Bonfiglioli VF-W Explosion proof Worm Gear Reducer: ATEX Selection and Installation Complete Guide

Bonfiglioli VF-W Explosion proof Worm Gear Reducer: ATEX Selection and Installation Complete Guide

In industrial fields such as chemical, petroleum, natural gas, and dust treatment, flammable gases, vapors, or dust are inevitably present in the production environment. In these locations classified as potentially explosive hazardous areas, any conventional electrical or mechanical equipment may become a source of ignition, causing catastrophic consequences. Therefore, selecting explosion-proof equipment that complies with the EU ATEX Directive 2014/34/EU is not only a mandatory requirement of the regulations, but also the cornerstone of safe production.

As a global leader in power transmission and control solutions, Bonfiglioli's VF-W series worm gear reducers are renowned in many industrial fields for their compact design, efficient transmission performance, and excellent reliability. When this series of products is combined with ATEX explosion-proof technology, the Bonfiglioli VF-W ATEX series explosion-proof worm gear reducer is born - providing an ideal safe transmission solution for applications in hazardous areas.

Understand ATEX directive and VF-W series explosion-proof rating

Before choosing an explosion-proof gearbox, it is necessary to first understand the classification of explosive environments it is suitable for. According to the ATEX directive, hazardous areas are divided into different "zones" based on the frequency and duration of explosive environments.

Gas environment (G): Zone 0 (persistent), Zone 1 (may occur during normal operation), Zone 2 (unlikely to occur, or only exists briefly).

Dust environment (D): Zone 20 (persistent), Zone 21 (may occur during normal operation), Zone 22 (unlikely to occur, or only exists briefly).

The Bonfiglioli VF-W series ATEX gearbox is mainly designed for Zone 1, 21, 2, and 22 areas, covering the vast majority of industrial application scenarios. The product category and protection level are clearly indicated on the equipment nameplate, for example:

2G/3G class (gas): suitable for Zone 1 and Zone 2. The provided temperature levels include T3 (maximum surface temperature of 200 ° C) and T4 (maximum surface temperature of 135 ° C). T4 level represents higher safety and allows equipment to be used in more hazardous gas environments.

2D/3D category (dust): suitable for Zone 21 and Zone 22. The surface temperature level can be selected as ≤ 130 ° C or ≤ 160 ° C, depending on the minimum ignition temperature of the dust on site.

Note: Bonfiglioli explicitly states that its products are not suitable for underground coal mines (Group I) and Category 1 (Zone 0/Zone 20) areas in Group II categories. This is the primary boundary condition when selecting.

Core selection process and parameter calculation for VF-W ATEX series

The correct selection is a prerequisite for ensuring the longevity and safe operation of equipment. The selection process is not simply about matching power and speed, but a system engineering that comprehensively considers load characteristics, working conditions, and environmental factors.

Step 1: Determine the application parameters and service coefficient (fs)

Firstly, it is necessary to clarify the required output torque (Mr2), output speed (n2), daily working hours, and number of starts per hour (Z) for the application. Then, the load type is determined by calculating the acceleration coefficient (K) of the load.

Definition of K coefficient: K=Jc/Jm, where Jc is the moment of inertia of the driven load converted to the motor shaft, and Jm is the moment of inertia of the motor.

K1 (Uniform Load): For example, a conveyor belt with a constant load.

K2 (medium impact load): such as mixers, small cranes.

K3 (heavy impact load): such as crushers and large elevators.

Retrieve the service factor (fs) from the chart provided in the product catalog based on the K value and the number of startups per hour.

Step 2: Calculate the selection torque (Mc2)

This is the most crucial step in selection, especially for worm gear reducers, whose efficiency is greatly affected by speed ratio and temperature.

Calculate application demand power (Pr1):

Pr1 = (Mr2 * n2) / (9550 * ηd)

Where η d is the dynamic efficiency. It is necessary to estimate the efficiency curve from the catalog based on the speed ratio (i).

Determine the calculated torque (Mc2):

For worm gear reducers (VF/W series), the formula for calculating torque is:

Mc2 = Mr2 * fs * ftp

FTP is the environmental temperature adjustment coefficient.

When the ambient temperature is ≤ 30 ° C, ftp = 1.0。

When the ambient temperature is 40 ° C, ftp=1.06 (for K2 load) or 1.17 (for K3 load).

Select gearbox model:

In the technical parameter table, find the minimum machine base size that can meet the output speed (n2) requirements and has a rated torque (Mn2) greater than or equal to the calculated torque (Mc2). Meanwhile, it is necessary to ensure that the rated input power (Pn1) meets the application requirements.

Installation specifications: Details determine explosion-proof performance

The installation of explosion-proof equipment has more stringent requirements than ordinary equipment. Any negligence in installation may result in the loss of explosion-proof function of the equipment.

Installation Position:

The VF-W series reducer supports multiple installation methods (B3, B6, B7, B8, V5, V6). Installation must be strictly carried out in accordance with the installation position specified on the order and nameplate. Any deviation must be approved in advance by Bonfiglioli's technical department. Changing the installation orientation without authorization can affect the distribution and cooling effect of lubricating oil, leading to surface temperature exceeding the standard.

Input speed limit:

For ATEX designated equipment, the motor speed must not exceed 1500 min ⁻¹. If a frequency converter is used for driving, it must be ensured that the parameter settings of the frequency converter do not cause the motor to exceed this limit speed, and the motor itself must be suitable for frequency conversion speed regulation conditions.

Shaft seal and lubrication:

Shaft seal: The standard configuration of this series of ATEX reducers is a FKM material oil seal, which has better high temperature resistance and chemical corrosion resistance.

Lubricating oil: An appropriate amount of long-lasting synthetic lubricating oil (such as SHELL OMALA S4 WE 320) has been added according to the installation position at the factory. Sealed plugs are used during transportation, and users must replace them with the Vented Plug that comes with the shipment before use to prevent internal pressure buildup during operation.

Surface temperature management:

The surface temperature of the reducer is a key indicator for explosion-proof safety. The temperature rating indicated on the nameplate (such as T4, 130 ° C) is the highest surface temperature that the equipment can guarantee in the most unfavorable installation position within the ambient temperature range of -20 ° C to+40 ° C. It is necessary to ensure that this temperature is lower than the ignition temperature of combustible gases or dust on site.

Mechanical load verification: Ensure the reliability of the shaft

In addition to torque and heat capacity, it is also necessary to verify the external loads borne by the input and output shafts of the gearbox. These loads mainly include radial and axial forces.

Calculation and verification of radial load (OHL):

The radial force (Rc) generated by external transmission components such as pulleys, sprockets, or gears must be less than or equal to the allowable radial load (Rn) given in the sample.

Calculation formula: Rc [N]=(2000 * M * KR)/d

M: Torque (Nm)

d: Pitch diameter of transmission components (mm)

KR: Transmission coefficient (gear takes 1; sprocket takes 1.25; pulley takes 1.5-2.0, depending on belt tension).

Verification method: It is necessary to compare the calculated actual load with the allowable radial load (Rn1 or Rn2) under the corresponding seat number and speed ratio in the product manual. At the same time, the distance (X) between the load application point and the axis shoulder will also affect the allowable load value, which can be corrected through the "load position coefficient" in the directory.

Axial load verification:

The axial force (An) acting on the shaft is also limited. Generally speaking, when acting simultaneously with the rated radial load, the allowable axial force is 20% of the allowable radial force (An=Rn * 0.2). If there is no radial load on the shaft, the allowable axial force can reach 50% of the rated radial load. For applications where axial force is the main force, it is necessary to consult the manufacturer for specialized analysis.

Special circumstances and key precautions

To ensure long-term safe operation, the following special points must be highly valued:

Peak torque: The system may generate instantaneous peak torque (such as at the moment of start-up). The mechanical components of the gearbox can withstand 200% of the rated torque (Mn2). If the peak torque in the application exceeds this value, a torque limiter must be installed in the transmission system to protect the gearbox from damage.

Motor compatibility: When the gearbox needs to be matched with "non-standard motors" other than IEC standard motors, Bonfiglioli can provide a hybrid interface (i.e. non IEC standard input shaft and flange combination). When selecting, the specific dimensions of the motor interface must be clearly defined.

Lubrication precautions for special model W110: For W110 machine base size reducers, if the installation method is V5 or V6, or if the motor flange type is B14, the reducer will not contain lubricating oil when it leaves the factory. Users must add the specified brand and dosage of lubricating oil according to the manual requirements before debugging.

Oil level check: Before the first operation, the oil level must be checked through the yellow filler plug. Use the dipstick provided with the shipment to confirm the correct oil level.