FAQ

The load-bearing capacity of perforated plates depends on plate thickness, hole bridge width, open area ratio, and support span. The lower the open area ratio, the thinner the plate, and the greater the unsupported span, the lower the unit area load capacity. When supporting heavy filter media, high loading heights, or large spans, the plate thickness should be increased, the hole bridge width should be densified, and reinforced ribs or densified support beams should be welded underneath the plates to keep the span of individual plates within the allowable range. The specific load should be calculated item by item based on the bulk density of the filter media, loading height, liquid holding weight, and maintenance load to ensure a safety margin for plate stress and deflection. In design, reference can be made to the plate thickness and support spacing of similar equipment, and then verified against actual loads to avoid plate deflection, deformation, or even collapse during operation. For applications with high liquid holding capacity, the significantly increased weight of wet fill material compared to dry fill material should also be considered.

The sealing performance of a closed valve is entirely dependent on the soft seal ring, while rubber and elastomers exhibit significant differences in tolerance to various media; certain organic solvents, strong oxidizers, or oil mist can cause the seal ring to swell, harden, crack, and lose elasticity. PP valve bodies being corrosion-resistant does not equate to the seal components being corrosion-resistant; when ordering, the main components, concentration, and temperature of the exhaust gas must be provided, and the manufacturer must select compatible seal materials, with the medium provided for compatibility confirmation if necessary, otherwise, the valve body may remain intact while the seal fails, resulting in loss of isolation function.

Nipples inherently create certain local resistance, but smoothly transitioned formed nipples have a very low resistance coefficient, with limited impact on the system's total airflow. What truly affects airflow are eddies caused by sudden diameter reduction or expansion, as well as additional resistance resulting from excessively high velocity selection and excessively short length after diameter change. During design, it is essential to control the airflow velocity of the pipes before and after diameter change within a reasonable range. Appropriately expanding the outlet of the fan and reducing the velocity can minimize dynamic pressure loss and regenerative noise. Using nipples reasonably and smoothly not only avoids significant airflow loss but also enhances the matching between the fan and the pipeline network, ensuring stable operation. What must be avoided is directly connecting two pipes with significantly different diameters using short nipples. When necessary, extend the transition section or implement segmented diameter change.

Resistance increase is primarily due to the clogging of demister internals by dust, crystallization, or sludge, as well as the reduction in flow area caused by Dirt accumulation in baffle gaps and packing pores. Secondary causes include excessively high liquid level in the sump, liquid sealing, or blocked drain pipes, which submerge the internals, and the failure of the flushing system or infrequent cleaning, which exacerbate clogging. Regularly activating flushing water to clean the internals, clear drain pipes and liquid seals, and control suspended solids and crystallization in the upstream spray liquid are necessary. In severe blockages, open the maintenance door to clean or replace the internals. Monitoring the pressure differential before and after the demister and setting flushing cycles are effective management methods to prevent clogging.

The flange body is made of plastic material, which is not corrosive, but the connecting bolts are typically metal parts located outside the flange, not directly contacting the internal medium of the pipe. In general acidic or alkaline ventilation environments, the bolts are at the outer edge of the flange, contacting only trace leakage gases, resulting in slower corrosion. In high-concentration corrosive gas environments, during spray wetting, or outdoor rain exposure, stainless steel bolts or galvanized bolts can be selected, or plastic protective caps can be installed on the bolts, or anti-corrosion grease can be applied. During regular maintenance, check the rust and tightness of the bolts. Timely replacement is required for severely rusted bolts to prevent them from breaking inside the holes during disassembly. It is recommended to use bolts of the same material for the same set of flanges and to tighten them evenly to avoid additional corrosion caused by contact between different metals. In coastal or high-humidity, high-corrosion environments, stainless steel bolts are preferred, resulting in lower maintenance requirements in the long term.

Permanent magnet motor rotors operate normally within the designed temperature range with low demagnetization risk, and high-quality permanent magnets can achieve the motor's design lifespan. Demagnetization is primarily caused by prolonged over-temperature, severe overload, or poor heat dissipation. Therefore, selection should allow for a safety margin, ensure proper heat dissipation, avoid frequent overloading and stalling, and the controller must have over-temperature and overload protection. In corrosive environments, the motor housing and insulation must also withstand corrosive gases; corrosion-resistant models or proper machine room isolation and ventilation should be selected. Under normal maintenance, permanent magnet motors do not have wear-and-tear components like brushes, resulting in lower maintenance requirements compared to conventional asynchronous systems with belt drives.

The spring-return type maintains the valve in the working position when power is applied, as the motor overcomes the spring force. Upon power loss, the spring releases, pulling the valve disc back to the factory-set reset position. The reset direction (fully open or fully closed) is determined based on safety procedures: accident exhaust valves typically require power-off full open to ensure exhaust, while check and isolation valves usually require power-off full closed. The power-off safety position must be specified during ordering, and the actuator markings and spring action direction must be verified during on-site installation. Standard non-return actuators hold the valve in its original position upon power loss and do not provide fail-safe functionality. These two types cannot be used interchangeably.

Porous acoustic absorption materials lose their performance significantly when they absorb moisture and water fills the pores with water films and accumulated water. This is the most common cause of failure in corrosion-resistant exhaust mufflers. When the fan inlet after a spray tower carries water mist, it should first pass through a demister before entering the muffler. The muffler uses a protective fabric to seal the acoustic absorption layer and is equipped with a liquid drain outlet at the bottom. When necessary, moisture-resistant acoustic absorption materials should be selected, or the reactive section should be placed on the mist side. During maintenance, it is found that when the acoustic cotton panels are clogged, sagging, or the protective fabric is damaged, the noise reduction performance can only be restored after opening the maintenance structure to replace the acoustic absorption materials.

The full grid layer inside a circular tower is laid out using a combination of standard rectangular panels, custom-shaped edge panels, and curved edge panels. Standard panels are installed in the central area of the tower, while the curved zones near the tower wall are completed with edge panels cut to the matching curvature. Panels overlap and interlock with one another with edges pressed together, and the gaps between the panel edges and the tower wall are sealed with bulk packing, soft sealing strips, or edge trim strips to prevent packing from falling through the perimeter gaps. The grid panels rest entirely on support rings welded to the tower wall and on central support beams, and are secured where necessary with plastic hold-down blocks or clips to prevent lifting by gas flow. Panel dimensions should be selected so that each panel can pass through the manhole into the tower and be handled and assembled manually. Curved edge panels are cut to the actual tower diameter either on site or during prefabrication. After installation, each panel is inspected for stability, unsupported sections, and gaps larger than the packing size; packing is loaded only after all panels have passed inspection.

Venturi valves commonly use materials such as ABS engineering plastic, stainless steel, and aluminum alloy. ABS valve bodies are molded as one piece, rust-resistant, and exhibit good corrosion resistance to general acid and alkali ventilation, with low cost, making them a common choice for laboratory fume hood ventilation; stainless steel or corrosion-treated valve bodies can be selected for highly corrosive environments, with the specific material determined based on the composition and concentration of the ventilation. Aluminum alloy valve bodies are lightweight, but their corrosion resistance depends on surface treatment. When selecting, specify the common reagents and ventilation properties of the fume hood to the manufacturer, and verify the corrosion resistance table of the material if necessary, to avoid corrosion and jamming of moving parts such as valve cores and springs.

It is not recommended to use fume hoods as storage cabinets for long-term storage. Prolonged accumulation of reagent bottles and equipment inside the operational chamber will block the baffle plates and rear air intake channels, disrupt internal airflow organization, result in insufficient local velocity, create pollutant accumulation and eddies, and increase the risk of chemical mixing and leakage reactions. Fume hoods are operational protection equipment, designed to hold only a small amount of items currently in use during experiments. After experiments, chemicals should be stored in dedicated medicine cabinets, reagent cabinets, or explosion-proof cabinets to maintain the operational chamber, baffle plates, and exhaust channels clear. Waste liquids and debris should not be accumulated in the cabinet's cups/troughs, work surfaces, or behind the baffle plates for extended periods. For chemical storage, configure specialized cabinets that meet storage requirements, and store chemicals by compatibility classification to fundamentally eliminate safety and ventilation hazards caused by accumulation inside the fume hood.

Moisture or white mist discharge may be caused by clogged, damaged, or improperly installed demisting plates, where liquid droplets cannot be effectively separated as air flows through the demisting layer; alternatively, it could result from excessively high gas velocity within the tower or excessive spray volume, carrying liquid droplets out of the tower. In winter, steam condensation can also form visible white mist. Inspect, clean, or replace the demisting plates, control airflow and gas velocity within the design range, adjust spray volume, and increase the demisting section or add a secondary demisting stage if necessary. Water carryover can corrode fans and ducts and cause water dripping from the exhaust stack, requiring prompt treatment upon detection.

The standard interlocking logic is as follows: the start command first sends an open valve signal to the actuator, which actuates to full open. The open position contact closes and feeds back to the control system. The system then starts the fan after receiving the open position signal. During shutdown, the fan is stopped first, followed by sending a close valve signal to close the damper. This prevents the fan from starting while the valve is closed, which could cause pressure buildup, and also prevents gas backflow after shutdown. In multi-circuit systems, the dampers of operating equipment are opened first, and the fan operates according to the number of open circuits. Emergency dampers operate according to safety logic to rapidly open or close. Interlocking is implemented via PLC or relays, and the position signal is a necessary condition for the interlocking sequence.

Corrosion-resistant actuators can significantly extend service life in corrosive environments, but their corrosion resistance is related to protection level and medium strength, not immune under all conditions. Corrosive gases may still penetrate when exposed to direct spray of strong acid/alkali mists, sealing leaks from pipe flanges and valve shafts, failed junction box seals, or damaged enclosures. Ensure the damper itself is airtight, avoid direct spray and water accumulation areas for the actuator, regularly inspect seals, junction boxes, and fasteners, and promptly address enclosure damage or corroded terminals. For special highly corrosive media, inform the manufacturer of the composition concentration, and select higher protection levels or isolated installation solutions.

Acoustic absorption materials exposed directly to acidic or alkaline mist will absorb moisture, harden, or even corrode, leading to pore blockage and reduced sound absorption capacity. Corrosion-resistant mufflers feature corrosion-resistant PP shells and perforated facings. The acoustic absorption materials are covered with a protective fabric to isolate droplets and dust, and moisture-resistant and corrosion-resistant acoustic materials are selected when necessary. Misted and dusty gases should be pre-treated with spray washing and de-misting before entering the muffler to reduce moisture and dust accumulation on the acoustic absorption materials. During maintenance, if the facings are damaged or the materials have hardened, they should be replaced promptly, otherwise the muffling performance will significantly degrade.

Vertical Shaftless Seal-Channel Pumps rely on liquid transport for cooling and lubrication, allowing brief idling, but prolonged dry running without water will cause overheating and wear of plastic components and bearings inside the pump, which should be avoided. Horizontal Mechanical Seal Pumps are strictly prohibited from idling; water shortage during operation will cause the mechanical seal to experience short-term dry friction and burn out, leading to leaks. During operation, ensure the water level in the tank is higher than the pump suction inlet or the specified submersion depth. Install low-level alarm or interlock with the pump, and shut down the pump when the water level is too low. If suction vacuum, air ingress, or abnormal sounds are detected, immediately check the water level and suction piping, and do not allow the pump to continue running in a water-deficient state.

The increase in resistance is primarily due to the blockage of activated carbon pores and channels by dust, oil mist, water mist, or crystallization, or the compaction of the carbon bed due to moisture. Pre-treatment at the front end should be strengthened: install filter cotton and demisters before the carbon chamber, and replace filter materials and drain condensate regularly; cleaned honeycomb carbon with blockage is difficult to restore performance, and is usually replaced directly; granular carbon can be sieved and partially replaced. Additionally, check if the airflow distribution plate and drawer seals are dusty. Maintaining a clean and dry state of the exhaust gas before entering the carbon chamber is key to extending the life of activated carbon and stabilizing resistance.

Venturi-type airflow measurement sections feature stable flow channels and a clear correlation between differential pressure and airflow. When paired with high-quality differential pressure sensors, measurement accuracy can meet air velocity control requirements under proper installation and regular calibration conditions. Measurement drift primarily stems from dust accumulation or leaks in the sampling tubing, sensor aging due to long-term use, or crystallization or dust contamination within the valve. In corrosive environments, corrosion-resistant valve bodies and sensors should be selected. Periodic checks of the sampling tube, cleaning of the measurement section, and calibration of zero points and ranges are essential. Ensuring valve protection during laboratory renovation phases with dust control measures can effectively prevent drift.

The replacement cycle of activated carbon is not fixed and depends on factors such as exhaust gas concentration, treatment air volume, operating time, and activated carbon loading. Generally, the outlet exhaust gas concentration is monitored to determine the need for replacement. When the outlet concentration approaches emission standards or the activated carbon reaches adsorption saturation, it should be replaced promptly. It is recommended to install inspection ports at the inlet and outlet of the equipment to regularly test the purification efficiency. Alternatively, a replacement schedule can be developed based on operational experience, such as every three to six months, with the specific frequency determined by actual conditions. Used activated carbon is classified as hazardous waste and should be properly disposed of by qualified third-party agencies.

The cyclone tower is available in two types: packed and unpacked. The unpacked type consists of multiple cyclone plates and a spray layer as its core components, featuring a simple structure, low pressure drop, and completely avoiding the maintenance challenges of packed bed clogging. It is primarily used for treating viscous, oily, or fiber-containing exhaust gases, or in scenarios where only dust removal and cooling are required. The packed type consists of cyclone plates, a packing layer, and a spray layer as its core components, mainly used for treating non-viscous, non-clogging exhaust gases, which can further enhance gas-liquid contact area and purification efficiency. The specific selection should be determined based on the nature of the exhaust gas.