Pendant Type Coils Boiler Superheater & Reheater With Claps Ovality And Thickness Both Less Than 15%

Pendant type coils boiler superheater & reheater with claps Ovality and thickness both less than 15%

Description

·The temperature of steam in boilers depends on the pressure but whilst it is in contact with the water it never exceeds the boiling point for that pressure.

·This is referred to as the "saturated steam" temperature. So long as the pressure and temperature remain the same the steam will not contain water and is referred to as "dry saturated steam".

·As the steam travels from the boiler to the engine,however,despite insulation of the pipework etc,it will experience a drop in temperature and condensation will immediately result.

·Condensation will also occur when the steam comes into contact with the cooler cylinder walls and,as energy is extracted from the steam in the cylinders by performing work on the piston, a further drop in temperature will occor resulting in further condensation.

·Apart from the resulting loss of efficiency,the presence of incompressible liquid water in the cylinder is potentially disastrous.

·If it were trapped between the piston and the cylinder end-cap it could result in the end being blown off.

Historical review

·Steam-dryers and steam-traps can remove condensed water from the pipes,and steam-jacketing can reduce cylinder condensation they do not eliminate the problem.

·It was realised in the 19th century that once the steam was removed from proximity with water in the boiler it could receive additional heat and its temperature could be raise above the boiling point.

·This is referred to as "superheating".

·With sufficient additional heat,the rise in the temperature of the steam would more than compensate for the fall in temperature as it passed through the pipe-work and engine and condensation could be eliminated.

·Tube failure is one of the leading causes of forced outages in power plants. One of the key ways of preventing failure is to predict the remaining useful life of tubes.

·By gaining an accurate assessment of the predicted lifespan of the tube, power plant operators have the necessary information to make decisions on prioritising future inspections, and whether to run, repair or replace tubes.

·How we analyse the remaining useful life of tubes:

·The lifespan of a superheater or reheater tube is affected by time, temperature and stress.

·To measure the remaining useful life of the tube, information on the steam pressure, original and present wall thicknesses and the tube’s outside diameter (OD) is used to calculate the stress history of the tube. ·The steamside scale thickness is used to gauge the effective temperature history of the tube.

·The stress history and the effective temperature history are compared to the creep rupture material of the specified tube material. From this information, the remaining useful life of the tube can be calculated – as well as the temperature profiles across the boiler.

·Hot spots and wastage patterns can also be identified.

Advance technology

·HDB has extensive experience using their remaining useful life analysis system to predict the lifespan of tubes.

·The system measures the oxide and wall thickness of the tube during an on-site non-destructive test and this is used to calculate the remaining useful life.

·HDB developed the oxide measuring technology in 1991 and it is now used as the standard throughout the world.

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