6th02 Plant Utitly System

8/3/2019 6th02 Plant Utitly System

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Dr\Usama Mohamed Nour B05-03-23, ext 7612, [email protected]

CAB4323 Plant Utility Systems

CAB 4323

Plant Utility Systems

L6



Steam Turbine•Heat is the flow of thermal energy. Thermal energy can bechanged to mechanical energy.•A steam turbine changes thermal energy to mechanicalenergy.•When water boils and turns to steam, the steam has more

energy than the water had.•Steam pressure in a boiler is increased by adding heat. Andthe pressure builds up in that container.

•If that container provided with a nozzle, the higher pressureforces steam to expand through the nozzle.•Steam is forced out of the nozzle at high speed or velocity. In

the shape of something like jet.• A jet of steam strikes the bucket, and the bucket moves.•When the steam expands through the nozzle its pressuredecreases.

•When steam expands through the nozzle, its pressure isreduced, the velocity of the steam increases.



•The rotor consists of ”blades” or bucketsmounted on o shaft.•The nozzle directs the flow of steamtowards the buckets.•Increasing the steam pressure at the boilerthat at the rotor increases the amount offlowing steam.

• After steam strikes the buckets, steamvelocity decreases.•The rotor turns and produces mechanicalwork. The steam has lost energy.

•If more nozzles are used, more work isproduced.•The purpose of nozzle is to direct steam atthe buckets and to convert steam pressureto steam velocity.

•The rotor in the turbine differs from that atthe previous drawing. The bucket aremounted on a wheel.



•The three basic parts of the steam turbine are:1-the rotor 2-the nozzle 3- the source•The nozzles are located on the wall of steam chest;

the flow of the steam chest is controlled by thegovernor valve.•By controlling the amount of steam flowing into thesteam chest, the governor valve controls the output

of mechanical energy.•The rotor is located inside a metal casing.•For the steam flow into the casing through thenozzle the steam pressure in the casing must belower than the steam pressure in the steam chest.•Without that steam pressure difference, the steamcan not flow and no mechanical work can beproduced.



•Single and multi stage turbines:•The area which the steam expands the area at which the steamexpands is called a “stage”.•When the pressure is reduced in one stage only, a turbine iscalled “single stage turbine”.



•When the turbine has many wheels it is called “multi stageturbine”.

•In a multi stage turbine, each stage is isolated by a diaphragmwhich holds the nozzle.



Types of turbines:•Condensing turbines:

1.Condensing turbines operate with exhaust pressures less

than the atmospheric pressure.2.It is larger in size and power output than the back pressureturbine.



Steam expands from higher pressure to a lower pressuretherefore, steam exhausts from the turbine at low pressure.That low pressure steam can be used in another area to run aturbine, so low pressure steam can expand to a lowerpressure.

In the drawing, a condenser removes heat and thus lowerspressure, which cools the steam leaving the turbine andchanges it into water.

The exhaust steam pressure of turbine A is higher thanexhaust pressure of turbine B.When steam is condensed to water, this water could return tothe boiler.The condensing turbine utilizes all the thermal energyavailable in the steam. So, large pressure drops are commonin condensing turbines.





•Back pressure turbines:- It is usually work at faster speeds than the condensing turbinedue to efficiency considerations.- operate with exhaust pressures equal or higher than theatmospheric pressure. Back pressure turbines are a type of steamturbine that is used in connection with industrial processes where

there is a need for low or medium pressure steam.

- The high pressure steam enters the back pressure steam turbine

and while the steam expands - part of its thermal energy isconverted into mechanical energy. The mechanical energy is usedto run an electric generator or mechanical equipment, such aspumps, fans and compressors etc.

- The outlet steam leaves the back pressure steam turbine at"overpressure" and then the steam returns to the plant for process

steam application such as heating or drying purposes.















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6th02 Plant Utitly System

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