Drives for petrochemicals: explosion-proof gearboxes, motors, brakes and couplings
Petrochemical plants and refineries are continuous hazardous areas: hydrocarbon vapors, reformer hydrogen, hydrogen sulfide, aromatics. Per IEC 60079, virtually every process unit falls into Zone 1, 2, 21 or 22, so motors, brakes, thrusters and drives must carry mandatory Ex protection — Ex d, Ex e or combined Ex de with T3/T4 temperature classes (most of the installed base). General-purpose enclosures are not used here at all: even a catalyst-conveyor gearmotor needs Zone 2 certification, while a syngas compressor motor must be Ex d IIB+H2 T4. This shifts selection logic, equipment cost and lead times.
Industry-typical tasks
- Agitators and bottom discharge screws of FCC, reforming and hydrocracking reactors — 30–500 kW gearmotors in Ex de IIB T4 design
- Reflux and circulating pumps of fractionating and absorption columns — large fleet of centrifugal and reciprocating pumps from 11 to 2,500 kW with Ex d IIB T3/T4 drives
- Process gas compressors for syngas, hydrogen, ethylene, propylene — 1–25 MW HV drives with gear couplings and explosion-proof terminal-box flanges
- Induced-draft fans and blowers of feedstock heaters — 200–1,500 kW motors, speed control via Ex-rated VFD
- Conveyors for catalyst, adsorbents, sulfur and delayed-coking coke — gearmotors with Ex-rated brakes and thrusters
- Loading systems at tank farms and racks — Ex e/Ex d crane drives and transfer pumps with static-discharge protection
- Metering pumps and valve actuators for reagents, corrosion inhibitors and additives — hydraulic power units with Ex-rated electrics
- Reactor-block overhead cranes for catalyst replacement and column-tray service — dual braking systems with Ex thrusters
Gearboxes and gearmotors
In petrochemical units the gearbox itself does not require explosion protection — that requirement applies to the electrical part of the drive (motor, brake, limit switches). For this reason petrochemicals overwhelmingly use packaged gearmotors in which the Ex envelope covers the motor, terminal box, RTDs and brake, while the mechanical part is standard with reinforced seals against hydrocarbon-vapor diffusion. Service factor is selected with a 1.4–1.8 margin for continuous S1 24/7 duty and the inability to swap equipment quickly in a live process line.
Agitator drives for FCC and hydrocracking reactors
Inline or helical-bevel gearmotors with an Ex de IIB T4 motor. The reactor runs at 1–20 MPa and 350–500 °C, so the gearbox is mounted on the top head via a thermal-isolation lantern that shields the bearings from heat flow. BONENG K/HB Ex series are used with forced oil circulation and a separate DEO oil cooler.
- — Ex de IIB T4 motor (minimum), Zone 1
- — Ratio 25–125, output torque 5–80 kN·m
- — Thermal-isolation lantern between gearbox and reactor head
- — Oil pump unit with filtration and cooling
- — Dual mechanical seals with buffer fluid
Bottom discharge screws of reactors and regenerators
Low-speed gearmotors for catalyst and coke discharge from FCC and delayed-coking reactors. The medium is abrasive (catalyst) and hot (up to 250 °C on the screw casing). Helical or planetary gearboxes with increased bearing radial clearance and heat-resistant FKM/FFKM seals are used. The motor is Ex d IIB T3, 30–250 kW.
- — Low output speed 5–30 rpm
- — Output-shaft radial load up to 200 kN
- — FKM/FFKM seals, heat resistance up to +200 °C
- — Ex d IIB T3 motor, IP56
- — Service factor no less than 1.5
Conveyors for catalyst, adsorbents and sulfur
General-purpose helical-bevel (K-series) gearmotors in Ex design. At catalyst-regeneration and sulfur-pelletizing units the conveyor runs in a "full-load start every few minutes" pattern, which calls for upgraded motor thermal sizing and a verified gearbox thermal rating. The brake is Ex e/Ex d on the motor non-drive end to hold the inclined belt.
- — K-series 7.5–75 kW, ratio 20–80
- — Ex e IIC T4 or Ex de IIB T4 motor
- — Ex brake with response time ≤ 0.3 s
- — Gearbox protection in case of belt jam
Drives for metering pumps and reagent dosing systems
Compact 0.75–7.5 kW gearmotors driving piston and plunger metering pumps for corrosion inhibitors, neutralizers and additives. Ex e or Ex d design for Zone 2. Capacity is adjusted via an Ex-rated VFD or mechanical variator.
- — Power 0.75–7.5 kW
- — Ex e IIC T4 or Ex d IIC T4 motor (per zone)
- — Compatibility with piston/plunger load (starting torque factor 1.5–2)
- — 1:10 turndown when operated with an Ex-rated VFD
Open-gear drives and large-column valve actuators
Worm and planetary gearmotors driving block valves on large-diameter process pipelines (DN 600–1,400). Operation is infrequent but guaranteed actuation is required after long idle periods. The design is always Ex-rated, with gearbox heating below −20 °C.
- — Self-locking (worm) gearing or holding brake
- — Ex de IIB T4 motor, IP67
- — Crankcase heater for winter start-up
- — Ex limit switches and torque-limiting couplings
Explosion-proof electric motors
The electric motor is the critical Ex-protection link in petrochemicals. Wolong is the key brand for this industry in the SDS portfolio: the YBX3 and YBKK series cover 0.75 kW to 6 MW with Ex d/Ex de IIB or IIC protection and T3/T4 temperature classes. For hydrogen compressors and reforming units the IIB+H2 marking is specifically used to address the higher hazard of hydrogen mixtures. All Ex motors are certified to GOST R 31610 (IEC 60079) and carry Rostechnadzor permits for use in hazardous areas.
Motors for process pumps
The largest segment — 11–2,500 kW induction motors in Ex d IIB T4 design driving centrifugal, reciprocating and screw pumps for product transfer, column circulation and reflux. The Wolong YBX3 series is the workhorse motor of petrochemicals: class F insulation with class-B thermal margin, IP55, anti-friction bearings with 40,000 h life, ATEX/IECEx and EAEU certification. For 6 kV HV duty, YBKK is used up to 6 MW.
- — Ex d IIB T4 (minimum), Ex d IIC T4 where hydrogen/acetylene is present
- — Class F insulation with class-B thermal margin
- — IP55, Zone 1 or Zone 2 design
- — Compatibility with Ex-rated VFD (NEMA MG1 Part 31)
- — Pt100 in windings and bearings, anti-condensation heaters
HV motors for process gas compressors
Syngas, hydrogen, ethylene and propylene compressors are driven by Wolong YKK/YBKK HV motors, 1–25 MW at 6 or 10 kV. Ex d IIB T4 (for most gases) or Ex d IIB+H2 T4 (for hydrogen units). Continuous S1 duty, speed control via an MV drive, IC81W (water-to-air) closed-circuit cooling. An insulated non-drive-end bearing is mandatory for HV drives running on a VFD.
- — Power 1–25 MW, voltage 6/10 kV
- — Ex d IIB T4 or Ex d IIB+H2 T4
- — Forced IC81W (water-to-air) cooling
- — Insulated bearing, shaft-current protection
- — Vibration monitoring per ISO 10816-3 zone B
Motors for ID fans and blowers of feedstock heaters
Feedstock heaters (atmospheric and vacuum distillation, reforming, hydrotreating) need draft machines — ID fans and blowers with 200–1,500 kW motors. The paradox: the heater itself is not Ex-rated (combustion takes place inside), but the motor and its terminal box must be Ex de IIB T3 because they sit inside the refinery hazardous area. Speed control via an Ex-rated VFD saves up to 30 % of energy compared with damper throttling.
- — Power 200–1,500 kW, 0.4 or 6 kV
- — Ex de IIB T3 (standard class for heaters)
- — Vibration monitoring, PTC thermistors in the windings
- — Compatibility with Ex-rated VFD
- — IP55 with protection against coke dust
Motors for loading and tank-farm pumps
Tank farms and loading racks are Zone 1 or Zone 2 across the whole perimeter. Transfer pumps and loading pumps for rail and road tankers are equipped with Wolong YBX3 motors, 22–315 kW, in Ex de IIB T4 design. Equipment grounding for static-discharge dissipation and a certified packed gland or magnetic coupling instead of an ordinary mechanical seal are also required.
- — Ex de IIB T4, IP55 minimum
- — Grounding and grounding-continuity monitoring
- — Anti-condensation winding heaters (Russia)
- — Compatibility with magnetic coupling/dual mechanical seal
Industrial brakes in Ex design
Braking systems are less common in petrochemicals than in metallurgy, but the requirements are tougher: every electrohydraulic thruster and every limit switch in the brake assembly must be Ex-certified. At reactor blocks where catalyst-replacement cranes operate, and on inclined sulfur and coke conveyors, HUAWU and ZHONGHAI brakes with Ed-Ex series thrusters are used. For tank-farm portal cranes — JINGU and ZHONGHAI rail clamps and storm brakes with pneumatic or Ex-rated electric release.
Brakes for reactor-block cranes
Overhead cranes used for catalyst replacement in FCC, reforming and hydrocracking reactors work in Zone 2 (intermittent presence of explosive vapors). A two-brake scheme is used: service + emergency electrohydraulic disc brake HUAWU YPZ2 with an Ed-Ex IIB T4 thruster. Closing time on power loss is 0.2 s, with braking torque margin of 1.75–2.0 over the rated hoisting torque.
- — Ex de IIB T4 thruster (Ed-Ex series)
- — Dual brake set (service + emergency)
- — Response time ≤ 0.2 s
- — Ex e limit switches on brake levers
- — IP55, Rostechnadzor certification
Brakes for inclined sulfur and coke conveyors
Shoe and disc brakes with an Ex electrohydraulic thruster hold the conveyor on shutdown and prevent runaway under load. Surrounding atmosphere: sulfur dust, hydrocarbon and hydrogen vapors. ZHONGHAI YWZ Ex and HUAWU YPZ2-Ex series with Ed-Ex 50–301 thrusters are used.
- — Ed-Ex IIB T4 thruster, frame size 50–301
- — Shoes or discs with heat-resistant linings
- — Manual release via Ex-rated valve
- — IP65 minimum against sulfur dust
Disc brakes with Ex actuator for process winches
JINGU SBD disc brakes with Ex actuators are used on winches that service column trays and catalyst baskets. Operation is occasional, but the Ex-protection requirement applies for the entire time the equipment sits in the hazardous area.
- — Braking torque 5–80 kN·m
- — Hydraulic or Ex-rated electromechanical actuator
- — Spring-set (fail-safe) closing
- — Lining-wear monitoring via Ex limit switch
Storm brakes / rail clamps for tank-farm portal cranes
Portal and gantry cranes at open-air tank farms and marine product-terminal jetties use ZHONGHAI SB-Ex and JINGU CWZ-Ex rail clamps. They hold the crane on its rails in wind up to 35 m/s, triggered by an anemometer signal or on power loss. Especially important in coastal areas and locations exposed to strong gusts.
- — Holding capacity in wind up to 35 m/s
- — Ex IIB T4 design for electrical components
- — UPS backup power
- — Automatic triggering on anemometer signal
Couplings for process equipment
A coupling itself does not require Ex protection — it is a passive mechanical element. But in a drive train with an Ex motor the coupling must be compatible with Ex flanges and provide a non-sparking design in case of rubbing under shaft misalignment: non-sparking materials (bronze, treated aluminum alloys) or a guard made of a non-sparking metal are used. Sizing follows torque with a 1.5–2 service factor and the allowable shaft offset after equipment warm-up and thermal expansion of the piping.
Gear couplings for process gas compressors
Drum-type double-engagement gear couplings YONGJING GIICL and LONGXUAN WGZ transmit torque from 1–25 MW HV motors to syngas, hydrogen and ethylene compressors. The crowned tooth profile compensates angular misalignment up to 1.5° after thermal growth of the casings. The gear ring runs in thick grease with a 6-month service interval. The guard is made of non-sparking aluminum.
- — Torque 50–800 kN·m
- — Angular misalignment up to 1.5°, axial offset 5–15 mm
- — Guard made of non-sparking material (Al, bronze)
- — G6.3 balancing at circumferential speeds > 15 m/s
- — Conformity certificate for Zones 1/2
Flexible pin-bushing couplings for process pumps
LONGXUAN LX (LMC) and JIAOHUA YOXp series — pin couplings with elastic bushings driving 11–2,500 kW centrifugal pumps. They damp start-up shocks and absorb small shaft offsets after mounting on a concrete baseplate. On drives with a brake they are often combined with a brake drum (drum-coupling).
- — Torque 0.2–125 kN·m
- — Radial offset compensation 0.2–1.0 mm
- — NBR/HNBR elastic bushings (resistant to petroleum products)
- — Brake-drum integration option
- — Elastic-element life no less than 30,000 h
Fluid couplings for process pumps with heavy start-up
JIAOHUA YOX/COX fluid couplings drive reciprocating and slurry pumps with heavy start-up (catalyst injection, heavy-residue circulation). Nominal slip of 2–4 % protects the motor from overload on jam. A fusible plug set at 145–160 °C dumps oil externally on overheat. The housing is grounded for static discharge.
- — Nominal slip 2–4 %
- — Fusible plug 145–160 °C
- — Oil fill 70–85 % of internal volume
- — Housing grounding (static dissipation)
- — Thermal margin for 4–6 starts per hour
Gear couplings on heater ID fans and blowers
Between the 200–1,500 kW motor and the ID-fan shaft sits a YONGJING gear or disc-pack coupling. The challenge is the fan-casing temperature up to +250 °C, so the coupling is fitted with a thermal-isolation spacer and an extended intermediate shaft to draw heat away from the motor bearings. On large ID fans, double-pack disc couplings (DBSE — double bearing space element) are used.
- — Torque 5–125 kN·m
- — Intermediate shaft 500–1,500 mm long (heat sink)
- — G6.3 balancing before installation
- — Tolerance for ID-fan casing displacement under thermal growth
Applications gallery
Our solutions for this industry
SDS portfolio brands that cover typical applications in this industry.
- WOLONGKey brand for petrochemical motors — explosion-proof YBX3 (low-voltage 0.75–315 kW) and YBKK (high-voltage up to 6 MW) series, Ex d/Ex de IIB or IIC, T3/T4, IIB+H2 marking for hydrogen units
- BONENGK, F, HB gearmotors in Ex de IIB T4 design for reactor agitators, discharge screws, catalyst conveyors and reagent dosing systems
- HUALIGeneral-purpose motors for non-hazardous auxiliary areas (enclosed e-rooms, control rooms), plus Ex series for Zone 2
- HUAWUYPZ2/YWZ5 brakes and Ed-Ex electrohydraulic thrusters for reactor-block overhead cranes and inclined conveyors
- ZHONGHAIYWZ-Ex explosion-proof brakes and SB-Ex rail clamps for portal cranes at tank farms and marine terminals
- JINGUSBD disc brakes with Ex actuators and CWZ-Ex rail clamps for process winches and outdoor-area cranes
- YONGJINGGIICL drum gear couplings and disc-pack couplings for 1–25 MW process compressors, heat-resistant intermediate shafts for heater ID fans
- LONGXUANFlexible LX pin couplings with NBR/HNBR elastomers (resistant to petroleum products) and WGZ gear couplings for process pumps and compressors
- JIAOHUAYOX/COX fluid couplings for heavy-start pumps (catalyst injection, heavy-residue circulation), fusible plugs at 145–160 °C
- DONLYHydraulic power units for column regulators, metering pumps and reagent dosing systems with Ex-rated electrical components
- HUADEHydraulic valves and directional control valves, including Ex-rated, for actuating large-diameter valves
- INIHydraulic components for presses and shaft lines of auxiliary units, pumps and motors with Ex-rated drives
- DEODFL/DFLA oil coolers for reactor-agitator gearboxes and process-compressor lube-oil systems
- INVTEx-rated variable-frequency drives for ID fans, heater blowers and variable-capacity pumps
Image credits: MBH (CC BY 4.0) · Wikimedia Commons (Public domain) · Quintin Soloviev (CC BY 4.0) · Carlos Valenzuela (CC BY-SA 4.0) · DWI (CC BY-SA 3.0)