Drives for the chemical industry: gearboxes, motors, brakes and couplings
Chemical production is not one but several technological worlds under a single industry umbrella: mineral fertilizers with multi-ton granulators and dryers, base chemicals with reactor parks, fine chemistry with precision dosing, polymers with high-torque extruders. What unites them is the aggressive environment. Sulfuric acid, ammonia, chlorides, and alkalis eat through shafts and seals in months where a standard drive should last years. That is why equipment selection here does not start with torque or ratio, but with housing material, seal type, and lubricant compatibility with the process media.
Industry-typical tasks
- Reactor agitator drives 7.5–500 kW — from lab units to 500 m³ vessels in base chemistry and mineral fertilizers; frame, paddle, turbine and anchor designs
- Main drive for single- and twin-screw extruders in polymer chemistry (PVC, PE, PP, petropolymers) at 75–2200 kW, with high torque at low speed
- Drives for centrifuges — decanters, drum and disc-stack — at 22–800 kW with VFD or hydraulic speed control
- Drives for drum, belt and frame filters — low rotational speed and precise torque holding under variable load
- Process pumps for chemically resistant media at 5.5–2000 kW — motors with stainless-steel shafts and seals or protective coatings
- Conveyors for powder products and granular fertilizers — IP65 dust-tight gear motors with thermal margin
- Rotation drives for drum and spray dryers — continuous S1 duty, low rotational speed, plus separate drives for exhaust fans and extraction blowers
- Crushers and granulators for mineral fertilizers and inerts — heavy start under load with a fluid coupling between motor and gearbox
- Liquid and solids dosing systems — variable-speed drives with encoder and flow feedback
Gearboxes
In the chemical industry, a gearbox almost always operates in one of three regimes: constant low speed with high torque (reactor agitators, dryers, drum filters), variable torque at variable speed (centrifuges, extruders, dosing units), or heavy start under full load (fertilizer crushers, granulators). On top of the basic torque and service-factor requirements come specific ones — corrosion-resistant housings (stainless steel, aluminum or epoxy coating from 200 µm), chemically compatible lubrication (PAG-based synthetic oils for reactors in ammonia environments, NSF H1 lubrication for pharma intermediates), and shaft seals with dust shields against aggressive aerosols.
Reactor agitator drives in base chemistry
Helical or bevel-helical gearboxes with a vertical output shaft, sized for high radial and axial loads from a long agitator shaft. For 5–50 m³ vessels — Boneng R/M series in standard execution; for 50–500 m³ vessels and heavy frame agitators in slurries, CGC custom gearboxes are used with a double angular-contact bearing at the output and forced circulating lubrication. For ammonia plants an aluminum-alloy housing is preferable to cast iron — aluminum does not corrode under NH₃ vapors.
- — Output torque 1–250 kN·m
- — Gear ratio 25–400
- — Reinforced angular-contact bearing pair on output shaft
- — Aluminum or stainless-steel housing for plants with NH₃ and chlorides
- — Double mechanical seal on output shaft with buffer chamber
Main drive for polymer-chemistry extruders
Twin-screw extruders for PVC and petropolymers require a gearbox that splits torque between two parallel output shafts and integrates a thrust block sized for screw axial loads up to 1500 kN. This is a dedicated class of extruder gearboxes — CGC ZLY-T series or equivalents with a built-in distribution block. On single-screw PE/PP lines, standard planetary or helical gearboxes with an elevated service factor are used.
- — Gear ratio 8–25
- — Integrated thrust bearing rated 800–1500 kN
- — Forced lubrication with oil cooler
- — Service factor ≥ 1.8 for twin-screw, ≥ 1.5 for single-screw
- — Pt100 temperature monitoring on bearings and oil
Gearboxes for centrifuges and decanters
Decanter centrifuges for sludge dewatering and crystalline-suspension separation use two-stage planetary gearboxes with a high ratio (60–125) to generate the differential speed between bowl and scroll. Housing in AISI 304/316L or with a protective coating. Differential-speed control is provided by a hydrostatic drive (Donly) or a second VFD-driven motor.
- — Gear ratio 60–125
- — AISI 304/316L housing or 250 µm epoxy coating
- — Compatibility with hydraulic differential drive
- — Rotor dynamic balancing to G2.5
- — Vibration monitoring on output bearings
Drives for drum dryers and calciners
Two- to four-stage gearboxes with a high ratio, mounted on the bull gear of the support shell. Continuous S1 duty, low rotational speed (1–4 rpm), significant radial load. They often run in pairs driving one bull gear — this simplifies maintenance (one unit can be taken out without stopping production) and splits the torque.
- — Gear ratio 200–500
- — Twin operation with torque balancing
- — Lube oil station with filtration and heat exchanger
- — Standby oil pump with auto-start
- — Vibration and bearing-temperature monitoring
Conveyor drives for powders and granules
General-purpose Boneng K (bevel-helical) and F (parallel-shaft) gear motors with IP65 dust-tight protection. The chemical-industry specific is constant fine dust in the workshop air, which deposits on the housing, bearings and labyrinth seals. For sulfuric-acid and fertilizer plants the housing is epoxy-coated and standard seals are replaced with double seals purged with inert gas.
- — K-series (15°/45° bevel) or F-series (parallel-shaft)
- — IP65 minimum, IP66 for wet workshops
- — Acid-resistant epoxy coating 200–250 µm
- — Labyrinth or double mechanical shaft seals
- — Service factor of at least 1.5 to cover heavy starts under load
Electric motors and variable-frequency drives
In chemistry, the motor is where electrical requirements (power, efficiency, control) meet chemical ones (corrosion, aggressive vapors) and explosion protection (for organic chemistry and finished-goods warehouses). Mineral fertilizers, sulfuric acid and inorganic chemistry are usually served by standard IP55–IP56 motors with acid-resistant coating — there is no hazardous zone. Organic chemistry, alcohols, aromatics and polymerization monomers are always Zone 1 or 2 per IEC 60079, and there Ex motors are required — Wolong YBX3/YBKK or Huali YB3 certified Ex d IIB T4. Variable-speed drives for agitators and centrifuges via INVT/Inovance VFDs typically save up to 30 % of electricity compared with throttling.
Motors for organic-chemistry reactor agitators
Flameproof induction motors Ex d IIB T4 — Wolong YBX3 (cast aluminum, up to 315 kW) or YBKK (cast iron, up to 1600 kW) for large reactors and autoclaves. Often supplied with forced cooling (IC416) — the integral fan is ineffective at low speed with VFD operation, an independent blower is required. Insulation class H with class-B thermal margin provides reserve for sustained overloads.
- — Ex d IIB T4 certification for Zone 1 and 2
- — IP55 minimum, IP65 for wet workshops
- — VFD-compatible (class H insulation, NEMA MG1 Part 31)
- — Forced IC416 cooling for VFD operation
- — Pt100 sensors on windings and bearings
Motors for centrifuges and extruders
Variable-speed induction motors with encoder, driven by Inovance MD500/MD800 or INVT GD350 VFDs. Centrifuges require fast torque response (10–30 ms) and precise speed holding during start and braking. Extruders need constant torque over a wide speed range (1:20 without torque drop) with thermal reserve for S1 24/7 duty. Energy savings when switching from throttle control to VFD reach 25–35 % in the field.
- — Class H insulation, NEMA MG1 Part 31 (IGBT inverter)
- — Encoder 1024–4096 ppr
- — Constant torque from 5 to 100 % speed
- — Auxiliary cooling at low speed
- — VFD with brake resistor for fast centrifuge deceleration
Motors for process pumps
Continuous S1 duty, 5.5–2000 kW. Key requirements: tight terminal-box entry (double cable glands for ammonia plants), corrosion-resistant shaft (AISI 304 where needed), and bearing protection against aggressive condensate. For sulfuric acid and ammonia transfer, hermetic monobloc canned-motor pumps are often used — motor and pump share one housing with no shaft seal and a shielded rotor.
- — IP55 minimum, IP65 for aggressive media
- — Acid-resistant epoxy housing coating
- — Double cable-gland entries
- — Class F insulation with class-B thermal margin
- — Optional canned-motor hermetic execution
Motors for dryer exhaust fans and extraction systems
Continuous duty, 75–4000 kW, operating under variable process flow. Speed control via VFD or inlet vanes — VFDs are preferred, saving up to 30 % of electricity. The motor runs under vibration from the fan and is surrounded by aggressive dryer-exhaust condensate, so a reinforced foundation, vibration monitoring and bearing vapor protection are required.
- — Class F insulation, class-B thermal margin
- — Vibration monitoring per ISO 10816-3
- — VFD or soft-starter compatibility
- — IP55, dust and aggressive-condensate protection
- — Reinforced bearings sized for radial and axial loads
Industrial brakes
In chemistry, brakes are not a high-volume component (unlike in metallurgy), but they are installed wherever a stop must be guaranteed: on reactor-block cranes (lifting and placing reactor lids, servicing agitators), on inclined fertilizer conveyors (anti-runback), on large centrifuges (emergency rotor stop on imbalance), and at mining and hazardous-area sites. On top of standard torque and response-time requirements come corrosion-resistant execution and explosion protection.
Brakes for reactor-block cranes
Huawu YPZ2/YWZ5 electro-hydraulic disc brakes on hoist drums of cranes serving the reactor park. Dual-brake scheme — service brake plus fail-safe emergency brake. In organic-chemistry zones, Zhonghai SBZ Ex d IIB T4 flameproof execution is used. Housing with acid-resistant coating for areas with nitric and sulfuric acid vapors.
- — Braking torque 1.75–2.0 of hoisting torque
- — Engagement time on de-energization ≤ 0.2 s
- — Ex d IIB T4 for organic chemistry
- — Acid-resistant housing coating
- — Dual brake set (service + emergency)
Brakes for inclined fertilizer conveyors
TKT/TKK shoe brakes with an electro-hydraulic thruster hold the conveyor with granular product at shutdown and prevent runback. Specific issue: fine fertilizer dust clogs the gap between shoe and pulley, so a dust-tight cover with regular compressed-air cleaning is required. Often backed up by a backstop clutch as redundant protection.
- — Electro-hydraulic thruster Ed-50 to Ed-301
- — Dust-tight cover with purge
- — Manual release option
- — Lining-wear monitoring
- — Backstop clutch on the conveyor as backup
Emergency brakes for centrifuges
Large decanters and disc-stack separators are fitted with a hydraulically clamped disc brake for emergency rotor braking when imbalance or vibration protection trips. Coast-down time of an 8–15 t centrifuge from 3000 rpm without a brake reaches 40 minutes; with an active brake it is 3–5 minutes, which is critical under dangerous imbalance.
- — Hydraulic clamp with spring engagement
- — Engagement time 0.2–0.4 s
- — Compatibility with the centrifuge PLC
- — Position and clamping-pressure monitoring
- — Regenerative braking via VFD as primary means
Flameproof brakes for organic chemistry
In Zone 1 and 2 plants per IEC 60079 (aromatics, alcohols, polymerization monomers), flameproof brakes Zhonghai SB-Ex and Jingu YPZ-Ex are used, certified Ex d IIB T4. Housing in AISI 304 or with a coating resistant to organic-solvent vapors. Typically supplied as a single certified package with an Ex hoist or conveyor motor.
- — Ex d IIB T4 certification
- — AISI 304 housing or coated execution
- — Compatibility with the Ex motor under a package certificate
- — IP65 ingress protection
- — Backup from UPS or dedicated hydraulic accumulator
Couplings
Four coupling types are used in chemical drives: drum gear couplings on large reactor agitators and centrifuges (high torque plus misalignment compensation after thermal vessel expansion), pin-and-bush flexible couplings on process pumps (vibration damping, protection of pump seals from shock loads), fluid couplings on extruders and granulators (soft start, motor protection against screw jamming), and torsionally rigid couplings on dosing units (damping without loss of transmission stiffness). Selection always considers the corrosive environment — in ammonia and acid zones gear couplings are supplied with protective covers and the lubricant is switched to a chemically compatible grade.
Gear couplings for agitators and centrifuges
Drum-type double-engagement gear couplings Yongjing GIICL / Longxuan WGZ transmit 5–250 kN·m and accommodate shaft misalignment after the reactor body warms up. In ammonia plants the coupling is enclosed in a stainless-steel guard with a labyrinth seal — this prevents vapors from reaching the steel teeth and stops corrosion. Lubrication: synthetic PAG-based, compatible with NH₃.
- — Torque 5–250 kN·m
- — Angular misalignment up to 1.5°
- — AISI 304 protective guard for aggressive zones
- — Synthetic PAG or PAO lubricant
- — G6.3 balancing for tip speeds > 15 m/s
Pin-and-bush flexible couplings for process pumps
Longxuan LX/LMS and Yongjing LMC series — pin couplings with elastomeric bushings. They damp shock loads at pump start-up and accommodate small radial misalignment, protecting the pump mechanical seal from side loads (the main cause of seal failure on chemical pumps). Bushing service life is at least 30,000 h under normal conditions.
- — Torque 0.5–25 kN·m
- — Radial misalignment 0.2–0.8 mm
- — NBR or HNBR elastomeric elements
- — Pin service life at least 30,000 h
- — Bushing replacement without removing the pump
Fluid couplings for extruders and granulators
Jiaohua YOX/COX oil-filled fluid couplings provide a soft start for an extruder or granulator under heavy load and protect the motor from overload when the screw jams. Rated slip of 2–3 % prevents transmission of shock impulses to the gearbox. Series with a fusible plug release the oil on overheating (above 145 °C) and automatically trip the drive.
- — Rated slip 2–4 %
- — Fusible plug set at 145–160 °C
- — Oil fill 70–85 % of internal volume
- — Thermal capacity for 4–6 starts per hour
- — Flange compatibility with motor and gearbox
Torsional and jaw couplings for dosing units
Precision couplings for liquid and solids dosing systems in fine chemistry and pharma. The key requirement is to combine sufficient torsional stiffness (dosing accuracy) with compensation of small shaft misalignments (bearing protection). Longxuan ML jaw couplings with an elastomeric spider and disc-membrane torsional couplings transmit torques up to 5 kN·m with angular accuracy down to 5 arc-minutes.
- — Torque 0.1–5 kN·m
- — Torsional stiffness no lower than 50 N·m/deg
- — Misalignment 0.1–0.3 mm
- — Compatibility with encoder and servo drive
- — Stainless-steel execution for pharma applications
Applications gallery
Our solutions for this industry
SDS portfolio brands that cover typical applications in this industry.
- WOLONGflameproof motors YBX3/YBKK for organic chemistry (Ex d IIB T4) and general-purpose YE/WD3000 for agitators, centrifuges, pumps and dryers
- BONENGR, M, K, F gear motor series for reactor agitators of various designs, fertilizer and powder conveyors; aluminum housing for ammonia plants
- CGCheavy-duty gearboxes for large 200–500 m³ agitators, twin-screw extruders (ZLY-T) and dryer rotation drives
- HUALIgeneral-purpose and flameproof YB3 motors for chemical plants, series for continuous duty with thermal margin
- HUAWUYPZ2/YWZ5 brake systems for reactor-block cranes and agitator servicing, Ed electro-hydraulic thrusters for fertilizer conveyors
- ZHONGHAISB-Ex flameproof brakes with aggressive-media protection for Zone 1 and 2 organic chemistry
- JINGUbrakes for reactor-block cranes and hydraulically clamped emergency brakes for centrifuges
- YONGJINGGIICL/LMC drum-type gear couplings for heavy agitators, centrifuges and dryer drives with protective guards
- LONGXUANLX/LMS pin-and-bush flexible couplings for process pumps with vibration damping, ML jaw couplings for dosing units
- JIAOHUAYOX/COX fluid couplings for extruders, granulators and fertilizer crushers with overload protection
- DONLYhydraulic power units for presses, polymer-chemistry injection molding machines and decanter differential control
- HUADEhydraulic components for control, dosing and press clamping systems
- INIhydraulic components for presses and injection molding machines in polymer plants
- INVTGD350 VFDs for variable-speed agitators, centrifuges and exhaust fans — 25–35 % energy savings
- INOVANCEMD500/MD800 VFDs and servo drives for precision dosing units, centrifuges and extruders with torque feedback
- DEODFL/DFLA heat exchangers for lube-oil systems of agitator, extruder and dryer gearboxes
Image credits: PEO ACWA (CC BY 2.0) · PEO, Assembled Chemical Weapons Alternatives (CC BY 2.0) · Alf van Beem (CC0) · Bruderb (CC BY 3.0) · Heyl & Patterson Inc. (CC BY 3.0)