Bonfiglioli VF-W series ATEX explosion-proof reducer selection guide

2. Calculate the required input power (P ᵣ₁)

Based on the required output torque (M ᵣ₂) and output speed (n ₂) for the application, combined with the dynamic efficiency of the worm gear reducer (η d_d, please refer to the efficiency curve), calculate the required motor power:

Pr one=Mr two×n two

nine thousand five hundred and fifty×ηd[kW]

P r1= 9550×η d M r2×n two [kW]

3. Choose the specifications of the gearbox

For models with IEC motor flanges: refer to the Rating Charts to find the machine base number and speed ratio that satisfies the rated input power Pn ₁ ≥ P ᵣ₁× f ₛ at the required output speed n ₂. Then select the actual motor power P ₁ ≥ P ᵣ₁, and finally verify the safety factor S=Pn ₁/P ₁ ≥ f ₛ.

For solid shaft input models: Calculate and calculate the torque M c ₂=M ᵣ₂ × f ₛ× f_tp (f_tp is the temperature correction factor, and the worm gear is taken as 1.0~1.17). Select a gearbox with a rated output torque Mn ₂ ≥ M ₂ c ₂.

4. Post selection verification (key steps)

After the selection is completed, the following three checks must be carried out:

Peak torque: The gearbox should be able to withstand an instantaneous peak of at least 200% of the rated torque. If there is frequent impact in the application, it is recommended to install a torque limiter.

Radial Load: The radial force exerted by external transmission components (sprockets, pulleys, gears) on the input/output shaft must be less than the allowable value (Rn ₁/Rn ₂) specified in the manual. When calculating, it is necessary to consider the distance between the load application point and the axle shoulder (load position coefficient, see manual). The formula for calculating the actual radial force Rc is: Rc=(2000 × M × Kr)/d, where d is the pitch diameter of the transmission component and Kr is the transmission type coefficient (sprocket takes 1.0~1.25, gear takes 1.25~1.5).

Thrust Load: The allowable axial thrust is usually 20% of the corresponding radial allowable value. If there is no radial load, the maximum allowable axial thrust can reach 50% of the radial allowable value. If exceeding this limit, please contact the manufacturer.

Key points of lubrication management

Worm gear reducers are extremely sensitive to lubrication, especially in ATEX environments, where the correct oil level can effectively control temperature rise.

When the VF-W series leaves the factory, synthetic oil (Shell Omala S4 WE 320) is added according to the installation position ordered, and it is equipped with a closed transport plug. Before trial operation, the user must replace it with the breathable plug that comes with the box to prevent internal pressure accumulation.

The amount of lubricating oil varies depending on the seat number and installation position. For example, the B3 installation position of VF 30 requires 0.045 liters, while the B3 position of W110 (high speed ratio) requires 2.8 liters. The user manual provides a detailed fuel quantity table, please make sure to fill according to the table.

Special attention: When W110 is in V5/V6 position and equipped with B14 flange, due to structural limitations, there is no lubricating oil available at the factory. Users must fill it to the specified oil level by themselves.

Common errors and maintenance tips

Unauthorized change of installation position: It may alter the circulation of the oil circuit and the position of the vent hole, which may result in poor lubrication or oil leakage, directly violating ATEX compliance.

Neglecting the replacement of breathable plugs: If the transport plug does not exhaust, the increase in internal pressure during operation will damage the oil seal, causing lubricant leakage and increasing the risk of fire.

Overspeed operation: Even short-term overspeed may cause the worm bearing to overheat, with surface temperature exceeding the T-level limit, becoming a potential ignition source.

Radial load exceeding limit: Without considering the offset of the load center (such as the pulley being too convex), the actual radial force far exceeds the manual value, which can lead to premature bearing failure, shaft fracture, and even spark ignition.

Selection Examples and Decision Suggestions

Assuming a certain chemical mixer needs to output a speed of 20 min ⁻¹, an output torque of 300 Nm, run for 8 hours a day, start 10 times per hour, and a load inertia ratio K ≈ 2 (moderate impact). According to the table, f ₛ ≈ 1.2. Calculate P ᵣ₁=(300 × 20)/(9550 × 0.55) ≈ 1.14 kW (efficiency estimated at 0.55). Then Pn ₁ needs to be ≥ 1.14 × 1.2=1.37 kW. Check that the W 63 series has Pn ₁ of 1.1 kW (insufficient) when n ₂=20, and the W 75 series has Pn ₁ of 2.2 kW (satisfied) when n ₂=20. The final selection is W 75 with a 1.5 kW motor, with a safety factor S=2.2/1.5=1.47>1.2, which is qualified. Simultaneously verify the radial load: If a sprocket is selected with a pitch diameter of 100mm and a torque of 300Nm, then Rc=2000 × 300 × 1.25/100=7500N. The allowable radial load Rn ₂ (at n ₂=20) for the W 75 output shaft is 3050N, which is obviously insufficient. At this point, it is necessary to increase the diameter of the sprocket or switch to gear transmission, or choose a larger machine base size. Radial load is often the real bottleneck in selection, and engineers must be vigilant.