PP Electric Closed Damper

Product Model	PP Electric Soft-Sealed Air Tight Valve
Category	PP Machined Products
Reference Price	Price on request

Hot Customizable for Working Conditions 10 Technical Parameters

Product Overview

The PP Electric Hermetic Damper is an electric corrosion-resistant damper designed for high air-tight closing. It resembles a conventional electric damper but features soft-seal structures on the vane edge and seat. The electric actuator provides sufficient clamping torque at the closed position, pressing the seal against the seat to reduce air leakage to a very low level. It primarily addresses the issue of conventional electric regulating valves still having noticeable gaps when fully closed, failing to reliably isolate gases.

In waste gas treatment systems, certain applications require the valve to truly cut off airflow after closure: isolating harmful gases during equipment shutdown and maintenance, preventing cross-contamination between standby and operating equipment, preventing corrosive gases or outdoor cold air from backflowing after fan shutdown, and preventing short circuits between parallel pipelines. Conventional dampers have gaps between the vane and body, allowing only regulation but not sealing. The Electric Hermetic Damper, with its soft-seal ring compression and electric actuator for remote automatic isolation, is the specialized valve for these applications.

The PP Electric Hermetic Dampers supplied by Xicheng Environmental Protection have PP or PPs corrosion-resistant bodies and are equipped with switching electric actuators and soft-seal vanes. They come with switch position signals and are available in circular, square, formed, and plate-welded large diameters. They can also be selected with a power-off reset actuator to meet emergency safety position requirements.

Working Principle

The air-tight principle of the hermetic damper is soft-seal compression. Corrosion-resistant elastic seals (such as rubber or flexible plastic strips) are embedded on the vane edge, and flat seats are set on the corresponding positions of the body. After the actuator drives the vane to the fully closed position, it continues to apply and maintain clamping force. The seal is compressed and deformed to fill the gap between the vane and seat, cutting off the gas passage with the elastic seal, resulting in significantly lower air leakage compared to conventional metal or plastic hard-contact dampers.

During opening, the actuator first detaches the vane from the seat before moving to the fully open position, avoiding prolonged friction on the seal. The electric control principle is the same as that of switching electric valves. The actuator receives switching signals to drive the valve shaft to rotate approximately 90 degrees. Limit switches control the fully open and fully closed positions and provide feedback signals. The PP body is resistant to acid and alkali corrosion, and the seals are selected to be compatible with waste gas components, corrosion-resistant and non-swelling. This is key to maintaining long-term air tightness of the hermetic valve.

Structural Components

The Electric Hermetic Damper consists of a body, a sealing vane, a shaft, a seat, an electric actuator, a bracket, and end connections. The body is a PP-formed cylindrical or plate-welded cylindrical structure with a flat seat ring at the fully closed position. The vane is a rigid plate with a sealing groove on the edge and embedded soft seals, fixed to the shaft, which is supported by a sealed shaft sleeve.

The shaft's extending end is installed with a switching electric actuator via a bracket. The actuator's output torque must exceed the clamping torque required for the seal and provide a margin. Some structures use a four-bar or cam mechanism to generate clamping action at the end of closure. The actuator includes full-open and full-closed limits and feedback, with optional spring reset. Square hermetic dampers use multi-leaf vanes, circumferential sealing strips, and leaf overlapping seals. The body connects at both ends via socket or flange, with reliable sealing at the shaft holes to prevent external leakage.

Specification Model Table

The table below shows the differences between hermetic dampers and conventional regulating dampers. Selection should be based on isolation requirements.

Item	Electric Hermetic Valve	Conventional Electric Valve
Sealing	Soft ring compression	Hard contact gap
Full-closure air leakage	Very low	Higher
Application	Air-tight isolation	Regulation and actuation
Actuator	High-torque clamping	Standard torque

Product Features

The PP Electric Hermetic Damper features soft-seal compression, low air leakage, and remote isolation, making it the specialized valve for harmful gas pipeline automatic isolation. Its main features are as follows.

Soft-seal ring compresses the seat, resulting in low air leakage at full closure
Electric actuator enables remote automatic isolation, eliminating the need for on-site operation
Prevents backflow during shutdown, cross-contamination between equipment, and pipeline short circuits
PP or PPs body, acid and alkali-resistant, flame-retardant
Seals selected for compatibility with waste gas components, corrosion-resistant and non-swelling
Includes switch position signals, suitable for interlock monitoring
Available in circular, square, and various sizes, with optional power-off reset

Body Material	PP / PPs
Sealing Form	Soft Seal Ring Compression
Drive Type	Electric Actuator
Control Type	Switching type
Fully Automatic Performance	Low Leakage Air Tight Seal Partition
Corrosion Resistance Performance	Acid and Alkali Salt Resistant
Sealing Selection	By Media Compatibility
Feedback Signal	Fully open and fully close in place
Connection Method	`Spigot / Flange`
Reset Options	Spring return optional

Application Industries

Isolation electric closed valves for maintenance of spray towers and adsorption equipment
Windproof isolation between primary and backup fans and equipment
Closed valves to prevent corrosive gas backflow after fan shutdown
Isolation valves between hazardous gas pipelines and personnel areas
Isolation valves to prevent short circuits between parallel exhaust gas treatment branches
Air-tight isolation valves for laboratory ventilation system floor isolation
Corrosive gas pipelines requiring automatic shutdown in emergency conditions

Typical Process Locations

The electric closed air valves are installed in positions requiring airtight isolation rather than airflow regulation: at the inlets and outlets of purification equipment (for equipment isolation during maintenance), connecting pipes between backup fans and backup equipment, fan outlets (to prevent backflow during shutdown), branch points of parallel pipelines, and where hazardous gas areas connect to other areas. The valves are interlocked with fans and equipment, opening during operation and automatically closing during shutdown or maintenance. In emergency conditions, they open or shut according to safety logic.

During installation, ensure the valve disc closing direction facilitates pressure-sealing using air pressure, and install the valve body according to the airflow indicators on the valve body. Both ends of the pipelines should have independent supports to prevent pipeline stress from deforming the valve seat and affecting the seal. The actuator is pre-wired for power supply, control, and feedback connections. During commissioning, focus on checking whether the sealing ring is evenly compressed in the fully closed position, whether the air leakage in the fully closed state meets requirements, and whether the power-off reset direction aligns with safety specifications.

Soft-sealed closed valves exhibit significantly lower air leakage compared to conventional dampers, achieving very low leakage levels under specified pressure differentials and with intact seals, but plastic ventilation dampers typically do not guarantee absolute zero leakage like industrial check valves. Selection should be based on allowable air leakage rates or leakage levels rather than a vague requirement for zero leakage. In scenarios involving highly toxic, flammable, or explosive gases or requiring strict isolation, additional measures such as blind flanges, double-valve series with venting should be employed, not relying solely on a single ventilation closed valve.

The design objective of the closed valve is to achieve full open, full close, and airtight isolation. The soft seal ring is pressed against the seat when closed and detaches from the seat when open. If it is left in the intermediate position for long-term adjustment, the seal ring will be continuously eroded by high-speed airflow accompanied by vibration wear, and the valve disc's pulsation at small openings will also damage the sealing surface and clamping mechanism, leading to increased air leakage when fully closed and reduced seal life. For pipe sections requiring frequent air volume adjustment, analog control valves should be selected, and closed valves should be installed separately at isolation points to perform their respective functions. In practical engineering, regulating valves and closed valves are often arranged in series. The regulating valve is responsible for daily air volume balance, while the closed valve only operates during maintenance or shutdown. This approach ensures both adjustment accuracy and protects the closed valve's sealing components, avoiding premature failure of a single valve being used for two different operating conditions.

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.

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.

Whether the valve should open or close during a power outage depends on the site's safety logic and cannot be generalized. In most anti-backflow and maintenance isolation scenarios, the valve is required to automatically close when power fails, using spring-return closing type actuators to cut the pipeline upon power outage, preventing gas crossover and backflow. In cases like emergency ventilation and smoke exhaust, where ventilation must remain unobstructed after a power outage, the valve may need to automatically open during a power failure. When ordering, the fail-safe position must be clearly specified. The spring return direction of the actuator is set at the factory, and open and close types cannot be mixed. Standard non-return actuators maintain their original position after power failure, failing to meet fail-safe requirements. During design, each unit must be marked with the power-off state, and the reset direction and interlock relationships must be clearly stated in the control instructions. Upon arrival, a power-off test must be conducted to confirm that the operation aligns with the design.

Yes. Closed valves are usually marked with airflow direction or valve disc closing direction; correct orientation helps the pipeline pressure to push the disc toward the seat, enhancing the seal; reverse installation may push the disc away from the seat with pressure, increasing air leakage. The valve stem should be installed horizontally to avoid the disc's self-weight affecting the seal and operation. Centering the valve body ends and evenly tightening the flanges ensures that additional pipeline stress does not deform the valve body and seat or cause uneven seal surface contact. A full-closure air leakage check should be performed after installation, not just relying on actuator position signals.

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