Skip to main content

Blow- Down Procedure for a Marine Boiler & Why its Done?

Boiler blowdown is of two types:
  1. Scum Blowdown
  2. Bottom Blowdown
Procedure for scum and bottom blowdown:
Below is the procedure for boiler blowdown using the blowdown valve located at the bottom of the boiler. In order to do scum blowdown, instead of bottom blowdown, the scum valve is to be opened.
  1. Open the overboard or shipside valve 1 first.
  2. Open the blowdown valve 2, this valve is a non-return valve.
  3. The blowdown valve adjacent to the boiler 2 should be opened fully so as to preventing cutting of the valve seat.
  4. The rate of blowdown is controlled by valve 3.
  5. After blowdown close the valve in reverse order.
NOTE: A hot drain pipe even when all valves are closed indicates a leaking blowdown valve.

Boiler blowdown is done to remove sludge deposits and other impurities from the boiler water. Blowdown of the boiler is done to remove two types of impurities-scum and bottom deposits. This means that blowdown is done either for scum or for bottom blow down. Moreover, the reasons for boiler blowdown are:
  1. To remove the precipitates formed as a result of chemical addition to the boiler water.
  2. To remove solid particles, dirt, foam or oil molecules from the boiler water. This is mainly done by scum valve and the procedure is known as "scummimg".
  3. To reduce the density of water by reducing the water level.
  4. To remove excess water in case of emergency.


Comments

Popular posts from this blog

Load Line & Why it is Important

Merchant ships have a marking on their hull know as the Plimsoll line or the Plimsoll mark, which indicates the limit until which ships can be loaded with enough cargo, internationally, the Plimsoll line on a ship is officially referred to as the international load line. Every type of ship has a different level of floating and the Plimsoll line on a ship generally varies from one vessel to another.  All vessels of 24 meters and more are required to have this Load line marking at the centre position of the length of summer load water line. There are two types of Load line markings:- Standard Load Line marking – This is applicable to all types of vessels. Timber Load Line Markings – This is applicable to vessels carrying timber cargo. These marks shall be punched on the surface of the hull making it visible even if the ship side paint fades out. The marks shall again be painted with white or yellow colour on a dark background/black on a light background.  The comp

Difference Between A, B & C-Class Divisions?

IMO Symbol A Class Division  IMO Symbol B Class Division  SOLAS has tables for structural fire protection requirement of bulkheads and decks. The requirements depend on the spaces in question and are different for passenger ships and cargo ships. The Administration has required a test of a prototype bulkhead or deck in accordance with the Fire Test Procedures Code to ensure that it meets the above requirements for integrity and temperature rise. Types of Divisions: "A" Class "B" Class "C" Class "A" Class: "A" class divisions are those divisions formed by bulkheads and decks which comply with the following criteria: They are constructed of steel or equivalent material They are suitably stiffened They are constructed as to be capable of preventing the passage of smoke and flame to the end of the one-hour standard fire test. they are insulated with approved non-combustible materials such that the average tempera

Pump Shaft Alignment Procedure

Types of shaft alignment methods: Visual Line-Up Straightedge/Feeler Gauge Rim and Face Cross Dial Reverse Dial Laser Visual Line-Up The visual line-up method is the most common method of alignment. Used in initial installations, visual line-up allows technicians to analyze the working conditions and feasibility of installation. Straightedge/Feeler Gauge Straightedges are used to determine the offset between coupling halves. Corrections are made under all four of the machines feet. Feeler gauges or taper gauges measure the gap between coupling halves at the bottom and top of the coupling. Rim and Face This method is similar in principle to using a straightedge and feeler gauge, but more accurate since dial indicators are used. The rim reading measures the offset between the coupling halves. The face reading measures the angular difference between the faces of the coupling. Changes are calculated with the same formula as the straightedge/feeler gauge met