Leather and tanning factories present one of the most demanding industrial environments for an electric motor. Tanning drums and tumblers demand high torque at low speed; presses and squeezing machines produce shock loads; and almost the entire line is in constant contact with water, lime, chrome solutions and acidic chemicals. Under these conditions a standard motor quickly corrodes and suffers winding failure. In this guide we cover leather and tanning factory electric motors machine group by machine group, explaining which speed, torque, IP protection and frame material is correct at the drum, press and squeezing stations, and how to plan supply suited to harsh environments.

Drum and tumbler drive electric motors in a tanning factory

Conditions a Motor Faces on the Leather Tanning Line

Three core challenges set motor selection in a leather processing plant apart from an ordinary industrial application:

  • Constant moisture and water: Washing, soaking and tanning processes raise the environment to saturated humidity; water splashes directly onto the motor body.
  • Chemical attack: Chrome, lime, acid and salt solutions make both the air and the floor corrosive; standard casting and paint deteriorate quickly.
  • Low speed, high torque: Tanning drums turn heavy loads slowly but powerfully; sudden starts and stops create shock torque.

When these three conditions combine, the frame material, IP protection class, insulation class and torque characteristic must all be chosen correctly at the same time. We addressed the logic of motor selection in environments open to hygiene and washing in a similar framework in our food factory motors article; since the chemical load in a leather plant is heavier, the protection requirements move up a notch.

Tanning Drum and Tumbler Drive: Low Speed High Torque

The tanning drum is a large drum that rotates the heavy leather load together with the solution. In this application the motor runs not at high speed directly but at low output speed through a gearbox. Typical output speed is around 10-20 rpm, and to reach this speed the motor is always matched with a gearbox.

Motor + Gearbox Combination

In the drum drive, a 4-pole (1500 rpm) motor is combined with a high-reduction-ratio gearbox. At medium powers worm gear reducers are preferred, and at higher power and continuous heavy duty helical worm gear reducers. We explained step by step how the reduction ratio (for example 1/30, 1/50) determines output speed and torque in our monoblock geared motor selection article. If you want to evaluate the low-speed direct-drive alternative, our high-pole low-speed motor article is also a guide.

Starting Torque and Duty Type

When a full tanning drum stops, high starting torque is required to start again. Therefore the motor starting torque characteristic must match the application. You can examine torque class selection by load in our torque classes (Design N/H) article. Since drums do not run continuously but intermittently (load-empty-rotate), an S6-like duty profile rather than S1 is often involved; we clarified this difference in our duty type selection article.

Press, squeezing and wet-environment IP65 protected electric motors in a leather factory

Press, Squeezing and Vacuum Machines

After tanning, the leather passes through squeezing (sammying), press and vacuum drying machines. These machines produce shock and high-torque loads. Squeezing rollers and hydraulic units demand motors resistant to sudden load changes. When evaluating motor selection in hydraulic press units and heat management under continuous load, you can find our approach to heavy-duty applications in our rolling mill and foundry heavy-duty article.

At these stations B5 flanged or B35 foot-and-flange mounting types are common; for units directly coupled to the machine, choosing the correct mounting type is important, with details on our mounting types page.

Wet and Chemical Environment: IP Protection and Corrosion Resistance

The most critical motor selection parameter in a leather plant is the protection class. In areas exposed to constant water splash and chemical vapour, IP55 falls short; IP65 protection is recommended at these points. We explained the difference between IP55, IP65 and IP66 and where each is required in detail in our IP protection class article.

Frame Material and Surface Protection

In a corrosive environment, a cast iron frame is generally a more durable base than aluminium; when cataphoresis coating and epoxy paint are applied over it, its life is significantly extended. You can find surface protection and painting options against corrosion in our cataphoresis coating article, and the protection approach in salty and chemical environments in our salt environment protection article. The sealing of the terminal box is at least as important as the frame; for the correct cable gland and IP-protected box selection, see our terminal box and cable connection article.

Efficiency and Correct Supply

Since drums and presses run long hours in leather plants, efficient motor selection lowers energy cost. IE4 Super Premium motors are a strong choice for continuously running main drives, and IE3 motors a balanced one for auxiliary units with lower running hours. When extra protection is required in a corrosive environment, cast iron frames and special coating options can be offered in our high-efficiency electric motors range. Our chemical and detergent factory motor selection article, where we cover motor selection in chemical-intensive reactor and mixer applications more broadly, is also complementary for leather plants.

As HEM Motor, we supply leather and tanning plants with motors between 0.55 kW and 355 kW, in IE3 and IE4 efficiency classes, with 100% copper windings, F-class insulation and, where required, IP65 protection, together with gearbox matching.

Beamhouse, Liming and Fleshing Machines

Leather processing is not limited to tanning drums; after raw hide enters the plant, it passes through pre-treatments such as soaking, liming, fleshing and scraping. All these stations operate in an intense water and alkaline chemical environment. Fleshing and scraping machines are rotary-blade units that remove the flesh and fat layer from the hide; these drives run with both continuous load and water splash. Here, sealing on the shaft side is as important as the motor protection class, because if water enters through the shaft seal, the bearing and winding are damaged quickly.

We addressed how shaft-side sealing and the oil seal should be protected in a wet, oily environment in our oil seal and sealing article. Since the mixers and pumps in the liming section contact high-pH solution, frame and terminal box protection must be raised a notch. The motor grounding and electrical safety are also critical at these stations; you can find correct grounding for motors operating on wet floors in our grounding and electrical safety article.

The pumps on the water line run continuously for solution transfer and circulation. These pump motors, exposed to chemical vapour and moisture, must be selected protected and sized at the correct power according to flow and pressure. We explained the flow-pressure matching of pump motors in our centrifugal pump motor selection article. For pumps in corrosive environments, our pump motor in salty and corrosive environments article shows our approach.

Drying, Vacuum and Finishing Line Motors

Tanned leather passes through vacuum drying, hang drying, stretching and finishing (surface treatment) lines. These stations are sections where the moisture load is relatively reduced, but fine dust, paint and solvent vapour appear. If solvent-based paint is used in the spray cabins of the finishing line, the environment may fall into an explosion zone classification; in this case the fan and extraction motors must be exproof. We addressed motor selection in explosive environments and what is required in which zone in our exproof (ATEX) motor article.

Since drying fans and extraction systems run continuously, both efficiency and protection are evaluated together. You can find the selection of these fan motors at the correct power and speed in our centrifugal and axial fan motor article. In stretching and hanging systems, low-speed, controlled drives are used; here the motor is generally matched with a gearbox. To calculate the output speed and torque correctly, our worm gear reducers and helical worm gear reducers range can be evaluated.

Across the whole leather plant, the annual running hours of the motors are high; this makes the efficiency class decision economically important. An efficient class on continuously running main drives pays for itself quickly by lowering energy cost. We quantified the effect of an efficient motor on total cost of ownership in our TCO article.

Efficiency Class, Press Units and Hydraulic Drives

The press and hydraulic units of a leather plant operate with both high torque and sudden load changes. Squeezing presses and hydraulic units require the motor to produce stable torque at start and under load; therefore torque class selection directly affects press performance. In hydraulic units the motor usually drives the pump and operates under variable load according to system pressure. In this application the motor heat balance under continuous pressure is important; we addressed heat management under continuous load in our cooling under continuous full load article. For press and hydraulic motors, the efficiency class decision is made according to running hours, with IE4 Super Premium motors on continuous units and IE3 motors on intermittent presses.

Frequently Asked Questions

What speed and torque are required for a tanning drum?

Tanning drums run at low output speed (typically 10-20 rpm) and high torque. Therefore a 4-pole (1500 rpm) motor is matched with a high-reduction-ratio worm gear or helical worm gear reducer. Since restarting a full drum requires high starting torque, the motor torque class and duty type must be selected according to the application. If you share the drum diameter, leather load and tipping load with us, we will recommend a suitable motor-gearbox combination.

Is an IP55 motor sufficient in a leather factory?

IP55 may be sufficient in dry storage and office areas, but tanning, washing and press areas have constant water splash and chemical vapour. IP65 protection is recommended in these areas; IP66 can be considered at some points. Alongside the protection class, protecting the frame with cataphoresis and epoxy paint and sealing the terminal box are decisive for long life.

Should cast iron or aluminium frame be preferred in a corrosive environment?

In the chemical-intensive environment of a leather plant, a cast iron frame, together with cataphoresis coating and epoxy paint applied over it, is generally a more durable solution. An aluminium frame is light but, without surface protection, is affected faster in acidic and chrome environments. The correct choice is made according to the chemical and moisture load at the motor location; protected cast iron is recommended in critical areas.

Get a Quote

If you want to supply drum, press and squeezing motors for your leather or tanning factory with a protection class suited to wet and chemical environments, contact us with your machine and environment information. Let us offer motor-gearbox solutions matched with the correct speed, torque, IP protection and corrosion resistance at a suitable lead time and price. Call now on +90 (532) 345 49 86 or send your quote request through our contact page.