FAQ

The choice between 90-degree elbows and 45-degree elbows primarily depends on the pipeline layout requirements and the airflow pressure drop requirements. 90-degree elbows are used for right-angle turns in pipelines, featuring a compact structure and minimal space occupation, making them the most commonly used type suitable for confined spaces requiring right-angle turns. 45-degree elbows are used for oblique turns in pipelines, providing smoother airflow redirection and lower pressure drop, making them ideal for applications with higher system pressure requirements where pipeline space allows. Generally, 90-degree elbows are more frequently used in systems, while 45-degree elbows can be selected at critical points such as fan inlets and outlets to reduce resistance.

PP processing ducts are fabricated by welding sheet materials. Theoretically, the diameter is not limited by the extrusion die, and large-diameter ducts can be manufactured based on customer requirements. The specific dimensions are constrained by the sheet material width and welding processes. In actual engineering projects, large-diameter main ventilation ducts typically range from hundreds of millimeters to several meters in diameter. Ultra-large-diameter ducts can be produced by welding multiple sheet materials together, with flanges and reinforcement bars added to ensure structural strength. The specific maximum diameter must be determined based on sheet material specifications, structural strength requirements, and on-site transportation and installation conditions. Non-standard customization is supported.

Both models exhibit corrosion resistance. The PP fireproof spray tower is lightweight, easy to process and form, features excellent welding and sealing performance, offers high cost-performance, and has a wide acid and alkali resistance range, making it the mainstream choice for acidic and alkaline exhaust gas treatment currently. The fiberglass spray tower has better temperature resistance and structural rigidity, making it suitable for applications with higher exhaust gas temperatures or requirements for large diameters and high mechanical strength. When selecting, factors such as exhaust gas composition, temperature, treatment air volume, on-site installation space, and budget should be comprehensively considered. The manufacturer can provide tailored solutions based on specific conditions. Both materials have their applicable scenarios, with no absolute superiority or inferiority; the key is to match the actual conditions.

PP spray towers are widely used in the waste gas treatment fields of multiple industries such as PCB, electroplating, chemical industry, pharmaceutical, food, electronics, textile, rubber and plastic, automobile, cement, ceramics, etc., especially suitable for acid-base waste gas treatment.

Both rely on packing layers and spray absorption liquid to purify exhaust gas, with the same purification principle but differences in material performance and applicable conditions. PP spray tower is lightweight, easy to process, and has lower cost. It is well-proven for use in ambient temperature dilute acid and alkali conditions, offering good economy. Stainless steel spray tower has higher temperature resistance, greater overall rigidity, and stronger pressure-bearing capacity. It is less prone to softening when exposed to higher inlet gas temperatures. Its performance in fire resistance, anti-aging, and anti-mechanical damage is better, making it more reliable for large diameters and long-term outdoor use. Selection should be based on comprehensive judgment considering exhaust gas temperature, composition, tower diameter, installation location, and budget. Ambient temperature conventional conditions are suitable for PP, while high temperature, fireproof, or large tower diameter conditions are more suitable for stainless steel. Both have their respective applicable ranges.

V0 PPs housing is acid and alkali resistant, capable of contacting acidic and alkaline mist gases. However, it is not recommended to allow large amounts of water mist or acidic and alkaline mist to directly enter the activated carbon layer in the process: liquid droplets will cause the activated carbon to become damp, block pores, and reduce adsorption capacity. Acids and alkalis may also react with the carbon or adsorbed organic substances. The proper approach is to first pass through spray washing and demisting to remove acidic and alkaline mist, then enter the activated carbon housing for adsorption of residual organic compounds, forming a washing plus adsorption combination process. The carbon housing should be in a dry or low-humidity airflow. This approach leverages the corrosion resistance of the PPs housing while protecting the activated carbon.

Qualified hot melt welding strength and sealing can meet the requirements of corrosion-resistant ducts. Air leakage and cracking are often caused by construction quality and operating conditions, such as improper welding temperature and speed, mismatched welding electrodes and sheet material or flame retardant grade, incomplete penetration or porosity in welds, aging of flange gaskets, excessive pipe support spacing causing stress, and failure to account for thermal expansion and contraction. Control measures include: using V0 welding electrodes of the same material, welding by skilled workers following the process, ensuring full welds and conducting inspections, uniformly tightening flanges, rationally setting supports and thermal compensation, and performing air leakage volume testing after installation.

The process itself does not use water or generate wastewater. The salt produced during the adsorption reaction is fixed within the adsorbent, and there is no wastewater or mist emission during operation, resulting in minimal secondary pollution. However, saturated SDG adsorbents contain acid reaction byproducts and residual chemicals, which are classified as solid waste requiring regulated management. They should be collected, temporarily stored, and disposed of according to their composition and local environmental regulations (typically handled by qualified units), and should not be dumped arbitrarily or mixed with domestic waste. As long as the waste filter media is disposed of properly, the secondary pollution risk of dry adsorption is significantly lower than that of wet processes that generate wastewater.

The length of the flexible joint must meet the requirements for vibration isolation and compensation, but it is not necessarily the longer, the better. If the length is too short, it cannot fully absorb vibration and installation deviations, resulting in poor vibration isolation performance. If it is too long, it tends to collapse under negative pressure and oscillate or bulge under positive pressure, which Conversely increases resistance and wear. Generally, standard lengths are selected based on the fan's diameter, vibration amplitude, and installation spacing, ensuring that the flexible joint maintains a natural, slightly slack state after installation without being stretched or compressed. For tapered flexible joints, it is essential to ensure that the large and small ends match the fan and duct, respectively, with a smooth transition. Specific dimensions can be selected by referring to the product specifications based on the diameters of the two ends and the required axial and transverse compensation amounts. If unsure, provide the fan model and interface dimensions, and the supplier will provide matching components. When installation space is limited, prioritize ensuring the required length for vibration isolation; do not forcefully insert excessively long flexible joints into confined spaces.

When the spigot ends of the insert PVC air damper are inserted into the PVC air duct, PVC special adhesive is applied to the mating surface for bonding and fixing. Before bonding, clean the spigot ends and the pipe ends, insert to the correct position, and mark the depth. After applying the adhesive evenly, insert it fully once, hold it for a moment to allow it to cure, and avoid applying force or rotation during this period. Once the adhesive connection is formed, it cannot be disassembled and is suitable for fixed pipe sections. For disassembly, maintenance, or connections with equipment, flanged valves should be selected, connected with bolts and gaskets, offering convenient assembly and disassembly. The bonding construction environment should be well-ventilated and dry, avoiding work in humid or low-temperature conditions to prevent bonding strength issues. Use an appropriate amount of adhesive and ensure complete coverage on the bonding surface. After bonding, cure it according to the specified time before putting it into use. There should be no gaps or weak bonding at the spigot ends to ensure long-term air leakage prevention.

Common practice involves using the bottom section of the tower as a circulating water tank (integrated), where the tower bottom space stores circulating liquid and receives reflux, featuring compact structure and short piping; large horizontal towers can also have the tank independently placed below or beside the tower body for easier increase in liquid storage capacity and maintenance. Integrated tanks must ensure effective volume meets circulating pump flow rate and retention time, equipped with level, overflow, drain, and chemical addition interfaces. Whether to use integrated or separate design depends on equipment size, on-site layout, and circulating flow rate, which should be confirmed with the manufacturer during ordering.

The long-term operating temperature of flame-retardant PPs panels is similar to that of general polypropylene, making them suitable for handling corrosive gases in ambient to medium-temperature ranges. The specific temperature upper limit depends on the panel thickness, equipment structure, reinforcement method, and fixing form. The equipment should also avoid localized contact with high-temperature heat sources and radiant heat to prevent single-point overheating, which could cause the panels to soften and deform. For high-temperature exhaust gases, a pre-cooling section with a spray cooling stage should be installed before entering the plastic equipment to reduce the gas temperature to within the material's allowable range through gas-liquid contact. If the exhaust gas temperature remains high for extended periods or experiences instantaneous high-temperature impacts, consider selecting high-temperature-resistant stainless steel or fiberglass materials instead of directly using PP panels. When selecting, provide the continuous temperature, peak temperature, and composition of the exhaust gas to determine if pre-cooling or material replacement is necessary.

PPs sheets are inherently non-toxic and odorless, with polypropylene being one of the commonly used food-contact materials; however, flame-retardant grade sheets contain flame-retardant additives, and whether they meet specific food-contact scenario compliance requirements depends on reviewing the corresponding batch test reports and applicable standards. For tanks and containers directly contacting food materials, it is recommended to select pure PP sheets explicitly labeled as food grade; flame-retardant PPs sheets are more suitable for applications such as exhaust emission, ventilation, and peripheral corrosion where they do not directly contact food.

This is a manifestation of closed-loop instability, common causes include electromagnetic interference on control signals, improper tuning of controller adjustment parameters (excessive gain or too small deadband), insufficient actuator torque, valve shaft jamming, and inherent fluctuations in sensor measurements. Check shielding grounding, ensure signal wires are away from power cables, adjust controller proportional-integral parameters and deadband, eliminate mechanical jamming, and verify actuator torque. Frequent small oscillations of the valve disc accelerate actuator wear; closed-loop tuning must be completed before operation.

Variable frequency fan low-speed operation may cause positive pressure difference near the valve disc opening critical point, leading to vibration and slapping of the valve disc, generating noise and affecting airflow. Solutions include selecting check valves with damping or adjustable weights to stabilize the valve disc after opening; optimizing fan control by setting a lower operating frequency limit to avoid the critical zone; for systems with significant operating condition variations and long-term low-speed operation, the check valve can be replaced with an electric sealed valve linked to the fan, which closes with a delay when the fan stops, ensuring smooth and controllable operation.

The welded seams of the PP medicine drum are fused with the base material, ensuring no leakage under normal use. Leakage typically occurs at welding defects, stress concentration points at joints, or cracks in the drum body due to deformation. Before putting a new drum into use, a full water test should be conducted: fill the drum with clean water and let it stand for the specified duration to check for any leakage or sweating at all longitudinal seams, bottom seams, and joints. For square drums, observe for deformation at the reinforcement points. If leakage is detected during operation, drain and clean the drum before repairing the welding; never perform hot work with the drum containing the chemical. Flexible connections or supports should be installed on the inlet and outlet pipelines to prevent the weight of the valves and pipes from being applied to the drum wall joints for extended periods.

Cannot be directly mixed, circular tee for circular pipe, rectangular tee for rectangular pipe, as their interface shapes and flange standards differ. Forcing them to connect will result in cross-section misalignment and air leakage. When converting between circular main pipes and rectangular branch pipes in the same system, use square-to-round adapters or directly create square-round transition sections at one of the tee's interfaces before connecting the corresponding cross-section pipe segments. When ordering, clearly specify the cross-sectional shape, dimensions, and flange standards for each of the three interfaces, indicating which one is square and which one is round to avoid incompatibility upon arrival. Square-round transition tees can be manufactured as a single piece by the supplier, resulting in smoother surfaces and lower resistance compared to on-site assembly. When arranging piping, minimize frequent square-round cross-section conversions. Ensure smooth transitions at conversion points to avoid abrupt expansions or contractions that increase resistance and noise.

Okay, but focus on UV and temperature effects. PP material will age and become brittle when exposed to direct sunlight for a long time. Outdoor-mounted PP ducts are recommended to use weather-resistant sheet material with UV-resistant additives, or to have a UV-protective coating applied to the outer wall, or to install sunshades. Pipe supports must consider wind load, snow load, and thermal expansion and contraction. Fixed supports and sliding supports should be set up reasonably, and thermal expansion compensation should be reserved for long straight pipe sections. In cold regions, the material's low-temperature toughness must be noted to avoid impacts and concentrated loads. Outdoor flanges and bolts should be made of corrosion-resistant materials or have corrosion protection to prevent rust from rain. Installation indoors or in pipe galleries away from direct sunlight ages slower, with more favorable usage conditions. Regardless of indoor or outdoor installation, flammability and corrosion resistance requirements should be configured according to the medium and fire protection regulations.

Do not mix. The welds of fire-resistant air dampers and fire-resistant air ducts must use PPs fire-resistant welding electrodes to ensure that the welds match the fire resistance level of the base material, with no fire-resistant weak points in the entire pipeline. If ordinary PP welding electrodes are used to weld fire-resistant panels, the welds become fire-resistant breaks on the pipeline. During a fire, the welds may melt and crack first, leading to pipeline failure and failing fire inspection. During processing, ensure that the plates, valve plates, welding electrodes, and flanges are all made of the same fire-resistant compatible material. Sealing materials should also be selected as fire-resistant or flame-retardant materials. On-site, store fire-resistant welding electrodes and ordinary welding electrodes separately with clear markings to prevent workers from picking up the wrong ones. After welding, verify the welding electrode packaging and material certification to ensure that the weld areas have the same self-extinguishing properties as the base material.

Cannot be directly connected, as the rectangular and circular cross-section shapes are different, and the flanges are also different, making it impossible to achieve a sealed connection. Rectangular elbows can only be connected to rectangular ducts or square fittings via square flanges, while round elbows are connected to round ducts. When converting between rectangular and circular pipes in the system, a square-to-round transition fitting should be installed between them, and then the elbows and pipe sections corresponding to the respective cross-sections should be connected. Attention should also be paid to smooth transition of the cross-section at the conversion point to avoid sudden expansion or contraction, which increases resistance and noise. When ordering, select elbows and transition components based on the actual cross-section of each section. For nodes with frequent use of both square and round sections, the manufacturer can provide integrated processing of transition-shaped elbows with built-in transitions. Using soft connections or variable-diameter hard connections for square-round cross-sections on-site will cause flow deviation and air leakage, and should not be used.