Coils Boiler Superheater And Reheater Claps Ovality Thickness Both Less Than 15%

Coils Boiler Superheater And Reheater Claps Ovality Thickness Both Less Than 15%

Description

The temperature of steam in a boiler depends on the pressure, but when it comes in contact with water, it never exceeds the boiling point.

· this is called the "saturated steam" temperature.As long as the pressure and temperature remain constant, the steam will not contain water, known as "dry saturated steam."

· when steam flows from the boiler to the engine, it will experience a drop in temperature and immediately coagulate, although there is insulation in the pipe and so on.

Condensation also occurs when steam enters steam.

Function

The superheater is responsible for heating the steam first vaporized in the boiler to high quality superheated steam.After the superheated steam has done work in the high-pressure cylinder of the steam turbine, the low-pressure and low-temperature steam (called cold reheating) is reintroduced into the reheater. The reheater is responsible for reheating this part of steam into high-temperature steam.The reheated steam (called reheat) enters the steam turbine and the low-pressure cylinder, and finally enters the condenser to condense into water.

It can be seen from the above process that both reheater and superheater are used to heat steam, but the parameters of steam are different.The steam in the superheater belongs to high temperature and high pressure, and the material is required to be higher than the reheater, while the steam in the reheater belongs to high temperature and low pressure, and the material is required to be lower than the superheater.

Setting the safety valve is because any material has its own working limit, as superheater or reheater, its material also has certain working limit, including temperature and pressure.The setting of the safety valve is to make the superheater or reheater discharge pressure through the action of the safety valve when the steam pressure exceeds the set value, so as to avoid the accident of pipe explosion or even furnace explosion due to the material exceeding the limit.

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.