FAQ

The main differences lie in the manufacturing process and applicable scenarios. Fabricated ducts are welded from PP sheet material with flange reinforcement, suitable for large diameters, non-standard sizes, and special-shaped ducts, offering high flexibility but relatively lower production efficiency. Formed ducts employ extrusion technology for one-piece molding, featuring uniform wall thickness, smooth inner surface, and low air resistance, making them ideal for standard specifications and mass production. Both materials are corrosion-resistant and acid/alkali-resistant. Large-diameter main ducts are typically selected for fabricated ducts, while standard branch ducts are chosen for formed ducts. The two can be used together to form a complete ventilation system.

Mainly handles various acid, alkali, and acid mist exhaust gases, such as sulfuric acid mist, hydrochloric acid mist, nitric acid mist, alkali mist, and chromic acid mist. It can also be used for pre-treatment cooling, dedusting, and demisting of organic exhaust gas before entering activated carbon or catalytic combustion equipment. For viscous exhaust gas with more paint mist and dust, it is recommended to choose a swirl tower structure, utilizing the centrifugal separation generated by swirl vanes and the adhesive effect of liquid film to remove particulate matter. The absorption liquid needs to be matched according to the pollutant composition, such as using alkaline solution to absorb acidic gases and acidic solution to absorb alkaline gases. For high-concentration exhaust gas, multi-stage series treatment can be adopted to ensure compliance at the outlet.

Xicheng Environmental Protection's permanent magnet energy-saving fans adopt advanced permanent magnet frequency conversion technology, with significant advantages such as high efficiency and energy saving, stable operation, low noise, and long service life. They are developed through industry-university-research cooperation with universities including Xi'an Jiaotong University and Tongji University.

The main difference lies in the corrosion-resistant level. 304 can meet general acid, alkali, oil mist, and conventional corrosion conditions, with higher usage. 316L adds molybdenum, offering stronger resistance to chloride pitting and crevice corrosion. It is more suitable for chlorine-containing gases, salt spray, coastal environments, and heavier corrosion conditions. When selecting, first clarify the chloride content, acid/alkali types, concentration, and temperature of the exhaust, then determine the grade. Don't just focus on initial cost; a lower grade can lead to early corrosion of the tower, resulting in downtime and replacement costs. For complex compositions or uncertainties, provide test data for technical personnel to judge. Avoid blindly stacking higher grades.

The V0 PPs board is made by adding a flame retardant system to polypropylene, with the main material still being PPs. Its acid, alkali, and salt corrosion resistance performance is basically comparable to that of ordinary PPs, and it can handle general acid and alkali mists and organic exhaust gases without issues. However, some strong oxidizing agents or high-concentration special organic compounds may affect the material or flame retardant components. When treating complex mixed exhaust gases, the manufacturer should be provided with the gas composition, concentration, and temperature to verify material compatibility, and immersion testing may be necessary if required. When selecting materials, attention should be paid to both the flame retardant test report and corrosion resistance applicability—neither should be considered in isolation.

Required. V0 Flame Retardant addresses the issue of the duct material itself being difficult to ignite and not spreading flames, which falls under material fire protection. Fire dampers are fire separation measures for ventilation systems. In cases where ducts pass through fire compartments, machine room partition walls, or floors, they automatically close to block smoke and fire from spreading through the ducts during a fire, which belongs to system fire protection design. The functions of the two are different and they cannot be mutually replaced. Whether to install fire dampers, their installation locations, and temperature ratings must be implemented in accordance with building fire protection design codes and fire review opinions, determined by the design unit. Fire dampers cannot be omitted simply because the duct is V0 flame retardant.

Yes. Although the SDG process does not have water and scaling issues, if the exhaust gas contains dust, oil mist, or a large number of droplets, dust will adhere to the filter media surface, and liquid droplets will cause the filter media to become damp and cake, leading to increased resistance and uneven airflow distribution. Therefore, dust removal, oil removal, and fog removal pretreatment should be performed before the gas enters the cabinet to maintain relatively dry and clean exhaust gas. If the pressure differential rises, first check whether the pretreatment filter media has failed or whether the filter media surface has accumulated dust. Clean or replace the surface filter media if necessary. Proper pretreatment and airflow distribution are key to extending the service life of SDG filter media and preventing blockages.

PVC flexible connectors will gradually age under long-term exposure to vibration, ultraviolet light, temperature fluctuations, and corrosive gases,Manifested as tubing wall hardening and yellowing, loss of elasticity, crack formation, whitening at wave patterns, and even cracking or air leakage. Replace the connector promptly if it becomes hard, damaged, or if the clamp area tears, or if vibration isolation performance declines or abnormal shaking occurs. Flexible connectors have a longer service life in indoor moderate-temperature corrosive environments, but their lifespan is significantly reduced under outdoor exposure to sunlight, near high-temperature pipelines, or in highly corrosive environments. Consider adding shading measures or selecting weather-resistant and temperature-resistant materials for flexible connectors. During routine inspections, check for signs of collapse, bulging, cracking, or loose clamps on the connector, and replace aging components regularly during fan maintenance. As flexible connectors are wear parts, it is recommended to keep a small stock based on pipe diameter, allowing for immediate replacement upon issue to prevent vibration damage to ductwork and equipment after vibration isolation failure.

Whether flammability is required depends on the fire protection requirements of the installation location. Standard PVC has a certain self-extinguishing property, but this does not equate to an engineering flammability rating and cannot be used in concealed spaces with clear fire safety requirements. When installed in indoor suspended ceilings, pipe shafts, crowded areas, or high fire protection requirement zones, it is essential to explicitly require flammable materials and review test reports. In such cases, selecting flammable PPs dampers is generally more reliable. For underground spaces, laboratories, high-rise buildings, and exhaust systems crossing fire compartments, it is recommended to select flammable dampers according to design specifications. Outdoor open, non-fire-rated general corrosive exhausts can use standard materials. The specific material should be determined based on building fire protection design and local review requirements. The material's combustion performance rating must be noted in drawings and purchase orders to avoid substituting standard materials with flammable products on-site.

Horizontal airflow in Horizontal Tower causes liquid droplets to fall perpendicular to the airflow due to gravity. If the tower's air velocity is too high and the spray rate is excessive, liquid carryover at the outlet is more likely. Design-wise, controlling the horizontal air velocity below the empty tower velocity of the vertical tower, providing sufficient gas-liquid separation space between the spraying section and the outlet, and installing baffle plates or filler demisting sections at the gas outlet can effectively dehydrate. During operation, if liquid carryover is detected at the outlet, check whether the air volume exceeds the design value, whether the demister is blocked or damaged, and whether the spray is excessive. Clean the demisting section promptly and adjust the operating parameters back to the design range.

The plate thickness should be comprehensively determined based on equipment dimensions, pressure-bearing requirements, and installation location; it is not necessarily more reasonable to use thicker plates. Coiled round ducts typically use thin plates, while tower cylinders are selected based on diameter using medium-thick plates. Only liquid-containing tanks and load-bearing bases require thicker plates. During selection, calculate the required wall thickness based on working pressure, medium density, and stiffener layout. Strength and stiffness meeting the requirements are sufficient. Excessive thickness not only increases material costs but also adds to equipment self-weight, coiling difficulty, and welding workload, ultimately reducing overall cost-effectiveness. Thin plates combined with a reasonable strengthening structure are often more economical than blindly increasing thickness. If uncertain, provide equipment diameter, height, and medium conditions, and the design or manufacturer can offer thickness recommendations based on experience.

PPs sheets should be stored on flat and solid ground or shelves, ensuring even distribution of weight to prevent localized suspension that may cause long-term bending and deformation of the sheets. Thick sheets should be placed flat and stack height controlled to avoid compression and warping of lower layers. Storage environment should be away from open flames and high-temperature heat sources, maintaining dryness and ventilation to prevent surface aging, discoloration, and performance degradation due to prolonged sun exposure. The protective film on the sheet surface should be removed before processing to minimize scratches and contamination during handling and cutting. Sheets should not be stored with oil stains, solvents, or sharp metals. During handling, lift and place gently to avoid dragging. In winter, when low temperatures reduce the material's toughness, sheets should be warmed indoors before bending or coiling to minimize the risk of brittleness.

The opening area of the fume hood's door continuously changes as it moves vertically; to maintain a constant face velocity at the door, the exhaust airflow must vary continuously with the door opening. On/off valves can only be fully open or closed and cannot track the continuous airflow demand; analog valves can continuously adjust their opening under controller commands, forming a closed loop with the door displacement or face velocity sensor to adjust the exhaust airflow in real-time, ensuring the face velocity remains stable within a safe range, preventing harmful substances from escaping while avoiding the energy waste of constant airflow operation in fixed airflow systems.

On-site simple inspection can be performed after the fan shutdown: observe if the valve disc seats fully, if the seal ring fits uniformly on the valve seat, and check for any air leakage sound or airflow sensation; under conditions, release tracer smoke on one side of the valve or use a manometer and anemometer to detect post-valve leakage. Quantitative acceptance can involve testing the air leakage rate of the valve section using air duct leakage detection methods and comparing it with the manufacturer's committed leakage level. During inspection, focus on checking for foreign matter, aging, or deformation in the seal ring, whether the valve shaft is horizontal, and if the petals of multi-leaf valves return synchronously.

When adding solid agents (such as caustic soda, soda ash) which require dissolution, where the liquid solution tends to precipitate, or when a uniform concentration throughout the entire drum is required, a top-mounted agitator should be used to accelerate agent dissolution and prevent active ingredients from settling at the bottom of the drum. For using finished liquid agents with uniform concentration and small dosage, an agitator is not necessary; manual stirring or circulation pump backflow stirring can be used instead. The power, impeller type, and rotation speed of the agitator should be selected based on the drum volume, liquid properties, and dissolution rate. The rotation speed should not be too high to avoid air entrapment, splashing, and drum wall damage. Even with an agitator installed, the solution should be stirred evenly before re-adding agents after long-term static storage, and the corrosion resistance and sealing condition of the impeller and shaft should be checked. The material of the agitator must be corrosion-resistant to the matched liquid agent, and leakage prevention measures should be taken at the shaft seal. During operation, the agitator's effectiveness should be monitored in conjunction with liquid level and concentration checks.

High resistance in tees should first prioritize the use of inclined tees, allowing branch pipes to connect along the main pipe airflow direction while controlling the angle between the branch pipe and the main pipe to avoid excessive angles, generally using acute-angle Bevel . Additionally, flow guides can be installed inside the tee to smoothly merge the two airflow streams, preventing the branch pipe's airflow from directly opposing the main pipe's incoming flow. Properly configure branch pipe dampers for airflow balance to prevent excessively high branch pipe velocities, entrainment, and backflow. The diameter reduction transition in reducing tees should be gradual to avoid sudden contractions. During installation, ensure the tee orientation is correct with the inclined end facing the airflow, smooth welding seams on the inner wall without weld ridges. These measures can significantly reduce the local resistance of the tee; if the system resistance remains high, consider appropriately increasing the main pipe or branch pipe diameter or reducing the internal pipe velocity.

The ability of circular ducts to withstand negative pressure is directly related to wall thickness, diameter, and the spacing of reinforcement rings. The larger the diameter and the higher the negative pressure, the more wall thickness needs to be increased, and the reinforcement rings on the outer wall need to be densified. Otherwise, the tube wall may be sucked and deformed under negative pressure. During design, the wall thickness and reinforcement ring spacing should be verified based on the total pressure of the fan and the negative pressure at various points in the pipeline. The negative pressure is the highest at the fan inlet section, which should be given special attention. For large-diameter pipe sections, the spacing of supports and hangers should also be controlled to prevent deformation of the pipeline under its own weight and negative pressure. Selecting an experienced manufacturer to configure wall thickness and reinforcement structure according to the negative pressure level can fundamentally avoid collapse issues. If concave deformation, abnormal sounds, or airflow anomalies are detected in the tube wall after operation, the machine should be shut down to inspect the reinforcement rings and wall thickness. If necessary, the weak sections should be reinforced or replaced.

Outdoor suspended ducts have a relatively low risk of fire spread, and the use of flame-retardant materials primarily depends on local fire codes, building spacing, and owner requirements. However, ducts in indoor spaces, suspended ceilings, crowded areas, and fire compartments typically require the use of flame-retardant materials. The main issues for outdoor ducts are ultraviolet degradation and temperature resistance; UV-resistant panels or sun shading and painting treatments should be selected to slow down plastic aging. For systems connecting indoors and outdoors, the pipe sections entering the building should comply with indoor requirements, using PP flame-retardant dampers and ducts. It is not acceptable to use standard materials for the entire pipeline just because the initial section is outdoors. When selecting materials, determine them based on the actual installation location of the dampers: outdoor sections should prioritize weather resistance, while indoor sections should prioritize flame retardancy. Fireproof sealing and fire dampers must be used when passing through building exterior walls and fire compartments.

With a large radius of curvature, the airflow transition is smooth, resulting in low resistance and noise, but the elbow occupies more space and consumes more materials. With a small radius of curvature, the installation is compact and material-saving, but the airflow transition is abrupt, leading to increased resistance and noise. When space permits, using a larger radius of curvature is beneficial for energy saving and reducing fan load. When space is limited, small-radius elbows can be used, and the resistance can be compensated by adding guide vanes. In engineering practice, the radius of curvature is typically selected as a certain multiple of the duct side length to balance installation space and system resistance, avoiding an exclusive pursuit of either large or small radii. For high-speed, high-capacity duct sections and elbows near the fan, the radius of curvature should be prioritized. Low-speed branch ducts can be appropriately reduced. During selection, the layout space, air velocity, and noise reduction requirements should be comprehensively considered, and resistance calculations may be necessary for critical elbows when required.

The weld seams and flange lengths of square tubes are typically longer than those of round tubes with the same cross-sectional area. If the processing and installation quality are the same, there may be slightly more potential air leakage points. However, as long as the four-corner longitudinal seams are continuously welded through, the flanges are flat, the gaskets are intact, and the bolts are tightened diagonally evenly, the air leakage rate can still be controlled within the design requirements. The key to controlling air leakage lies in the processing and welding quality, as well as flange sealing, rather than the cross-sectional shape itself. For negative pressure systems with high air leakage requirements, the weld seam appearance inspection and flange tightening acceptance should be strengthened, and air leakage testing should be conducted in sections if necessary. The rigidity of rectangular flanges is relatively weaker, so care should be taken during tightening to prevent flange warping, which could cause local gaps. After installation, combine system commissioning to inspect the flanges, weld seams, and openings, and promptly repair leaks by welding or replacing gaskets. The overall sealing performance of square tubes can meet the requirements for corrosion-resistant ventilation.