BOILER COMMISSIONING - MISC TANKS SMALL ,LARGE OF THERMAL POWER PLANT

There are different sizes of tanks are available in boiler ( Fuel oil storage tank , LDO tank , day tank

CBD tank , IBD tank , CC pump emergency tank , Drain oil tank , FST (feed storage tank & Deaerator) 

etc.  These tank can be divided according to their size and there process requirement . However Feed 

Storage tank comes under pre-boiler system and need separate chapter for its erection and 

commissioning . This I will discuss when I will be discussing turbine erection and commissioning.

STORAGE TANK ( SMALL AND MEDIUM) –GENERAL CHECK LIST

Access to the plant item is adequate

Illumination in the plant area is adequate.

Any other requisite safety provision is adequate for the immediate commissioning activity.

Plant item is in a clean condition.

All necessary locks and keys for padlocks interlocks etc. are available.

Hot surfaces lagged for screened sufficiently to provide protection for personnel.

Check the installation as per drawing specially orientation of nozzles.

Check that all internal items, grills, trays filter elements etc. are installed.

Check that float valves if fitted are correctly installed and operating freely.

Check that tank is internally clean, free from debris, and that the internal and external protective coating.

Check that all external fittings, gauges and indicators are as per drawing and securely fitted and supported. Unused bosses to be plugged or blanked off.

Check that all pipe work systems connected to the tank are complete at least to isolating valves.

Check that filling, overflow, vent and drains are complete, at least to isolating valve.

Hydraulically test tank as appropriate and check for leaks. Record if tank settlements are made.

Check that heating arrangements (steam heating or electrical heating) is fitted, is to specification and complete.

Check that lagging and cladding (if required) is complete to specification.

Check that support structure, ladders and handrails are satisfactory.

Check access doors (if fitted). Sealing arrangement of access door to be checked.

All the checks to be made and protocol for future use.

STORAGE TANKS LARGE –GENERAL CHECK LIST – A FEW MORE ADDITION TO ABOVE

Check all valves, switches, pressure switch etc. as per drawing and check list.

Check  tank is internally clean and finished as per drawing.

Check the  fire protection arrangements available or not available.

Check all the access manhole covers fitted . Specially check roof manhole cover and locking arrangements.

Confirm that the vent area is at least 1.5 times the filling pipe or suction pipe area (whichever is the greater) and fitted with a 4 mm mesh non ferrous wire cage.

Oil tanks, check the  combined water draw off and clean-out sump drainage arrangement

Check  the tank drain valves locking arrangements.

Check all the lines (overflow ,drain etc) connected to designated sump .

Check the gradient also for these lines.

Check  the local and remote, high and low level alarms together with the testing facility

For oil tanks, Check the heater trip and other protection logic as per approved scheme.

Check the operation of pneumatic valve as per check list given in earlier dispatch.

Check the tank earthling arrangements comply with the requirements specified for the particularly size of the tank. (Tanks up to 30m dia, 2 opposite spared earth strips; tanks over 30m dia, 3 equally spaced earthling strips).

Check the tank calibration certificate ( if available)

Check the level gauge and the level on tank body on big letters so that same can be seen from distance.

Check the bund arrangement of the tank . It should have been completed and free from debris.

Fill tank, proving manual and automatic system of control (if applicable)

1.            Record rate of filling; Height/minute

2.            Record rate of filling: Quantity/minute

3.            Record operation level of low level alarms.

4.            Record cut in level of auto filling

5.            Record cut out level of auto filling

6.            Record operation level of high level alarms.

With all points of consumption at maximum flow and inlet valve shut, measure:

1.   Rate of emptying: Height/minute

2.   Rate of emptying: Quantity/minute

Protocol all the reading for future use. During commissioning all big tanks reading to be taken as such tank does not get empty very often. If you miss to note them you may not get chance to do that in near future. Therefore all the activities to be completed once for all.

continued to part-vi

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COMMISSIONING OF BOILER ( PART -V) PNEUMATIC VALVE ,PIPIING CHECKS

Pneumatic valve.

Check the valve position with reference to PID.

Check the availability of secure platform , operation flexibility etc.

Consult manufacturer’s manual to know the detail of the valve

Check the basic characteristic of the valve whether it is air to open /air to close.

Check the damage of the valve controller box and other small items like air filter regulator ,

air lock relays ,small gauges connected with controller box ,position transmitters ( if available) and 

limit switches.

Study the system requirement of the valves in the process.

Check the power air supply ( 0 to 7Kg/cm2 ) and control air supply ( 0.2 to 1.0 Kg /cm2)

Check the function of EP (electro –pneumatic) controller before mounting.

Check the cu-tube /ss –tube connection at different places by charging air . Checking should be done by 

soap solution. Control air piping to be checked thoroughly as signal strength is less and can give 

erroneous reading during calibration.

Charge the air for commissioning. Test jig having ( 0.2 to 1.0 Kg/cm2) to be connected otherwise DCS 

to charge for signal. Before charging of air please flush the line well to remove dirt specially of 

control air line.

Valve operation to  be done five to six times to set the open- close limit switches.

Check the valve in different position through  control air supply jig. Calibrate the valve with zero and 

span . Calibrate the valve position transmitters.

Check the valve stay put condition on failure.

Check the manual operation of the valve ( if available)

Protocol all the checks and readings for future reference.  

Keep the valve in close position.

Checking of Pipelines   :-  General checks

The installation is complete and correct in accordance with the latest approved drawings and 

specification.

Check that all bosses, flanges and tapping points have been adequately made off.

Check that all cold pulls, if required, have been made and records completed.

Check that all pipe falls to drainage points are satisfactory.

Confirm that all blanks still required in the system are identified and recorded in the Blanks Schedule

Check that drains are provided at all points on the steam range where water may collect.

Check that steam traps are fitted with bypass and test connections.

Confirm that all pipework that can be touched from walkways etc, and that reaches a temperature of 60 

deg C or over is adequately lagged.

Check that adequate number of vents are provided on the pipe at highest points.

Check that all supports are undamaged, fixed and mounted vertically, (Except where design requires the support 

at a specified angle).

Check that all support loadings have been correctly set and recorded.

Confirm, where possible, that there is a radial clearance between the pipe and the support clip.

Check that all roller and sliding supports are clean, free to move and so constructed that dirt and water 

cannot accumulate.

Check that all thrust/anchor points are correctly installed.

Check that all the supports as required as per the drawing.

Flush the pipe line properly to open drain to clear of all debris from pipe.

Test the pipeline hydraulically to the relevant standard in presence of Boiler Inspector if required.

Check that all temporary supports have been withdrawn.

Confirm adequate support for small bore, horizontal pipes that may be stood upon (or adequate 

protection for the pipes and supports for system not strong each to withstand additional loads).

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COMMISSIONING OF BOILER ( PART-IV) ,VALVES

It is expected that after completion of Full Hydro ( except re heater) completion of

stage1B next step is conducting Boiler Hydro test within 21 days . But there may be

some problem to achieve that then one should proceed for wet preservation of the Boiler.

The Boiler is pressurized to 5-10 Kg/cm² with hydrazine and Ammonia treated DM

water containing not less than 200 ppm of Hydrazine and sufficient quantity of

Ammonia to have pH value of 9.5-10.0 and retained at this value for preservation.

Boiler water samples can be collected periodically say once a week or fortnight,

depending on the pressure holding worthiness of the system, and tested for

pH and hydrazine content. Sampling point will be low point drain.

In case the sample water does not meet the criteria for preservation of Boiler

the same is to be boosted up using Boiler fill pump and dozing arrangement and

at the same time venting sufficiently through the air vents in the top level of the boiler.

Alternatively, preservation can also be done under nitrogen capping at

0.35 Kg/cm² at vents of separator and Super-heaters.

Next system commissioning will be Pre- boiler flushing with temporary pumps

and piping . Same facility will be used for acid cleaning/ alkali boil out operation.

However we will first discuss about the individual items like valves ( manual,

electrical ,Hydraulic ) , Pipe installation ( oil ,air ,steam ) hanger supports ,misc.

accessories of the system.

A commissioning engineer should look for the technical deficiency in the

erection and get it rectified before commissioning the system. If it is not possible

then same is to be recorded in the register so that early action can be taken to

resolve the issue.

Manual Valve ( only big valves are considered)

Following common aspect to be looked after by commissioning engineer

before he starts any activity. Deviation from that may lead to unsafe condition

for commissioning.

Access to the plant item is adequate

Illumination in the plant area is adequate.

Any other requisite safety provision is adequate for the    immediate commissioning activity.

Plant item is in a clear condition.

All necessary locks and keys for padlocks, interlocks etc. are available.

Hot  surfaces lagged or screened or screened sufficiently to provide protection for personnel.

Ensure that manual valves installed correctly as per latest PID.

Heavy valves are supported properly and independent of the pipe line. Valve should

not carry the load of the pipe line.

Direction of flow marked and correct.

Also see that valve position is such that it is easy for repair, replacement and maintenance.

Ensure that if limit switches are available then they are set by physically moving the valve

open or close.

No fouling with near by structure or equipment noticed. After commissioning, valve

should be kept in closed condition and protocol to be made and kept as future reference.

Motor operated valve.

Ensure that motorised valves installed correctly as per latest PID. Check the Tag No.

and name plate.

Heavy valves are supported properly and independent of the pipe line. Valve should

not carry the load of the pipe line.

Direction of flow marked and correct.

Also see that valve position is such that it is easy for repair, replacement and maintenance.

Adequate space is available for setting of limit switches of the valve.

Ensure that limit switches are set and position transmitters are also set. Indication

on the valve is available. For small bore valve the valves can be set manually but same

can also be set electrically by keeping the valve in middle position. Before checking

with electrical please ensure that direction of rotation of motor is checked.

It is a thumb rule that set the valve open position with position limit switch and

set close position with torque switch.

Each motorised valve has minimum two position limit switches and two torque

limit switches. Torque limit switches are factory set should not to be disturbed.

Before commissioning of motorised valve please talk to senior about the valve

position. I remember in my early days I was commissioning a motorised valve and

about to break the wet preservation of the Boiler.

Commissioning protocol to be made that is current take by motor, limit switch

setting , manual operation, clutch – gear operation, indication, local /remote operation etc.

You  need good communication set up as  manpower required to assist you in MCC ,

control desk , logic panel /DCS simultaneously all the place.

After commissioning keep the valve in closed condition.

 

continued to part-v


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