Bonfiglioli 3/H series heavy-duty gearbox selection and verification guide



Bonfiglioli 3/H series heavy-duty modular reducer: full analysis of selection process and engineering verification

In heavy industries such as mining, building materials, metallurgy, power, and ports, large conveyors, bucket elevators, ball mills, and mixers have high requirements for the reliability, power density, and adaptability of reducers. Bonfiglioli's 3/H series heavy-duty modular gearbox innovatively combines planetary gear stages (300 series) with spiral bevel gear stages (HDO series) to achieve a rated output torque of up to 1200 kNm, providing an ideal solution for applications with high power density and medium to low speed output. This article will analyze in detail the technical architecture, selection process, thermal power verification, and configuration methods of key components of the 3/H series reducer from the perspective of engineering practice.

Technical architecture and core design features

The 3/H series reducer is the culmination of Bonfiglioli's modular design concept. It combines the high torque density advantage of planetary gear stages with the power splitting advantage of spiral bevel gear stages, forming a unique "planetary+spiral bevel gear" combined transmission structure.

1. Gears and materials

All bevel gears and cylindrical gears are made of alloy steel, which has undergone carburizing, quenching, grinding, and tooth profile modification. This can not only significantly reduce operating noise and optimize smooth transmission of high-speed stages, but also maximize the transferable torque of the final drive.

The input shaft is also treated with carburizing, quenching, and grinding to ensure wear resistance and fatigue strength at high speeds.

2. Modular size

This series offers 10 machine base sizes (11, 13, 15, 16, 17, 18, 19, 21, 23, 25), with rated torque values evenly distributed across the entire speed ratio range, ensuring that engineers can find the best cost-effective solution for each specific application.

3. Compact structure

The compact design of the 3/H series not only saves installation space, but also improves the rigidity of the system. There are multiple optional options for its output shaft configuration, including a hollow shaft (FP) with a shrink disc and a spline hollow shaft (FZP) with an axial locking device, to accommodate different installation methods.

Key requirements for installation and lubrication

1. Installation rules

The reducer must be firmly fixed on the foundation structure to prevent vibration. The manual emphasizes that the machined mating surfaces and the outer edge of the oil seal must be protected before painting to prevent the paint from coming into contact with the rubber seal and causing it to harden and fail.

Fit tolerance: The internal holes of the components installed on the output shaft of the reducer should be machined to ISO H7 tolerance to avoid damage to the gears or bearings during assembly due to over tight fit.

2. Lubrication system

The internal gears of the 3/H series adopt oil bath splash lubrication (oil immersion splash). For operating conditions where the output speed is below 1 rpm or the input speed is above 1800 rpm, it is necessary to consult Bonfiglioli's technical service department.

Key limitation: In the installation position of AB6 (vertical installation, output axis upward), the upper bearing needs to be lubricated through a forced lubrication system with an electric pump (MOP option). This is not optional, but a mandatory requirement.

Factory state: The reducer does not contain lubricating oil when it leaves the factory. Before the user runs it for the first time, they must add the correct amount of oil according to the installation position and the selected oil according to the manual.

Selection process and service coefficient

1. Determine the speed ratio and power demand

Determine the total speed ratio based on the motor speed (n ₁) and the required output speed (n ₂): i=n ₁/n ₂. Then calculate the power demand of the input shaft of the gearbox:

Pr one=Mr two×ntwo nine thousand five hundred and fifty×η[kW]

P r1= 9550×ηM r2×n two [kW]

among which

Mr two

M r2

It is the output torque required by the load,

η is the efficiency of the gearbox (usually requires consulting the manual or consulting the manufacturer).

2. Selection of service coefficient (f ₛ)

The service factor is a numerical value used to quantify the severity of application conditions, taking into account the uniformity of load, start-up frequency, and total operating time.

Load types: divided into three categories: uniform load, moderate impact load, and strong impact load (determined by acceleration coefficient K).

Table lookup method: Select the minimum required f ₛ value from the service coefficient table provided in the manual based on the number of starts per hour (Z) and the number of running hours per day (or total running time).

Selection formula: The rated input power (Pn ₁) of the selected reducer must meet the requirement of Pn ₁ ≥ P_ {r1} × f ₛ.

3. Motor adaptation and speed ratio matching

Confirm the compatibility between the selected motor power and the flange size of the gearbox by referring to the motor adaptation table (IEC or NEMA) in the manual. Attention: If the peak power of the motor far exceeds the rated power of the gearbox, a torque limiter must be installed to prevent overload damage to the gearbox.

Thermal power verification (key verification step)

After the mechanical selection is completed, thermal power verification must be carried out. Thermal power (P_TB/P_TFAN) refers to the maximum mechanical power that can be safely transmitted by a gearbox during continuous operation, with the internal temperature not exceeding the damage limit (usually 90 ° C~100 ° C oil temperature). If the input power loss exceeds the natural heat dissipation capacity of the gearbox, the oil temperature will continue to rise, leading to oil degradation and bearing failure.

1. Basic thermal power (P_TB)

The P_TB value in the manual is calculated based on the following standard operating conditions:

Input speed 1800/1500 rpm

Environmental temperature 20/40 ° C

Horizontal installation position (AB3)

Installed in open areas with good air circulation

Use ISO VG 220 mineral oil

If the actual working conditions do not meet the standards, corrections or auxiliary cooling measures need to be taken.

2. Determination of heat capacity

Must satisfy: P_TB ≥ P_ {r1}. If P_TB<P_ {r1}, an auxiliary cooling device needs to be selected:

FAN (forced ventilation): Install a cooling fan on the input shaft, but the efficiency decreases significantly when the input speed is below 900 rpm.

SR (Cooling Coil): Install water-cooled coils in the gearbox oil tank (only for AB3 installation position), using external cooling water to remove heat.

MCRW/MCRA (Independent Cooling Unit): They are water oil coolers and air oil coolers, respectively, suitable for high ambient temperatures or extreme power loss situations. The heat exchange power value can be found in the relevant chapters of the manual.

MOP (forced lubrication pump set): AB6 installation position comes standard, with lubricating oil circulated through an electric pump and filtered to ensure effective lubrication and cooling of the upper bearings.

3. Environmental temperature correction

When the ambient temperature exceeds 40 ° C or falls below 0 ° C, there will be a significant change in thermal power. In high temperature environments, it is necessary to reduce input power or enhance cooling; In low-temperature environments, it should be considered to add an oil heater (HE option) to ensure that the oil temperature reaches the viscosity conditions required for start-up.

Selection and configuration of backstop

For applications that require prevention of load reversal, such as inclined belt conveyors and bucket elevators, a check valve is a crucial safety device.

1. Function of backstop

It ensures that the gearbox can only rotate in one direction, preventing motor reversal and equipment runaway accidents caused by gravity or load reverse torque.

2. Torque limit conditions

When selecting, the following conditions must be strictly followed to ensure that the input shaft torque does not exceed the ultimate bearing capacity of the backstop:

M two η×i≤M one max η×i

M two ≤M 1max

among which

M one max M 1max

The maximum allowable input torque of the backstop corresponding to the machine base number/speed ratio given in the manual. This is a mandatory condition and cannot be exceeded.

3. Rotation direction and installation

When placing an order, it is necessary to specify the free rotation direction of the output shaft (clockwise CW or counterclockwise CCW).

The manual provides detailed installation dimensions and the minimum overspeed speed (n1min). In steady-state operation, it is recommended to maintain the input speed higher than the n1min listed in the table to ensure the normal operation of the centrifugal separation mechanism inside the backstop and avoid wear caused by continuous contact between the rollers and the inclined surface.

Radial/axial load verification

The external transmission components (sprockets, pulleys, gears, etc.) on the output shaft will generate radial force (R_c) and axial force (A_n).

1. Radial load

The manual provides the maximum allowable radial load (R_max) for each machine base number and speed ratio, as well as the displacement coefficient K ₁ at different load application points (distance x from the shaft shoulder). The actual radial load R_c must meet:

R_c ≤ R_n × K₁

Among them, Rn is the allowable radial force of the base, and K ₁ is the displacement correction coefficient of the load application point (the farther the load is from the bearing, the smaller the K ₁ value, and the smaller the allowable radial force).

2. Axial load (thrust)

The allowable axial thrust is: A_n ≤ 0.2 × Rn ₁. If the thrust exceeds this value or axial force dominates, it is necessary to contact Bonfiglioli's technical service department for detailed analysis.

Suggestions for configuring key optional components

1. Sealing system (TK/VS)

TK (Taconite Seal): Used in environments containing abrasive dust, it combines triple protection of oil seal, labyrinth seal, and grease chamber. Regularly add lubricating grease.

VS (Fluororubber Oil Seal): Standard fluororubber seal, resistant to high temperature and chemical corrosion.

2. Sensor (TG/PT100)

Bimetallic thermostat (TG): When the oil temperature exceeds 90 ° C ± 5 ° C, it outputs a switch signal and can be connected to an alarm or shutdown circuit.

PT100 thermistor: It outputs continuous analog temperature signals and can be connected to PLC to achieve precise oil temperature monitoring and closed-loop heating control.

3. Dry salt breath filter (DBF)

The optional DBF filter can effectively prevent external moisture and fine dust from entering the interior of the gearbox, avoiding oil emulsification and component wear. The discolored gel contained in the filter can indicate the moisture absorption state. The built-in one-way valve is opened at 0.017 bar to prevent positive pressure in the box.

4. Heater (HE)

When the ambient temperature is too low, high viscosity of the oil can cause difficulty in starting. The HE option includes an electric heater and temperature controller installed in the gearbox oil tank, which preheat the oil temperature to a usable range (usually above 25 ° C) before starting to ensure the normal operation of the lubrication system.