Lubricants

Here you can find useful tips on lubricants.

  • Industrial gear oils for Stiebel gearbox requirements
  • Oil filling
  • Oil change
  • Miscibility of lubricants

Industrial Gear Oils for Stiebel Gearboxes

Requirements:

Industrial gearbox oils have a number of tasks:

  • Separation of paired surfaces (e.g., toothed wheels, rolling bearings) by forming a lubrication film.
  • Avoidance of wear
  • Reduction of friction
  • Improve performance
  • Removal of contamination and wear particles to the filter
  • Removal of heat
  • Reduction of vibrations and noises
  • Corrosion protection
  • Long product life /High aging resistance
  • High temperature application range

The lubricating oils have to meet or exceed the minimum requirements according to DIN 51517 part 3 or ISO / DP 6743-6. Important features are:

  • FZG damage force level of at least 12

  • Viscosity-index of at least 95

  • Addition of EP-additives (oil additives)

  • for improvement of corrosion protection, aging resistance and capacitance- for the reduction of friction and wear in the mixed-friction area

The ISO viscosity classification corresponds to DIN 51519 or ISO 3448. The lubricant manufacturers recommend the products listed in the gear oil table, as mentioned in our operating manuals. The lubricant manufacturer is responsible for the quality and the technical suitability of his products. In cases of using of products, which are not listed in the oil table, consultation with Stiebel is required. Gearboxes of the P2000, P3000 and B2000 series can also be operated with SAE 90 or SAE 85W-90 SAE J 306 gearbox oil.

These oils have to meet the following criteria: API GL-4 or API GL-5, MIL-L-2105 D; EP-Additivation.

Oil Filling

Depending on the model series Stiebel gearboxes are delivered with or without oil filling. In any cases, it must be ensured that the lubricant is filled in the prescribed quantity before start-up. Quantity and quality of oil can be taken from the type label or the operating manuals. The oil quantity mentioned there could serve as a guideline.

Decisive is the marking of the oil dipstick, oil level glass or the overflow plug, as long as these are part of the equipment.

In cases of connections of e.g. pipes, hoses, pumps the oil level must be checked again after a certain switch-on time (e.g. 1h regarding to the operation manual) and, if necessary, filled up to the mark. The gearbox must not be operated without venting (filter or valve). Otherwise, an oil volume change can lead to leaks during heating or cooling.

Oil Change

The oil must be drained in an operating temperature to ensure complete oil replacement during the oil changing.

Recommendation:

If the oil is heavily contaminated, the gearbox should be rinsed with the new lubricant. At every change of oil, all seals and screw connections must be checked for leaks and tighten the screws if necessary. The magnet of cap screws with permanent magnet must be thoroughly cleaned. Generally Stiebel gearboxes can be operated with mineral oil CLP 220 according to DIN 51517-3. This quality is suitable for operating conditions with an ambient temperature of -10°C up to + 40°C. The choice of synthetic lubricating oils CLP HC (also called PAO, poly alpha olefins) results from the special operating conditions of the gearboxes, e.g. the ambient temperature. Significant hereby is the reached operation oil temperature.

Before using other oils, e.g. CLP-PG, food-compatible or biodegradable oils, please contact Stiebel.

To avoid overheating damage, dirt and dust deposits should be regularly removed from the gearbox surface. Additional oil cooling or heating systems can be provided in consultation with Stiebel.

Oil Change intervals, permissible oil temperatures for mineral oil CLP:

Oil Change intervals for mineral oil CLP

Oil Change intervals, permissible oil temperatures for synthetic oil:

Oil Change intervals for synthetic oil

The oil life time changes depending on the operating temperature.

As a rule the following assignment applies:

  • At operating temperatures > 60°C ► halved oil level per 10°C to 15°C rise in temperature.

Example:

  • Oil change interval P2000, mineral oil, operating temperature 95°C → 2000 h
  • Oil change interval P2000, mineral oil, operating temperature 80°C → 4000 h

The optimum time for the oil change can be determined by oil analyzes. For this purpose, an oil sample is taken, analyzed and evaluated by an authorized service provider (e.g. lubricant manufacturer). As a result the further use can be mentioned up to the due oil change or renewed oil sampling. Thus, a permanent monitoring of lubricant and gearbox conditions is possible.

Miscibility of Lubricants

Synthetic lubricants are not miscible with each other or with mineral oils. CLP HC oils (PAO = poly alpha olefins) are miscible with mineral oil residues. The possibility of oil miscibility can only be judged by the lubricant manufacturer. For the changing of lubricant type (CLP ↔ CLP PG, CLP HC ↔ CLP PG), the gearbox has to be flushed with the new lubricant before.

Rinsing process: Fill new oil up to specified oil level. Operate the gearbox for approx. 15 minutes without load, then drain the oil and fill in the new lubricant. Waste oil and flushing oil have to be disposed of in an environmentally acceptable manner.


Vibrations

The power train normally consists of:

  • Driving element (prime mover)
  • Coupling element (coupling, gearing, etc,)
  • Driven element (driven machine)

The power train transmits mechanical power which can be calculated from speed and torque. In the area of mobile hydraulics, mainly used are prime movers that employ the piston principle (diesel engine). These engines do not transmit their power uniformly to the crankshaft during a revolution. The torque induced in the crankshaft by the cylinder varies significantly, but can be reduced by increasing the number of cylinders through larger centrifugal masses. The driven machines frequently used in this area are pumps, compressors or generators.

Vibrations are caused by the firing order of the engine on account of the frequency. Since the material (steel) has an elastic behaviour with a specific weight, these vibrations are transmitted, producing an oscillatory system with a specific frequency. If this system is excited with natural frequency and not damped, this could cause resonance as the oscillation amplitude increases dependent upon the excitation amplitude, resulting in failure of the system.

To prevent this happening, highly elastic torsional vibration dampers (couplings) are normally used that serve not only for amplitude damping, but also set the first natural frequency to an uncritical state.

Used in these torsional vibration dampers are special elastomers with highly elastic and damping properties. The materials used are natural rubber or temperature-resistant silicon based. These couplings can nonetheless fail due to high dynamic loads attributed to different causes.

Failure cases:

  • Fatigue (fatigue fracture)
  • Thermal destruction (reversal)
  • Forced rupture
  • Ageing

The most frequent cases of damage can be attributed to failure as a result of fatigue and thermal destruction. The high damping work gives rise to heat development which has a negative effect on the elastomer material, whereby the molecule chains are split and the material hardens.

There are now no specific vibrating damping properties and the vibrations produced by the diesel engine are transmitted via the coupling into the gearbox where they are also liable to cause damage.