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The steam to steam generator working principle and operational procedure

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.



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.

The coils are supplied with high-pressure, hightemperature steam from the main boiler.


Water tube boiler

Fig:Water tube boiler


Raising Steam

Fuel Quality

Boilers are usually fired using heavy fuel oil. If it is necessary because of insufficient steam for fuel heating, to use Diesel Oil or other lower viscosity fuel a single pressure jet burner with the smallest available tip is to be used. If this is not available, then the smallest steam atomising or steam assisted tip can be used, provided that the steam connections are blanked off. The boiler is to revert to firing on heavy fuel oil once appropriate steam heating pressure is reached.

Purging

Should the burner fail to ignite, or flame failure occur, then it is essential that the furnace is visually examined for unburned fuel and purged before any attempt is made to re-ignite the burner. If the boiler furnace or furnaces are fitted with automatic purging systems then these must be fully operational. If the furnace or furnaces are not fitted with automatic purging sequence systems or they are not operational then prior to burner ignition, and on each subsequent occasion prior to re-igniting the burner or burners the furnace spaces are to be purged using the forced draft fans to give a minimum of five full changes of furnace air.

Manual Firing

If manual firing has to be resorted to, then the procedure must be in accordance with the manufacturer’s instructions and as agreed with the Technical Department of the relevant management office.

Firing

The procedure for firing must be in accordance with manufacturer’s instructions. Heating should be gradual and uniform, starting with one burner using the smallest tip available. A period of six hours should normally be allowed for raising steam, but in cases where repairs to refractory, or parts subject to pressure, have been carried out the period should be extended to 24 hours with alternate registers used.

Flow through Superheaters

Steam flow through superheaters must be maintained at all times. In cases of emergency when steam is required at short notice the boiler manufacturer’s instructions are to be adhered to.

Venting

Throughout the steam raising process, provision is to be made for venting all air from the boiler. This should be done solely by means of a designated air release cock or, if this is not fitted, by means of the steam pressure gauge cock. Under no circumstances are the steam connections of the water level gauge glasses to be used for venting purposes.



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Related Info:

Requirement for various boiler types on board cargo ships

Safety precautions for working with marine boiler

General arrangement for marine boiler

Water tube boilers

Fire tube boilers

The use of boiler mountings

Combustion process - supply of air

Various designs burners

Purity of boiler feedwater

Boiler feedwater treatment

The steam to steam generator

Combustion process - supply of fuel oil

Safety valves

Water level gauges

Double evaporation boilers

Exhaust gas heat exchangers

Safety precautions



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