Bonfiglioli C Series ATEX Explosion proof Reducer Selection

Core logic of selection calculation: complete derivation from required torque to rated power

The selection calculation of C Series explosion-proof reducers is consistent with standard industrial reducers, but the selection of service factor needs to be particularly cautious, as explosion-proof applications often involve critical safety functions such as emergency ventilation, fire pumps, etc.

1. Determine the service coefficient [fs]

The manual provides a graphical method for selecting service coefficients on page 11. The service coefficient depends on three factors:

Daily running time (hours/day)

Number of starts per hour (Z)

Mass acceleration coefficient (K):

K=Jc/Jm, i.e. the ratio of load inertia to motor inertia

The three curves K1 (uniform load), K2 (moderate impact load), and K3 (heavy impact load) correspond to different load characteristics. The manual specifically states that for applications involving lifting, if the failure of the gearbox may pose a risk of injury to personnel, the technical department should be contacted directly - this means that such applications require far greater safety margins than usual.

2. Selection of IEC motor flange with reducer (most commonly used configuration)

When the C Series is equipped with IEC standard motor flanges (IM B5), the selection steps are as follows:

Step 1: Calculate the required power on the motor side

Pr one

Pr one=Mr two⋅n two nine thousand five hundred and fifty⋅ηd[kW]

Pr one= 9550⋅η d Mr two⋅n two[kW]

among which Mr two

To achieve the required output torque (Nm) for the application,n two

To output the rotational speed (min ⁻¹),ηd

To improve the dynamic efficiency of the gearbox (manual recommendations: 0.98 for level 1 transmission, 0.96 for level 2, 0.93 for level 3, and 0.90 for level 4).

Step 2: Select a gearbox from the rated power meter (pages 19-26 of the manual) that satisfies the following equation:

Pn one≥Prone×fs among which

Pn one Rated power of the gearbox (kW), corresponding service factor

fs=one

f s=1.

Step 3: Select the rated power of the motor

Pone≥Pr one And finally verify:

S=Pnone

P one≥fs

In the formula

S is the safety factor, which must be greater than or equal to the service factor required for the application.

Special constraint: If C122, C222, or C322 is selected and the speed ratio is i>forty

i>40， And the number of starts per hour

Z> thirty

Z>30， Then the service coefficient needs to be multiplied by a correction factor of 1.2 before verification.

3. Selection of solid input shaft reducer (power source not directly connected to motor flange)

For situations where a solid input shaft is used, the calculated torque (Mc ₂) needs to be calculated:

Mc two=Mr two×fs×ftp  

among which

ftp Correction factor for ambient temperature (page 10 of the manual):

When the ambient temperature is ≤ 30 ℃,

ftp=one

f tp=1.0

When the ambient temperature is 40 ℃,

ftp=one point zero six

f tp=1.06 (uniform load) or

one point zero four

1.04 (heavy impact load)

Then select from the rated torque table

Mntwo≥Mc two

The gearbox.

Key post selection checks after selection

After completing the preliminary selection, page 10 of the manual requires three mandatory verifications:

1. Instantaneous peak torque verification

The instantaneous peak torque that the reducer can withstand is approximately the rated torque Mn two 200% of it. If the peak load of the application exceeds this limit (such as the impact when the crusher is stuck), a torque limiter must be installed to protect the gearbox.

2. Radial Load (OHL) Verification

The radial force generated by external transmission components (such as sprockets, gears, and synchronous pulleys) on the shaft must be less than or equal to the allowable radial bearing capacity of the gearbox (pages 17-18 of the manual). The calculation formula is:

Rc=two thousand×M×Ktd[N] among which

M is the transmitted torque (Nm),

d D is the pitch diameter of the transmission component (mm),

Kt The transmission type coefficient is 1.25 for sprocket/gear and 1.5-2.0 for belt transmission.

Rc Must be less than the rated value in the manual table

Rn one(Input shaft) or Rn two(Output shaft).

Important note: On page 18 of the manual, it is stated that when the load application point is not at the axis centerline but at an eccentric position, it needs to be multiplied by a position coefficient (see table for values a, b, and c). For example, the C 22 2 model has output shaft load position coefficients of a=253, b=285, and c=50.

3. Axial Load Verification

Allowable axial thrust An

An is the coaxial radial load Rn 20% of Rn (page 18 of the manual). If under pure axial force conditions without radial load, the allowable value can be increased to Rn 50% of Rn. If the axial force exceeds this limit, it is necessary to contact Bonfiglioli's technical department for a special calculation of bearing life.

Strict restrictions on ATEX explosion-proof applications

The mandatory constraints for ATEX certified gearboxes during operation are specifically listed on page 10 of the manual, and any deviation will result in certification failure: