FAQ

Valves installed in suspended ceilings are difficult to operate and maintain. During installation, inspection openings must be reserved at corresponding positions for the handle, linkage rod, and actuator. The valve shaft orientation and handle orientation should allow for easy operation and observation from the inspection openings. For electric valves, space must be reserved for power supply, control cables, and actuator heat dissipation. Valves must be securely connected to air duct flanges with proper alignment to prevent flange misalignment and air leakage caused by ceiling settlement. It is recommended to select valves with sealed vanes for suspended ceilings to reduce concealed air leakage points. Before commissioning, air flow adjustment must be completed, and the valve position must be marked on the valve body and drawings. During construction, valves should not be installed tightly against beams, slabs, or other pipelines to ensure sufficient space for handle operation and actuator assembly/disassembly. Before closing the ceiling panels, the valve installation, wiring, and commissioning must be inspected to prevent inoperability and difficulty in maintenance after panel closure.

If the actuator does not move or the motor is overloaded, common reasons include: the actuator torque selection being too small, the valve shaft being jammed due to dust accumulation and crystallization, the valve disc being stuck by foreign objects, the valve shaft and actuator being misaligned, the valve body deforming due to heat causing the valve disc to rub against the wall, and the limit switch position being improper causing the mechanism to jam. The actuator should be selected with sufficient margin based on the valve disc's aerodynamic torque, keep the valve shaft sealing area clean, align the valve shaft and actuator, and manually rotate the valve disc to ensure full flexibility before powering on for debugging. Prolonged overload will burn out the motor; it cannot be resolved by forcibly increasing the power supply or short-circuiting the overload protection. In case of an overload alarm, power off and troubleshoot mechanical issues first, address jamming and deformation, and then restart operation. If the valve itself has excessive torque, replace it with a higher torque actuator or reduce the valve disc and increase bearings to fundamentally eliminate overload.

The inlet and outlet diameters of the fan are determined based on the fan series and often do not match the selected duct diameters in the design. Transition pieces (reducers) are required to smoothly connect the fan interface with the duct. The inlet typically uses a conical or eccentric reducer to ensure uniform and symmetrical airflow into the impeller, preventing swirl flow-induced vibration, noise, and efficiency degradation. The outlet commonly employs an expanding reducer to decelerate high-speed airflow and increase pressure, reducing exit dynamic pressure loss. Transition pieces are typically used in conjunction with flexible connectors: reducers handle alignment and transition, while flexible connectors isolate vibration, forming the standard combination for fan piping installations. During installation, the length and orientation of the transition piece must comply with the manufacturer's piping requirements, and the inlet should be avoided with sharp bends or swirl flow. Proper fan inlet and outlet transition design maximizes fan performance, whereas improper design can result in airflow and pressure failing to meet design specifications.

During the hot melt welding of polypropylene, the gun temperature must be controlled within the range where the material is fully melted without carbonization. The actual setting should be adjusted based on the plate thickness, ambient temperature, and welding rod specifications. Higher temperatures are used for thick plates and winter construction, while lower temperatures are used for thin plates and summer conditions. If the temperature is too low, the welding rod and base material will not fuse properly, resulting in incomplete welding, cold joints, and leakage. If the temperature is too high, the material will carbonize and turn yellow, the weld joint will have porosity, and the plate may even be burned through. Before the actual welding, test weld using scrap material of the same material to observe the melting state of the welding rod, the luster of the molten pool, and the weld formation. Determine the appropriate temperature and gun travel speed before welding the final weld. Maintain stable parameters during welding and avoid frequent temperature adjustments. If the weld turns yellow, immediately lower the temperature. If incomplete welding occurs, grind it off and reweld.

Follow the sequence to troubleshoot: First, confirm that the power voltage matches the actuator nameplate, check if the control signal and valve opening command are present, and verify if the interlock conditions are met; then inspect if the connection between the actuator and valve stem is loose, and if the manual or electric switch is in the disengaged position; next, loosen the actuator's manual handwheel to determine if the valve disc is mechanically jammed or if the actuator itself is faulty. Mechanical jamming is often caused by dust and crystallization in the shaft seat, foreign objects stuck in the valve disc, shaft misalignment, or thermal deformation of the valve body, while electrical faults are typically related to the motor, limit switch, capacitor, or wiring issues. Do not repeatedly force power-on before identifying the cause to avoid burning out the actuator motor. After confirming the mechanical part is flexible, test the actuator with power-on alone to distinguish between mechanical and electrical faults before proceeding with repairs. After completing the repairs, perform several full open/close cycles to verify that the valve position feedback matches the actual opening degree.

The inner diameter of the sleeve socket is designed according to the standard outer diameter of the ductwork. As long as the outer diameters of the two connected sections of ductwork are consistent, even with slight variations in wall thickness, they can generally be spliced together. However, significant differences in wall thickness can result in one end being too loose and the other too tight, affecting alignment and weld quality. Excessive looseness can also increase the amount of welding filler required. The outer diameter tolerances of ductwork from different series or manufacturers may vary. Purchasing matching ductwork and sleeve sockets from the same manufacturer ensures better dimensional fit. When the outer diameters are inconsistent, do not force the connection, as misalignment and stress can cause air leakage. Instead, replace with a matching sleeve socket or use machined parts or flanges for transition. Standardizing the outer diameter standards and tolerances of ductwork during ordering can prevent mismatched connections on-site.

Most temperature-regulating plastic welding guns feature a replaceable heating core. To replace it, first power off and allow the gun body to cool completely. Then, remove the outer casing screws, disconnect the wiring terminals of the old heating core, install the new one, and restore it as before. When replacing, use a heating core of the same model and power specification. Ensure the wiring terminals are securely connected, the heat insulation and sealing components are properly reset, to prevent air leakage or excessive heat buildup on the casing. After assembly, perform an empty-load test run to check if heating, temperature regulation, and airflow are normal before putting it into welding. If the fan motor and temperature control circuit are both damaged, or the gun casing is aging, deformed, or exhibits reduced insulation, it is recommended to replace the entire unit to avoid temperature control failure after repair, which could lead to overheating and fire hazards. When in doubt, it is safer to leave the repair to professionals.

Common reasons for the handle not turning include dust and crystallization jamming at the valve shaft, deformation of the shaft seat due to heat or stress, the valve disc being stuck by foreign objects, misalignment between the valve stem and valve body, and excessive operating torque in large-diameter valves due to the lack of bearings. After shutdown and power-off, inspect the valve shaft and valve disc, remove crystallization and foreign objects, apply appropriate lubrication at the shaft seat, and correct the shaft alignment before slowly turning the handle. Large-diameter air valves should be selected with bearing structures to reduce rotation resistance. In highly corrosive environments, uncoated metal shaft sleeves should not be used to avoid rust and jamming; plastic shaft sleeves or metal components with corrosion protection coatings can be selected. If jamming persists after treatment, check if the valve disc is deformed and rubbing against the wall, or if the actuator is properly matched. In such cases, replace bearings or the valve if necessary, and strictly avoid using force pipes for Forceful manipulation .

Small observation windows are primarily used for observation, lighting, and sampling. After removing the observation panel, hands or tools can be inserted for simple inspection and cleaning, but they cannot replace standard manholes for personnel entry and exit. When personnel need to enter towers or inspect and repair boxes, they should use manholes that meet safety requirements in size and follow confined space work procedures, including ventilation, gas detection, and dedicated supervision. The openings of observation windows are typically small, and flanges and covers are not designed to support personnel loads. Forcing them to serve as entry/exit points will damage the equipment and pose safety risks. A few large-sized observation windows, if designed and manufactured with manhole standards in mind from the outset, considering opening size, flange strength, and sealing, can be used for both inspection and entry/exit. However, this falls under the category of observation manholes and requires specific specification during selection. Under standard configurations, observation windows and inspection manholes should be separately installed.

Strict directional requirements apply. The arrow or directional indicator on the valve body must align with the forward airflow direction, and the valve shaft must be installed horizontally to allow the valve disc to smoothly settle onto the seat under its own weight. Check valves for horizontal and vertical pipelines have different structures and cannot be interchanged: horizontal pipes require swing check valves, vertical upward pipes require vertical check valves, while vertical downward and horizontal downward airflow scenarios require the corresponding types. Incorrect installation can prevent the valve disc from opening properly, causing air restriction and fan overload, or result in failure to close and loss of check function. After installation, manually operate the valve disc to verify correct swing direction, smooth reseatment, absence of sticking or abnormal wear. The valve shaft levelness and the clearance between the valve disc and seat must also be checked. Any directional or levelness issues must be adjusted before operation.

The closed valve should be installed close to the inlet and outlet of the equipment or pipe section to be isolated, minimizing the isolated area. The valve position should be convenient for personnel to operate, observe, and lock, avoiding installation in hard-to-reach locations. When equipment maintenance is required, two closed valves can be installed before and after the equipment to form dual isolation. If necessary, a vent or inspection port can be provided between the two valves to ensure reliable isolation of the maintenance section from upstream and downstream. The valve should be installed according to the airflow indicator on the valve body, so that the positive pressure in the pipeline after closure helps to press the valve disc toward the seat, enhancing the seal. Fixed supports should be installed before and after the valve to prevent the valve body from experiencing cantilever stress deformation after disassembling adjacent equipment, which may affect the seal surface contact. For valves used to isolate hazardous gases, a full-closure air leakage check should be performed after installation, and the operating position and open/close status should be clearly marked and included in on-site safety management.

The height of the packing layer is determined based on the inlet concentration of pollutants, the required purification efficiency, and the mass transfer performance of the packing itself. The higher the inlet concentration and the stricter the emission requirements, the more mass transfer units are needed, and the taller the bed becomes. Packing height is not always better; excessive bed height increases bed resistance and fan energy consumption. When liquid distribution is poor, wall flow and channel flow occur, further increasing packing height offers limited efficiency improvement. In engineering practice, the total height is often divided into several sections, each controlled within a reasonable height, with liquid redistributors installed between sections to evenly distribute liquid flowing down the walls across the cross-section. Design calculations determine the height of each section and the total height based on material balance and gas-liquid mass transfer, with a certain margin reserved. Once determined, the number of packing layers should not be arbitrarily added or removed on-site. If adjustment is necessary, it should be based on recalculations considering measured resistance and outlet concentration.

The tread is fixed to the lower support or beam via Overlapping edge and plastic fasteners. The panels overlap and constrain each other, ensuring that the installation, when properly executed, prevents the tread from warping under normal foot traffic. The key is to ensure the support spacing aligns with the tread's allowable span. The fasteners must be installed correctly and in full quantity, with edge and end fastening on both sides of the walkway to eliminate free edges. If the support spacing is too far apart, causing the tread to sag, or if fasteners are missing or loose, warping, sliding, and abnormal noises may occur during walking. In such cases, additional supports and fasteners should be installed. During installation, first secure the support beams and level them, then lay the panels one by one, securing each as it is placed to prevent any panels from Suspended . After installation, inspect the fasteners and Splice for tightness. Address any looseness or missing fasteners promptly to maintain a flat panel surface and prevent tripping hazards due to warping.

Either method can be used, determined by whether disassembly is required for specific sections. For fixed pipe sections that are rarely disassembled, the air damper socket can be welded directly to the duct, ensuring good weld seam sealing, saving flanges, maintaining continuous corrosion protection, and reducing costs. For sections requiring maintenance, disassembly, or where the vane or seal may be replaced, flange connections are recommended. The flanges at both ends of the valve are secured with gaskets and bolts, allowing for easy assembly and disassembly without damaging the pipeline. It is recommended to use flange connections with flexible connections at the fan inlets/exits and near equipment for convenient equipment maintenance and vibration isolation. In actual projects, main fixed sections are typically welded, while flanges are used at both ends of equipment, fans, and valves requiring maintenance. Regardless of the method, ensure the valve body is coaxial with the pipeline and the vane rotates without interference. Avoid high temperatures during welding that could damage the vane and seals.

The clearance exists between the vanes of a conventional multi-leaf valve and between the vanes and the valve body, resulting in air leakage even when fully closed. This is a normal characteristic of regulating valves and cannot be measured by the requirements of a sealed valve. If the air leakage increases significantly compared to before, it is necessary to check whether the sealing strips on the vane edges are aging or falling off, whether all vanes are aligned synchronously, whether there are any Miscellaneous Items in the valve body, and whether the vanes are deformed or warped. After cleaning the Miscellaneous Items , aligning the synchronization, and replacing the failed sealing strips, the air leakage generally returns to normal levels. For applications requiring higher gas tightness, an enclosed multi-leaf valve with soft sealing strips on the vanes and side sealing at the ends should be ordered, along with a handle, worm gear, or actuator capable of providing sufficient closing force. When ordering valves for isolation maintenance, the gas tightness specifications must be clearly defined at the time of ordering, and they cannot be replaced with conventional regulating valves afterward.

Ceiling plenums and indoor fire compartments typically require fire-resistant duct materials. Standard PP lacks fire resistance and should be replaced with fire-resistant PP electric square dampers and fire-resistant rectangular ducts, meeting the fire code's material combustion performance requirements. Standard PP electric square dampers are more suitable for outdoor, open workshops, or corrosive exhaust applications without fire resistance requirements. Whether fire-resistant materials must be used depends on the building fire design, duct installation location, and local review requirements. Material selection should not solely consider corrosion resistance. Dampers installed in ceilings, pipe shafts, vertical shafts, and high-traffic areas should generally be configured with fire resistance. When ordering, specify the material and fire resistance grade in the list and request a test report to prevent the use of standard materials as substitutes for fire-resistant products on-site.

A single-stage packed tower has its absorption capacity limit. When the exhaust gas concentration is high, the required removal efficiency is high, or the solubility of pollutants is low, the gas-liquid contact time and mass transfer stages are insufficient, and a single tower cannot meet the standards. In engineering, two-stage packed spray Series , increasing the packing height and spray volume, or increasing the liquid-to-gas ratio can be adopted. Intermediate circulation can be set between the two stages of the tower to allow pollutants to be absorbed step by step. Whether multiple stages are needed should be determined by designers based on material balance and absorption calculations, and cannot be simply scaled up from a single tower. High concentration and fast-reacting gases can be handled with a single stage, while difficult-to-absorb or strictly regulated emissions often require multiple stages.

When the fan has a circular interface while the connected ductwork is rectangular, a square-to-round shape conversion is required; if both the fan interface and the ductwork are circular, a reducer with a flexible coupling can be used without a square-to-round conversion. In actual engineering projects, when indoor rectangular ducts connect to circular roof or machine room fans, a combination of square-to-round conversion, flexible coupling, and reducers is often employed: the square-to-round conversion handles shape transformation, the flexible coupling isolates fan vibration, and the reducer addresses diameter differences. Whether to use a square-to-round conversion depends on whether the fan interface and duct cross-sectional shape are consistent. During layout, try to place the square-to-round conversion near the fan with smooth transitions to ensure uniform airflow. Before ordering, verify the fan interface dimensions and duct cross-sectional dimensions to ensure this set of transition fittings can be matched in one go, reducing on-site duct modifications.

Diameter selection should balance purification efficiency, bed resistance, and tower diameter compatibility. Small balls have a larger specific surface area, ensuring thorough gas-liquid contact and high efficiency, but with relatively smaller voids, higher resistance, and a greater tendency to be clogged by dust and crystallization. Large balls offer larger voids, better anti-clogging performance, and higher throughput, but with a smaller specific surface area per unit volume and slightly lower efficiency. For clean gas and high purification requirements, choose smaller balls; for dusty, sticky, or low-pressure drop, high-flow scenarios, select larger balls. The ball diameter should maintain a reasonable ratio with the tower diameter. If the tower diameter is too small while the ball diameter is too large, severe wall and channel flow will occur, concentrating gas and liquid near the tower wall, significantly reducing the effective mass transfer area. In the same tower, smaller balls can be installed in the upper section, while larger balls in the lower section, with the lower section providing anti-clogging performance and the upper section for fine treatment. After determining the ball diameter, calculate the packing height, support grille openings, and plate gaps accordingly.

When the fluid contains suspended solids, crystals, adhesives, or fibers, the small holes of the porous plate may gradually become clogged, leading to increased resistance, reduced flow rate, and uneven distribution. The appropriate hole size and type should be selected based on the cleanliness of the medium. Fibrous or easily crystallizing media should preferably use long-round holes, slot holes, or larger hole diameters to reduce the probability of bridging blockage, and reverse flushing or regular cleaning measures should be implemented. Porous plates in exhaust towers can be regularly flushed with spray water to remove plate surface crystals and dust; sieve plates in the tank should be designed as removable and detachable structures for easy periodic removal and cleaning. During operation, blockage severity can be determined by pressure drop or flow rate changes, and cleaning should be scheduled when resistance continuously increases. If necessary, filtering or pre-washing should be added at the front end to reduce impurities entering the porous plate, extending the cleaning cycle from the source.