Specification of Boiler Kapal Tanker/Fabrikasi Boiler Marine Tank-PT Indira Dwi Mitra
Marine boilers used in ships today are mostly for auxiliary purposes in vessels that run on marine diesel engines or diesel electric propulsion. In case of ships using steam turbines (mostly found in high speed vessels used by navies), boilers are a part of the main propulsion system. However, in this article, we will focus on auxiliary boilers, i.e. boilers used for running auxiliary systems in a ship.
To look at this from a ship designer’s point of view, he/she should be able to choose the right kind of boiler for a particular ship depending on the requirement for that particular project. The process is pretty much an application of first principles, but in a somewhat different way.
Requirement 1- Steam consumption required to compensate heat losses in tanks:
Most ships run by diesel engines have fuel oil tanks that are used to store Heavy Fuel Oil (HFO). Since the viscosity of HFO is very high, stored HFO is almost as dense as tar, and its high viscosity makes it unable to flow. But in order to transfer the stored HFO to the settling tanks and then the HFO service tank, the viscosity needs to be maintained at a level corresponding to which easy flow is possible. For this, HFO storage tanks are equipped with heating coils to maintain the fuel at a certain temperature. The heating fluid in the heating coils is steam that is produced in the auxiliary boiler.
First, each HFO storage tank is located in the general arrangement drawing, and the surrounding space adjacent to each tank bulkhead is noted. Depending on the surrounding of each tank bulkhead (Engine Room, Void, Ballast Water Tank, Sludge Tank, etc.) the ambient temperature is fixed for heat transfer through each bulkhead of the tank in analysis.
For most auxiliary boilers, shell and tube boilers are used, where the boiler drum holds the water reserve, and fire tubes run along the length of the drum. The hot gases produced by the burner are carried in the fire tubes that provide more surface area for heat transfer to the water. In most cases, the auxiliary boilers are horizontally oriented in case there are no space constraints, as they prevent pressure fluctuations which is more in case of vertically oriented boilers.
