Features

High installation location: Elevated ducts are generally installed at the top of buildings, above ceilings, or on steel structures at high elevations to provide ventilation or air conditioning coverage for specific areas.

Efficient use of space: It can deliver air to the required areas without occupying floor space. This is particularly important for places with limited space, such as industrial plants, large warehouses, and gymnasiums, as it can effectively utilize vertical space and improve space utilization.

Long air delivery distance: Due to the high installation position, the air duct can utilize natural air flow and pressure differences to deliver air over long distances, thereby achieving large-area ventilation or air conditioning coverage.

Aesthetically pleasing: Elevated ductwork is typically installed at a height where it is not easily visible to people, thereby minimizing its impact on the appearance of the building and keeping the interior neat and attractive.

High construction difficulty: Installation at high altitudes requires specialized high-altitude work equipment and technical personnel. Safety issues must be addressed during construction, which also increases the difficulty and cost of construction.

Maintenance inconvenience: Due to its elevated position, maintenance personnel need to use professional climbing equipment to perform repairs, maintenance, and other tasks, which increases the difficulty and cost of maintenance and places higher demands on the skills and safety awareness of maintenance personnel.

application scenarios

Industrial plants: Used to remove exhaust gases, dust, and heat generated during production, provide fresh air, improve the working environment, protect workers’ health and safety, and also help protect equipment and improve production efficiency.

Large warehouses: such as automated multi-level warehouses, which can control the temperature and humidity of different areas within the warehouse to ensure proper storage conditions for goods and prevent them from becoming damp, moldy, or spoiled.

Commercial buildings: such as shopping malls, supermarkets, shopping centers, etc., used to regulate indoor air temperature, humidity, and air quality, providing customers and employees with a comfortable shopping and working environment.

Sports venues: Able to meet the ventilation and air conditioning needs of large numbers of spectators and athletes in sports venues, ensuring fresh air and comfortable temperatures inside the venue, thereby enhancing the spectator experience and the competitive performance of athletes.

Transportation hubs: such as train stations and airports, can effectively regulate the air environment in areas such as lobbies, waiting rooms, and waiting areas, providing passengers with a comfortable waiting space.

Installation points

Construction plan formulation: Based on the specific conditions of the construction site, including building structure, duct installation location, height, quantity, specifications, and models, formulate a detailed construction plan, clarify construction objectives and construction sequence.

Safety measures: Set up safety warning signs at the construction site, cordon off the construction area, and prevent non-construction personnel from entering. Set up a suitable aerial work platform, ensure that the platform legs are evenly distributed, install guardrails and anti-slip boards, and set up safety nets below the work platform.

Duct inspection and hoisting: Inspect the ducts before construction to ensure that they are free of damage, deformation, and other issues. Set hoisting points based on the length and weight of the ducts, generally at both ends and in the middle, and use special lifting lugs to secure them firmly. During hoisting, a designated person should be in charge to ensure that the ducts are lifted vertically and do not hit nearby obstacles.

Duct connection and sealing: Align the duct ends and ensure that the interface is flat and straight. Use sealing tape, sealant, or flanges to seal the duct system and prevent air leakage. For duct bends and diameter changes, use special elbow components and diameter change pipes, and pay attention to the sealing of the interface.

Installation Quality Inspection: After installation is complete, inspect the installation quality of the ductwork section by section, including whether the ductwork is straight, whether the connections are secure, and whether there are any air leaks. Use professional testing instruments to conduct airtightness tests, airflow and air velocity tests, etc., on the ductwork system to ensure that it meets design requirements.

In the chemical and electroplating industries, the production process often produces various gases with strong corrosive properties, such as sulfuric acid, hydrochloric acid, sodium hydroxide, etc. PP ducts can easily cope with these “acid and alkali attacks” by virtue of their excellent chemical resistance. In the sulfuric acid plant, PP ducts are used to transport high concentration of sulfuric acid vapor, and after a long time of use, the inner wall of the ducts is still smooth as before, without the slightest trace of corrosion. While the traditional metal duct, in the same environment, may be just a few months will appear serious corrosion, resulting in pipe leakage, not only affect the production, but also may bring potential safety hazards. According to relevant data, in the chemical industry, the use of PP duct equipment maintenance frequency than the use of metal duct equipment reduced by more than 50%, greatly improving production efficiency.

(ii) Sealing: “zero air leakage” guarantee

PP ducts are connected by heat fusion connection, flange connection and many other advanced connection methods. These connection methods can ensure that the ducts are tightly bonded to each other and realize “zero leakage” of air. In hospital operating rooms, good sealing is crucial. If there is leakage in the ventilation system, it will not only affect the air quality in the room, but may also lead to an increased risk of surgical infections. the excellent sealing of PP ducts can effectively prevent the leakage of harmful gases, providing a safe and clean environment for patients and healthcare workers. In industrial production, for some processes that require high gas purity, such as electronic chip manufacturing, the sealing of PP air ducts can ensure that the production environment is not interfered by external impurities, ensuring the stability of product quality.

(iii) Low noise: quiet ventilation system

PP material has good damping properties, which is the key to its noise reduction. As air flows through the duct, the PP material absorbs and attenuates sound waves, thus reducing the transmission of noise. Compared with metal ducts, PP ducts are significantly quieter in operation. According to professional tests, under the same conditions of air speed and air volume, the operation noise of metal ducts can be over 60 dB, while the noise of PP ducts can be controlled at about 40 dB, which is about 30% lower. In hospital wards, school classrooms and other noise-sensitive places, PP ducts can provide a quiet and comfortable environment, which is conducive to the recovery of patients and students’ learning.

(iv) Thermal insulation: energy saving and comfort

PP ducts can be equipped with specialized insulation, which effectively reduces heat loss. This feature is especially important in HVAC systems. In winter, PP square ducts with insulation can better retain heat in the room and reduce the energy consumption of heating equipment; in summer, it can prevent cold air from escaping and reduce the power consumption of air conditioning. Comparisons of real-world examples show that buildings with insulated PP ducts use 15% – 20% less energy for their HVAC systems than buildings with ordinary ducts. This not only saves energy costs for users, but also helps to reduce carbon emissions and realize green environmental protection.

(v) Long life: durable

PP material ages slowly, mainly due to its stable molecular structure and good chemical stability. Under normal operating conditions, PP ducts have a practical service life of 30 – 50 years. In some large industrial plants, PP ducts have been in continuous use for more than 30 years and are still performing well and do not need to be replaced. From a long-term cost perspective, although the initial investment in PP ducts may be slightly higher than some common ducts, the overall cost is lower due to their long service life and low maintenance costs. For example, while metal ducts require regular anti-corrosion treatment and repairs during use, PP ducts require little or no such additional costs, greatly reducing the operating costs of the enterprise.

1.Metal ducts: common metal ducts include galvanized steel ducts, stainless steel ducts and aluminum ducts. Galvanized steel duct price is relatively low, has good mechanical strength and fire performance, the most widely used, in general industrial and civil building ventilation system can see its figure. Stainless steel ducts have excellent corrosion resistance and are suitable for chemical, food and other industries with high requirements for hygiene and corrosion resistance, such as the ventilation ducts of food processing plants, stainless steel ducts are often used to ensure the purity of the air and the durability of the ducts. Aluminum plate duct is lightweight and not easy to produce sparks when collision, so it will be used in places with explosion-proof requirements, such as coal mine underground ventilation system.

2.Composite duct: Composite duct is made of a variety of materials composite, generally including thermal insulation materials and surface materials. For example, phenolic composite duct, it is phenolic foam as the core material, the surface covered with aluminum foil and other materials, with lightweight, good thermal insulation performance, sound insulation effect, etc., commonly used in the air conditioning and ventilation system with high requirements for thermal insulation and sound insulation, such as hotels, office buildings, central air conditioning ducts. There is also glass-magnesium composite air duct, which has excellent fireproof performance and high strength, and is used more in some buildings with strict fire safety requirements, such as shopping malls, hospitals and other places.

3.Polymer duct: Polymer duct is made of polymer material, such as polyvinyl chloride (PVC) duct, PVC duct has the characteristics of strong corrosion resistance, low price, easy installation, etc., which is widely used in some industrial places with corrosive gas emission, such as the ventilation system of electroplating workshop. However, PVC ducts have poor high temperature resistance and relatively narrow temperature range.

How to size ducts for 20000 air volume.

1.Assumed air velocity method
The assumed wind speed method is a common and relatively simple calculation method for determining the duct size required for 20,000 airflow. The core formula is: duct size (cross-sectional area) = air volume / air velocity / 3600. The principle of this formula is based on the relationship between flow rate, velocity and time. The unit of air volume is usually cubic meters per hour (m³/h), which indicates the volume of air passing through the duct in a unit of time; the unit of wind speed is meters per second (m/s), which describes the speed of air flowing through the duct; and 3600 is the conversion factor for converting hours to seconds, which gives the cross-sectional area of the duct in square meters (m²).
When applying this, it is first necessary to make reasonable assumptions about the wind speed. The choice of wind speed is not arbitrary, but to consider a variety of factors. For example, in the civil building ventilation system, if the noise control requirements are high, the wind speed should not be too large, generally the main duct wind speed can be controlled at 4 – 7m / s; in industrial plants and other relatively low noise requirements of the place, in order to reduce the size of the duct, reduce costs, the main duct wind speed can be increased appropriately, such as 6 – 12m / s . Suppose we have to determine the duct size for 20000m³/h airflow in an industrial project with general noise requirement, assuming the air velocity is 8m/s. According to the formula, the cross-sectional area of the duct = 20000÷8÷3600 ≈ 0.694m².
If a circular duct is used, we can further calculate the duct diameter according to the formula of the area of a circle S = πr² (where S is the area and r is the radius). From 0.694 = 3.14×r², we can get r² = 0.694÷3.14 ≈ 0.221, r ≈ 0.47m, then the diameter d = 2r ≈ 0.94m. If you choose rectangular duct, you also need to determine the ratio of length and width according to the actual installation space and design requirements, assuming that the ratio of length and width of 2:1, set the width of x meters, then the length of 2x meters, 2x × x = 0.694, that is, 2x ² = 0.694, can be obtained x ² = 0.347, x ≈ 0.59m, then the length of 2x ≈ 1.18m, that is, the size of the rectangular air duct can be 1180mm × 590mm.

2. Introduction to other calculation methods
In addition to the assumption of wind speed method, there are also a variety of methods to calculate the size of the duct, such as specific resistance method, area method, flow coefficient method. Specific resistance method is to calculate the friction resistance per unit length of the duct (specific resistance), combined with the total resistance of the duct and the air volume to determine the size of the duct, this method of calculation is relatively complex, you need to consider more resistance factors, such as the roughness of the duct, air viscosity, and so on. Area method is based on the known cross-sectional area of the duct and wind speed to calculate the air volume, and the assumption of wind speed method of calculation of the opposite idea, in the known air inference duct size, you need to determine the appropriate size through a number of trial calculations. Flow coefficient method is based on the flow coefficient of the inlet or outlet of the duct, combined with the wind speed and cross-sectional area to calculate the air volume, the method needs to know the flow coefficient of the duct in advance, and the flow coefficient is usually provided by the manufacturer or determined by experiments.
However, in practical engineering applications, the assumed air velocity method is most commonly used because it is relatively simple and intuitive to calculate, and can meet the accuracy requirements of most projects. In this discussion on 20000 air volume duct sizing, we also focus on the assumed air velocity method as an example to analyze and calculate, so that we can understand and grasp the basic method of duct sizing more clearly.

• PP Flame Retardant Fuel: This material adds a certain amount of flame retardant masterbatch to make the PP material achieve the effect of self-extinguishing from the fire. Flame retardant PP material is suitable for aerospace, chemical, electronic and electrical, machinery, automobile and railway industries, and is used to make machine parts with high strength, high temperature resistance and insulation with various high-performance requirements. The properties of flame retardant PP are affected by flame retardants and are more complex than ordinary PP. Almost all flame retardants will have a certain impact on the mechanical properties and melting index of PP, and if too many flame retardants are added, it may also lead to increased toxicity of products, and even cause serious pollution to the environment. Therefore, the selection of suitable flame retardant PP materials also needs to consider its performance and cost and other factors.

• PP material: This refers to polypropylene (PP for short) material, which is a semi-crystalline thermoplastic. It has the characteristics of thermoplasticity, light specific gravity, chemical corrosion resistance, etc., and is widely used in injection molded parts, pipes, films, fibers and other fields. Ordinary PP sheet is a semi-crystalline material with a high melting point and good heat resistance, but it is very brittle at temperatures above 0°C. In order to improve its properties, a certain proportion of ethylene is usually added for copolymerization to improve its impact strength and transparency.

About PP material

• Abbreviation for Polypropylene (PP). Together with polyethylene (PE), polyvinyl chloride (PVC) and polystyrene (PS), it is known as the four major general plastics. With the continuous progress of polymer modification technology, PP has shown better comprehensive properties than other general-purpose plastics, and its application is becoming more and more extensive. Electronic and electrical devices, auto parts, plastic pipes, films, fiber non-woven fabrics and other fields have traces of PP.
• There are many ways to classify PP, and the commonly used PP in the market can be boiled down to two types: homopolymer polypropylene (HOMO-PP) and copolymer polypropylene (COPO-PP). The molecular structure of homopolymer polypropylene is regular, high strength, and transparent or translucent particles, while copolymer polypropylene is milky white particles because of its structure containing ethylene components and good toughness.

About the performance modification of PP

• There are many ways to blend and modify PP, such as reinforcement, filling, toughening, flame retardant, electrical conductivity, coloring, etc., according to the different needs of the product, one or more functions can be superimposed to give PP excellent comprehensive properties.
• The oxygen index (the minimum oxygen concentration required to maintain its combustion under specified conditions) of PP is very low, only 18, so its positive combustion modification is a trend and inevitable. Flame retardants on the market: brominated flame retardants (decabromodiphenyl ether, decabromodiphenylethane, octabromoether, tetrabromobisphenol A, octabromoS ether, bromotriazine, hexabromocyclododecane, etc.), phosphorus-based flame retardants (coated red phosphorus, triphenyl phosphate, BDP, RDP, APP, MPP, etc.), nitrogen-based flame retardants (MCA, melamine, etc.), inorganic flame retardants (magnesium hydroxide, aluminum hydroxide, zinc borate, etc.), composite N-P intumescent flame retardants, etc., all have a certain flame retardant effect on PP. It is only because of the comprehensive cost, the flame retardant requirements of related PP products, and the shortcomings of the flame retardant itself that we must choose different flame retardants or composite flame retardant systems in different applications to meet the different needs of customers.

Five characteristics of PP air duct

1.Superior acoustic and thermal insulation

• PP air duct has excellent performance with low thermal conductivity. There are countless independent bubbles that are not connected to each other in the material, and the thermal conductivity of the gas in the bubble is low, so as to achieve excellent thermal insulation effect, and at the same time, this closed bubble structure makes the water vapor can not enter the material smoothly, even if the outer surface is damaged, because the bubbles are not connected with each other, the water vapor is still isolated. In non-closed-foam materials, water vapor can penetrate deep into the material, causing insulation failure.

2.Chemical stability

• Polymer is an inorganic material, which cannot be achieved by general foaming materials in case of acidic and alkaline substances.

3.High flame retardancy

• Because it is mainly an inorganic component, when it encounters fire, only the surface is carbonized, and the material is not deformed, and all the indicators of PP air duct are in line with national standards.

4.Non-toxic

• The polymer has been tested and has no harm to the human body, which is incomparable to glass fiber.

5.High airtightness

• According to the requirements, the air leakage volume can be zero.

Precautions for installation and transportation

• PP air ducts shall not be arranged on top of water that can cause combustion, blasting or damage to raw materials, products and equipment, and should be avoided as far as possible on the production equipment.
• PP air ducts shall not pass through the windows of shops, closets of civil buildings and wooden decorations. For workshops and buildings that are not allowed to cut off water, two introduction pipes should be set up, and the two-way water supply should be connected in a ring or through the branch indoors.

• Added ingredients: Ordinary PP materials do not contain flame retardants, while PP flame retardant materials achieve flame retardant effect by adding flame retardants (such as compounds composed of bromine, oxygen, phosphorus, titanium, aluminum and other elements).
• Performance differences: After adding flame retardants, the properties of PP flame retardant materials are more complex than ordinary PP, because flame retardants may affect the mechanical properties and melting index of PP. Too much flame retardant may lead to increased toxicity of the product and even cause pollution to the environment.
• Application field: Due to the fireproof and flame-retardant characteristics of flame retardant PP, it is widely used in building materials, electronic appliances and other fields, while ordinary PP is more widely used in some conventional products, but its application has been limited in the field that requires fire performance.
• Physical and chemical properties: Flame retardant PP sheet has high stiffness, high hardness and high strength, but the notched impact resistance is average. It can be used over a wide range of temperatures and has excellent chemical stability and electrical properties
• In summary, PP flame retardant materials give the material fire and flame retardant functions by adding specific flame retardants, which makes it especially important in applications where fire safety is required.

Application of PP flame retardant materials

PP flame retardant materials are widely used, mainly in furniture, automotive, electronics, home appliances, medical and construction industries

• In the furniture industry, flame retardant PP material is widely used in furniture legs, table legs, chair legs and other components, because these parts need to withstand huge pressure, and at the same time have good flame retardant properties to ensure the safety of furniture in fire
• In the automotive industry, flame-retardant PP material is used in car seats, armrests, dashboards and other parts, which are the parts that passengers touch the most, and if burned, they will produce thick smoke and fire, which poses a threat to the life safety of passengers
• In the electronics industry, flame-retardant PP material is used to manufacture the shell, base, etc. of electronic equipment to ensure that the equipment is not burned in a fire and to protect the electronic components inside the electronic equipment
• In the home appliance industry, flame retardant PP plastic is used in small household appliance casings, such as irons, hair dryers and other electrical parts, these materials have the characteristics of low smoke generation, low density, low cost input, and the formation of toxic and corrosive gases is relatively small
• In the medical industry, flame retardant PP material is used to make medical devices that need to be boiled and sterilized by high pressure because of its good heat resistance and flame retardancy
• In the construction industry, flame retardant PP materials also have certain applications, although the specific application is not as extensive as other industries, but its flame retardant performance can ensure the safety of personnel and equipment
• In addition, PP flame retardants are also used in the production of automobile axle pedals, document covers, caps, and various containers that need to resist bending fatigue, showing that they are widely used in a variety of fields

1.Product Structure:

• Round tubes are usually constructed of circular sections, which have high torsional strength and compressive strength, and are suitable for structures that bear complex loads

• The square tube is composed of four sides of a rectangular section, which has high strength and rigidity, and is suitable for supporting structures that bear large loadsThe cross-sectional shape of the square tube makes it have high torsional strength and bending resistance, and also has strong adaptability, which can adapt to various complex installation environments

2. Usage Scenarios:

• Round pipes are widely used in various fluid transportation fields, such as petroleum, chemical industry, electric power, etc., and are also used in building structures, bridges and other fields
• Square tubes are mainly used for structural support and carrying heavy objects, such as bridges, buildings, shipbuilding, etcIn addition, square tubes can also be used to manufacture various equipment brackets, frames, etc

3. Advantages and disadvantages:

• The advantages of round pipes include high strength and stiffness, good sealing performance, suitable for conveying corrosive media or high-purity liquids (gases)
• The advantage of square tube is its strong structural stability, the ability to withstand large loads, and high impact resistanceThe installation of the square tube is more complex and the cost is higher, but its cross-sectional shape makes it have high torsional strength and bending resistance, and can adapt to various complex installation environments

To sum up, the choice of PP round pipe or square pipe should be decided according to the specific use scenario and needsIf cost, ease of installation, and general requirements for conveying fluids need to be considered, round tubing may be a more appropriate choiceIf you need to bear a large load and have higher requirements for the stability and impact resistance of the structure, the square tube is more suitableIn practical applications, factors such as pipe size, wall thickness and length should also be considered to meet actual needs

Comparison of compressive resistance of PP round pipe and square pipe

• There are differences in structure and performance between square and round tubes, which directly affect their compressive performanceThe cross-section of the square tube is square, and this structure makes it have better bending resistance and stability, which is suitable for some special requirementsIn contrast, the cross-section of a round tube is round, and its bending resistance and stability are not as good as that of a square tubeIn terms of compressive performance, square tubes usually have high compressive performance, which is due to its special cross-sectional shape and structure, which makes it better able to withstand large load occasionsIn addition, the compressive performance of the square tube is also affected by the material, specification and processing technology, which further enhances its ability to withstand pressure
• In summary, the square tube is better than the round tube in terms of compressive performance, especially in the occasion of large loads, the choice of the square tube is more suitable

• PP pipe is characterized by no rust, wear resistance, no scaling, reduced vibration and noise, anti-freeze cracking (PP pipe freeze cracking at low temperature of more than -20 °C, decomposition in high temperature working environment as long as it exceeds 70 °C, and the use temperature is -20 °C to 70 °C), anti-condensation, less heat loss, simple installation, and long service life. There are three types of connection methods: welding, end edge welding, and heterogeneous material pipe.

Introduction to welding methods

Torch Welding Method:

• Grind off the surface layer of the joint end of the pipe or piping parts with sandpaper, if there is still grease on the surface, wipe it with vinyl chloride or acetone; Insert both ends into the welding sleeve, and the two ends must be inserted into the middle point of the welding sleeve, and there shall be no water at the two ends when inserting. Then insert the secondary wire of the welding controller and start welding. During the process, it is not allowed to move or touch the power supply or loosen the junction of the secondary wire. One hour after the completion of welding, the joint is completely cooled before pressurizing the tube and pulling the tube from the outside to ensure that the joint is not deformed.

• The straight pipe must be cut with a pipe cutter first, and the socket must be very flat, and the part of the socket inserted into the welding sleeve shall not have more than 1mm scratches or deformation. The used welding sleeve should not be used again, if the welding sleeve is damaged or deformed, it should be discarded and not used. If the connection fails, it should be replaced with a new welding sleeve and re-welded, if the welding sleeve fails due to power cut-off in progress, it will be completely cooled and then plugged in the secondary wire for re-welding. If the welding is completed, the pipe needs to be stressed immediately, and cold water can be poured to cool it.

Splicing of pipes made of different materials

(1) Compression ring joint connection method

A. Protruding flange method:The connection of polypropylene pipelines with other conveying pipelines or valves should be connected with flanges. First, the flange is inserted into the polypropylene pipe, and the flange joint part is welded to connect the flange end parts, and then the flange is joined with other pipe ends.

B. Plug-in mechanical joints (synthetic rubber joints):Polypropylene pipes and vents, drains, equipment and sinks should only be connected with plug-in mechanical joints. The coupling must be in the same series of products as the polypropylene pipe and parts, and be assembled according to the characteristics of the series of products.

C. Connecting sleeve connection method: When the polypropylene pipe and other materials of the pipe are connected, such as PP and PVC, PP and cast iron pipe, etc., the pipe is inserted into the connecting sleeve and then bolted the screws on the connecting sleeve, but the pipe diameter specification should meet the size of the connecting sleeve.

Inspection method after welding is completed

(1) Visual inspection: before, during and after welding, it can not produce the following situations:

A. The weld flange is uneven, too large or too small.

B. The two tubes are not on the same axis.

C. The weld flange surface is shiny (indicating overheating and excessive cooling stress).

(2) Non-destructive testing:

A. Attach a metal pin to the form of an electric pistol to detect air leaks and impurities at the weld.

B. X-ray inspection: all defects can be detected from the X-ray map.

C. Mechanical and destructive testing:Hydrostatic test: Some welding shortcomings can be detected by hydrostatic test.