Today, we want to find out as to when to replace lubricating oil. If you have a large quantity of lubricating oil to change, it is going to burn a hole in your pocket. So most plant operators try to preserve properties of lubricating oil for as long as possible.

One of most important functions of lubricating oil is to reduce friction between moving parts of machinery. But there are other features to look at.

When do you know that oil needs to be changed? Below is a rough guide: 1. Viscosity has changed by 10% 2. Flash Point has dropped to 150 degree Celsius 3. Water Content has reached 2% 4. TBN, or Total Base Number has reduced by 20% 5. Insoluble Content has increased to 5% of oil

Due to oxidation of oil when exposed to heat and oxygen, viscosity of oil tend to reduce. With reduction of viscosity, film of oil between rubbing metal surfaces becomes more difficult to maintain. This results in metal to metal contact, micro seizures that leads to scuffing, abrasion and other damages.

In large diesel engines, fuel oil from dripping injectors or fuel pumps sometimes finds their way into lubrication oil sump. This has tendency to reduce flash point of lubricating oil. In addition to reducing viscosity that is detrimental to lubrication, this contamination with fuel oil can be quite dangerous. If there is a hotspot in any of rubbing parts, this can lead to a crankcase explosion.

It's true that they are rugged, but one of most important advantages of these engines is fact that they can be started by manual cranking. In remote areas, diesel engines can be counted upon for starting up from scratch.

Once a small diesel engine is started, it can be used to drive a small electrical generator that can then be used to produce electrical supply for driving other machines like pumps, compressors, and for lighting.

How does a diesel engine work?

First there must be combustion of fuel. As we have discussed in our previous articles, combustion or burning of fuel occurs whenever there is sufficient heat, fuel and oxygen. When conditions are just right, combustion can be very rapid. Rapid combustion causes an explosion in an enclosed area. This is because of rapid built-up of hot gases during process.

In an internal combustion engine like a diesel engine, this rapid combustion, and built-up of hot gas pressure is used to push a piston away from enclosed combustion space.

The piston is attached to a crankshaft through a connecting rod. Because of this, engine is able to convert linear movement of a piston to a rotating movement of a crankshaft.