boiler are working on same principal but automatic and manual boiler has difference that manual boiler working at single element loop and automatic boiler work at three element loop.single loop means when fuel increase mean load increase on boiler by adjusting fuel operator has to adjust steam drum level manualy , while automatic means when load increas, fuel increase steam drum level adjust automaticaly by watching fuel consumption.
In the steam drum, where steam exits and flows to the superheaters.
For softening calsium or magnecium hardness and its become slury, other effect is by used phosphate can increased the Ph value. Shakhawat
The following extract taken from an article by Ingo Paul in Energy Issues No 19 April 1999 published by the World Bank [external link] briefly describes the difference between a subcritical and a supercritical boiler. "Supercritical" is a thermodynamic expression describing the state of a substance where there is no clear distinction between the liquid and the gaseous phase (i.e. they are a homogenous fluid). Water reaches this state at a pressure above 22.1 megapascals (MPa) The "efficiency" of the thermodynamic process of a coal fired power (sic) describes how much of the energy fed into the cycle is converted into electrical energy. The greater the output of electrical energy for a given amount of energy input, the higher the efficiency. If the energy input to the cycle is kept constant, the output can be increased by selecting elevated pressures and temperatures for the water-steam cycle. Up to an operating pressure of around 19 MPa in the evaporator part of the boiler, the cycle is sub-critical. This means, that there is a non-homogeneous mixture of water and steam in the evaporator part of the boiler. In this case a drum-type boiler is used because the steam needs to be separated from water in the drum of the boiler before it is superheated and led into the turbine. Above an operating pressure of 22.1 MPa in the evaporator part of the boiler, the cycle is supercritical. The cycle medium is a single phase fluid with homogeneous properties and there is no need to separate steam from water in a drum. Once-through boilers are therefore used in supercritical cycles. www.whizkris.com
I think a vessel is containing a fluid under high pressure whereas a drum contain a fluid with no or low pressure.
Steam drums are used on recirculating boilers that operate at subcritical pressures. The primary purpose of the steam drum is to separate the saturated steam from the steam-water mixture that leaves the heat transfer surfaces and enters the drum.
The steam drum separated the steam from the water and stream mixture in the boiler drum.
Purpose of the boiler drum is to collect steam from all the various tubes in a boiler, and send it to the turbine to spin the generator
boiler drum diffferential pressure level calculation explained
Generator
Overheating of water wall tubes may cause crack. Boiler will damage due to boiler drum level goes down.
as the boiler drum is cylindrical in shape due to low stress concentration and in both end the diameter will be less.so for easy entry into the drum for a man the drum man hole is elliptical in shape.
see results in attached link: Philips 3-drum 'Accessable' boiler
The swelling and shrinking effect in a boiler drum refers to the physical changes in the drum's volume due to temperature variations and pressure changes during operation. When the boiler is heated, the water inside converts to steam, causing the drum to swell as the pressure increases and the water expands. Conversely, when the boiler cools down or experiences a drop in pressure, the drum may shrink as the steam condenses back into water. This phenomenon is important to consider for the structural integrity and safety of the boiler system.
This is due to steam seperation the silica remains in the drum water.
1) Methods of circulation of water and Steam 2) Arrangement of tubing and boiler drum 3) Methods of superheating the steam 4) water softening plant
see results in attached link: Philips 3-drum 'Accessable' boiler