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vrmanisowmya_143
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Turbine Steam Flow

12/13/2012 6:12 AM

Consider, there's a Boiler with 975 TPH evaporating capacity & a Turbine with the same amount of steam input. The rating of boiler is: MSL temperature = 540 deg. Cel & MS pressure = 178 kg/cm2. At starting I am giving 100 tons of steam & my output is say 23.75 MW. Turbine RPM is 3000 rpm & Alternator rpm, too, is 3000. When load on Boiler increases, say from 100 TPH to 200, 250, 300 & so on, what actually happens in the Alternator & why.? Why I need to increase the steam flow through the turbine.?
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PWSlack
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#1

Re: Turbine Steam Flow

12/13/2012 6:27 AM

The load increase is expressed as additional torque needed from the turbine. If steam flow is not increased, then the turbine speed will drop.

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vrmanisowmya_143
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#3
In reply to #1

Re: Turbine Steam Flow

12/13/2012 7:00 AM

Sir, I would wanna know, if the Governor is installed on the main steam line inlet to turbine, then what role will ESV on the turbine play.? How will it monitor the stem flow rate.?
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PWSlack
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#4
In reply to #3

Re: Turbine Steam Flow

12/13/2012 7:16 AM

If ESV = emergency shutdown valve, then the question is meaningless. Valves don't monitor anything.

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kramarat
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#2

Re: Turbine Steam Flow

12/13/2012 6:55 AM

In the simplest terms...................

It's the same reason that you have to supply more gasoline to your car engine to provide the power to go uphill or go faster.

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PWSlack
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#5

Re: Turbine Steam Flow

12/13/2012 7:17 AM

Has the automation on this equipment failed, or something? Why is the equipment being driven manually?

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dhayanandhan
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#6

Re: Turbine Steam Flow

12/13/2012 8:49 AM

Dear vramanisowmya143,

It is the other way. When you increase the Load, the Load Governor comes int to picture and admits more steam as required, simultaneously the Speed Governor regulates/controls the Speed.

If you have understood the above mentioned philosophy, then you will understand that, when you increase the Load on the Alternator, by varying the position of the Load Governor, the Voltage of the Alternator drops down and AVR comes in to picture and regulates the Voltage, Simultaneously the Speed Governor senses the fall in speed and admits more steam and stabilises at rated speed, of course, a small fluctuation of Load and Speed is permissible to a small extent.

DHAYANANDHAN.S
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vir540
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#7

Re: Turbine Steam Flow

12/13/2012 12:26 PM

Efficiency of generator is given by Electrical power sent out to that of mechanical work output. Clearly to increase the electrical power sent to grid we need to develop more power. To develop more power we need more work to be developed in turbine. turbine work is a function of steam flow...to increase the work output of turbine we increase the steam flow...so gradually when you increase steam flow the load on TG set increases...and your MW increases.

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satendrakumart
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#8

Re: Turbine Steam Flow

12/13/2012 11:24 PM

Think it reverse.

Actually load on Boiler is not increased or decreased as per operator's desire. It varies automatically with load demand. If the load demand on the TG set is increased, (It happens by starting a load, say motor, or injecting more power to grid), then the steam demand by the TG set will increase. To full fill the steam demand, the steam flow generated by the boilers is increased or decreased/ dumped.

Now why the steam demand is increased with more load demand? It is because the current generated in TG opposes the cause generating it, the rotation of turbine. More load, more current, more opposition to rotate on constant frequency, more steam demand.
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vrmanisowmya_143
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#11
In reply to #8

Re: Turbine Steam Flow

12/14/2012 4:56 AM

Thanks a lot.
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IRSHAD
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#9

Re: Turbine Steam Flow

12/13/2012 11:50 PM

The alternator follows Lenz's law.
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Satish Menon
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#10

Re: Turbine Steam Flow

12/14/2012 1:20 AM

Boiler selection ( MT of Steam /hour MCR or Maximum Continuous Rating) and turbine selection ( SSC or Specific Steam Consumption of the turbine in kg steam/hr /kW ) go hand in hand.

The turbine has a Governor ( normally Woodward UG -8 or UG-10 models) which senses the increase in Load demand (kW) and correspondingly signals the hydraulically controlled Governor Valve opening to emit more steam. Hence the frequency ( 50 Hz) and the Voltage ( 415 V) of the alternator output is kept constant through turbine speed regulation to also keep it constant with variable steam flow.

The Governor Valve and the Emergency Shut-Off Valve is one and the same. The shut-off mechanism is also hydraulically controlled and set to trip for several conditions - overspeed, Low Lube Pressure and Axial Displacement of HSS ( High Speed Shaft).
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dhayanandhan (1); IRSHAD (1); kramarat (1); PWSlack (3); satendrakumart (1); Satish Menon (1); vir540 (1); vrmanisowmya_143 (2)

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