope of Application: Widely used for various types of fabrics, including natural fibers, chemical fibers, and blended fabrics; particularly suitable for apparel fabrics and home textile products.

2.4 Trapezoidal Method — Multi-Yarn Synergistic Stress Test

Standards: GB/T 3917.3-2025 (New Edition), ASTM D5587

Test Principle: The specimen is cut into a trapezoidal shape with a central slit on the short side. The two non-parallel sides of the trapezoid are clamped, positioning the slit between the two jaws. During tensile testing, the tear propagates across the width of the specimen, causing a group of yarns to break sequentially under stress.

Technical Features:

- Unlike the single-yarn failure mechanism of the pendulum or single-tongue methods, the trapezoidal method exhibits multi-yarn cooperative tensile behavior

- Test values are typically significantly higher than those obtained by other methods (plain-weave cotton fabric: pendulum method < single-tongue method < double-tongue method < wing method < trapezoidal method)

- Suitable for thicker or high-strength fabrics, such as denim, industrial fabrics, and coated fabrics

2.5 Wing Method — Angular Variation Test

Standards: GB/T 3917.5-2009, ISO 13937-3:2000

Test Principle: Similar to the trapezoidal method, but the specimen is wing-shaped (isosceles triangle). By changing the clamping angle, the number of yarns subjected to force is adjusted.

Important Note: Although the wing-shaped method and the trapezoidal method belong to the same type of test, the test results cannot be directly compared due to differences in the angle of force application.

III. Guidelines for Selecting Test Methods

Principles for Method Selection:

1. Routine quality control: Give priority to the pendulum method (high efficiency) or the trapezoidal method (wide applicability).

2. Apparel products: The tongue method or pant method is recommended to simulate the forces encountered during actual wear.

3. Heavyweight/coated fabrics: The trapezoidal method must be used; the pendulum method may not be able to completely tear the fabric.

4. Arbitration Testing: Follow the method specified in the product standard; typically, the pant-shaped method or trapezoidal method is selected

IV. Key Factors Affecting Tear Strength

4.1 Raw Material Factors

Fiber Type: High-strength fibers (polyester, nylon) > natural fibers (cotton, wool). For fabrics of the same specification, the tear strength of polyester is typically 30–50% higher than that of cotton.

Yarn Structure:

- Plied yarn > Single yarn (twisting increases strength)

- Filament yarn > Staple fiber yarn (higher breaking strength)

- Textured yarn > Regular filament yarn (higher elongation, larger stress triangle)

4.2 Fabric Structure Factors

Fabric Density: There is an optimal density range. If density is too low, yarns are prone to slipping; if too high, yarns cannot slide to form stress triangles, which actually reduces tear strength.

Weave Structure:

- Plain weave < Twill weave < Satin weave (the fewer the interlacing points, the greater the yarn’s ability to slide)

- Knit fabrics typically have lower tear strength than woven fabrics (the loop structure is prone to deformation)

Post-processing Techniques:

- Resin finishing: Improves dimensional stability but reduces yarn slippage, resulting in a 20–40% decrease in tear strength

- Coating finishing: The coating penetrates yarn gaps, restricting yarn movement; evaluation requires the trapezoidal method

- Softening finishing: Increases yarn lubricity, promotes stress distribution, and can enhance tear strength

V. Industry Applications

Key Application Areas

Protective clothing: Firefighting suits and chemical protection suits require warp/weft tear strength ≥100 N (GB 24539-2021)

Outdoor gear: Tent and jacket fabrics must be evaluated for both tear strength and seam performance

Industrial Textiles: Geotextiles and filtration materials are evaluated using the trapezoidal method, with a requirement of ≥250 N (GB/T 17634)

Automotive Interiors: Airbag fabrics are tested using the pendulum method, with a requirement of ≥200 N in both warp and weft directions (ISO 13937-1)

Conclusion

Textile tear strength testing is a comprehensive discipline involving materials mechanics, structural engineering, and standardization technology. From the rapid impact of the pendulum method to the multi-yarn interaction of the trapezoidal method, different testing methods reveal distinct mechanisms by which fabrics resist tearing.

If you require technical consultation regarding specific fabric types or testing methods, please contact the UTSTESTER technical team for customized solutions.

Email: hello@utstesters.com

Direct: + 86 152 6060 5085

Tel: +86-596-7686689

Web: www.utstesters.com

I. What Is Fabric Water Vapor Permeability?

Fabric water vapor permeability refers to a fabric’s ability to allow water vapor to pass through it, and it is one of the core indicators for evaluating the comfort of functional textiles. During physical activity, the skin continuously evaporates moisture (sweat). If the fabric cannot promptly expel this water vapor, a hot and humid microenvironment will form on the skin’s surface, leading to discomfort.

Water vapor permeability and water repellency together constitute the dual standards of “breathability” and “protection” for outdoor functional apparel. An excellent piece of functional apparel must both block the intrusion of external liquid water and rapidly expel water vapor from the body—this is precisely where the value of water vapor permeability research lies.

II. Testing Methods for Water Vapor Permeability

1. Desiccant Method (Positive Cup Method)

Standards: GB/T 12704.1, ASTM E96, JIS L1099 A-1

Principle: A desiccant (anhydrous calcium chloride) is placed in a moisture permeability cup, and the test sample is sealed at the cup opening. After being kept in a constant temperature and humidity environment for a specified period, the moisture permeability is calculated by measuring the weight gain of the desiccant.

Features: The test conditions are mild and closely resemble actual wearing conditions, making it the most commonly used testing method in China.

2. Evaporation Method (Water Method, Inverted Cup Method)

Standards: GB/T 12704.2, ASTM E96 BW, JIS L1099 B-1

Principle: A specific volume of distilled water is placed in a moisture transmission cup. After sealing the sample, the cup is inverted. Water vapor passes through the sample and evaporates outward; the moisture transmission rate is calculated by measuring the decrease in water mass within the cup.

Features: Testing conditions are relatively harsh, simulating a high-humidity environment, making it suitable for waterproof and breathable fabrics.

3. Sweating Guarded Hotplate Method

Standards: ISO 11092, GB/T 11048

Principle: A porous metal plate is used to simulate skin perspiration. The energy required to maintain a constant temperature is measured, directly yielding the fabric’s moisture resistance (Ret) and water vapor transmission index (imt).

Features: This method more closely approximates actual human physiological conditions and is considered the “gold standard” for evaluating thermal and moisture comfort.

III. Key Factors Affecting the Moisture Permeability of Fabrics

(Ⅰ) Fiber Raw Material Factors

1. Moisture Absorption of Fibers

The moisture absorption of fibers is the foundation for determining moisture permeability. Based on how fibers interact with water, they can be classified as follows:

- Hydrophilic fibers: cotton, viscose, wool, silk, etc. The molecular structure of these fibers contains hydrophilic groups (-OH, -COOH, -NH₂), which can adsorb water molecules via hydrogen bonding and transport them through diffusion within the fiber. Fibers with strong moisture absorption typically exhibit better moisture vapor permeability.

- Hydrophobic fibers: Synthetic fibers such as polyester, nylon, and polypropylene. These fibers do not absorb water themselves; water vapor is primarily transported through the pores in the gaps between fibers. Although the moisture vapor transmission capacity of a single fiber is limited, excellent moisture vapor transmission performance can be achieved through specialized structural designs.

2. Fiber Fineness and Cross-Section Shape

- Fiber fineness: The finer the fiber, the larger the specific surface area, and the more dense the capillary network formed between fibers, which facilitates the conduction of water vapor. Fabrics made from ultra-fine fibers (<0.5 dtex) typically exhibit superior moisture vapor transmission performance.

- Cross-sectional Shape: Fibers with non-circular cross-sections (such as cross-shaped, trefoil-shaped, or hollow fibers) can form more pore channels compared to circular fibers, thereby increasing the pathways for water vapor transmission. For example, hollow polyester fibers not only reduce weight but also significantly enhance moisture permeability and thermal insulation.

(II) Yarn Structure Factors

1. Yarn Twist

Twist directly affects the density and porosity of the yarn:

- Low-twist yarn: The yarn is loose, with large gaps between fibers, resulting in low resistance to water vapor transmission and good moisture permeability. However, the yarn has lower strength and reduced abrasion resistance.

- High-twist yarn: The yarn is compact, with reduced gaps between fibers, leading to increased resistance to water vapor transmission and reduced moisture permeability. However, the yarn has high strength, and the fabric feels stiff and crisp.

2. Yarn Blend Ratios

- Cotton/Polyester Blends: Cotton fibers provide moisture absorption and wicking capabilities, while polyester provides strength and quick-drying properties. When the cotton content is between 40% and 60%, moisture permeability and durability achieve a good balance.

- Wool/Nylon Blends: The natural moisture-absorbing properties of wool combined with the strength of nylon are commonly used in high-end outdoor apparel.

(III) Fabric Structure Factors

1. Fabric Density and Tightness

- Increased Density: Warp and weft yarns are arranged more tightly, reducing fabric porosity, increasing resistance to water vapor transmission, and lowering moisture permeability.

- Decreased density: Fabric porosity increases, improving moisture vapor permeability, but this may lead to reduced wind resistance and insufficient strength.

2. Fabric Thickness

Fabric thickness is inversely correlated with moisture vapor permeability: the diffusion resistance that water vapor must overcome to pass through the fabric is directly proportional to its thickness.

3. Weave Structure

The pore morphology formed by different weave structures varies significantly:

4. Multi-layer Composite Structures

Modern functional apparel often employs multi-layer composite designs:

- Two-layer fabrics: The outer layer is windproof and waterproof, while the inner layer wicks away moisture and sweat; the “pump effect” created by the pores between the layers enhances moisture vapor permeability.

- Three-layer composites: Fabric + waterproof and breathable membrane + lining. The membrane’s microporous structure allows water vapor molecules to pass through while blocking liquid water.

(IV) Post-processing Factors

1. Coating Treatments

Coating is a key method for modifying moisture vapor permeability:

- PU Coating: Standard PU coatings block fabric pores, significantly reducing moisture vapor permeability. However, microporous PU or hydrophilic PU coatings can maintain a certain level of moisture vapor permeability while retaining waterproofing properties.

- Microporous PTFE Membrane: Features extremely high porosity and very small pore sizes, offering high moisture vapor transmission rates and water pressure resistance.

- Non-porous hydrophilic membranes: These utilize a “adsorption-diffusion-desorption” moisture transmission mechanism via hydrophilic groups on the molecular chains. While their moisture permeability is slightly lower than that of microporous membranes, they offer better wash resistance.

2. Water-repellent and moisture-permeable finishing agents

- Fluorocarbon compounds: These impart water- and oil-repellent properties to fabrics but have a certain negative impact on moisture permeability.

- Silicone-based compounds: Form a breathable film on the fiber surface, with minimal impact on moisture permeability.

- Nanotechnology treatments: Such as nano-SiO₂ and TiO₂, which impart special functions while maintaining porosity.

3. Moisture-Wicking Finishes

Treating hydrophobic synthetic fiber fabrics with hydrophilic finishing agents (such as polyether-based or polyacrylic-based compounds):

- The finishing agents form a hydrophilic layer on the fiber surface, improving surface wettability.

- A wicking effect is created, rapidly transporting sweat from the skin side to the outer layer for evaporation.

- Moisture vapor transmission can be increased by 20%–40%, while maintaining the quick-drying properties of synthetic fibers.

(V) Environmental Factors

Both moisture vapor transmission testing and actual use are significantly influenced by environmental conditions:

1. Temperature

- Rising temperature: The kinetic energy of water vapor molecules increases, accelerating diffusion; simultaneously, fibers expand after absorbing moisture, enlarging their pores. Moisture vapor transmission rate increases significantly with rising temperature.

2. Relative Humidity

- High-humidity environment: The concentration gradient of water vapor on both sides of the sample decreases, reducing the driving force and lowering the moisture vapor transmission rate.

- Low-humidity environments: The concentration difference is large, resulting in high moisture vapor transmission rates.

- Isothermal and isohygric conditions: When the temperature and humidity on both sides of the sample are identical, the moisture vapor transmission rate is zero.

3. Wind Speed

- Increased wind speed accelerates the loss of water vapor from the sample’s surface, maintaining a higher concentration gradient and thereby increasing the moisture vapor transmission rate.

- In actual outdoor wear, wind speed is a key variable affecting perceived comfort.

IV. Balancing Moisture Permeability with Other Functions

1. Moisture Permeability vs. Water Resistance

Conflict: Water resistance requires extremely small or closed fabric pores, while moisture permeability requires open pores.

Solutions: Microporous membrane technology, hydrophilic non-porous membranes, and high-density weaving techniques (such as high-density fabrics made from ultra-fine fibers).

2. Moisture Permeability vs. Windproofing

Conflict: Windproofing requires a tightly woven fabric structure, while moisture permeability requires unobstructed pores.

Solutions: Multi-layer composite structures, membrane technology, and adding a windproof fabric layer on the outer side of the moisture-permeable membrane.

3. Moisture Permeability vs. Thermal Insulation

Conflict: Thermal insulation requires a layer of still air (loose structure), but excessive thickness reduces moisture permeability.

Solutions: Hollow fibers, 3D knitted structures, and phase-change materials for temperature regulation.

Conclusion

Fabric moisture vapor permeability is a complex system involving multiple interacting factors, spanning disciplines such as fiber science, textile engineering, polymer materials, and heat and moisture transfer.

UTSTESTER provides precise moisture vapor permeability testing equipment. If you encounter any issues during moisture vapor permeability testing, please feel free to contact our technical team at any time.

Email: hello@utstesters.com

Direct: + 86 152 6060 5085

Tel: +86-596-7686689

Web: www.utstesters.com

In today’s pool circulation systems, energy efficiency, operational stability, and intelligent control are no longer optional—they are essential. Traditional fixed-speed pool pumps are increasingly being replaced by variable frequency (VFD) pool pumps, which significantly reduce energy consumption while improving system adaptability.

The F-SP Pro Series Swimming Pool Pump with Frequency Converter is engineered to meet these evolving demands, offering a balance of performance, filtration capability, and intelligent control tailored for small to medium-sized residential pools.

What Makes the F-SP Pro Series Stand Out

The F-SP Pro Series integrates a high-efficiency hydraulic design with an embedded frequency converter, allowing dynamic speed adjustment based on system demand.

· Integrated Frequency Converter (VFD) 

· Dual Operation Modes 

· User-Friendly Digital Interface 

· Energy Savings up to 75% 

· Optimized for Slightly Dirty Water Conditions 

Unlike conventional pumps, this system is designed not just for circulation—but for intelligent water management.

Typical Use Cases:

· Residential swimming pools

· Small commercial pools

· Initial filtration stages

· Pools with moderate debris load

The F-SP Pro Series is more than just a circulation pump—it represents a shift toward intelligent, energy-efficient pool management systems.

For heat pump systems, underfloor heating mixing stations, and HVAC integrators, pump efficiency, control accuracy, and refrigerant compatibility are critical to system performance and regulatory compliance. The Shinhoo Grand 25-23 Pro – a permanent magnet variable frequency pump – delivers ultra low energy consumption, precise flow feedback, and an A3 explosion proof rating. It provides a safe, high efficiency circulation solution for systems using R290 and other eco friendly refrigerants.

IE5 Efficiency – EEI ≤ 0.23

The Grand 25-23 Pro achieves an EEI value as low as 0.23 (Part 2), far exceeding EU energy efficiency standards. Its high efficiency permanent magnet motor offers:

l Rated flow: 8 m³/h

l Rated head: 12.5 m

l Max. flow: 14 m³/h

l Max. head: 23 m

While delivering strong hydraulic performance, the pump minimizes energy consumption – helping systems earn green building certifications and meet low carbon operation targets.

Multiple Control Modes – Flexible Adaptation

The pump supports constant speed, constant pressure, proportional pressure, AUTO, and PWM control modes, easily adapting to different operating conditions. Whether in constant flow or variable flow systems, it delivers precise adjustment and avoids unnecessary energy waste.

High Accuracy Flow Feedback – Stable & Reliable

Flow feedback accuracy reaches ±0.2 m³/h, providing dependable data for system monitoring and optimization. Combined with IP44 protection, the pump ensures long term stable operation even in humid or mildly dusty environments.

A3 Explosion Proof – R290 Refrigerant Compatible

Certified with an A3 explosion proof rating, the Grand 25-23 Pro is specifically designed for systems using flammable eco friendly refrigerants such as R290. It meets safety requirements for heat pumps, chillers, and refrigeration equipment – helping customers address increasingly stringent environmental and safety regulations.

Global Certifications – Proven Quality

The pump holds CCC, TUV, CE, EMC, ROHS, and REACH certifications, confirming electrical safety, electromagnetic compatibility, and material environmental compliance. System integrators can specify the pump with confidence, shortening compliance review cycles.

Typical Applications

l Heat pump systems (air source / water source heat pumps)

l Underfloor heating mixing stations

l Domestic hot water circulation

l HVAC terminal circulation

Why Choose the Shinhoo Grand 25-23 Pro?

The Shinhoo Grand 25-23 Pro combines ultra low energy consumption, precise control, refrigerant compatibility, and robust quality – offering a highly efficient, safe, and compliant pumping solution for modern heat pump and HVAC systems. Lower your operating costs and strengthen system competitiveness – choose the Grand 25-23 Pro for your next project.

At Grundfos, we often say that the best sales are not achieved in meeting rooms, but accumulated through the daily operation of equipment. The experience of renovating a sewage treatment plant near the Songhua River in Harbin is the most vivid illustration of this statement.

The story began in 2008. As a core environmental facility in Harbin Qunli New District (home to a national-level urban wetland park) and situated along the Songhua River, the sewage treatment plant bore significant environmental responsibilities. From the outset, the water utility company responsible for its construction and operation decided to install eight Grundfos submersible pumps in the intake pump house—the most complex operational area with the highest debris accumulation and corrosion risk.

A "Perfect Score" in 17 Years

Fast forward to 2025, when the wastewater treatment plant launched its 'Legacy Equipment Retrofit' initiative, the client conducted a comprehensive 'health check' on these aging systems. The data was not only impressive but also astonishing:

This was a 17-year intensive operation—where the equipment was submerged 24/7 in complex, highly corrosive raw sewage, constantly subjected to fiber entanglement and debris impact. Yet among these 8 pumps, 5 had never undergone major overhauls, with their core hydraulic component—the impeller—replaced only once.

This chronicle of time objectively attests to Grundfos products' unparalleled reliability and durability, which has directly led customers to steadfastly choose the brand during subsequent upgrades.

Both "hold the line" and "charge forward"

The simple "trade-in" model is no longer sufficient to address Harbin's current urban scale. With the influx of population into the Qunli New District, the sewage treatment plant faces more complex challenges: not only does the daily inflow volume continue to rise, but the intake pump room must also undertake the function of flood prevention and rainwater regulation during the flood season.

"The current requirements differ from those in 2008. We must ensure stable sewage pumping during normal operations and rapid drainage during heavy rainfall. The equipment must possess dual-purpose capabilities." — Engineer, Sewage Plant Equipment Department

To address this dual requirement of 'maintaining stability in daily operations while handling peak demands,' we opted for a forward-looking 'scalable upgrade' solution rather than a simplistic homologous replacement.

We have uniformly upgraded all new pumps to 200kW capacity. The upgraded pump units demonstrate exceptional operational adaptability, ensuring stable sewage discharge while effectively handling peak flow surges during extreme weather events.

The Weight of Service: 17 Years of Invisible Protection

If product strength is the stepping stone, then 17 years of 'professional service' serves as the reassurance. In this project, our authorized service center has maintained uninterrupted service for the past seventeen to eighteen years.

When reflecting on this journey, Mr.Fan, the head of the service center, remarked:

In our profession, serving water treatment plants, the phone must never be turned off. A customer's call is a command; no matter when it rings, we must immediately respond to the scene. 

For over a decade, we've been on call for anything from minor component replacements to technical consultations. Our clients trust us not because of polished PPTs, but because we're there when they need us most.

—General Manager of Fanlixin Grundfos Authorized Service Center

This '24/7 response, same-day delivery' service commitment assures customers that choosing Grundfos means choosing a permanent on-call team of engineers.

Implementation and Delivery:Zero Production Stoppage in Complex Environment

The 2025 on-site implementation was fraught with uncertainties. As a typical municipal renovation project involving multiple stakeholders, the timeline and installation method of equipment would depend on the progress of other sub-projects. Confronted with complex on-site coordination and the strict requirement that the water intake pump room must remain operational, our team developed a meticulous 'non-disruption renovation' plan:

Seamless retrofitting: The new 200kW pump is engineered to seamlessly integrate with the existing guide rod system, significantly reducing civil engineering work and shortening single-unit operation time.

Rotating shifts: Implementing a relay mode of 'dismantling, installing, and commissioning' to ensure uninterrupted operation of the wastewater treatment plant.

On-site coordination: Our service team serves as 'on-site coordinators,' proactively liaising with clients, supervisors, and contractors to resolve any unexpected obstacles.

"The site is full of variables, so we need to keep a close eye on it. We'll break down the installation schedule day by day, assist the client in coordinating with the supervisor, and ensure these eight pumps are smoothly handed over this month." — Li Chao, Grundfos Sales Engineer

Seventeen years ago, our clients chose us because they trusted the Grundfos brand. Seventeen years later, they choose us again because they see the quality of Grundfos and experience our unwavering commitment.

Through this upgrade, Grundfos not only delivered eight high-performance 200kW pumps to the sewage treatment plant, but also extended its 17-year commitment to safeguarding water safety in Harbin.

The primary difference lies in the number of impellers and the generated pressure. A single-stage centrifugal pump uses one impeller and is ideal for high-flow, low-to-medium pressure applications like HVAC or general water transfer. A multi-stage centrifugal pump uses multiple impellers in series to generate extremely high pressure (head), making it the best choice for boiler feed, reverse osmosis, and high-rise water supply.

Choosing the right pump for your facility depends entirely on your specific requirements for flow rate and discharge pressure (head). Understanding the mechanical differences between these two designs is crucial for maximizing efficiency and minimizing maintenance costs.

Understanding Single-Stage Pumps

As the name suggests, this pump contains only one impeller rotating within the casing. Fluid enters the suction eye, is accelerated by the centrifugal force of the impeller, and is discharged through the volute.

● Best For: Applications requiring massive volumes of liquid to be moved quickly over relatively short distances or low elevations.

● Advantages: Simple design, easier maintenance, lower initial purchasing cost, and excellent reliability for standard industrial water supply and cooling tower operations.

● Limitations: They are heavily limited by their maximum head. If you try to achieve high pressure by simply increasing the speed of a single impeller, you risk severe cavitation and mechanical failure.

Understanding Multi-Stage Pumps

In a multi-stage configuration, fluid travels through two or more impellers connected in series on the same shaft. The fluid is discharged from the first impeller and fed directly into the eye of the next. Each stage increases the fluid's pressure while the flow rate remains constant.

● Best For: Applications requiring high discharge pressure. Think boiler feed systems, high-pressure cleaning, desalination plants, and deep-well water extraction.

● Advantages: Exceptional high-head capabilities. They are also highly energy-efficient because they use multiple smaller diameter impellers operating at tighter clearances rather than one massive impeller.

● Limitations: The internal design is far more complex, meaning higher initial costs and requiring more skilled technicians for maintenance and seal replacement.

The Verdict: How to Choose

If your operation demands moving a large volume of water horizontally across a factory floor, a single-stage pump is your most cost-effective solution. However, if you need to push water up a 50-story building or feed a high-pressure boiler, the multi-stage pump is your only viable engineering option. Always consult your pump curve and system resistance before making a purchasing decision.

Through rational selection of pump energy-saving 

To properly utilize water pumps, selecting the right model is crucial. Proper pump selection ensures adequate water supply volume and pressure while conserving energy. Conversely, inappropriate choices not only reduce equipment utilization efficiency but also lead to energy waste. Overly large pumps or excessively high head heights are common causes of energy inefficiency. Even high-efficiency pumps operating at low head heights will function inefficiently, resulting in increased energy consumption. Therefore, pump selection should prioritize understanding water supply requirements, including head height, flow range, and fluctuation patterns. When choosing pumps, focus should not solely on achieving peak efficiency during maximum flow periods but rather consider regular water supply volumes. Opt for pumps with wide high-efficiency ranges and compatible motors featuring high efficiency and low energy losses. Urban water demand exhibits constant variability—differing by year and season, with daily peak hourly flows reaching 1.3-1.5 times average levels. In smaller towns where water usage is concentrated, peak flow rates may surge to 2.0-2.5 times normal levels. Operating pumps based solely on maximum flow rates rather than actual demand patterns inevitably results in energy waste.

Selection of Pump Performance

For pumps with stable process flow rates, the key performance consideration is ensuring operational efficiency. When the average head fluctuates significantly and requires frequent flow rate adjustments, particular attention must be paid to the flatness of the Q-H and Q-y curves, confirming whether the pump operates within its high-efficiency range.

Energy conservation through rational matching and combined operation of water pumps

1、Rational matching of water pumps

Typical pumping stations are equipped with at least 2-3 working pumps. To optimize energy efficiency and economic operation, it is advisable to pair pumps with similar head but varying flow rates for a balanced configuration. When water demand fluctuates significantly and frequently, adding a variable-speed pump can better accommodate changes in water usage. During peak water consumption periods, the high-capacity pump operates while switching to a low-capacity pump during off-peak hours. This configuration not only reduces the number of pumps in operation but also ensures all units run within their high-efficiency range, resulting in substantial energy savings and enhanced water supply flexibility.

2、Parallel Combined Operation of Water Pumps

In applications requiring high flow rates or significant flow fluctuations, different pump configurations may be employed based on specific conditions to enhance operational efficiency (the maximum number of parallel pumps shall not exceed four).

In urban water supply systems, with the exception of small towns or large factories that utilize water towers for regulation, most cities directly pump water into distribution networks using centrifugal pumps. Flow control is achieved by adjusting the number of pumps in parallel operation—increasing or decreasing their count as needed. During peak daytime water demand periods, additional pumps are activated in parallel mode. This configuration enhances pump head capacity, effectively meeting both urban water consumption requirements and hydraulic pressure standards.

For instance, a water treatment plant experiences maximum pump head of approximately 50 meters during peak water usage periods, while dropping to around 25 meters during nighttime off-peak hours. The significant disparity in head performance between daytime and evening operations has led to the long-term parallel operation of pumps with identical head specifications. Although this configuration meets peak demand requirements, it becomes inadequate during low-water periods, resulting in reduced pump efficiency and high energy consumption. Therefore, pump selection should be tailored to the specific water supply system's operational conditions to ensure efficient operation within optimal performance ranges. To further enhance energy efficiency and accommodate variable flow demands, existing equipment modifications—including pump replacement systems designed for nighttime operation during low water consumption periods—can significantly improve pump efficiency and reduce power consumption per unit. Such upgrades can yield substantial annual electricity savings.

Energy-saving through Pump Speed Control Technology

1. Principle of Energy Saving through Pump Speed Regulation

The energy-saving principle of pump speed regulation can be derived from the similarity law of fluid mechanics. The relationship between performance and rotational speed is as follows: flow rate is directly proportional to rotational speed, head is proportional to the square of rotational speed, and power is proportional to the cube of rotational speed.

2. Conditions for pump speed regulation and selection of speed-regulated pumps

① Conditions for selecting pump speed regulation

When water supply volume exhibits significant seasonal/daily variations or demonstrates high time variation coefficients, pumps frequently operate at high head or off-design conditions characterized by large flow rates and low head within the high-efficiency range. In cases where pump model selection is not feasible, variable-speed pumps should be considered as an alternative solution.

② Selection of speed-regulating pump

When multiple pumps are available, the one with the highest flow rate and most frequent operation should be selected as the speed-regulating pump. The operating point of the speed-regulating pump must be positioned at the midpoint of the pump's high-efficiency range—specifically, at the right end of this range when operating at rated speed, or even slightly beyond it. Additionally, pumps with excessively low or high specific speed (ns) are unsuitable for this role. Centrifugal pumps with medium-to-high specific speeds (ns=80-300) demonstrate optimal performance as speed-regulating pumps.

3、Methods and Characteristics of Pump Speed Regulation

① Thyristor cascade speed control features high efficiency and mature technology, suitable for speed regulation within 70–95% range. However, the speed control device exhibits low power factor and causes grid pollution.

② Electromagnetic slip speed control features simple control, stable and reliable operation, ease of remote and automatic control, and high power factor, but has the disadvantage of slip loss.

③ Liquid viscosity governor (also known as oil film clutch) features large adjustment capacity, compact size, and speed regulation capability within the rated speed range of 30%–100%. It offers low manufacturing costs. However, oil film clutches require high-quality mechanical oil and exhibit certain slip loss.

④ Frequency conversion speed regulation is the most advanced method among speed control technologies, offering significant energy-saving potential, low noise levels, stable pressure in water supply networks, convenient maintenance and management, and minimal malfunctions, albeit at a high cost.

4. Determination of Optimal Speed Ratio for Water Pump

Pump theory indicates that within a limited speed range, variations in pump rotational speed alter the characteristic curve, thereby shifting the operating point to the high-efficiency zone.

Strengthen energy balance testing of water pumps, and promptly update or retrofit them to improve operational efficiency and achieve energy-saving objectives.

1. Regularly measure pump characteristics, primarily Q-H and Q-y curves. If the pump efficiency is found to be significantly low, promptly replace the pump or impeller.

2. For single-stage pumps with improper selection or excessive head and flow rate, reducing the head and flow rate by turning the impeller outer diameter can be employed to operate within the high-efficiency range. The turning amount of the impeller is related to specific speed; excessive turning may lead to insufficient pump efficiency, resulting in counterproductive outcomes. A stepwise turning method is generally adopted to achieve optimal impeller turning parameters.

Strengthen the maintenance and management of water pumps, actively adopt new technologies and materials, and improve pump efficiency.

1. Improve the processing and assembly quality of pumps to ensure safe and reliable operation, and minimize the clearance of the mouth ring as much as possible;

2. Enhance maintenance by promptly repairing appropriate leakage gaps. When leakage gaps exceed specified values due to detected rupture or wear of the port ring, repairs or replacements should be performed. Based on empirical data and actual measurements, the port ring radius gap should be determined to be 2.5–3.5% of the impeller port ring outer diameter.

3. Actively adopt novel sealing fillers. Fillers serve as water or gas barriers in shaft sealing devices. Selecting a filler with superior sealing performance can not only resolve leakage issues and reduce consumption but also enhance pump efficiency to a certain extent.

For HVAC integrators , efficiency, reliability, and cost control are top priorities. Shinhoo’s Mega S Series magnetic circulation pumps deliver high flow, low energy consumption, and intelligent controls—helping businesses optimize systems, cut operational costs, and meet stricter environmental standards.

High-Flow, Low-Energy Operation

The Mega S Series has been engineered to provide maximum flow while minimizing energy consumption. Its optimized hydraulic design, coupled with high-efficiency motors, allows the pumps to handle demanding HVAC systems, hot water circulation, air-conditioning, and commercial water supply. This balance of power and efficiency not only reduces operational costs but also supports sustainable energy goals.

Intelligent Control and Comprehensive Protection

Modern systems require flexibility. The Mega S Series supports 12 control modes, including Auto, Constant Speed, Constant Pressure, Proportional Pressure, Constant Flow, Temperature Control, ΔT Control, 0–10 V, 4–20 mA, PWM, and Communication Control. Coupled with 15 protection functions, these pumps ensure safe, reliable operation even in complex installations. Operators benefit from precise integration with their HVAC systems, while maintenance teams gain peace of mind from built-in safety features.

Built for Durability and Quiet Operation

Designed for longevity, the Mega S Series pumps feature robust construction with a specially coated shaft for extended service life. Noise levels are kept below 55 dB(A), ensuring unobtrusive operation in commercial or residential settings. A user-friendly TFT LCD display provides real-time monitoring and simple control, making both installation and maintenance straightforward.

Safe and Refrigerant-Compatible

Meeting modern environmental and safety standards, the Mega S Series carries an A3 explosion-proof rating and is compatible with eco-friendly refrigerants such as R290. This makes it a suitable choice for a wide range of heating, cooling, and refrigeration systems without compromising safety or sustainability.

Localized Expertise and Support

Understanding that global solutions require local expertise, Shinhoo’s European branch in Italy provides professional technical integration and after-sales services. Local experts assist with system matching, installation guidance, and troubleshooting, ensuring that each pump delivers optimal performance in its specific regional context.

A Sustainable Choice for Modern Systems

By combining energy efficiency, intelligent control, robust design, and localized support, Shinhoo’s Mega S Series delivers reliable performance for HVAC and water circulation systems. For system integrators, building operators, and OEM manufacturers, these pumps offer:

Reduced energy consumption and operational costs

High flow capacity for diverse applications

Intelligent monitoring for optimized system management

Shinhoo continues to drive innovation in pump technology, supporting a sustainable future for the global HVAC and water circulation systems.

As heating systems continue to evolve toward higher efficiency, lower noise levels, and smarter operation, circulation pumps play a crucial role in overall system performance. Classic Series circulation pumps are engineered to meet the demands of modern heating, heat pump, and hot water systems—combining intelligent control, robust design, and proven energy efficiency. 

Classic Series offers multiple control options to adapt to different installation requirements and user preferences, making system setup fast and intuitive.

Classic S Series – Smart Control

Equipped with simple button operation, Classic S Series allows users to switch easily between control modes. A dedicated night mode helps reduce noise and power consumption during low-demand periods, improving comfort while saving energy.

Classic Series – Rotary Control

With AUTO mode and Min–Max continuous adjustment, the rotary control version enables quick commissioning without complex settings. This makes it an ideal solution for installers who value efficiency and reliability on site.

Classic E Series – Easy-to-Control

Designed for straightforward operation, Classic E Series supports AUTO, Min, and Max manual modes, ensuring stable and consistent performance across a wide range of system conditions.

Energy Efficiency That Meets European Requirements

All Classic Series models feature a high-efficiency ECM motor, ensuring quiet operation and significantly reduced energy consumption. With an Energy Efficiency Index (EEI ≤ 0.20, Part 2), Classic Series complies with current European energy-efficiency regulations and supports sustainable heating system design. 

Classic series

Built for Reliability and Safety

Classic Series is designed for long-term, stable operation in demanding residential and light industrial environments. Its compact and robust construction is supported by comprehensive compliance with international standards:

• Power supply: 230V AC, 50/60Hz
• Protection class: IP42
• Max. system pressure: 1.0 MPa
• Medium temperature range: +2°C to +110°C (glycol up to 50%)
• Compliance: CE / GS / EMC / LVD / RoHS / REACH

These specifications ensure safe performance, durability, and compatibility with modern heating systems. 

Classic series

Versatile Applications Across Heating Systems

Thanks to flexible control modes and reliable construction, Classic Series is suitable for a wide range of applications, including:

• Domestic heating and hot water supply systems
• Air-source and ground-source heat pump systems
• Air-conditioning systems
• Industrial hot water circulation systems
• Solar thermal systems
• 

For both new installations and system upgrades, Classic Series circulation pumps deliver an optimal balance of energy efficiency, ease of use, and long-term reliability. Designed to support modern heating technologies while meeting European compliance requirements, Classic Series is a dependable solution for manufacturers, system integrators, and professional installers.