| When do you need to replace your lubricating | | | | |
| oil? If you have a large quantity of | | | | Water can also find its way into the |
| lubricating oil to change, it is going to | | | | lubricating oil from leaks in the cooling |
| burn a hole in your pocket. So most plant | | | | water system o-rings or gaskets. In addition |
| operators try to preserve the properties of | | | | to reducing the lubricating properties of |
| the lubricating oil for as long as | | | | the oil, the presence of water in the oil |
| possible. | | | | can give rise to bacteria or fungal growth, |
| | | | which will quickly damage the oil properties |
| One of the most important functions of | | | | as well as contributing to acid corrosion |
| lubricating oil is to reduce the friction | | | | and oxidation of the oil, changing the |
| between the moving parts of machinery. But | | | | chemical composition of the oil itself. |
| there are other features to look at. | | | | However, if the water content is below |
| | | | 0.5%, it can still be removed by centrifugal |
| When do you know that the oil needs to be | | | | purifiers. |
| changed? Below is a rough guide: | | | | |
| | | | The total base number is especially needed |
| 1. Viscosity has changed by 10% | | | | for the cylinder liner lubrication of |
| | | | engines that run on poor quality fuel with |
| 2. Flash Point has dropped to 150 degree | | | | high sulphur content. The base additive is |
| Celsius | | | | used to reduce the corrosive effects of the |
| | | | sulphuric acid fumes on the cylinder. |
| 3. Water Content has reached 2% | | | | |
| | | | With large diesel engine installations, the |
| 4. TBN, or Total Base Number has reduced by | | | | lubricating oils are continuously filtered |
| 20% | | | | and purified to reduce the insoluble |
| | | | particles in the oil. Special strainers |
| 5. Insoluble Content has increased to 5% of | | | | containing magnets are used to trap |
| the oil | | | | particles of carbon or iron particles. In |
| | | | large diesel engines, the carbon particles |
| Due to the oxidation of the oil when exposed | | | | are byproducts of combustion while the iron |
| to heat and oxygen, the viscosity of the | | | | particles comes from rubbing of gears, cams |
| oil tend to reduce. With the reduction of | | | | or other parts where wear down still occur. |
| viscosity, the film of oil between rubbing | | | | |
| metal surfaces becomes more difficult to | | | | The presence of these particles interferes |
| maintain. This results in metal to metal | | | | with the lubrication of bearings, most of |
| contact, micro seizures that leads to | | | | which contain soft white-metal coating. The |
| scuffing, abrasion and other damages. | | | | particles can become embedded into the soft |
| | | | metal and cause abrasion of the metal |
| In large diesel engines, fuel oil from | | | | parts. |
| dripping injectors or fuel pumps sometimes | | | | |
| finds their way into the lubrication oil | | | | The contents of this page are part of a page |
| sump. This has the tendency to reduce the | | | | from my e-book "General Engineering |
| flash point of the lubricating oil. In | | | | Knowledge Notes" that will help candidates |
| addition to reducing the viscosity that is | | | | prepare for the Marine Certificate of |
| detrimental to lubrication, this | | | | Competency Examinations. This e-book is |
| contamination with fuel oil can be quite | | | | available for FREE downloading at |
| dangerous. If there is a hotspot in any of | | | | |
| the rubbing parts, this can lead to a | | | | Until next time... |
| crankcase explosion. | | | | |