Debunking 9 Common Misconceptions About Machinery Lubrication

Mechanical lubricating oil refers to the special lubricating oil for special machinery, barrel-making machinery, loading and unloading machinery, stamping and processing machinery and other mechanical equipment.

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There are more than ten kinds of mechanical lubricating oil, including special oil for air compressor, special anti-wear hydraulic oil for barrel-making machinery, heavy load gear oil and hydraulic transmission oil.

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The correct lubrication method can improve the performance of the equipment and prolong the working life.

Any equipment can not work without lubrication, but there will be a variety of reasons to cause the misunderstanding of lubrication in the actual production.

For example, some think that oil can be lubricated, or others believe that the greater the viscosity of the oil, the better the effect, and so on.

In order to avoid the damage to the machine caused by the wrong operation, this article introduces nine common mistakes as reference.

1. The purpose of lubrication is to make the machine run faster.

The contact surface of the relative moving parts in the machine will produce friction and wear.

According to statistics, more than one third of the world’s energy consumption is friction loss.

When the wear exceeds the allowable limit, it directly affects the normal work and service life of the machine.

Therefore, the lubricant film is formed between the relative moving parts to reduce friction and wear.

At the same time, it can also has the functions of cooling, buffering, vibration absorption, sealing and so on.

The purpose of lubrication is not only to make the machine run faster, but also to ensure the normal operation and prolong the service life of the machine.

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Fig. 1 The functions of lubrication

Fig. 1 The functions of lubrication

2. It is believed that only oil can lubricate.

There are different kinds of lubricating oil and their working performance.

In order to improve the performance of lubricating oil, corresponding additives should be added.

In order to make the machine get reasonable lubrication, different types of lubricants and additives should be selected for different types, different working conditions and different oil supply methods.

Therefore, it can’t think that all kinds of oil can be lubricated.

What is more, improper selection of lubricating oil will cause lubrication accidents, which accounts for a large proportion of equipment failures.

3. The more lubricating oil, the better the lubricating effect.

If it is grease lubrication, excessive resistance will increase, causing bearing heating, leading to grease leakage, especially for high-speed and heavy-duty machines.

Generally, oil level indicator can be used to show the height of the oil level.

For example, the immersion depth of the high-speed gear in the gearbox should be 1-2 tooth height to avoid poor lubrication of the high-speed gear and reduce the movement resistance and oil temperature rise of the gear.

The filling amount of grease in rolling bearings is generally not more than 1/3 – 1/2 of the bearing clearance.

4. The higher the viscosity of lubricating oil, the better the lubricating effect.

Viscosity is the main index of lubricating oil, and its standard is usually determined at the temperature of 100 ℃.

The higher the grade is, the thicker the lubricating oil film is formed.

Although the friction on the friction surface is reduced, the resistance is increased, the power loss is increased, and the waste of energy is increased.

When the machine is just started, the temperature is low, and part of the lubricating oil on the friction surface is lost due to the increase of temperature after a period of time.

The lubrication can not form an effective lubricating oil film, and the oil can not be quickly added to the friction surface of the machine.

Due to the high viscosity and slow flow of the oil, the wear of the parts is large.

Some data show that if the viscosity of lubricating oil is reduced by 1mm2/s, 15% fuel can be saved.

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The selection of viscosity should consider the working speed, working temperature and other factors.

The low viscosity of lubricating oil is one of the current measures to save oil.

Fig. 2 The selection of viscosity

Fig. 2 The selection of viscosity

5. Select oil according to the oil grade specified in the equipment manual.

Most equipment technicians think that the oil specified by the equipment manufacturer is the regulation.

In fact, the oil specified in the instruction manual refers to the general working conditions, which may not be suitable for the actual working conditions.

So oil should be selected flexibly according to the actual working conditions.

6. Black lubricating oil means that it has deteriorated.

The blackening of lubricating oil means that the lubricating oil is deteriorated and needs to be changed.

However, this understanding is one-sided.

For example, it is normal for the machine oil with detergent dispersant to blacken soon after use.

It is not easy to think that the oil has deteriorated.

The lubricating oil with additives will often produce a dark protective oil film on the bearing surface.

It is normal to turn black during use, so it is unnecessary to remove the blackened lubricant.

Therefore, to determine whether the lubricating oil is deteriorated, a comprehensive analysis should be made and the oil should be changed according to the quality.

7. Used lubricating oil cannot be used and must be thrown away.

In fact, in addition to the deteriorated oil, there are more lubricants available.

If the replaced oil is only mixed with impurities, it can be reused after sedimentation and filtration;

After simple treatment, the oil with heavy pollution can be used as lubricant for rough machining equipment, antirust for outdoor equipment, or collect and hand over the waste oil for recycling; (it is used for other equipment with low requirements, not for air compressor)

The oil which is difficult to recycle can be burned as fuel oil after simple treatment.

8. All lubricants can be replaced with each other.

The selection of lubricating oil depends on the working conditions, working environment, specific characteristics of friction surface and lubrication mode of the machine.

The type and brand of lubricating oil selected are also different.

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Generally, it cannot be replaced.

9. Do not replace or supplement lubricating oil for a long time.

After using for a period of time, the performance of lubricating oil decreases or changes.

With the decline of oil quality, if the lubricating oil is not replaced or supplemented in time, the lubricity is poor, which is easy to cause high-temperature phenomenon.

In addition, many people lengthen the oil change cycle of air compressor in order to save money.

But in fact, poor lubrication will result in large current, serious waste of power, and increase the operating cost, which is not worth the loss.

10. The use of machinery lubricating oil and its precautions

1) Consult with lubrication experts, use proper lubricating oil and reduce the type of oil as much as possible.

2) For each kind of machinery, simple legend shall be used to show the parts to be refueled, the name of oil products, and the refuelling period (special person shall be responsible for avoiding using wrong oil products).

3) The name of the oil should be marked on the special container of each kind of lubricating oil to prevent pollution.

4) Make mechanical maintenance record in time after adding or changing lubricating oil every time.

5) Before refueling and changing oil, clean the relevant parts, and do not use water-soluble cleaning agent.

6) In case of abnormal oil products, samples shall be taken and submitted to professional departments for testing.

7) Different brands of lubricating oil can be mixed if necessary to obtain the required viscosity, but cannot be mixed.

8) The maintenance of lubricating filter system can maintain the quality of lubricating oil and prolong the effective service time of lubricating oil.

The filtration system in good technical condition can remove 80% – 90% of the mechanical impurities in the lubricating oil and reduce the wear by 30% – 40%.

9) The invasion of water in lubricating oil should be specially prevented.

When the lubricating oil is deteriorated and replaced, the old oil must be exhausted.

It is wrong to use the method of making up for what is missing, because the oxidation and deterioration dirt in the residual oil will accelerate the deterioration of the new oil.

10) Because gear oil contains a lot of colloids which have good adhesion to the metal surface, general mechanical lubricating oil cannot be used.

When using gear oil, the working temperature is not high, change in quality is little, with less consumption.

When changing oil, it does not have to change it all, timely replenishment to avoid oil shortage is fine.

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