### How do you calculate the Power generation in steam Turbines??

Power in the steam Turbines produces at every stage where the steam is taken out, whether it may be bleed, extraction or exhaust steam. As the steam out from the turbine increases the power developed on that particular stage will increase.
Power generation phenomenon.
Power generation in steam Turbines is calculated based on difference between the heat content of inlet steam & extracted steam.

Factors affecting the power generation:
• Power generation at particular stage increases, when there is more steam flow &vice versa
• Power generation at particular stage increases when there is more difference between inlet & extraction steam & Vice versa
• Power develop at particular stage decreases if its extraction pressure increases & vice versa
• Power developed at particular stage decreases if its extraction temperature increases & vice versa
• Power developed in steam Turbine decreases if inlet live steam pressure & temperature decrease
• If steam vacuum decreases power generation reduces or else Turbine will consume more steam to develop same power
• If exhaust steam temperature increases then the power power generation reduces or else Turbine will consume more steam to develop same power
• If wheel chamber pressure increases, then the power generation capacity of the Turbine decreases
In which part of the Turbine higher power can be produced at lower steam consumption? And why?
It is at the exhaust stage. Because at the exhaust stage pressure & temperature of the steam is very lesser than bleed &extraction stages.
In which part of the Turbine lowest power is produced at higher steam consumption? And why?
It is at the bleed stage. Because at bleed steam pressure & temperatures are higher than extraction & exhaust stages
Calculation part:
1-Calculate the power generated in a back pressure steam Turbine, where 50 TPH steam enters the Turbine at 66 kg/cm2 & temperature 485 Deg C.And steam exhausts to process at pressure 2 kg/cm2 & temperature 180 Deg C.
For calculation of power we need to know the enthalpy of inlet & exhaust steam.
Refer steam table
Enthalpy of inlet steam at rated parameters H1 = 806.5 kcal/kg
Enthalpy of inlet steam at rated parameters H2 = 677 kcal/kg
Now power developed in steam turbine P = Q X (H1-H2) / 860
Where Q is steam flow
P = 50 X (806.5-677) / 860
P = 7.52 MW
Note: 860 kcal = 1 KWH
2. Calculate the power developed by a steam turbine by using following data
 Sl No. Particular UOM Value 1 Turbine inlet steam flow TPH 145 2 Turbine inlet steam pressure Kg/cm2 88 3 Turbine inlet steam temperature C0 515 4 Bleed steam flow TPH 20 5 Bleed steam pressure Kg/cm2 12 6 Bleed steam temperature C0 250 7 Extraction flow TPH 100 8 Extraction steam pressure Kg/cm2 1.8 9 Extraction steam temperature C0 145 10 Exhaust flow to condenser TPH 25 11 Exhaust pressure Kg/cm2 0.08 12 Exhaust temperature C0 44 13 Dryness fraction % 90

Also calculate the specific steam consumption of this Turbine
Solution:
Note down the enthalpy of steam at various stages
Turbine inlet steam enthalpy H1 = 818 kcal/kg
Bleed steam enthalpy H2 =700 kcal/kg
Extraction steam enthalpy H3 = 657.2 kcal/kg
Exhaust enthalpy =Liquid heat + Dryness fraction X Vapour enthalpy = 41.77 + 0.9 X 615.5 = 595.72 kcal/kg
Also steam flow is given
Inlet steam flow Q1 = 145 TPH
Bleed steam flow Q2 = 20 TPH
Extraction steam flow Q3 =100 TPH
Exhaust steam flow Q4 = 25 TPH
Power generation at 1st stage (Bleed) P1 = Q2 X (H1-H2) / 860
P1 = 20 X (818-700) / 860 = 2.74 MW
Power generation at 2nd stage (Extraction) P2 = Q3 X (H1-H3) / 860
P2 = 100 X (818-657.2) / 860 = 18.69 MW
Power generation at 3rd stage (Exhaust) P3 = Q4 X (H1-H4) / 860
P3 = 25 X (818-595.72) / 860 = 6.46 MW
SO total power developed at Turbine shaft P = P1+P2+P3 = 2.74+18.69+6.46 = 27.89 MW
Specific steam consumption SSC = Turbine inlet steam flow / Power generation = 145 / 27.89 =5.19 MT/MW

3-By taking above example, explain how pure condensing steam Turbines have higher power generation & lower specific steam consumption (SSC)
Consider the above example, where Turbine inlet steam flow is 145 TPH & having 25 TPH exhaust steam flow to condenser.
If we condense 100% steam, then we will have reduced SSC
Let us see..
Q1=Q4=145 TPH..Where Q4 = Exhaust steam to condenser
Q2 & Q3 are considered zero (No flow)
Enthalpy of exhaust steam increases due to higher exhaust pressure
SO, Consider exhaust pressure = 0.1 kg/cm2 & Dryness fraction 0.9
Then, exhaust enthalpy becomes H1 = 46 + 0.9 X 617 = 601.9 kcal/kg
Total Power developed P= Q1 X (H1-H4) / 860
P =145 X (818-601.9) / 860 = 36.43 MW
So SSC = 145 / 36.43 = 3.98 MT/MW
This is very less as compared to bleed & extraction turbines

4-By taking an example No.2 explain how bleed steam flow will cause reduction in net power consumption
Solution:
We shall take the data of Example No.2
In this, we will increase bleed steam flow, pressure & temperature & parallel shall decrease extraction flow to match mass flow
 Sl No. Particular UOM Value 1 Turbine inlet steam flow TPH 145 2 Turbine inlet steam pressure Kg/cm2 88 3 Turbine inlet steam temperature C0 515 4 Bleed steam flow TPH 30 5 Bleed steam pressure Kg/cm2 15 6 Bleed steam temperature C0 285 7 Extraction flow TPH 90 8 Extraction steam pressure Kg/cm2 1.8 9 Extraction steam temperature C0 145 10 Exhaust flow to condenser TPH 25 11 Exhaust pressure Kg/cm2 0.08 12 Exhaust temperature C0 44 13 Dryness fraction % 90

Solution:
Note down the enthalpy of steam at various stages
Turbine inlet steam enthalpy H1 = 818 kcal/kg
Bleed steam enthalpy H2 =716.63 kcal/kg
Extraction steam enthalpy H3 = 657.2 kcal/kg
Exhaust enthalpy =Liquid heat + Dryness fraction X Vapour enthalpy = 41.77 + 0.9 X 615.5 = 595.72 kcal/kg
Also steam flow is given
Inlet steam flow Q1 = 145 TPH
Bleed steam flow Q2 = 30 TPH
Extraction steam flow Q3 =90 TPH
Exhaust steam flow Q4 = 25 TPH
Power generation at 1st stage (Bleed) P1 = Q2 X (H1-H2) / 860
P1 = 30 X (818-716.63) / 860 = 3.53 MW
Power generation at 2nd stage (Extraction) P2 = Q3 X (H1-H3) / 860
P2 = 90 X (818-657.2) / 860 = 16.82 MW
Power generation at 3rd stage (Exhaust) P3 = Q4 X (H1-H4) / 860
P3 = 25 X (818-595.72) / 860 = 6.46 MW
SO total power developed at Turbine shaft P = P1+P2+P3 = 3.53+16.82+6.46 = 26.81 MW
Specific steam consumption SSC = Turbine inlet steam flow / Power generation = 145 / 26.81 =5.41 MT/MW
So by increasing the bleed steam flow, the work done by the Turbine decreases & hence steam consumption will increase

5-A Turbine’s inlet steam enthalpy is 825 kcal/kg & Exhaust enthalpy is 590 kcal/kg. Calculate the work done by steam & specific steam steam consumption
We have,
H1 = 825 kcal/kg, H2 = 590 kcal/kg
Work done per kg of steam = (H1-H2) = 825-890 =235 kcal/kg
SSC = 860 / Work done = 860 / 235 =3.65 kg/kwh or 3.65 MT/MW
6-A steam Turbine inlet steam pressure & temperatures are 104 kg/cm2 & 540 C0 & exhausts at pressure 0.09 kg/cm2 & temperature 43 Deg C calculate the
a-      Work done per kg of steam
b-      Heat supplied per kg of steam
c-       Cycle efficiency
Enthalpy of inlet steam = 829 kcal/kg
Exhaust liquid enthalpy = 44 kcal/kg
Exhaust enthalpy by considering 90% dryness fraction = 44 + 0.9 X 616.44 =598.76 kcal/kg
A-Work done per kg of steam = (829-598.76) = 230.24 kcal/kg
B-Heat supplied per kg of steam = 829-44 = 785 kcal/kg
C-Cycle efficiency = Work done per kg of steam X 100 / Heat supplied per kg of steam
= 230.24 X 100 / 785 = 29.32%
Note:
Power developed at Generator terminals = Power developed at Turbine Shaft X Reduction gear box efficiency X Alternator efficiency
For example:
Calculate the net power developed at Generator terminal if 100 TPH steam enters the Turbine at 811 kcal/kg enthalpy & leaves the Turbine at enthalpy 565 kcal/kg .Assume Gear box efficiency as 98% & Generator efficiency as 95%
Power developed on Turbine shaft = 100 X (811-565) / 860 = 28.0 MW
Net power developed at Generator output terminals = 28.0 X 0.98 X 0.95 = 26.06 MW

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### Selected Questions & Answers on Rigging guidelines

1. What is rigging technology?
Rigging is the process of using hoists, ropes, pulley, slings, jacks and cranes for lifting, lowering or shifting the heavy objects.
2. Who is rigger?
A person who leads or carries out the rigging process.
3. What are the various rigging elements used in power plant?
• Synthetic and wire ropes
• Slings
• Chain hoist/chain block
• Pulley block
• Screw and hydraulic jacks
• Crane
• Winch machine
• EOT cranes
• Derricks…etc.

4. Write a short note on rigging plan.
In order to ensure the safety of workers and the equipment involved, any operation involving the use of a lifting item to lift items must be planned thoroughly before being carried out.
Rigging Plan Involves:
1. Determination of Task and Job Site Requirements:
a. What is to be lifted?
b. Who is the in charge person?
c. What are the job site requirements?
d. What type of lift?
Ordinary Lift: Involve the use of basic hoisting equipment directly above the load. The load must also have certified lifting points to relatively easy to sling. It is repetitive in nature.
Critical Lift: Involves lifting objects in congested space, heavy objects, high susceptibility to damage and precision.
Pre-Engineered Lift: Involves use of tooling, fixtures, sketches, analyses, and written procedures for handling.
2. Characterization of Load:
It involves weight and center of gravity judgment of an object to be lifted
There are mainly two types of loads that are generally handled:
Symmetrical Load: Spare, square and rectangular type loads. These have center of gravity (C.G) at their center, so it will be very easy to handle such objects.
Asymmetrical Load: An object with an off-center C.G due to the object’s irregular shape and/or composition. These objects are difficult to handle as their C.G lies out of center.
3. Selecting the Proper Rigging Element:
After characterizing the load, proper rigging elements are selected.
Examples:
• For lifting only, chain blocks and slings are selected.
• For lifting and shifting: Cranes.
• For lifting precision objects, lifting belts are selected instead of wire ropes and slings.

5. What is the safe working load of 25 mm Nylon rope?
Safe working load (SWL) of Nylon rope = D X D = 25 X 25 = 625 kgs.
Where D is the diameter of rope in mm.
6. What is the smallest size of nylon rope used for lifting?
Smallest size of nylon rope used for lifting is 12 mm.
7. What is the material of composition of wire ropes and slings?
MOC of wire ropes and sling is Steel of grade 80.
8. What is the smallest size of wire rope used for lifting?
Minimum size of steel wire rope for handling loads is 5 mm.
9. How do you calculate the safe working load of steel wire ropes and slings?
SWL of wire ropes slings = 8 X D X D, Where D is the diameter of sling in inches.
10. What are the different hitches of slings/ropes? And what is the relation between sling angle & angle factor?

Vertical Hitch:
In vertical hitch SWL = Capacity of the rope/sling.
Choker Hitch:
In choker hitch, SWL = Sling capacity X 80%. i.e. sling lifting capacity will reduce by 20% of its rated capacity.
In basket hitch, SWL of Sling = Sling capacity X 140%, i.e. sling lifting capacity increases by 40% of its rated capacity.
Relation between sling angle & its angle factor
As the sling angle decreases to the horizontal then the angle factor increases.That is for lower sling angles to the horizontal the capacity of the slings reduces.
it is maximum at 90 degree angle & minimum at 30 degree angle.Hence it is recommended that slings are not loaded at ange below < 30 degree

11. What are the different slings used in power plant rigging?
Types of Slings:
• Eye/Eye type
• Eye thimble
• Thimble/Thimble
12. What are the pre-use checks to be done on Nylon and wire ropes?
• Check its manufacturer name plate details and ensure lifting load capacity.
• Check for strand damages; discard if more than 10% of strands are damaged.
• Check for strand frying.
• Check for rope knotting.
• Check for overloaded rope (Rope which was overloaded in previous lifts should not be used for lifting at its rated SWL).
• Check for reduction in rope diameter, wear out should be less than 10%.
• Should not have exposed temperature more than 65 and 95 °C for synthetic and wire ropes respectively for long time.
• Check for corrosion/rusting of wire rope.
• Check for any scoring or abrasion marks on wire rope.
• Check for wire end attachments damages.
13. How do you calculate the SWL of Chain block?
SWL = 80 X 0.4 X D2
Where D is diameter of load chain link.
14. What are the safe checks carried out on chain block?
Following are the inspection checks carried out on chain blocks:
• Check tightness of block’s nut bolts.
• Check gearing system is well operating and its lubrication.
• Check hook of block as per hook check list.
• Check load chain links for elongation and wear out.
• Link 10% size less than its original diameter is discarded.
• Check for unauthorized welding and cutting marks on chain hoist.
• Check whether chain is in contact with acid or alkali for long time.
15. What are the safe checks carried out on hooks used for lifting?
Inspection checks of hooks:
• Check for manufacturer identification numbers.
• Check for cracks, nicks etc.
• Check for unauthorized welding and grinding.
• Check for increase in throat area (not to exceed more than 5%).
• Check for wear out (not to exceed more than 10%).
• Check twist from plane of un bent hook.
16. What are the different types of eye bolts used in lifting?
Straight and shoulder type eye bolts are generally used for lifting applications.
17. What is the function of turn buckle?
Turn buckles are used for leveling and distributing the loads.
18. List down the safe checks carried out before moving/shifting heavy jobs.
Following are the check points for moving/shifting heavy jobs by cranes, forklifts or Hydras:
Trained operator
• Weight to be lifted
• CG of load
• Lift points
• Crane capacity
• Crane length, speed and boom maximum height
• Environmental parameter’s like wind velocity, visibility and temperature
• Travel route clearance
• Travel floor capacity
19. What is the allowable wind speed during rigging?
It should be less than 9 meter per second
20. What do you mean by tandem lifting?
Rigging plan where two cranes are used for lifting a single object
21. What are the different types of cranes used in rigging?
• Mobile crane
• Tower crane
• Gantry crane
22. What is the allowable speed of wind while working at height?
It is around 10.3 meter per second
23. What are the different synthetic web slings?
Synthetic web slings are made of Nylons & Polyesters
24. How do you decide the capacity of the web sling?
It can be decided by its width
25. What are the advantages of Synthetic web slings over other slings?
• Flexible & can adjust as per required shape.
• Minimize twisting and spinning.
• Do not rust and are non-sparking.
• Are elastic and stretch. Nylon has 6% & Polyester  has 3% stretching capacity

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