Boiler Mountings

The boiler is fitted with essential mountings on the shell for safe operation. The list of mountings is given below:

• Safety valves: These are one of the most critical boiler fittings used in the event of unsafe excessive pressure inside the boiler. The boiler safety valve is designed to come into action to release the overpressure. The lifting pressure of the valve is set prior to its installation and locked in the presence of a surveyor so that it cannot be changed later on.
  
• Water level indicators: Boiler gauge glasses are fitted in pairs for manually checking the water level inside the boiler drum. It is on the basis of the boiler pressure that the construction of the gauge glass is decided. The boiler water level indicator is an important boiler fitting as it tells the status of the water level inside the steam drum of the boiler.g
  
• Water level controller: This device is essential to ensure appropriate water level in all load conditions and is fitted in the feed line. A multiple-element feedwater control system is used in boilers with a high evaporation rate.
  
• Water level alarms & cut-out assembly: These devices are used to initiate audible warnings at high and low water level conditions. Another shutdown alarm (burner cut off) is fitted below this level (Low-Low Level alarm) to prevent overheating of the boiler drum.
  
• Remote water level transmitter
• Main steam outlet valve: The steam generated in the boiler is supplied to the ship’s system through this valve. It usually is a non-return type of valve directly mounted on the steam space of the boiler shell. The body is made of cast iron, and the valve seat is of gunmetal.
• Auxiliary steam Stop Valve: In most steam systems on ships, a separate steam line provided from the boiler for the small auxiliary system is supplied through this valve. The valve is smaller in size and usually of a non-return type.
• Pressure gauge & Pressure switches: The pressure gauge and pressure switches can be fitted in the superheater, boiler drum, and wherever it is necessary to read the real-time pressure reading from the local station.
  
• Feedwater valves: The water supply from the hot well to the boiler water drum is controlled by this valve
  
• Burner assembly: The burner assembly comprises the pilot and main burner, along with the field line to supply oil to the burners and FDF to initiate combustion by supplying fresh air.
  
• Air vent: This valve is fitted in the headers, boiler drum, etc., to avoid imploding of the boiler when it is depressurized or when initially raising the steam pressure. The term implosion is just the opposite of an explosion. In this scenario, the pressure inside the boiler will reduce sufficiently below atmospheric pressure to cause the shell to buckle inwards.
  
• Water sampling valve: Generally, a sampling water cock arrangement is also fitted with the cooler, in series, so that water samples can be collected at any time for feed water analysis.
  
• Manholes, Mudholes & peepholes: The boiler is provided with multiple manhole doors, allowing inside access to the crew for inspection, cleaning, and maintenance of boiler tubes and internal parts. Usually, one door is provided in the steam drum and one in the water drum. The mud box in the boiler is provided at the bottom of the water drum to collect the mud (muddy impurities) of the water drum
• Bottom blowdown valve: A bottom blowdown valve is used to empty the boiler either completely for maintenance purposes or partially for water treatment of the boiler when the chloride level in the boiler water is on a higher side.
  
• Soot blowers: Required to blow the soot and the combustion products from the tube surfaces. It is operated by steam or compressed air.
• Feed check valves: This valve controls the supply of steam supply as per the demand and is fitted in both the main and auxiliary steam lines after the stop valve. They are non-return valves with a visible indication of open and closed positions.
• Whistle valve: If there is a provision for the steam whistle in the ship, then steam is supplied directly from the boiler through a small-bore type non-return valve known as a whistle valve.
• Scum blowdown valve: It’s a shallow dish-type arrangement fitted at the normal water level which allows the blowdown of floating impurities, oil foaming, etc. from the water surface.
  

The air purge valve is mounted on the steam drum and is used for purging the air during a cold start. The pressure gauge valve facilitates the replacement of the pressure gauge during operation.

The scum blowdown valve is mounted on the steam drum and the bottom blowdown valve is mounted on the water drum. The outlet of the valves is connected to the same pipe which in turn is connected to the ship-side blowdown valves.

The scum blowdown valve is used for removing the lighter contaminants like oil which floats on top of the water. The bottom blowdown valve is used for removing the heavier impurities which tend to settle down in the water drum.