Tuesday, October 5, 2010

Ship Systems

This article briefly shows some typical ship's ancillary services. These info are well applicable not only at concept stage but also during basic design when actual components have not yet been chosen.

Auxiliary oil fired boiler

-Steam production ability:

Saturated steam, 7bar g, 170°C.
1 kW corresponds to about 1,6kg/h steam or
1 MW corresponds to about 0,42kg/s steam

-Fuel oil (FO) consumption:
1,0kW corresponds to 0,105kg of HFO/h
1,0kg/h steam corresponds to 0,066kg of HFO/h

Fuel oil systems

- Main engine (ME) and auxiliary engine (AE) fuel oil consumption
Normally engine suppliers give the specific fuel oil consumption (SFOC) based on ISO 3046/1 standard.

Emergency diesel generator :

SFOC: typical value 0,25kg/kWh
100 kW of power means about 28-litre fuel oil consumption per hour.
FO tank to be dimensioned at least for 36 h constant running according to SOLAS.

Heavy Fuel Oil (HFO) Tanks :

Storage tanks-
Minimum temperature in storage tanks depends on the pour point of the HFO. The temperature of HFO should always be kept higher than pour point to avoid filter blocking, and other similar problems.

Settling tanks-
To allow reasonable separation the tank should be sized for 24h consumption.
The settling temperature to be calculated to be about 70degC.
According to the latest SOLAS rules double settling tanks are needed.

Service tanks-
Service tanks should be sized for 10h - 12h consumption.
The temperature in service tanks to be calculated to be 75°C.

According to the latest SOLAS rules two separate service tanks are needed.

Lubrication oil systems:

- Lubrication oil consumption

LO consumption for medium speed engines in average is about 1,0g/kWh.
-System oil tanks

In case main engines are so-called dry sump engines, there should be a system oil tank on the double bottom.

Sewage systems:

It is highly recommendable to specify a biological sewage treatment plant for all types of ships because of the environmental reasons, further reading required on latest Marpol MEPC159(55) requirement. The plant is typically dimensioned to treat full black water load.

Galley waste water is normally not led to sewage treatment plant, because it slows down the biological process.

Grey waters have been discharged directly overboard or collected to grey water storage tanks. Some times grey waters have been chlorinated before discharging overboard but not really biologically or chemically treated onboard.

Other systems not described could be referred to below slides or will be continued in next blog article.

Ship Designs - General Info

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