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