Lubrication Principles

Principles of Lubrication, lubricants lubricating system, safety storage and handling. Oil and gas production use many different types of equipment wi

This section explains the reasons why lubrication is necessary and discusses friction, the principal cause of wear and overheating. The section also covers some of the methods used to reduce friction and to increase operating life of machinery and equipment.

Oil and gas production use many different types of equipment with moving parts. Without the proper lubrication, this equipment will waste energy, overheat, and wear out.

PURPOSES OF LUBRICATION

Lubrication means the act of making slippery or smooth. It can also mean the application of a lubricant - the material that helps make surfaces smooth and slippery. Lubrication is used everywhere in oil and gas production: compressors, pumps, pumping units, valves, internal combustion engines, gears, etc. In other words, anywhere there are moving parts.

Lubrication is important to keep operating costs and downtime to a minimum and to increase operating efficiency. Understanding lubrication can make your job easier and can keep you from making costly mistakes.

The four general purposes for lubrication are :

Reduce Friction. Lubrication is used to reduce friction. Friction is the principal cause of wear and breakdown of production equipment and moving parts. Friction also consumes energy rather than allowing it to be transmitted into usable work.

Reduce Heat. Lubrication is used to carry heat away from moving parts. Heat causes parts to expand, making them fit together more tightly, and requires more energy to operate, heat build up can have a destructive effect.

Control Contamination. Lubrication can be used to keep dirt away from moving surfaces or to flush out dirt from the area. If dirt is allowed to get into the small spaces between moving parts, it car interfere with equipment operation. The contaminating materials can also wear parts, causing failure.

Reduce Oxidation and Corrosion. Lubrication is used to coat the surfaces of moving parts. This keeps oxidation or corrosion to a minimum. Of course the lubricating materials themselves must not contain corrosive components.

FRICTION

Friction is the resistance to one surface moving when in contact with another surface. It is caused by the roughness of the two surfaces. All surfaces have some roughness to them, no matter how smooth they may seem to be. Sandpaper and rasp files have very obvious rough surfaces. Polishing cloths and mirrors seem to have smooth surfaces. However, a close look at them will show that even these materials have some roughness.

Friction does have some advantages. You need friction to walk. If the surface is slippery, you may fall. Automobile brakes rely on friction to stop the car. The main disadvantages of friction are: wear of moving surfaces, heat, excessive noise, and wasted energy.

TYPES OF FRICTION

There are two types of surface friction: Sliding friction and Rolling friction.

Sliding Friction Sliding friction is the resistance of one surface sliding over another. A typical example of sliding friction is the resistance you feel when dragging or sliding an object over the ground. You’ll also encounter sliding friction as you move a skid- mounted piece of equipment. Sliding friction will vary according to these three factors:

• The rougher the two surfaces, the greater the sliding friction. 
• The greater the pressure forcing the two surfaces together, the greater the friction.
• Friction is greater when the surfaces are just beginning to slide than when they’re in motion. A good example of this is any skid mounted unit, such as a generator or compressor.

While most sliding friction occurs when one surface is trying to move in a straight line over another surface, there’s another kind that you may be familiar with. Large pieces of equipment, such as large centrifugal pumps, have journal bearings to support the ends of the shafts. This type of bearing will have rotational sliding friction. That is, the surface of the shaft is actually sliding over the inside surface of the journal bearing. That's because the shaft is rotating while the bearing is not.

Rolling Friction, An object rolling over a surface has less resistance than if it were sliding along that same surface. Rolling friction occurs because of small depressions caused as one surface rolls over another. Some typical examples of surfaces with rolling friction are: tires, roller bearings, and ball bearings.

Fluid Friction, Another type of friction occurs in fluids. Fluids experience friction as they flow through closed systems, such as pumps and pipelines. The fluid closest to the wall of the pipe tends to flow slower than the fluid in the center of the pipe. There’s also resistance to flow within a fluid itself. This resistance is called viscosity.

REDUCING FRICTION

Friction must be overcome in operating equipment to reduce heat, wear; noise, and energy usage and to increase operating efficiency. There are a number of ways in which this can be accomplished. Several methods can be used together to get the best results.

Make the surface smoother. Since friction is caused by roughness in the surfaces, friction can be reduced by making the surfaces smoother. This is generally done by polishing the surfaces to remove the roughness. Another method is to use materials that tend to get smoother as they rub or slide over one another. In other words, the two surfaces “polish” each other.

Some materials also have a greasy or oily feel to them. Teflon is a good example of this kind of material.

Change the shape. Since a rolling surface encounters less friction than a sliding one’ most rotating equipment uses roller or ball bearings in place of journal bearings. The rolling elements are placed between the moving surfaces to change sliding friction into rolling friction. However, even ball and roller bearings need something else to minimize heat and wear. They need to be lubricated.

Lubricate the surfaces. Heat, wear, and noise occur because of surface-to-surface contact. Therefore, a good method of reducing these problems is to separate the surfaces by some material that’s very slippery and fills in all the surface unevenness.

The moving surfaces are separated by a thin film of lubricating substance, called a lubricant. There are many different types of lubricants used for different operating conditions and different types of bearings. Lubricants are covered in the next section of this module.

• [accordion]
• 1. Lubrication Basic
• 
• 2. Refining Used Lubricating Oils
• 3. Practical Lubrication for Industrial
• 4. Encyclopedia of Lubricants and Lubrication
• 5. Lubrication Tactics for Industries Made Easy (2020)
• 6. Design Aspects of Used Lubricating Oil Re-Refining
• 7. ASM_HANDBOOK_Vol_18,_Friction,_Lubrication,_and_Wear_Technology
• 8. IADC Vol-2 03 Lubrication