Product Basics377
Sealing ring failure manifests as significantly increased air leakage after full closure, audible air leakage from the valve body, and abnormal changes in closing torque. Causes include normal aging, swelling from corrosive gases, wear from dust crystallization, high-temperature deformation, and permanent deformation from prolonged tightening. Replacement cycles have no fixed value and depend on medium, temperature, and operating frequency, requiring determination through regular air leakage checks. Spare parts must be selected for corrosion resistance compatible with exhaust composition, and full-closure sealing uniformity should be rechecked after replacement.
Standard injection molded reducer covers common size combinations, with fast delivery and smooth inner wall; for special sizes, irregular interfaces, or non-standard equipment, PP sheet can be rolled and welded to produce reducers, which involves cone unfolding, cutting, rolling, and welding. Machined reducers offer high flexibility, capable of producing any size, length, and eccentricity, making them ideal for non-standard projects and on-site modifications. However, they have slightly lower appearance consistency and inner wall smoothness compared to injection molded parts, with a longer production cycle. Standard specifications are preferred for molded parts due to stable quality and fast delivery, while urgent, non-standard, and irregular transition parts should be considered for sheet processing. When custom machining, provide the port sizes, length, concentric or eccentric requirements, and connection method for one-time formation.
The baffle channel of the water collection plate features open design, low resistance, and is less prone to blockage, making it easy to clean. It is suitable for applications with larger liquid droplets, dusty or crystalline gas, and low resistance requirements, being the most common form. The packed (or mesh) channel has a dense structure and a large specific surface area, demonstrating strong collection capability for fine mist droplets and high mist removal efficiency. However, it has slightly higher resistance and is prone to blockage by fine debris, making it suitable for scenarios with fine droplets, low dust content, and high mist removal requirements. For high-demand applications, a two-stage combination of baffle plates and packing can be adopted, first removing large liquid droplets and then capturing fine mist, balancing anti-blocking and efficiency.
The material of the gasket should be selected based on the composition of the exhaust gas, temperature, and pressure. For general acid-base ventilation, acid-resistant and alkali-resistant rubber gaskets or EPDM rubber gaskets can be used, which offer good elasticity and low cost. For applications requiring higher temperature and corrosion resistance, PTFE gaskets or PTFE-coated gaskets should be selected. The thickness of the gasket must be uniform, and its dimensions should match the flange sealing surface. During installation, place the gasket centrally and install it in one go without offsetting. Multiple layers of gaskets should not be used to Accumulate thickness . For exhaust gas containing organic solvents, oils, or special media, verify the compatibility of the gasket material to prevent swelling, softening, and failure of the gasket. It is recommended to replace a new gasket each time a flange is disassembled. Reused aged gaskets are a common cause of air leakage. When ordering, ensure the corresponding specification gaskets are matched based on the flange nominal diameter and sealing surface type to avoid incorrect usage on-site.
Pressure control involves installing a pressure sensor on pipelines or equipment, where the controller automatically adjusts the speed of the permanent magnet motor based on the deviation between the measured pressure and the set pressure: the speed decreases when the valve closes or the air usage point reduces, and the speed increases when air usage increases, maintaining stable network pressure and avoiding waste caused by constant-speed operation and air valve throttling. The permanent magnet motor is powered and speed-controlled by a dedicated drive controller, which integrates startup, protection, and speed-control functions. Therefore, traditional complex distribution devices such as star-delta startup cabinets are not required, but must still be configured for power supply, protection, and grounding by electrical professionals in accordance with specifications. The selection of the controller and cable laying should meet the equipment electrical drawing requirements, and electrical inspections must be completed before commissioning.
Check both electrically and mechanically. Electrically, verify if the power voltage is normal, if control signals have arrived, if connections are loose, and if internal protection has been activated. Mechanically, disconnect the actuator and manually rotate the valve to determine if the valve shaft is jammed (due to dust crystallization, valve disc jammed by foreign objects, or valve body deformation) or if the actuator itself is faulty. After confirming the valve is flexible, inspect the actuator motor and limit switch. Do not repeatedly power on under mechanical jamming of the valve disc, as the motor may overheat and burn out due to jamming. In corrosive environments, also check if the terminal connections and housing are corroded.
Common reasons include: insufficient sound absorption capacity or mismatch between the sound absorption band and the noise spectrum; excessive flow velocity inside the duct generating airflow Recycled noise; vibration of the fan transmitted through the pipeline and supports as solid-borne sound, which is ineffective for mufflers; thin walls of the pipeline and exhaust stack behind the muffler being excited by airflow and transmitting sound; unsealed sound leakage bypasses. System analysis is required: controlling flow velocity, adding vibration isolation soft connections and hangers, soundproofing the exhaust stack, positioning the muffler near the radiation outlet, and redesigning the sound absorption capacity based on actual measured frequency spectra if necessary. Relying solely on adding one muffler to solve all noise issues is not effective.
It's not the same. They have different positions and functions. Grating plates are installed below the packing layer, primarily to support the entire packing layer, bearing the weight of the packing and the liquid retained. They require high load-bearing capacity and non-leakage openings. Packing support plates, also known as packing limit plates or packing screens, are installed above the packing layer. Their function is to prevent the packing from being blown, fluidized, or carried away by the gas flow at high gas velocities. They experience relatively lower stress, allowing for larger openings. The two work together in an upper-lower combination: the grating below supports the packing to prevent it from falling, while the plate above holds the packing in place to prevent it from floating. They are often installed together in packed towers operating under high gas velocities and large flow rates. When selecting, grating plates are determined based on load-bearing capacity and packing dimensions, while support plates are determined based on gas velocity and anti-carrying requirements. They cannot be mutually substituted. The installation sequence is first to lay the grating, then install the packing, and finally cover the support plate. The reverse sequence is used for maintenance.
Ventilation hoods with fixed sash openings and constant airflow rates are suitable for mechanical Venturi variable air volume (VAV) dampers, which offer low initial investment, no power supply requirement, and simple maintenance. For hoods requiring constant face velocity during sash sliding and reduced airflow when the sash is closed to save air conditioning fresh air energy consumption, variable airflow Venturi dampers are recommended. These dampers are equipped with actuators and controllers to dynamically adjust airflow based on sash displacement or face velocity signals. Modern laboratories with multiple hoods, long operating hours, and high energy savings requirements often use VAV systems. Budget constraints or limited cabinet space may make fixed airflow dampers a more suitable option.
Constant airflow fume hoods maintain a constant exhaust volume with a simple structure and low investment. However, when the viewing window is partially closed, the wind speed increases and energy consumption does not decrease, making them suitable for laboratories with a small number of fume hoods and low usage frequency. Variable airflow fume hoods adjust the exhaust volume by the displacement of the viewing window or through the linkage with venturi variable airflow valves, increasing the exhaust volume when the window is opened and decreasing it when closed, while maintaining a constant face velocity. This ensures safety and significantly reduces the energy consumption of air conditioning fresh air, making them suitable for modern laboratories with a large number of fume hoods, long operating hours, and energy-saving requirements. However, they require a higher initial investment and more stringent control and maintenance requirements.
No fixed cycle; it depends on the acid mist generation volume and the saturation level of the circulating liquid. In engineering practice, pH meters and salt concentration (density) are used for control: when the pH drops below the set lower limit, alkaline reagents are automatically added. When the salt concentration in the circulating liquid becomes excessively high, absorption efficiency decreases, or the discharge standard is reached, some or all of the circulating liquid is discharged and replaced with fresh water and fresh alkaline reagents. It is recommended to configure automatic pH dosing and regular discharge systems. Wastewater must be sent to a wastewater treatment facility and cannot be discharged directly. For manual management, pH and liquid level should be tested by shift, and records for reagent dosing and water replacement should be established to avoid long-term liquid replacement based on subjective judgment.
Under normal conditions, the worm gear reducer in the valve mechanism has a self-locking function, preventing the valve disc from being moved by airflow once positioned. The return of the valve disc is usually caused by: the actuator torque being undersized, the valve disc being impacted by pulsating airflow exceeding its self-locking capacity; loose fixing of the jaw plate to the valve shaft causing relative rotation; wear of the reducer leading to failure of self-locking; improper limit position preventing the valve disc from reaching its actual position. Check the jaw plate tightness and the actual position of the valve disc. For large-diameter high-pressure valves, select an actuator with higher torque and reliable self-locking function, and add mechanical locking if necessary. Avoid keeping the valve in a semi-open semi-closed state in vibrating airflow for extended periods.
For scenarios requiring only full open/close, remote on/off, and device interlocking of dampers, select the corrosion-resistant on/off actuator. It features simple control and low cost, with a typical power supply of 220V. For dampers that need continuous position adjustment based on signals, used in variable air volume ventilators, negative pressure control, and airflow balancing, select the corrosion-resistant analog actuator. Its typical power supply is AC/DC 24V, capable of receiving standard control signals and providing valve position feedback. When both on/off and regulating valves are present in the same project, they should be configured separately. Frequent on/off actuation for analog regulation is not recommended, as it may lead to inaccurate positioning and potential motor damage.
Attenuation level increases with length within a certain range, but not infinitely linearly, and length increase also raises resistance, occupies space, and increases cost. The attenuation level of resistive mufflers is approximately proportional to effective length, but high-frequency sound may be attenuated completely within the channel, rendering excessively long ends ineffective; there is also an upper limit failure frequency issue in inter-plate channels. In engineering, the required length is calculated based on target attenuation and octave bands, with segmented design generally being more economical and reasonable than single excessively long sections, determined by acoustic design.
The circulating liquid in the exhaust tower contains acids, alkalis, and salts, which will corrode ordinary cast iron and stainless steel pumps. Specialized pumps with PP, PVDF, FRPP, or other corrosion-resistant material impellers must be selected. Generally, PP or FRPP is sufficient for acidic/alkaline and ambient temperature circulating liquids; for media with higher temperatures, strong oxidizing properties, or special solvents, PVDF or higher-grade materials should be selected. When selecting, the composition, concentration, and temperature of the circulating liquid should be provided to the manufacturer to verify material compatibility. Additionally, attention should be paid to the corrosion protection of the motor and metal frame to prevent corrosion from tower area gases. Using the wrong material or substituting with ordinary fresh water pumps will lead to issues such as impeller corrosion and pump body leakage in the short term.
Honeycomb activated carbon is a block form with straight-through channels, featuring a large specific surface area, low airflow resistance, resistance to clogging, and neat installation. It is suitable for high-airflow, low-concentration organic waste gas and is the most commonly used type in drawer-type carbon boxes. Granular activated carbon offers high adsorption capacity, lower cost, and bulk filling capability; however, it has higher resistance and may cause channeling, making it suitable for low-airflow, higher-concentration applications or scenarios requiring frequent replacement. For special gases such as acids and alkalis, modified activated carbon impregnated with specific chemical agents can be selected. The specific carbon type and parameters such as iodine adsorption value shall be determined during the design phase according to the type of pollutants.
Most of the time, the sash of a fume hood is in the closed or slightly open position. The constant airflow system continuously exhausts air at maximum airflow regardless of the sash opening, often discharging air that has been conditioned by air conditioning, resulting in high energy consumption. The variable airflow system reduces the exhaust volume to a very low maintenance airflow when the sash is closed, significantly reducing the exhaust volume per hood. The VAV dampers of multiple fume hoods aggregate the airflow demand to coordinate the variable frequency drives of the exhaust and supply fans, thereby reducing the overall laboratory air conditioning and ventilation energy consumption. The more fume hoods there are and the longer the sash remains closed, the more significant the energy savings become, typically allowing the increased investment to be recovered within several years.
The drawer-type activated carbon adsorption box features a drawer-style tray design, allowing for convenient and quick loading and replacement of activated carbon without disassembling the entire unit. It is suitable for medium-low airflow applications requiring frequent activated carbon replacement. The fixed-type activated carbon tower has a large activated carbon loading capacity and a thicker adsorption layer, making it ideal for high airflow and continuous operation scenarios. Activated carbon replacement requires opening the maintenance door for operation. When selecting, factors such as treatment airflow, exhaust gas concentration, replacement cycle, and on-site maintenance conditions should be comprehensively considered. If unsure about the selection, field conditions can be provided for technical personnel to recommend the most appropriate structural form.
The cyclone tower is primarily used for treating paint mist, viscous exhaust gas, and dust-laden exhaust gas, such as paint mist exhaust gas in the coating spraying industry, dust-containing exhaust gas in the metal grinding and polishing industry, dust exhaust gas in the building materials and cement industry, wood dust and paint mist exhaust gas in the woodworking and furniture industry, and smoke and dust exhaust gas in the rubber and plastic industry. For conventional acid-base exhaust gas, a standard packed tower can be selected; for high-concentration or difficult-to-treat exhaust gas, a series configuration of cyclone tower and packed tower or a multi-stage cyclone tower combination process can be adopted. For exhaust gas containing organic pollutants, an activated carbon adsorption box can be connected in series after the cyclone tower for deep treatment.
PP ducting is primarily used for conveying corrosive gases and acid-base exhaust fumes, such as hydrogen chloride, hydrogen fluoride, ammonia gas, sulfuric acid mist, and other water-soluble gases, as well as organic exhaust fumes and dust exhaust fumes. The PP material is resistant to acid and alkali corrosion, making it suitable for exhaust gas transportation in industries such as chemical, electronics, and coating. For high-temperature gases, it is necessary to confirm that the temperature is within the temperature resistance range of the PP material; for gases with a high concentration of organic solvents, material compatibility should be evaluated, and alternative materials or additional protective measures should be selected if necessary.
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