Round butterfly damper for corrosive process exhaust ducts: PP/PVC or stainless steel
Round butterfly dampers for acid, solvent and scrubber exhaust ducts · PP and PVC bodies against stainless steel, temperature limits, stroke time and fail position of the actuator
Exhaust from laboratory fume hoods, semiconductor process tools, chemical reactors and wet scrubbers can carry acid, solvent or humid vapour, and it runs in round ducts of polypropylene, PVC or stainless steel. The damper in that duct is a single disc on a shaft, turned by hand or by an electric or pneumatic actuator. The two decisions that separate one damper from another are the material against the gas temperature, and the actuator: how long it takes to move and where the disc goes when power or air is lost.
Round single-blade (butterfly) dampers installed in process exhaust ducts that carry corrosive or humid fume: injection-moulded or fabricated PP, PVC and flame-retardant PP dampers, and stainless steel round dampers, with manual, electric or pneumatic operators. Welding fume local exhaust ventilation, its hoods, filters and fans is covered on the Welding fume extraction systems page; the general families of HVAC and industrial airflow dampers, rectangular blade types and their leakage classes on the Airflow control dampers page. Fire and smoke dampers as life-safety products and the scrubbers themselves are outside this page.
CNFX editorial research · Sources checked October 12, 2026 · 3 sources
PVC stops at 60 °C, PP at 80 °C: when the exhaust needs a stainless damper
XiCheng lists operating temperatures for its injection-moulded damper bodies of −10 to 80 °C for PP, 0 to 60 °C for PVC and up to 60 °C for flame-retardant PP. [1] SIMONA's data sheet for its PVC-CAW (PVC-U) gives a service temperature of 0 to +60 °C, a Vicat B softening temperature of 74 °C and a mean coefficient of thermal expansion of 0.8 × 10⁻⁴ K⁻¹. [2]
SIMONA rates PVC-CAW DIN 4102 B1 (flame retardant) at 1 to 4 mm and UL 94 V-0 from 1 mm. [2] Editorial calculation: at 0.8 × 10⁻⁴ K⁻¹, a 3 m PVC duct run that warms by 40 K grows 3,000 mm × 0.00008 × 40 ≈ 9.6 mm, which the duct supports and the damper flanges have to take. [2]
Editorial note: above those temperatures, or where no gas may pass a closed damper, the alternative is a metal damper with a sealed blade. Greenheck's HBTR-151 round isolation damper has a butterfly blade with a full perimeter seal in a seal-welded flanged frame, in 304 or 316 stainless or painted steel, rated to 10 in. wg, 3,900 fpm and 250 °F with 0 cfm/ft² leakage at 10 in. wg, tested bubble-tight to AMCA 500-D. [3] Editorial calculation: 10 in. wg × 249.1 Pa ≈ 2.5 kPa, 3,900 fpm ≈ 19.8 m/s and 250 °F ≈ 121 °C.
Give the supplier the gas composition, its maximum temperature including upset conditions, and whether the damper only throttles or must also isolate; the material decision follows from those three.
02
Stroke time, control signal and fail position of the damper actuator
XiCheng's motorized PP and PVC dampers take 220 V AC or 24 V AC/DC actuators for either two-position control or 0–10 V / 4–20 mA modulating control with a 0–10 V position feedback. It lists a full stroke of 30 to 90 seconds for motor-driven units and 60 to 150 seconds for spring-return units, and a manual override on every actuator. [1]
The maker describes the spring-return actuator as driving the damper to a set position on loss of power or signal, closed for a fire-smoke duty or open where the exhaust must keep running. [1] Editorial note: for a fume exhaust that serves a hood or a tank line, the open position is the one that keeps the fume captured if the actuator loses power, so state the fail position on the order rather than taking the actuator's default.
XiCheng lists 50 to 1,100 m³/h of air volume per round damper across DN50 to DN315 and a control accuracy of ±5% of air volume with a modulating actuator. [1] Its overview page states DN63 to DN315 for the same injection-moulded range, so confirm the smallest size with the supplier. Editorial calculation: 1,100 m³/h through a 315 mm bore (0.0779 m²) is about 3.9 m/s, taking the nominal diameter as the bore.
03
Thermoplastic and stainless round dampers side by side
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Exhaust gas: [acids, solvents or alkali present; humidity; condensate]
Temperature: [normal and maximum, including upset]
Duct: [material; round diameter; flange or spigot connection]
Duty: [throttling, open-close or isolation; allowed leakage when closed]
Flow and pressure: [air volume; duct static pressure; velocity]
Actuator: [electric 24 V or 220 V; pneumatic; modulating 4–20 mA or two-position; feedback]
Fail position: [open, closed or stay put on loss of power or air]
Installation: [indoor or outdoor; orientation; access for manual override]
XiCheng EP's motorized range pairs injection-moulded PP, PVC or FR-PP round dampers with 220 V or 24 V actuators, alongside the plastic ducting and wet scrubbers the dampers are fitted to.
XICHENG EP LTD
Manufacturing site to be confirmed for the order
Lists the XC-11E electric motorized damper: injection-moulded PP, PVC or FR-PP round dampers from DN50 to DN315 with 220 V AC or 24 V AC/DC actuators, two-position or 0–10 V / 4–20 mA modulating, spring-return option and manual override; also lists manual PP/PVC dampers and PP ducting.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
Up to what temperature can a PVC exhaust damper be used?
XiCheng lists 0 to 60 °C for its PVC damper bodies and SIMONA gives 0 to +60 °C for PVC-CAW; XiCheng lists −10 to 80 °C for PP. [1][2]
How long does a motorized plastic damper take to move?
XiCheng lists 30 to 90 seconds full stroke for motor-driven units and 60 to 150 seconds for spring-return units. [1]
What does bubble-tight mean on a round damper?
Greenheck's HBTR-151 is tested to AMCA 500-D and rated 0 cfm/ft² leakage at 10 in. wg. [3]
Sources and what still needs a direct check
Sources checked 2026-10-12. Damper temperatures and stroke times are XiCheng's published figures for its own PP and PVC range; the PVC material data are SIMONA's for PVC-CAW sheet; the stainless damper ratings are Greenheck's for the HBTR-151.
