Showing posts with label Boiler. Show all posts
Showing posts with label Boiler. Show all posts

How to calculate the cost of steam???


In power plant, calculation of cost of steam is very vital in commercial point of view. Following are the parameters which affect the cost of steam.

  1. Steam pressure
  2. Steam temperature
  3. GCV of fuel
  4. Price of fuel
  5. And Boiler efficiency

Following gives you the relation among steam cost & above all parameters & vice versa

  • Steam cost increases as the enthalpy or heat content in steam increases and vice versa
  • Steam cost increases as the GCV of fuel decreases and vice versa
  • Steam cost increases as the fuel price increases & vice versa
  • Steam cost increases as the Boiler efficiency decreases & vice versa

Understanding with examples.

1.Calculate the cost of steam per kg, which is been using for Steam turbine having pressure 121 kg/cm2 & temperature 550 deg C.The boiler of efficiency 75% uses coal of GCV 4200 kcal/kg to produce this steam.Cosnsider the price of coal is Rs 5000/MT

Enthalpy of steam at above pressure & temperature H = 830.43 kcal/kg

Boiler efficiency b= 75%

GCV of coal = 4200 kcal/kg

Now, cost of steam = Heat content in steam in kcal/kg  X Fuel price / (GCV of fuel in kcal/kg X Boiler efficiency b)

                                     = 830.43 X 5000 / (4500 X 0.75)

                                     = 1230.26 rupees / MT of steam or Rs 1.23 / kg of steam

 2.Calculate the cost of steam per kg, which is been using for chemical process plant having pressure 5 kg/cm2 & temperature 180 deg C.The boiler of efficiency 65% uses biomass of GCV 2800 kcal/kg to produce this steam.Cosnsider the price of biomass is Rs 2400/MT

Enthalpy of steam at above pressure & temperature H = 670 kcal/kg

Boiler efficiency b= 65%

GCV of coal = 2800 kcal/kg

Now, cost of steam = Heat content in steam in kcal/kg X Fuel price / (GCV of fuel in kcal/kg X Boiler efficiency b)

                                     = 670 X 2400 / (2800 X 0.65)

                                     = 883.51 rupees / MT of steam or Rs 0.88 / kg of steam

3. Calculate the cost of saturated steam given to sugar process for juice boiling plant having pressure 1.5 kg/cm2 & temperature 130 deg C.The boiler of efficiency 68% uses bagasse (biomass) of GCV 2200 kcal/kg to produce this steam.Cosnsider the price of biomass is Rs 2500/MT

Enthalpy of steam at above pressure & temperature H = 650 kcal/kg

Boiler efficiency b= 68%

GCV of coal = 2200 kcal/kg

Now, cost of steam = Heat content in steam in kcal/kg X Fuel price / (GCV of fuel in kcal/kg X Boiler efficiency b)

                                     = 650 X 2500 / (2200 X 0.68)

                                     = 1086.22 rupees / MT of steam or Rs 1.086 / kg of steam


 Deaeartor & HP heaters steam consumption calculations


 Questions & Answers on steam blowing


Questions & Answers on Boiler Hydraulic test

1-According to which law or regulation Boiler hydraulic tests are conducted?

Boilers hydraulic tests are conducted as per IBR 1950 Regulation 379

2-Why do Boilers Hydraulic tests are conducted?

  • To ensure there is no leakages in joints after erection & welding works
  • To ensure the healthiness of pressure parts & correctness of workmanship
  • To identify the weakness & defect of pressure parts
  • To complete the compliance of Boiler inspector authority
  • To avoid any incidents during boiler start up or operation

3-When shall you conduct Boiler Hydraulic tests?

Boiler Hydraulic tests are carried out;

  • After erection of new Boiler
  • After replacement of drum gaskets
  • After any repair works in pressure parts
  • After repair of replacement of critical (root valve, MSSV, MSNRV) valves
  • Yearly as per Boiler inspector compliance
  • After any alteration or modification in pressure parts

4-At what pressure do you take the Boiler Hydraulic test?

Boiler Hydraulic tests should be taken at pressure 1.25 times the maximum operating pressure or Design pressure of the Boiler

5-When shall you carryout Boiler hydraulic test at 1.5 times the maximum operating pressure or Design pressure of the Boiler?

If all the Boiler components are not tested in manufacturer premises as per Regulation 268, then Boiler hydraulic test should be conducted at pressure 1.5 times the maximum operating pressure or Design pressure of the Boiler.

6-What is the recommended temperature of Water for Boiler Hydraulic test?

The temperature of the water used as medium of pressure testing shall not be less than 20°C and greater than 50°C.

7-What are the desired parameters of water used for Boiler Hydraulic test?

Boiler water parameters

  • PH-8.5-9.2
  • Conductivity-5-10 mic S/cm
  • Silica-0.02 ppm
  • Hardness-Nil

8-Up to what time you are going to hold the Boiler at Hydraulic test pressure?

Boiler can be held up to 30 minutes at rated Hydraulic test pressure

9-When shall you conclude the completion of Boiler Hydraulic test?

The boiler shall satisfactorily withstand maximum allowable operating pressure without appreciable leakage or undue deflection or distortion of its parts for at least 10 consecutive minutes.

10-Is test pressure affects the Boiler ageing?

Yes, Boiler hydraulic test pressure should be reduced based on their ageing

11-What you will do if you observed any defects or deflection in Boiler parts during hydraulic test?

In such cases, Boiler hydraulic test should be stopped immediately & pressure shall be released

12-Is Pneumatic testing of Boilers is recommended before hydraulic test?

Yes pneumatic test of Boiler is done at pressure around 2-3 kg/cm2 to ensure leakages to avoid loss of DM water.

13-What is the rate of pressure rising during Boiler Hydraulic test?

It is around 3 to 3.5 kg/cm2/minute

14-Explain the Boiler Hydraulic test procedure

Preliminary checks

  • Ensure Boiler erection & maintenance related works are completed
  • Ensure Boiler feed pumps are healthy & ready to use (Ensure 1W+1S)
  • Ensure Initial water fill up line & pumps are ready to use
  • Ensure required quantity of DM water is available
  • Ensure DM water parameters are normal
  • Ensure DM temperature is 20 deg C to 50 deg C
  • Ensure Pressure gauges are mounted at steam drum, super heater & any other required location
  • Ensure the transmitters/pressure parts whose operating /hydraulic pressure is not recommended for hydraulic test are isolate
  • Ensure sufficient number of competitive team is available for conducting test
  • Ensure safety valves gags are available & kept near safety valves
  • Ensure, hydraulic test planning is done properly


  • Keep open Boiler’s all drum, super heater & economiser header air vent valves.
  • Ensure all drain valves of drum & headers are closed
  • Fill the Boiler, by initial fill up line by starting Deaerator or feed water tank make up pump.
  • If Boiler is completely empty, it will take 2 to 3 hours’ time to fill the Boiler (It depends on size of initial fill up line)
  • After filling the Boiler water will come out from vents of economiser, drum & super heater header.
  • Initial close the economiser header vents
  • Then close the Super heater & drum vents at pressure > 2 kg/cm2 to ensure air present in water is vented out completely (Sequence of vent closing should be from bottom elevation to top)
  • After closing the vents slowly raise the Boiler pressure by starting Boiler feed water pump or reciprocating pump (For newly erected Boilers, feed pumps may not available, so in such cases separate positive displacement pumps of required head are made available)
  • Ensure, initially the pressure rising rate is 3-3.5 kg/cm2/minute up to 25% of Hyd.test pressure, after that raise the pressure at rate 1 to 2 kg/cm2 / minute.
  • AT pressure 4 to 5 kg/cm2, flush the pressure gauge impulse lines & mount pressure gauges
  • After reaching Boiler pressure 90-95% of the operating pressure, mount the gags & apply force to ensure gags are fitted properly
  • Then continue pressurizing until Boiler pressure reaches the hydraulic test pressure. Ensure hydraulic test pressure not crossed the 6% of maximum allowable pressure
  • Hold this pressure for 30 minutes & then release the pressure to normal operating pressure
  • Then inspect all the joints, valves glands, other pressure parts for leakages & deflection.
  • Once found normal, release the Boiler pressure through blow down valves
  • AT pressure 10-15 kg/cm2 flush Boiler bottom headers
  • Remove the gags
  • Open the vent valves


 Read Boiler refractory dry out procedure


 Questions & Answers on steam blowing





Interview questions & answers on Boiler Alkali Boilout


1-Why do you carry out an Alkali boil out of a Boiler?

Alkali Boil out is done for

  • To remove oil & grease
  • To remove rust, scale  

2-When you will carry out alkali boil out on Boilers?

Alkali boil out is carried out for new boilers or Boiler where maintenance works like Bank tubes replacement, SH coils replacement are done.

3-List down the chemicals required for Alkali boil out of a Boiler

  • Hydrous Tri-Sodium Phosphate (Na3PO4.12 H2O)
  • Anhydrous Di-Sodium Phosphate (Na2HPO4)
  • Wetting agent (Surfactant / Detergent)

4-What is the ratio of selection of Disodium phosphate & detergents for alkali boil out

Quantity of Anhydrous Di-Sodium Phosphate (Na2HPO4) = Hydrous Tri-Sodium Phosphate X 20-25%

Quantity of Wetting agent (Surfactant / Detergent) = Hydrous Tri-Sodium Phosphate X 5-6%

 5-What are the two conditions for newly erected boilers for carrying out Alkali Boil out?

Boiler’s Hydraulic test should be completed

Boilers’ refractory dry out procedure should be completed

6-What are the pre-checks to be carried out before carrying out Alkali Boil out?


1-Ensure Boiler erection work is completed & its all auxiliaries trials taken & found okay

2-Ensure Fuel handling & fuel feeding system is okay & trial is being taken with respect to Mechanical, Electrical & instrumentation

3-Ensure Deaerator & related pumps are ready & can be taken into line readily

4-Ensure DM water is available

5-Ensure sufficient quantity of fuel is available at yard or at bunker

6-Ensure all equipment are hooked up to DCS

7-Ensure sufficient local PG & TG are avail be at Boilers

8-Ensure competent team is available

9-Ensure chemicals required for boil out & testing are available

10-Ensure all sample points are identified & competent person/team is there to collect the sample as per per decided frequency.

11-Ensure chemical dosing system is available

12-Ensure drain lines/flushing lines sample/sample lines are extended to safe location

7-Write down the procedure of Alkali Boil out in detail?


  1. Maintain the drum level just 6” -8”below the drum man hole door
  2. Initially, collect the required chemicals at drum platform as per dosage quantity decided
  3. Dissolve all the chemicals into water & then pour the chemical mixture into the drum from man hole
  4. After pouring, close the manhole door & raise the drum level up to normal operating level or just 2” below the normal operating level.
  5. Light up the boiler as per Boiler start-up & light up SOP
  6. Raise the Boiler pressure & temperature as per Boiler pressurizing curve
  7. Ensure thermal expansion of Boiler is happening & is uniform at all the headers
  8. Give IBD when drum pressure reaches 5 to 6 kg/cm2
  9. Raise the boiler pressure slowly & bring it to 50% of normal operating pressure or 40 kg/cm2, whichever is lower.
  10. Boil the chemical at same pressure for 10-12 hours.
  11. During boil out keep crack open CBD valve to avoid line & valve chocking
  12. During boil out period, operate the IBD for 15-20 second at every one hour & ensure water is replenished every time you give blow down.
  13. Note: Do not take drum level gauge glass into line during alkali boil out, keep one set of drum level transmitter on line
  14. At the end of the boiling period, collect the sample of IBD sample & test for oil traces. If the oil level is not in the allowable limit, then again add the chemicals & start boiling until the sample oil parameter meets the desired value.
  15. In order to decide the boil out is completed, the oil traces of 3 samples collected at 15 minute span should be < 5 ppm (Ensure consistency in results)
  16. After boil out, stop the boil out procedure & Box up the boiler & allow to cool the Boiler.
  17. During cooling period operate the blow down valves of drum & water wall panel bottom headers at least 2-3 times throughout the cooling period. And ensure normal water level in drum every time.
  18. Open the drum & super heater vents at pressure 2 kg/cm2
  19. Start rinsing the boiler, until the drain water pH equals to feed water pH
  20. After rinsing, drain the boiler completely & at the same time start to make up the boiler with DM water until the drain water pH becomes equal to feed water pH
  21. For flushing the super heater coils, raise the boiler pressure up to 40 kg/cm2 by Boiler feed pump (Hydraulic test of boiler at 40 kg/cm2 pressure) & then flush the water with from drain valve present before MSSV.This rinsing procedure is continued until the drain water pH becomes the makeup feed water
  22. Open the drum manhole doors & clean the internal surfaces with wire brushes
  23. Cut the stub ends/inspection caps of bottom headers & put wooden block in cut caps tightly.
  24. Again fill the boiler with feed water up to normal operating level & remove the wooden blocks one by one to remove the debris, scale or any other foreign materials from headers.
  25. Repeat above procedure for all bottom headers, then inspect all bottom headers for any debris, scale & foreign materials.
  26. After ensuring, everything is okay, then inspection caps should be welded subsequently radiography & hydraulic test should be done.

Travelling grate Boilers, cold, warm and hot start up procedures

15-Emergencies in Power plant


  • Ensure DM water storage tank level normal and healthy condition of WTP for adequate water
  • Ensure availability of fuel quantity and power supply with DG backup.
  • Ensure trial runs (healthiness) of all equipment including fuel handling, ash handling / auxiliaries, motorized valves, actuators, control valves and PRDS controls are completed successfully.
  • Ensure that all interlocks / protection and controls are checked & taken in line.
  • Ensure expansion points are cleaned & tramps are in good condition.
  • Ensure Boiler manholes and flue gas path system manholes are boxed up.
  • Ensure availability of chemical dosing system and readiness of drum level gauge glass with illuminator assembly.
  • Ensure availability of cooling water, instrument air and service air.
  • Start the ACW pump, Instrument Air & Service Air Compressor.
  • Ensure all rotary air lock valves of modular bank hopper and economizer hopper gates are opened and then start RAVs.
  • Ensure healthiness of all dampers and keep them in open/close marked positions as and when required.
  • Open all air releases/vent valves in boiler drum and open super heater header drains and its vent valves.
  • Ensure all boiler bottom ring header drains, blow down valves and main steam stop valves including its bypass valves are closed.
  • Ensure Deaerator level normal. If level is low, make it normal through control valve by DM transfer pump.
  • Ensure oil level of bearings normal, minimum recirculation, balancing leak off valves & suction valves open, cooling water pressure normal.
  • Ensure sufficient suction pressure & suction differential pressure across strainer is normal.
  • Start BFP from control room. Ensure suction pressure, balancing pressure & discharge pressure normal. Bearing temperature & Vibrations normal. Ensure motor draws current normal & sound normal. Shut the BFP immediately if any abnormal condition and check thoroughly before restart.
  • Start water filling the boiler drum through 30 % control valve and maintain the drum level up to 30%.
  • Start the Ash handling plant prior to light up the Boiler. Then start all hoppers RAV.
  • Charge the hopper heaters, Insulator heaters of ESP prior to Boiler light up.
  • Start the purge air blower, collecting & emitting rapping motors prior to boiler light up.
  • Stack fire wood / baled bagasse inside the furnace for light up, put the fire and maintain the moderate temperature of furnace without fan by keeping suction damper & discharge damper of ID fan open.
  • Spread the fire throughout the furnace.
  • Raise the furnace temperature up to 150 °C to 250 °C.
  • After ensure the furnace temperature of 250 deg C, start ID, FD & SA. And maintain the furnace draft -2 to -10 mmwc, FD air discharge pressure by maintaining the rpm in the range of 10 to 15 %, SA air discharge pressure by maintaining the rpm in the range of 40 to 45 % with feedback of field supervisor.
  • Start screw feeder and then drum feeder including fuel feeding system (Fuel Handling System) and slowly rise the furnace temp by feeding fuel (maintaining the rpm of screw feeder and drum feeder in 20 % & 10 % respectively)
  • Maintain the steam drum level and if exceeds, maintain the level by giving IBD.
  • When drum pressure rises to 2-3 kg/cm2, close the drum air vents.
  • When drum pressure raises 5 kg/cm2, close all super heater vents, drains except secondary super heater outlet header vent & drain valves in crack opened condition. Open start up vent valve (5%) initially and increase the start up vent valve opening gradually according to steam pressure & temperature as per start up curve to allow the steam flow through SH.
  • At drum pressure of 5 kg/cm2, quickly give the blow down through IBD and furnace bottom ring header for 3 minutes.
  • Start HP & LP dosing and maintain recommended drum water parameters of boiler. Keep the CBD at minimum opening to maintain recommended residual PO4 & conductivity of drum water.
  • Check & record thermal expansion of boiler pressure parts and record the bearings temperature & vibrations of auxiliary equipment’s associated with Boiler.
  • Start & Stop the traveling grate as per requirement during light up and
  • Ensure sub merge belt conveyor for bottom ash disposal is in running condition.
  • Follow the cold start up curve and raise the pressure & temperature of Boiler as per the    curve. Start another ID, FD & SA fan and BFP as per requirement.
  • When boiler raises above pressure of 60 kg/cm2 & 350 deg C, charge the main steam line. Before charging the main steam line, open all the drains at 100 % and warm up vents at minimum opening and then open the MSSV bypass valve.
  • After ensured all condensate removed & colorless steam comes through drains, keep all the drains in crack position, then open main steam stop valve and close the bypass steam valve.
  • Charge the PRDS of pegging steam and charge the Deaerator. Maintain the PRDS pressure at 1.5 kg/cm2 and temperature at 120 deg C.
  • After getting the start permissive of ESP, charge the ESP.
  • Observe seal air pressure, conveying air vessel pressure of AHP is normal.


  • Start the DG set
  • Keep the boiler in hot box up.
  • Maintain the drum level accordingly.
  • After this give clearance to start the boiler.
  • Start the ash handling system accordingly
  • Ensure the de-aerator level.
  • Start ACW & compressor.
  • Start & regulate ID, FD & SA fans as per furnace draft.
  • Start fuel handling system.
  • Open start-up vent.
  • Start boiler feed pump.
  • Take fuel to boiler & Raise the pressure and temperature gradually warm start-up curve.
  • After reaching the pressure 25 kg/cm2 give blow down through ring headers.
  • After reaching the pressure 40 kg/cm2 and temperature 350deg c, open MSSV by pass valve and warm up the line up to TSSV.
  • Give clearance for vacuum pulling.
  • Slowly raise the pressure to 105 kg/cm2 and temperature to 540 deg C.


  • Check the availability of import power and start DG set.
  • Check the reason for tripping and after the analysis give the clearance to start the boiler.
  • Close the MSSV and keep boiler in hot box up.
  • Start the ACW and compressor.
  • Start the boilers feed pumps and maintain the drum level.
  • Start the ash handling system.
  • Observe seal air pressure, conveying air vessel pressure of AHP is normal.
  • Start ID, FD, SA fans as per the requirements.
  • Start the fuel feeding system and monitor the combustion feedback continuously.
  • After reaching the pressure 40 kg/cm2 and temperature 350deg c, open MSSV by pass valve and warm up the line up to TSSV.
  • Open the MSSV main valve.
  • Raise the pressure and temperature up to 105kg/cm2 & 545 deg C.
  • Give the clearance for rolling of the turbine.

 Read Steam turbine start up procedure

 Read Boiler Alkali Boil out procedure

Questions & Answers on Ash Handling Plant

15-Emergencies in power plant operation

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