Type a line (cylinder oil 45 l in 4 h 85 % of 9960 kW density 0.94) or fill in the fields: the line and the fields stay in step.
Enter the cylinder oil used and the hours it was used over, the density of the oil for litres, and the engine power, directly or as a load in % of the MCR, and the calculator gives the cylinder oil feed rate of a two-stroke crosshead engine in g/kWh, with the oil per hour and per day in kilograms and litres. The other way round, from a feed rate in g/kWh and the power, it gives the oil the engine uses per day. With the number of cylinders, the totals are split evenly per cylinder. It shows the working with your numbers and gives a line you can copy or add to a request.
The calculator does not assume a density: for litres and m3 it asks for one. It gives no recommended feed rates, no factors for the base number (BN) or the fuel sulphur and no figures from maker guidance: the result is compared with the engine maker’s cylinder oil guidance and the drain oil analysis.
The feed rate f = m x 1000 / (P x t): the oil in kg over the energy in kWh delivered in the same time. 45 l at 0.94 kg/l is 42.3 kg; at 85 % of an MCR of 9960 kW the power is 8466 kW, over 4 h 33 864 kWh; f = 42 300 / 33 864 = 1.25 g/kWh.
The other way round: the oil per hour = f x P. At 0.9 g/kWh and 11 000 kW that is 9900 g/h, 237.6 kg per day and, at 0.95 kg/l, 250.1 l per day. Without a density the calculator gives the kg and asks for the density for the litres.
With the number of cylinders the totals are split evenly. 0.3 m3 in 24 h at 16 MW and 0.93 kg/l is 279 kg and 0.73 g/kWh; for 6 cylinders, 46.5 kg or 50 l per day and 2667 kW for each. With an even share, the feed rate in g/kWh is the same for each.
| Quantity | Relation | Note |
|---|---|---|
| Feed rate | f = m x 1000 / (P x t) | g/kWh; m the oil in kg, P the power in kW, t the running hours |
| Mass of oil | m = V x density | V in l, density in kg/l; 1 m3 = 1000 l |
| Power at a load | P = load / 100 x MCR | load in % of the MCR |
| Oil per hour | f x P | g/h; / 1000 for kg/h |
| Oil per day | f x P x 24 / 1000 | kg/day; / density for l/day |
| Per cylinder | total / number of cylinders | an even share |
| Units | 1 MW = 1000 kW; 1 bhp = 0.7456999 kW; 1 PS = 0.7354988 kW | bhp and hp are mechanical horsepower, PS metric horsepower |
The oil, the hours and the power must belong to one period: the oil used over those hours and the average power over them. The density comes from the data sheet or the delivery note of the oil; the calculator does not assume one. No recommended feed rates are given.
The feed rate as the oil used over the energy delivered in the same time, in g/kWh, follows the definition of the specific cylinder oil consumption in independent marine engineering references, and cylinder oil consumption tools work it out the same way from the energy the engine delivers, with the load as a per cent of the MCR. The feed rate is expressed in g/kWh in the engine makers’ service letters on cylinder lubrication too: they give their guidance by the BN of the oil and the sulphur content of the fuel and call for the drain oil to be analysed, and independent marine engineering references say the same. The horsepower factors are those of the SI conversion tables: 1 hp (550 ft lbf/s) = 745.6999 W, 1 metric hp (PS) = 735.4988 W; 1 kWh = 3.6 MJ and 1 l = 0.001 m3 exactly.
From the oil used and the energy the engine delivered over the same time: feed rate (g/kWh) = oil in kg x 1000 / (power in kW x running hours). A volume is turned into kg with the density of the oil: kg = l x density in kg/l, and 1 m3 = 1000 l. Example: 45 l of cylinder oil in 4 h at 85 % of an MCR of 9960 kW, density 0.94 kg/l. 45 x 0.94 = 42.3 kg; P = 0.85 x 9960 = 8466 kW; 8466 x 4 = 33 864 kWh; 42.3 x 1000 / 33 864 = 1.25 g/kWh. At that rate the engine uses 10.6 kg/h, or 253.8 kg and 270 l per day.
The other way round: the oil per hour in g = feed rate in g/kWh x power in kW; per day x 24; in litres divided by the density. At 0.9 g/kWh and 11 000 kW: 0.9 x 11 000 = 9900 g/h, or 9.9 kg/h; 9.9 x 24 = 237.6 kg per day; at 0.95 kg/l, 237.6 / 0.95 = 250.1 l per day. Without a density the calculator gives the kg and asks for the density for the litres.
Because the feed rate is a mass over the energy, while the lubricator counter or the tank sounding gives a volume. The calculator takes the density of the oil in use from what you enter, from its data sheet or its delivery note, and does not put in a figure of its own. With the oil in kg no density is needed; the litres then follow only when a density is entered.
As a share of the maximum continuous rating: P = load / 100 x MCR. 85 % of 9960 kW is 8466 kW. Enter the average power over the hours the oil was counted: if the load changed over that time, the feed rate shown is the average for the period. bhp and hp are read as mechanical horsepower, 1 hp = 0.7457 kW, and PS as metric horsepower, 1 PS = 0.7355 kW.
With the number of cylinders, the totals are split evenly: kg and l per day, kW and g/h for each cylinder. 0.3 m3 of oil in 24 h at 16 MW with a density of 0.93 kg/l is 279 kg and 0.73 g/kWh; for 6 cylinders that is 46.5 kg or 50 l per day and 2667 kW for each. With an even share, the feed rate in g/kWh of each cylinder is that of the engine.
The calculator gives no recommended feed rate and no factors for the base number or the fuel sulphur. The cylinder oil feed rate is expressed in g/kWh, and engine makers publish their cylinder oil guidance by the BN of the oil and the sulphur content of the fuel. Compare the figure with the engine maker’s cylinder oil guidance and the drain oil analysis.
The calculator gives the cylinder oil feed rate and the oil per day. When parts for the lubricators or the cylinder lubrication system are needed, send the line from the calculator with the engine details and a photograph of the nameplate, and Vessel Core checks the details before an offer goes back.
