FAQ

The engine builders advise to have a minimum TBN of 20 of the lubricant in service when combusting high sulphur fuels, which is sufficient to tackle sulphuric acid production of high sulphur fuels. Lubricant analysis generally report a caution as of TBN of 23-24, to avoid alerted analysis reports a TBN of 24 is a save limit.

TBN stands for Total Base Number. Lubricant manufacturers add a calcium additive to the lubricant (TBN) to neutralize sulphuric acids formed during the combustion process of the fuel sulphur. The higher the TBN of the fresh lubricant the more calcium additive per liter of lubricant. The TBN of the lubricant in service goes down due to the consumption of the TBN additive which transforms during the neutralization process from free to react calcium additive to calcium-sulphates, these calcium sulphates are not measured in the TBN of the lubricant in service.

The sulphuric acids formed during combustion of sulphur fuels consume the TBN additive. New TBN additive is added to the process by topping up the sump tank with fresh lubricant. The amount of added TBN additive should be in balance with the production of sulphuric acids in the combustion process. As the engine lubricant consumption of modern engines is very low, this consumption is not sufficient to add enough TBN additive to the process. The remaining TBN additive has to be added additionally, which means the engine lubricant consumption has to be increased by doing additional partial replacements.

No, TBN additive is a calcium additive which is part of the lubricant formulation. The lubricant formulation is a very delicate balance between base oils and additives, adding additional additives to this formulation can interfere with the delicate balance of the product with the possibility of additive dropout.

The SLOC (Specific Lubricating Oil Consumption) is the lubricant consumption of an engine system in gr/kWh. The higher the power on the engine, the more kW, the more fuel the engine is combusting, the more lubricant is needed to neutralize the sulphuric acids created by the combustion of sulphur containing fuels. The total SLOC needed is depending on the sulphur % of the fuel. The higher the sulphur % the higher the total SLOC needed to stabilize the TBN at 24.

The Lubetimizer unit is constantly balancing the total SLOC (Specific Lubricating Oil Consumption) versus the fuel sulphur % and engine load.

Example: An engine with 7500 kW, combusting a fuel with 2% sulphur. For a fuel with 2% sulphur a total SLOC of 0,57 gr/kWh is needed to stabilize the TBN at 24. The SLOC of 0,57 gr/kWh @ 80% engine load is a lubricant consumption of 90 ltr/24 hrs. If the engine consumption is 40 ltr/24 hours being 0,2 gr/kWh @ 100% load, the difference has to be created by doing partial replacements, 90 – 40 = 50 ltr/24 hrs or 0,32 gr/kWh. This difference is controlled by the Lubetimizer, draining the 0,32 gr/kWh and adding the full 0,57 gr/kWh (if engine fill is switched on). The drained quantity is depending on the engine load, a direct load connection from the engine management to the Lubetimizer unit is controlling this.

The total SLOC is the lubricant consumption in gr/kWh, if the engine load reduces, the amount of kWh reduces.
The total lubricant consumption is calculated from the total SLOC, engine power (MCR) and engine load%. The lower the load, the lower the total lubricant consumption in ltr. The engine’s lubricant consumption in a constant rpm medium speed engine is stable, which means to control the lower total lubricant consumption at lower loads, the partial replacement volume has to be reduced.

The HMI setting arranges the balance between the fuel sulphur level and the lubricant consumption (Total SLOC). The higher the fuel sulphur, the higher the lubricant consumption (total SLOC) needed.

If the total SLOC x engine power x engine load is equal or lower than the engines lubricant consumption, the Lubetimizer stops draining, and only the regular sump top up (fill) is done. This can occur by running low loads, or by using low sulphur fuel, the lower the fuel sulphur the lower the SLOC needed to stabilize the TBN at 24.

In the Lubetimizer menu the engine consumption can be changed. By pressing button F3 the engine consumption setup appears. To add the engine consumption during the feed cycle of the Lubetimizer unit, this fill option has to be switched on. Switching on the fill option can be done pressing the buttons ESC-    and select option 1. If 1 is selected the engine consumption is automatically added, if selected 0 then this option is switched off. The engine consumption in ltr/24 hrs can be adjusted by using the buttons HMI+ & HMI-. If the option was already selected 1 (on) then the engine consumption can be increased or decreased to create sufficient engine top up.