A regenerative thermal oxidizer (RTO) is an essential element in any facility that performs operations that produce industrial process exhaust. RTOs are responsible for cleansing the environment of air toxins, odors, volatile organic compounds (VOCs), and hazardous air pollutants (HAPs) that can be detrimental to one’s health, work environment, or production itself. RTOs are found in a wide variety of industries that perform procedures that require ventilation ranging from waste management facilities and chemical plants to food processing and vehicle manufacturing factories.
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The way RTOs work is by utilizing ceramic material to absorb heat from industrial exhaust gas and using it to preheat incoming gas. The RTO uses this stored heat to kill off any pollutants in the air discharged from process exhaust streams at a temperature ranging anywhere from 815 °C (1,500 F) to 980 °C (1,800 F).
Industrial dampers (or valves) in a regenerative thermal oxidizer system are there to supply tight shut-off of process air to maintain destruction and removal efficiency (DRE) and appropriate heat exchanger operation thermal energy recovery (TER). Industrial dampers regulate airflow and allow for isolation of ducting and other equipment for maintenance purposes.
Choosing the right industrial damper for your RTO is imperative for maintaining optimal efficiency over a long period of time. Considerations such as maximum system pressure, air type, system design, temperature changes, and any stressors must be taken into account when selecting your custom industrial damper to maximize your RTO usage and maintain efficient VOC destruction. At Flexcom we’re determined to provide our customers with the appropriate custom industrial damper for your regenerative thermal oxidizers based on research, experience, and industry needs.
The standard for RTOs for over 30 years, Butterfly Industrial Dampers inhabit less space than other valves and are extremely versatile owing to their design. These custom industrial dampers utilize a solid center-mounted rotating disc (or discs) that turns 90 degrees (activated by an actuator) for opening and closing to control the gas stream flow. In the closed position it blocks close to the entire stream flow (approximately 99.75% of airflow), and in open provides little in the way of flow restrictions. They are reliable in both modulating and on-off applications.
Butterfly industrial dampers require relatively low operating torque requirements while maintaining a fairly tight seal in closed positions. While the size and type of the custom industrial damper will determine torque and actuator requirements, the butterfly industrial damper is known for its versatility and effectiveness. The industrial butterfly dampers used in RTOs are the on-off type. Multi vane dampers are typically rectangular or square and can have several vanes or blades. These dampers can withstand temperatures up to degrees fahrenheit.
Initially created for use in fabric filter systems, poppet industrial dampers were later used in RTOs and have been ever since (for over 15 years now). Activated by an electric or pneumatic actuator the custom poppet industrial damper is a flat circular plate that is raised and lowered to press against or move away from a cylinder shaped seat. In the closed position gas seeking to flow past the cylinder is blocked, and in the open position there’s a one to two foot gap between the cylinder opening and flat plate.
Flexcom’s custom poppet industrial dampers are not for use in modulating applications. These are meant for on-off control only.
In RTO’s, poppet industrial dampers are particularly advanced sealing several gas paths while redirecting gas in various directions simultaneously. These dampers are activated by pneumatic or hydraulic cylinder actuators that provide high-cycle service and low-leakage isolation – poppet industrial dampers with zero-leak blades and seats are available as well. Poppet valves with three and four-way configurations are also common in some RTOs. A three-way poppet has one inlet and two outlets and cycles between two seats diverting flow through one while sealing the other. And four-way poppet dampers have two inlets and two outlets.
While most regenerative thermal oxidizers operate at temperatures ranging from º-º F, there are times when the heat may exceed that limit. For this reason installing a hot side industrial damper (or bypass damper) is an integral step for securing your RTO. A bypass damper will control the core temperature of your RTO and support it in maintaining a consistent temperature. Note that if temperatures in your RTO do not remain consistent, it will not convert gases and result in minimal heat recovery and conversion. This can also result in your RTO shutting down.
A hot side damper is vital under conditions where the level of volatile organic compound (VOC) concentration increases and pushes temperatures above their limit. When this occurs a variable energy-recovery (VER) system will activate the bypass damper opening it up to control the temperature. As the bypass damper opens, some of the hot gas from the burner chamber is diverted from the heat-exchange beds, thus regulating the temperature.
A: Rotary dampers contain oil inside, and when the shaft connected to the lid or door rotates, the oil is stirred or flows through a narrow passage,
causing the oil’s viscosity (stickiness) to act as resistance, thereby slowly moving the lid or door.
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What Is a Rotary Damper?
A: We use resins (POM, PBT, PA, etc.), zinc die-castings, silicone oil, and other materials.
Resins and die-castings are materials that can be mass-produced in complex shapes by making molds, making them ideal for rotary damper parts.
Additionally, resin is relatively lightweight and offers the advantage of being able to select from various types to meet requirements such as chemical resistance and heat resistance.
Since rotary dampers utilize the viscosity of oil, silicone oil is essential, and the oil viscosity is selected according to the damper torque.
A: Broadly speaking, you should choose based on usage, torque, and size.
Usage refers to how the lid is closed, such as horizontally or vertically, and the type of rotary damper you choose will vary depending on how the lid closes.
Torque is determined by the shape and weight of the lid, while size refers to the physical dimensions of the rotary damper.
The higher the required torque, the larger the rotary damper that should be selected.
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A: Partial rotation angle dampers have a limit on the rotation angle.
Partial rotation angle dampers have a structure where a partition is installed inside the rotary damper, and oil is flowed through a narrow passage to achieve high torque.
This partition causes the rotation angle limit.
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A: Basically, yes.
Rotary dampers are designed with rubber parts to seal the oil and prevent leaks, so they can be used outdoors.
Among the products in our catalog, those made of resin are susceptible to hydrolysis, sunlight (ultraviolet rays), and those made of zinc die-cast are susceptible to white rust.
In both cases, measures such as avoiding direct sunlight and installing in locations where rain does not directly hit are recommended.
A: Some rotary dampers have a proven track record of use in low-temperature environments,
but since viscosity changes depending on temperature, we recommend individual evaluation under severe conditions.
A: Since the damper shaft is inserted into the center of rotation of the lid, the weight of the lid is applied to the rotary damper.
In the case of a lid that closes horizontally, the weight of the lid is applied when the lid is opened 90°.
At this time, it is preferable to design the rotary damper shaft to be inserted as deeply as possible into the lid.
A: If used at a torque higher than the rotary damper’s specifications, the damping torque will be insufficient, and the lid will not close slowly.
The greater the torque difference, the more the lid will close forcefully like a lid without a rotary damper,
and the rotary damper’s internal pressure will exceed the intended level, potentially causing component damage, oil leaks, and loss of normal functionality.
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A: Depending on the conditions, there are cases where the product has been used beyond the specified number of cycles,
but such use is not covered by the warranty.
Please consult us separately for evaluation and verification based on long-term use.
A: Attach the damper housing to the fixed side (casing) and the shaft side to the movable part (lid or door).
It must be positioned appropriately relative to the center of rotation.
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Rotary damper applications
A: A highly rigid structure with minimal deformation and deflection is required.
If the installation accuracy is low, the damper may not perform properly.
A: Yes, it is possible. Our rotary dampers are designed to slow down at the end of the closing cycle.
We can adjust the closing speed to some extent to meet your requirements, such as “slow at the beginning and fast at the end” or “slow only in the middle of the closing cycle.”
A: Detailed data on temperature characteristics and durability is provided in the product catalog, so please check it.
A: There are two possible reasons why the lid does not close completely.
One is that a rotary damper suitable for the closing angle of the lid has not been selected,
and the other is that there is a discrepancy between the operating range of the lid and the operating angle range of the rotary damper.
In the former case, if a horizontal use rotary damper is used for a lid that hangs vertically in the closed position,
the damping will not work at first, and the lid will close very slowly, preventing it from closing completely.
In the latter case, if the rotary damper shaft cannot rotate any further before the lid reaches the closed position, the lid will not close.
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A: It depends on the purpose, but since linear dampers are visible when the lid is opened,
it is better to choose a rotary damper if you do not want them to be visible for design reasons.
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A: Only TD27 and TD28 series are equipped with torque adjustment functions.
Customized rotary dampers with torque adjustment functions are also available.
A: When switching from the open direction to the closed direction, there is some play before the damper starts to work.
This play is called backlash.
The amount of backlash depends on the presence of microscopic air pockets inside and the responsiveness of the internal parts.
A: To reduce backlash, the following methods are generally available:
A: The continuous rotation damper has both bidirectional dampers and unidirectional dampers,
and the unidirectional dampers can be turned lightly in the opposite direction of the damper.
However, since the one-way mechanism is built into the oil-filled area (damper chamber),
there is some resistance from the oil seal and slight viscous resistance.
If lighter rotation is desired, a custom design can be made with the one-way mechanism outside the damper chamber,
reducing the idling torque to 3 mN·m (30 gf·cm) or less.
A: To increase the falling speed, the following methods are generally available:
A: Custom orders are possible provided that a mold is manufactured and the customer bears the cost of mold production.
The housing shape must be uniform in thickness to stabilize the degree of shrinkage during molding, so consultation is required.
A: Yes, it can. We can accommodate this by changing the internal structure design.
A: Please refer to the article on custom-ordered rotary dampers examples.
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If you cannot find the rotary damper you are looking for, or if you need more detailed information, please feel free to contact us.
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