Mastodon Power plant and calculations

Various IBR forms, acts & regulations for a power plant engineers

Sl No.
IBR Form No.
Details of forms
1
I
Memorandum for Boiler inspection or registration
2
II
Issued by inspection authority during new construction
3
II A
Issued by inspection authority during new construction for foreign code boilers
4
III
Certificate of manufacture issued by constructor
5
III A
Steam pipe line test certificate  issued by manufacturer
6
III B
Tubes  test certificate issued by manufacturer
7
III C
Test certificates for  fittings & mountings (Valves,bend,elbow,tee etc)
8
III F
Test certificates of casting & forging issued by manufacturer
9
V
Boiler use provisional order issued by Boiler inspector authority
10
VI
Certificate issued by  directorate of steam boiler for boiler use
11
VII
Inspecting authority (directorate of steam boiler) certificate for constructional Boiler
12
XI
Certificate for the use of an Economiser
14
XII
Welder qualification record
15
XIII
IBR welder certificate
16
XVI-F
Certificate for approval of tube maker
17
XVI-G
Certificate for approval of pipe maker
18
XVI-H
Certificate for approval of material testing laboratory
19
XV-I
Certificate for approval for RLA organisation
20
Form No.C
Certificate for 2nd class Boiler attendant issued by Directorate of steam Boilers under rule-41
21
Form No.B
Certificate for 1st class Boiler attendant issued by Directorate of steam Boilers under rule-41
22
Form No.B
Certificate for BOE  issued by Directorate of steam Boilers under rule-40 Boiler operation engineer-2011

Power plant consruction materials & welding electrodes used

Various sections and their significance of IBR act 1923.

Sl. No.
Section No.
Used for
1.
Section-7
New boiler registration
2.
Section-8
Renewal of boiler on form VI
3.
Section-9
Provisional order on form V
4.
Section-12
Boiler alteration, modification
5.
Section-23
Penalties on illegal use of boilers












Power plant maintenance Questions & Answers

Various regulations and their significance of IBR regulation 1950.

Sl. No.
Regulations
Used for
1.
376
Preparation for boiler inspection
2.
379
Boiler hydraulic test
3.
390
Boiler open inspection
4.
391A
Boiler RLA test or NDT tests



Why do the Boilers Explode???

10-Tips to reduce LOI in Boilers

Batteries & troubleshooting


  

1-List down the applications of auxiliary DC power supply system in Power plants?
  •  Protections relays
  • Circuit breakers
  • DCS
  • Trip circuits
  • Signaling
  • Telephone system & communication
  • Emergency lighting
  • Transmitters & Positioners
  • Emergency oil pumps
  • Metering panels

2-List down the various DC voltages & their applications in power plants
Sl No.
Voltage
Applications
1
220 VDC & 110 VDC
Protection system
Emergency lighting
Trip & closing coil of circuit breakers
Operating mechanisms
2
48 VDC
Telephone communication
3
+/- 24 VDC
Control circuits
Measuring instruments
Static relays

3-What is the power source for DC supply?
Main power source is lead-acid storage battery & AC/DC rectifier set
4-What are the installation requirements for lead acid battery ?
  • The room should be isolated from other system
  • Room should have adequate lighting & ventilation
  • The room walls & floor should have acid proof tiles
  • Battery cells should be installed on insulated racks
  • Racks should be placed on insulator generally porcelain insulators
  • Cables should be acid proof
  • The DC bus bars should be of round or flat copper materials
  • Bus bars connections are made by soldering or brazing
  • The positive terminal of the battery is Red & negative terminal should be blue
30-selected QnA on power Transformers
5-How do you calculate the maximum discharge current of batteries?
Maximum discharge current = (Continuous load (W1) + Short time Load (W2)) / Rated Voltage
6-How do you specify the batteries?
Batteries have following specification:
  • Rated voltage
  • No.of cells
  • AH capacity
  • Arrangement of cells
  • Details of charging equipment

7-What do you mean by AH of batteries?
AH (Ampere hour) is the capacity of battery. It is the product of current and total time required for discharge. It depends on the magnitude of discharge current.
8-How do you decide the number of batteries for a particular battery bank?
No. of battery cells = Bus bar voltage / Voltage of one cell
9-What are the various charging methods employed for batteries?
  • Initial charging
  • Quick charging
  • Trickle charging
60-Basic questions & Answers on power plant electrical system

10-What do you mean by trickle charging? & what is its significance?
Trickle charging is constant charging current that is supplied to battery to compensate its discharge current.
Batteries get discharge when not in use. Hence to avoid sulphating, the batteries should be kept continuous charging by trickle charging.
11-What do you mean by primary cells (dry cell) & secondary cells?
Primary cells are non rechargeable cells & Secondary cells are storage batteries
12-What are anode, cathode & electrolyte in Lead-acid batteries?
  • Cathode: Sponge lead
  • Anode: Lead Peroxide (PbO2)
  • Electrolyte: Sulphuric acid & water

13-What is the voltage level of lead acid batteries that are generally employed?
It is 2 V
14-What is the voltage level of fully charged & fully discharged lead acid battery?
Voltage of fully charged cell is 2.5 V & 1.75 V for fully discharged cell
15-What will happen during battery discharge & charging of lead acid battery?
During discharging process, the lead & lead peroxide het change into lead sulphate. And during charging lead sulphate gets convert into lead & lead peroxide
16-How do you check the specific gravity (SG) of electrolyte of lead acid battery?
Specific gravity (SG) is checked with the help of Hydrometer
17-What is the SG of fully charged & fully discharged electrolyte
SG Fully charged electrolyte: 1.28 & 1.12 for fully discharged electrolyte
18-What is the proportion of Sulphuric acid & water in Lead acid batteries?
Sulphuric acid: 64% & Distilled water: 36%
19-How do make up electrolyte level in lead-acid batteries?
Lower level of electrolyte is due to evaporation of water.
If the lower electrolyte level is due to evaporation of water, then add distilled water. And if If the lower electrolyte level is due to spilling over bubbling, then add acid & water solution.
20-Explain the charging method of lead-acid battery?
During charging process current forced into battery from opposite direction to its normal direction of current flow.
That is during normal use current leaves from positive terminal & enters through negative terminal. During charging current enters through positive terminal & leaves through negative terminal
21-Why do the lead-acid batteries get discharge when they are not in use?
This is because internal discharge current due to impurities in the electrolyte
22-What electrolyte is used in Nickel-Iron batteries?
Potassium hydroxide
23-What is the voltage level & density of electrolyte of Nickel-Iron battery?
It is 1.2 V & 1.2
24-Which electrolyte is used for Nickel Cadmium batteries?
Potassium hydroxide
25-What precautions do you take to avoid over discharging of battery?
  • Over discharging can be avoided by
  • Regular charging of battery
  • Avoid excessive discharge rate
  • Avoid short-circuit currents & leakage current
  • Schedule charging & discharging
  • When not in use, battery terminals should be considered
Basics of power plant instrumentations
26-What do you mean by sulphated Battery?
Discharge battery with abnormal hardened lead sulphate on its plate is a Sulphated battery
27-What actions you will take if Battery is charging slowly?
  • Check battery connections & rectify if there are loose connections
  • Check charger capacity
  • Add distilled water or acid water solution if electrolyte is low
  • Check sulphatation of battery & rectify it
  • Increase current rating
  • Check connection that is positive lead of charger to positive of battery & negative to negative

28-What are the reasons for overheating of battery while charging?
  • Poor ventilation
  • High charging rate

Lower specific gravity of electrolyte
29- What are the reasons for overheating of battery while discharging?
High discharge rate
Separators between plates have damaged
30-What are the reasons for cells having unequal voltages?
  • Over discharge
  • Lower electrolytes level
  • Foreign material in electrolyte
  • Positive plate worn out



Valves: DO you know these..???


  •  Valve is a Mechanical or electromechanical device which is used to control the flow, pressure & temperature of fluid.
  • Generally Globe valve, Gate valves, Butterfly valve, diaphragm valve, needle valve, Non return valves etc used in power plant various applications.
  • The materials which are directly in contact with high pressure & temperature fluid are called trim materials.
  • IBR Valves materials are manufactured according to the ASME class 16.34 B
  • “Y” type globe valves have minimum pressure drop as compared to normal globe valves
  • WCB indicates cast carbon steel, includes the standard A 216 . Used for fluid temperature up to 425 deg C
  • WC-6 indicates Chromium Molybdenum steel, includes the standard A 217. Used for fluid temperature up to 575 deg C
  • WC-9 indicates Cast alloy steel, includes the standard A 217. Used for fluid temperature up to 593 deg C
  • SA 105 indicates forged & SA 182 indicates forged alloy steels

Equivalent grades of valves:
  1. SA 216 WCB/WCC: SA 105N
  2. SA 217 WC6: SA 182 F11
  3. SA 217 WC9: SA 182 F22
  4. SA 217 C12A : SA 182 F91

  • The MOC of Stud & nut materials of high pressure valves are SA 194 Gr.B7 & SA 194-2H
  • Stem nuts of all high pressure valves is of Aluminium bronze materials
  • The yoke of all high pressure valves are made up of material A-216 WCB
  • Hand wheel of all HP valves are made up of SG iron 400/12
  • Stems of all HP valves are made up of A 479-410-2
IBR acts, regulations & forms used

Comparison between Gate valve & Gate valve
  • For a same size of valves, the size & weight of gate valves is more as compared to globe valves
  • Time required for operating the gate valve is more as compared to globe valve
  • Effort required to operate the gate valve is less as compared to globe valve
  • Complicated maintenance procedure for larger size gate valves & simple maintenance procedure for globe valves
  • In gate valve pressure drop of fluid is very less as compared to globe valve
  • Gate valves cannot be used for flow regulating valves whereas globe valves can be used
  • Very less or no turbulence of fluid in gate valves whereas there is much turbulence in globe valves
  • Upon prolonged exposure of cast carbon steel or forged carbon steel valves to temperatures above 425°C, the carbide phase of steel may be converted to graphite. Permissible but not recommended for prolonged use above 425°C.
Basics of safety valves


33-most frequently asked questions & answers on air compressors


1-What are the functions of air compressors in power plants?
The functions of the compressor is to take a definite quantity of fluid (air or gas) & deliver it at a required pressure
2-What are the applications of compressed/pressurized air in power plants?
Operating the control valves
Operating the solenoid valves
Operating the dome valves in ash handling system
Air dampers operation in fans
Operating pneumatic tools
3-How does air compressor work? & what are the effects of compression on air?
An air compressor takes in atmospheric air. Compresses it and delivers this air to a storage vessel from which it will be conveyed by the pipe line to the required equipments.
Effects of compression:
Air pressure & temperature increases & moisture content in air increases
4-What are the various types of air compressors used in power plants?
Generally reciprocating, screw & centrifugal air compressors are used.
5-How does the positive displacement compressors work?
These compressors work by increasing the pressure of the air by reducing its volume
5-How does the centrifugal compressors work?
Centrifugal compressors initially increase the air velocity & then pressure at compressor outlet.
6-What are the various types of reciprocating compressors?

  • Single stage & multi stage
  • Single cylinder & multi cylinder
  • Air cooled & water cooled
  • Lubricated & Non lubricated
7-What are single acting compressors?
It is a compressor that has one discharge per revolution of crankshaft.
8-What are double acting compressors?
Compressor that completes two discharge strokes per revolutions of crankshaft
9-What do you mean by compression ratio in compressors?
It is the ratio of volume of air before compression to the volume of air after compression.
10-What do you mean by air compressor capacity?
It is the quantity of air actually delivered by a compressor in m3/minute or m3/sec.
11-What do you mean by Free Air delivery (FAD)?
It is the volume of air delivered by compressor under the compressor intake conditions like pressure &temperatures. FAD is not calculated on standard atmospheric conditions, it is measured in terms of CFM.It means that, amount of compressed air converted back to actual inlet air conditions.
12-What are the various parts of centrifugal compressors?
Impellers, Vanes, Volutes, Suction Eyes, Discharge lines, Diffuser Plates, Seals, Shaft, Casing
13-What do you mean by swept volume?
The volume displaced or swept by piston when it moves between two ends.
14-What do you mean by clearance volume?
 It is the difference between the total volume and the swept volume.
It is the space between the cylinder end and the piston to allow for wear & for easy movement. And also clearance is for valves reception.
Therefore clearance volume should be small as possible, but cannot be reduced to zero since, for mechanical reasons to avoid contact of moving parts in compressors.
15-Compressors efficiency
1. Volumetric efficiency:-
It is the ratio of actual volume of the FAD at standard atmospheric condition in one delivery stroke (Actual air intake) to the swept volume (theoretical air intake) by the piston during the stroke.
2. Isothermal efficiency:-
It is the ratio of isothermal work done to the actual work done
3. Volumetric efficiency:-
It is the ratio of free air delivered to the displacement of the compressor.
It is also defined as the effective swept volume to the swept volume
4. Mechanical efficiency:
It is the ratio of mechanical output to the mechanical input
Mechanical efficiency = Indicated horse power / Shaft horse power
16-Why do the compressors located at higher elevation consume more power as compared to those of lower elevation compressors?
As the altitude increases, air pressure goes on decrease; hence inlet pressure to the compressor decreases. For this compressor has to consume more power to provide required discharge pressure.
17-What is the relation between Relative humidity & moisture carrying capacity of air?
As the relative humidity (RH) increases, Moisture carrying capacity of the air increases
18-What are the reasons for reduction of volumetric efficiency of a reciprocating compressor?

  • Very high speed of compressor
  • Very large clearance volume
  • Obstruction in inlet valves
  • Malfunctioning of valves
  • Overheating of compressed air
  • Inertia effect of air in inlet pipe
19-Why the FAD is actually less than compressor displacement?
Because

  • The fluid resistance through air intake valve& valves prevent the cylinder being fully charged with air at atmospheric conditions.
  • Losses due to leakages
  • The high pressure air trapped in the clearance space, must expand to a pressure below the atmospheric pressure before the automatic suction valves open
20-What is the significance of inter coolers & after coolers in Heat exchangers?
Intercooler & after coolers are the shell & tube type heat exchangers in which hat is removed from air which has been compressed & its temperature has risen as a result of compression.
The cooler which is placed in between the stages are called Inter coolers & coolers are fitted after the last stage is called after coolers. Generally after coolers are used for removing the moisture from air by reducing its temperature.
21-How do you increase the isothermal efficiency of reciprocating compressors?
Isothermal efficiency can be increased by;
Water jacketing: where water is circulated around the LP & HP cylinders, which helps to cool the air
Inter-cooling: Intercoolers are fitted between the two stages to cool the air coming out from 1st stage. In inter coolers air temperature is maintained around atmospheric temperature.
Adding external fins for smaller compressors
22-Why do you prefer multistage compression rather than single stage?
Because;

  • Air can be cooled between interstages
  • For the same pressure & FAD, multi stage compressors consume less power
  • These are having good mechanical balance
  • The pressure & temperature range can be kept as per requirement. This results into reduced wear & tear & increased volumetric efficiency
  • However multistage compressors with coolers arrangement is more expensive than single stage compressor
23-A single stage reciprocating air compressor takes 1.5 M3/min of air at pressure 1.013 bar & 25 Deg C temperatures & delivers at 6 bar. Calculate the final air temperature
Solution:
Assume law of air compression pVn = Constant
That is pV 1.35 =Constant
P1 = 1.013 bar & T1 = 25 + 273 = 298 K
P2 = 6 bar
We have
T2 / T1 = (P2 / P1) (n-1) / n
T2 = 298 X (6/1.013) (1.35-1)/1.35
T2 =470.36 K
T2 = 470.36 – 273 = 197.36 Deg C
24-Suction pressure of a double stage air compressor is 350 mmwc & discharge pressure 6 kg/cm2 .Then calculate the 1st stage outlet pressure?
P1 = 350 mmwc = (1.03-350/1000) = 0.995 kg/cm2
P2 = √(P1 XP3) = √(0.995 X 6)
P2 = 2.44 kg/cm2
25-What do you mean by perfect cooling in compressors heat exchangers?
The condition, where the inlet temperature of air at each stage of multi-stage machine should be the same as it was at the first stage inlet is called perfect cooling.
26-Is volumetric efficiency of a compressor is less at higher delivery pressure?
Yes, at higher delivery pressure volumetric efficiency of any compressor is less & vice versa
27-What do you mean by loading & unloading in air compressors?
It is the two step control of delivery pressure, where compressor is loaded when there is air demand and unloaded when there is no demand.
During unloading air compressors consume lesser power, say 30 to 40% of full load. Positive displacement compressors consume less power & screw compressors more during unloading.
28-Does incorporating VFDs to reciprocating compressors save energy?
No...Compressors are required to run at full RPM, if run at lower RPM time required for loading will increase. So loading & unloading by using VFDs is not recommended for reciprocating compressors However sometimes it can be applied for centrifugal compressors.
29-Explain the process of loading & unloading in reciprocating air compressors?
In reciprocating air compressors, suction valves of compressors are fitted with un loader. Suction valves get forced open by actuating Solenoid valve (SOV) when discharge goes higher than requirement.
During loading: The SOV de-energies & the suction valves open & close as per the operation of flat springs fitted with SOVs.
During unloading: As the pressure increases more than set pressure, SOV on actuating air line opens to allow air to force open the suction valves. During compression stroke air discharges through already opened suction valves & pressure does not increase during suction stroke.
For 50% unloading 50% of suction valves get forced open & for 100% unloading all the suction valves get opened.
30- Explain the process of loading & unloading in screw air compressors?
Screw compressors are silent in operation & also consume very less power as compared to reciprocating compressors.
Unloading: When the demand of the air reduced, a device known as suction slide valve or suction throttle valve is activated. Then very less quantity of air is allowed to pass through it.
Loading: During loading, suction slide valve remains open 100%.
31- Explain the process of loading & unloading in centrifugal air compressors?
For controlling the discharge pressure of a centrifugal compressor, VFDs are installed. As the air consumption decreases, discharge pressure increases & motor speed decreases accordingly to maintain discharge header pressure.
Inlet guide vanes & Anti surge valves are also used for controlling speed.
Thumb rules on air compressors
Every 4 degree rise in inlet air temperature results in a higher energy consumption by 1%  to achieve equivalent power output
For every 250 mmWC pressure drop in increase across at the suction path will increase the power consumption of air compressor by 2%
An increase 5.5 deg C in the inlet air temperature to the second stage results in a 2% increase in the specific energy consumption.
A reduction in the delivery pressure of a compressor by 1 kg/cm2 would reduce the power consumption by 6-10%
32-What are the functions of air receiver tank?
Functions

  • Serves as air reservoir
  • Prevents frequent loading & unloading of air compressor
  • Separates moisture from air
33-What are the different types of air dryers used?
1. Refrigerent type
Adsorption type
a.Desiccant heat less drier
b.Desciccant type hot air drier



15-Emergencies in power plant operation

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