COMMISSIONING BOILER ALKALI BOIL OUT ,ACID CLEANING PART -I -ABC OF THERMAL POWER PLANT.

I have discussed about commissioning fans and its lubrication oil system . I have also discussed

the commissioning of fuel oil ( light Diesel Oil and Heavy  Fuel oil) system. This commissioning

includes acid cleaning ,rinsing and flushing of lines and restoration. There are other equipment

also which can be commissioned separately. Those are valves and dampers , soot blowers (specially

air heater soot blower which is required early because of oil firing of unit at the beginning ) .

However commissioning as system will be starting from ALKALI BOIL OUT AND ACID

CLEANING ACTIVITIES.

For these activities original equipment Manufacturer's

recommendation should be followed as they are best judge of their

Boiler.  

OBJECTIVE

However here I will try to give a glimpse of the activities and its requirement to the benefit of the

reader. My project will be restricted to standard 500MW set and also 660MW set .

The objective of this commissioning schedule is to clean the internal surface of the steam generating

portion and heating surface (Economiser) using specified chemicals.

  

The objectives are achieved by carrying out the following testing proposals.

 

By carrying out an effective boil-out, grease and any protective coatings applied are removed.

 

Then, it is subjected to acid cleaning for the removal of patchy mill scale and rust.

 

Finally, the acid pickled surface is passivated for the formation of uniform and coherent magnetite l

layer.

REQUIREMENT OF SERVICE

Prior to the commencement of chemical cleaning, all the demineralised water storage tanks

should be kept full and the demineralising units kept in regenerated condition.

Approximately, 6000 m3  of demineralised water will be consumed for the  entire process. At

any time of acid cleaning, a minimum of two boiler volumes (app. 1400 m3 ) of

demineralised water should be available in ready stock to facilitate rapid flushing of the

system in the event of chemistry upset.d valves

Temporary pumping station will be required for filling up boilers with chemical. For a

power station where two to three units are there 05 numbers pumps are planned. This

need temporary foundation ,electrical connections ,pipelines ,valves and tanks etc to

be installed . Adequate safety precaution to be taken though it is temporary work.

Now a- days a few vendors are available to do the alkali boil out and acid cleaning

with their own equipment .

Advantage of having own equipment is that the same can be used for pre boiler flushing

of condensate ,feed water ,drip lines etc. We have seen the system is being used time

and again as per requirement.

Neutralising pit will be required to neutralize the chemical acid /alkali coming out from

boiler during draining and rinsing . Pit capacity will be three times the volume of boiler

water.

continued to PART -ii

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OIL FLUSHING ,COMMISSIOINING OF LDO ,HFO SYATEM OF BOILER PART -IV -ABC OF THERMAL POWER PLANT

OIL FLUSHING

After steam blowing is completed, Fuel oil system is normalised for commissioning the LFO

and HFO pumps.

LFO and HFO Pumps are commissioned with pump re-circulation and ready for oil flushing.

LFO pumps of auxiliary boiler are commissioned and available for regular operation.

 

LFO Lines

Fuel lines are lined up for LFO flushing through LFO return line from Boiler.

LFO Pump started and line flushed for 24 hours. Pump suction filter is taken out and

cleaned.

Again flushing continued for 8 hours. If condition of the filter remains clean, flushing can be

terminated.

LFO lines are subsequently normalized and released for regular operation.

HFO LINE FLUSHING:

HFO pump started and first section of the line flushed for 24 hours. In between from time to

time, filter is cleaned.

Again flushing continued for 8 hours. After every 8 hour or as per requirement, filter is

cleaned. Depending on the condition of the filter remains clean, flushing can be terminated.

HFO lines are normalized and released for regular operation.

Oil flushing can be declared completed after minimum of 24 hrs flushing or  minimum of

8 hours running without filter chocking.

HFO /LDO COMMISSIONING INCLUDING OIL GUNS AND CORNER STATIONS

Following equipment  and system will be under commissioning.

Air cooled Oil Gun Assembly :- 

No. of burners  :  20 nos. per boiler arranged in 5 elevations. All Burners will be suitable for

firing heavy oil/LSHS/HPS and bottom most elevation  will be suitable for firing light oil also.

 

LDO Supply & Return Trip Valves

Corner Trip nozzle (Air, Oil & Steam) Valves

High energy arc ignitors assembly

Discriminating Scanner Assembly

Fuel Oil Heaters

Fuel oil lines from HFO/LDO Pump to Burners

Atomizing steam line from Aux. PRDS to burners

HFO Steam Tracing Lines

Pressure Filters are provided before HFO Heating Station and HFO Trip Valves

Plant Completion List to be prepared at site prior to commissioning of oil firing system for

mechanical, electrical and C&I areas.

All manpower ( operation) is in position .Necessary safety precaution is taken oil will be

charged and possibility of fire increases.

As per the normal starting/  operating procedure initially LFO firing is taken up for warming

up the boiler before firing HFO fuel.

Hydraulic Test, Steam blown and oil flushing of LDO/HFO and atomising steam line

completed.

The Fuel Oil Burner Assembly with Scanners and Ignitors are erected as per required

drawing. (Oil Gun ‘dimension, scanner orientation etc are checked from outside and inside

the furnace  & Igniior Advance / Retract mechanisation checked).We termed as Burner

alignment i.e to check the fireball position. It is major and important activity to be completed

before light up.

Steam tracing lines are erected and terminated to suitable outlet point.

Power supply system to scanner, ignitor and trip and corner nozzle valve solenoids are

commissioned and available for operation

Require local/remote I&C input are made available. (List to be prepared at site).

Filter elements in the system are erected in position

 

Corner station are steam blown and corner nozzle valves and burner flexible hoses are

fitted

Trial run of LDO/HFO Pumps through pump RC completed.

 

Steam blowing of LDO, HFO, Atomising Steam Line from Pump House to Ring Header

completed.

Steam Tracing lines are completed with steam traps station.

24 V DC, 220 V Dc supply with UPS are in charged condition

Dry simulation of FSSS System for LDO/HFO oil elevation (AB-LDO & CD-HFO) completed

with required permissive and interlocks (List to be prepared at site)

Scanners and ignitors are mounted as per drawing.

Trial run of ID/FD Fans System and Scanner Air fans completed and released for normal

operation of plant.

Trial run of SAPH and availability of ESP to be ensured.

Boiler cleared for light up (Refer to Boiler O&M for other preparatory checks to be made

prior to light up)

Boiler expansion constraints are removed and ensured for free expansion. Expansion Trans

erected at pre-determined locations.

Availability of instruments and service air to be ensured

Boiler filled up to normal operating level.

Ash handling system erected and provides required sealing at all required locations / areas.

Method

 Start ID/FD/APH Systems as per normal start up procedure. (Respective Testing

Schedules or O&M to be referred) and establish required furnace draft (Around –5 to –10

mmwc).

Depending on the availability of SCAPH, it can be charged (SCAPH charging is optional

during trial light up of LFO burner, which is done to prove the burners)

Start the LDO Pump and ensure charging up to fireman’s floor

Adjust the boiler airflow and wind box DP to the required level

Put the RC valve operation of LFO Pump on ‘auto’

Give command for “start” of LFO burners and watch for flame establishment

Once the flame is established, ensure

a.   Oil combustion is proper and

b.      Flame scanner pick up the flame.

 
After few minutes of operation, trip the burner and observe and ensure that shutdown

sequence take place as envisaged. 

Repeat the above procedure for other LFO Oil Guns

HFO Firing

Start ID/FD/APH Systems as per normal start up procedure. (Respective Testing Schedules

or O&M to be referred) and establish required furnace draft (Around –5 to –10 mmwc)

Charge SCAPH and raise the air temperature to around 60⁰C.

Adjust the boiler airflow and windbox DP to the required level

Charge    a.     Atomising Steam System and

                b.     Steam Tracing System

Start any one of the HFO Pump and after charging HFO Heater, charge HFO line up to

boiler and put under short recirculation first and then long recirculation for raising HFO

temperature.

After attaining HFO firing temperature (around 115⁰C -- 120⁰C), give command for HFO

burner “start”. Watch the flame establishment.

Once the flame is established, ensure

a.   Oil combustion is proper and

b.      Flame scanner pick up the flame.

After few minutes of operation, trip the burner and observe and ensure that shutdown

sequence take place as envisaged.

Repeat the above procedure for other HFO Oil Gun, in that elevation.

Oil Gun, in other elevations are commissioned on similar lines as explained above.

 With the Commissioning of LFO/HFO System, boiler is ready to commence all pre-

commissioning activities, such as alkali boil-out, steam blowing, safety valve floating, steam

dumping etc.

LFO/HFO - Light diesel oil /Heavy fuel oil

mmwc- mili meter of water column

SCAPH - steam coil air preheater.

SAPH - Secondary Air pre heater.

FSSS- Furnace Safeguard Supervisory System ( Burner Management System.

typical PID of LDO/HFO SYSTEM

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OIL FLUSHING ,STEAM BLOWING ,COMMISSIONING OF LDO,HFO SYSTEM OF BOILER PART III-ABC OF THERMAL POWER STATION.

In continuation of Part -I and II of FO,LDO system description and commissioning this article

will cover the oil flushing and Steam Blowing of the system.

To remove debris and clean the internal surface of oil lines in the LFO/HFO system,

including atomising steam lines and steam tracing lines oil flushing and steam blowing

are being carried out in systematic manner . This will prevent particle to be passed into

screw pumps and burner nozzle.

  

Auxiliary Boiler or Low temperature APRDS will be used for steam blowing the Fuel Oil

lines. Now -a days auxiliary boiler with requisite parameter is available on rent .They will

bring their boiler and cater all the pre-requisite steam for the system. APRDS can only be

used if there is an existing running boiler.

 

Steam blowing the Fuel Oil line by continuous blowing method for the duration of 20-30

minutes at a pressure of 10-12 Kg/cm² and a super heat of at least 50⁰C at source.

Depending upon the site conditions, the different sections / circuits for steam blowing may

be decided by consulting PIDs of the system ,equipment manufacturer's recommendation.

Following are pre-requisite for steam blowing

Hydraulic test ,support work and insulation completed on all the lines where steam blowing

is to conducted.

All safety precautions and emergency safety precaution are in place .

 

Auxiliary boiler is fully ready for supplying steam for steam blowing F.O. lines.

 

Steam drawn either directly from Aux. Boiler outlet through a temporary lines connected to

F.O lines or from APRDS. This is to be decided at site as per the erection readiness of

these system.

 

Trip valves, control valves, flow elements are not erected and suitable spool pieces are

erected at these places. A check list will be prepared for activities of their type which will be

used during restoration.

 

Filter elements and NRV internals are removed.

Temporary exhaust pipes lines are erected avoiding equipment and buildings.

 

All vents and drains are properly routed and supported.

Day Tanks and storage tanks for LFO and HFO are ready for operation.

All steam lines as well as oil lines are insulated.

No permanent instruments has been installed in the lines being steam blown/oil flushed.

They are totally isolated from steam blowing / oil flushing, in case erected.

SL.             PIPELINES                                         PR       DURATION    NO.OF BLOWS(min)

1.   Steam lines from Aux .Boiler/APRDS             10.0          20-30 min             3

2.  FO lines from Pump House to Boiler               10.0          20-30 min             3

3.  LFO lines from Pump House to Boiler             10.0          20-30 min             3

4.  Steam lines from Boiler to Pump House          10.0          20-30 min             3

5. Steam tracing & Condensate lines                     6.0           20-30 min             3

6. All the other FO /LDO Lines                              10.0          20-30 min             3

7. FO unloading Header                                         2.0           10  min                 3.  

Brief method of Steam Blowing

Auxiliary Boiler is lighted up as per O & M manual start up procedure after attaining steam

pressure about 10-12 kg/cm²  carry out the warnming of the line to be steam blown at a

lower pressure. Raise the steam pressure at the drum to 10-12 kg/cm²  and give the blow

for a duration of 20-30 minutes. Maintain the pressure during the blowing period.

 

Allowing it to cool down for 2 hours, above process is repeated for another one or two times

till it meets the completion criteria. Between every blows, 2 hours cooling time will be given.

Keeping the line pressure 5 kg/cm²  carry out the purging of drains/vents & instrument

taping points for 10 minutes each.

 

Similarly, repeat other loops/sections/sub-sections are steam blown.

 

Drains/vents of F.O lines are kept open as required during steam blowing and after, for

draining condensate. Allow to cool down the piping. Dry them with compressed air.

NOTE: During the cooling period of one section, other section as per convenience, will be steam blown.

After completion of steam blowing, all spool pieces are removed and Trip valves, control

valves and flow elements, filler elements and NRV internals are restored / normalized. Pipe

connections to LFO/HFO pumps are normalized and pumps are commissioned.

continued to Part -iv oil flushing and final commissioning

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FO,LDO UNLOADING AND PRESSURING STATION FOR STEAM GENERATOR -ABC OF THERMAL POWER PART-II

This is in continuation of my last Blog ( FO ,LDO UNLOADING AND PRESSURING

STATION PART-I.

Fuel Oil Pump House: Consist of following items

Fuel Oil Pump House is located close to Fuel Storage Yard. This Pump house is housing.

1.              HFO Pump set & Heater for Auxiliary Boiler

2.              HFO Pump set for Main Boiler (3 Nos)

3.              HFO Heater Set

4.              LDO Pump set (2 Nos)

5.              Drain Oil Tank & Pump Set

6.              Electrical & control Panels for all the F.O. Pump House auxiliaries.

Heavy Oil Pumping Unit (Common for two boilers):

No. of Pumps     :     3 x 50% (2W + 1 S )

Capacity             :     Each pump to meet 50% capacity of two

                                 Boiler requirement

Type                   :     Screw Type

Suction Strainer   :     4 nos. Simplex basket type with SS

HFO Heating Unit (Common for two boilers)

No. of Heaters     :     3 (2W + 1S)

Capacity              :      Each Heater to meet 50% capacity of

                                   two boiler requirement

Type                    :      Oil outside, U-type, hair pin BEU type

Discharge Strainer :    4 nos. Simplex type with S.S. Meth

Oil temperature    :      130⁰C (approx.)

At heater outlet

Light oil Pumping Unit (Common for two boilers)

No. of pumps        :     2 (1W + 1S)

Capacity               :      Each pump to meet 7.5% BMCR Heat

                                    Input

Type                     :     Screw type

Suction Strainer   :      2 nos. Simplex type with S.S. Meth

A typical view of FO PUMP HOUSE (pressuring unit) under construction

A typical lay out of FO Pump House with mono rail.

Fuel Oil Lines (LFO/HFO)

Fuel Oil lines from Fuel Oil Pump House to Main Boiler is routed through trestle with

supports given suitably for thermal expansion. The HFO line is lagged with insulation inside

which steam tracing heating arrangements are provided for the entire length of HFO lines

from day tank to Boiler and back to day tank.

 A Cooler arrangement is provided in the HFO return line near the Fuel Oil Pump House

area for controlling the HFO day tank oil temperature.

CONTINUED TO PART -III HT, STEAM BLOWING AND OIL FLUSHING OF LDO/FO LINES ETC.
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