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Boiler mountings working procedure
The use of boiler mountings - Safety valves, Mam steftm stop valve, Auxiliary steam stop valve etc.
A boiler is used to heat feed water in order to produce steam. The
energy released by the burning fuel in the boiler furnace is stored (as
temperature and pressure) in the steam produced.
Certain fittings are necessary on a boiler to ensure its safe operation.
They are usually referred to as boiler mountings. The mountings
usually found on a boiler are:
Safety valves :These are mounted in pairs to protect the boiler against
overpressure. Once the valve lifting pressure is set in the presence of a
Surveyor it is locked and cannot be changed. The valve is arranged to
open automatically at the pre-set blow-off pressure.
Mam steftm stop valve :This valve is fitted in the main steam supply line
and is usually of the non-return type.
Auxiliary steam stop valve: This is a smaller valve fitted in the auxiliary
steam supply line, and is usually of the non-return type.
Feed check or control valve :A pair of valves are fitted: one is the main
valve, the other the auxiliary or standby. They are non-return valves and
must give an indication of their open and closed position.
Water level gauge :Water level gauges or 'gauge glasses' are fitted in
pairs, at opposite ends of the boiler. The construction of the level gauge
depends upon the boiler pressure.
Pressure gauge connection :Where necessary on the boiler drum,
superheater, etc., pressure gauges are fitted to provide pressure
Air release cock :These are fitted in the headers, boiler drum, etc., to
release air when filling the boiler or initially raising steam.
Sampling connection :A water outlet cock and cooling arrangement is
provided for the sampling and analysis of feed water. A provision may
also be made for injecting water treatment chemicals.
Blow down valve :This valve enables water to be blown down or emptied
from the boiler. It may be used when partially or completely emptying
Scum valve: A shallow dish positioned at the normal water level is
connected to the scum valve. This enables the blowing down or removal
of scum and impurities from the water surface.
Whistle stop valve:This is a small bore non-return valve which supplies
the whistle with steam straight from the boiler drum.
Boiler mountings (water-tube boilers)
Watertube boilers, because of their smaller water content in relation to
their steam raising capacity, require certain additional mountings:
Automatic feed water regulator. Fitted in the feed line prior to the main
check valve, this device is essential to ensure the correct water level in.the
boiler during all load conditions. Boilers with a high evaporation rate
will use a multiple-element feed water control system .
Low level alarm. A device to provide audible warning of low water level
Superheater circulating valves. Acting also as air vents, these fittings
ensure a flow of steam when initially warming through and raising steam
in the boiler.
Sootblowers, Operated by steam or compressed air, they act to blow
away soot and the products of combustion from the tube surfaces.
Several are fitted in strategic places. The sootbiower lance is inserted,
soot is blown and the lance is withdrawn.
Fig:Auxiliary steam plant system
Summarized below marine boiler detail Info pages:
Requirement for various boiler types - water tube boilers and more The watertube boiler is employed for high-pressure, high-temperature, high-capacity steam applications, e.g. providing steam for main propulsion turbines or cargo pump turbines. Firetube boilers are used for auxiliary purposes to provide smaller quantities of low-pressure steam on diesel engine powered ships.....
- Fire tube boilers working principle and operational procedure
The firetube boiler is usually chosen for low-pressure steam production on vessels requiring steam for auxiliary purposes. Operation is simple and feedwater of medium quality may be employed. The name 'tank boiler is sometimes used for firetube boilers because of their large water capacity. The terms 'smoke tube' and 'donkey boiler are also in use....
- Exhaust Gas Boilers And Economisers working procedure
The use of exhaust gases from diesel main propulsion engines to
generate steam is a means of heat energy recovery and improved plant
efficiency.The auxiliary steam installation provided in modern diesel powered
tankers usually uses an exhaust gas heat exchanger at the base of the
funnel and one or perhaps two watertube boilers .....
- The use of boiler mountings
Watertube boilers, because of their smaller water content in relation to their steam raising capacity, require certain additional mountings: Automatic feed water regulator. Fitted in the feed line prior to the main check valve, this device is essential to ensure the correct water level in.the boiler during all load conditions. Boilers with a high evaporation rate will use a multiple-element feed water control system ....
- Purity of boiler feedwater Most 'pure' water will contain some dissolved salts which come out of solution on boiling. These salts then adhere to the heating surfaces as a scale and reduce heat transfer, which can result in local overheating and failure of the tubes. Other salts remain in solution and may produce acids which will attack the metal of the boiler. An excess of alkaline salts in a boiler, together with the effects of operating stresses, will produce a condition known as 'caustic cracking'. This is actual cracking of the metal which may lead to serious failure.....
- The steam-to-steam generator working principle and operational procedure
Steam-to-steam generators produce low-pressure saturated steam for domestic and other services. They are used in conjunction with watertube boilers to provide a secondary steam circuit which avoids any possible contamination of the primary-circuit feedwater. The arrangement may be horizontal or vertical with coils within the shell which heat the feedwater.....
- How to control combustion in a marine boiler
The essential requirement for a combustion control system is to correctly proportion the quantities of air and fuel being burnt. This will ensure complete combustion, a minimum of excess air and acceptable exhaust gases. The control system must therefore measure the flow rates of fuel oil and air in order to correctly regulate their proportions.....
- Safe boiler operation - Preparations & raising steam
All boilers have a
furnace or combustion chamber where fuel is burnt to release its energy.
Air is supplied to the boiler furnace to enable combustion of the fuel to
take place. A large surface area between the combustion chamber and
the water enables the energy of combustion, in the form of heat, to be
transferred to the water.....
- Fuel oil burning process - various design burners Marine boilers currently burn residual low-grade fuels. This fuel isstored in double-bottom tanks from which it is drawn by a transfer
pump up to settling tanks. Here any water in the fuel may
settle out and be drained away.
- Boiler arrangement - combustion process - supply of air
Combustion is the burning of fuel in air in order to release heat energy.
For complete and efficient combustion the correct quantities of fuel and
air must be supplied to the furnace and ignited. About 14 times as much
air as fuel is required for complete combustion....
- Ordinary spring-loaded safety valve and improved high-lift safety valve for a marine boiler
Safety valves are fitted in pairs, usually on a single valve chest. Each valve must be able to release all the steam the boiler can produce without the
pressure rising by more than 10% over a set period.....
- Correct working level for marine boilers - use of water level gauges
The water level gauge provides a visible indication of the water level in the boiler in the region of the correct working level.
- How to maintain water level in a marine boiler ? A modern high-pressure, high-temperature watertube boiler holds a small quantity of water and produces large quantities of steam. Very careful control of the drum water level is therefore necessary. The reactions of steam and water in the drum are complicated and require a control system based on a number of measured elements......
- Safety precautions for working with marine boiler All boiler controls, regulators, alarms and trips must be tested regularly in accordance with the applicable Planned Maintenance System and makerís recommendations. Each test is to be recorded with the signature of the Engineer Officer who conducted the test....
Marine machineries - Useful tags
Marine diesel engines ||Steam generating plant ||Air conditioning system ||Compressed air ||Marine batteries ||Cargo refrigeration ||Centrifugal pump ||Various coolers ||Emergency power supply ||Exhaust gas heat exchangers ||Feed system ||Feed extraction pump ||
Flow measurement || Four stroke engines || Fuel injector || Fuel oil system || Fuel oil treatment ||Gearboxes || Governor ||
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Lub oil filters ||
MAN B&W engine ||
Marine condensers ||
Oily water separator ||
Overspeed protection devices ||
Piston & piston rings ||
Crankshaft deflection ||
Marine pumps ||
Various refrigerants ||
Sewage treatment plant ||
Starting air system ||
Steam turbines ||
Steering gear ||
Sulzer engine ||
Turbine gearing ||
Two stroke engines ||
UMS operations ||
Drydocking & major repairs ||
Critical machinery ||
Deck machineries & cargo gears
|| Control and instrumentation
||Engine room safety ||
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