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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COMMISSIONING OF BOILER PART III-HT PROCEDURE- THERMAL POWER PLANT

The first activity commissioning engineer will associate is Hydraulic Test of the Boiler.

Though the Hydraulic Test is erection activity and to be conducted by them only.

I will discuss the procedure of Hydraulic test of a Supercritical/subcritical unit .

Calculate the water  volume  of different section :-

a) Economiser b) Furnace  c) Super heater  d) Separator  and collector  d) Re heater

e) Start up system.

In  660MW unit the volume worked out is around 710 cu. metre. This is required to

calculate the chemical requirement for the test.( Ammonia and Hydrazine Hydrate)

The Unit shall be hydraulically tested for conformation to IBR code requirements.

                                                                                                                                     

It is preferable to do the hydraulic test of the complete Boiler (except Re-heater section)

in one stroke at the stipulated Hydraulic test pressure. If it is not possible to accomplish this,

the hydraulic test may be conducted in two sub stages.

Stage IA - Hydraulic Test of the drainable portion only may be conducted at a pressure

1.5 times the design pressure. Suitable dummies shall be provided at SH platen inlet link

pipes. After completing the hydrostatic test for drainable portion, the system will be

drained and vented for drying and released for subsequent work.

Stage IB – Later Hydraulic test for the entire system comprising both drainable and

non-drainable portions up to Boiler Stop valves is conducted at a pressure 1.5 times

the design pressure.

Stage II - This covers the total Reheat circuit comprising CRH lines starting from

CRH NRV, tap off lines emanating from CRH lines up to first isolation valve, HPBP

valve downstream line, Re heater hot reheat lines up to IV, LPBP lines up to LPBP valves .

                                                                                                                                                                                                                                                                                                    

                                                                                                                                                 

Air tightness test shall be performed before filling water in the Boiler (for carrying

out the hydrostatic test ). This is done to detect leakages due to valves left in open

position, forgotten gamma plugs, any cuts not observed by visual inspection etc.

For doing this station compressor should be ready to deliver air .

During testing at least two properly calibrated standard test pressure gauges of

suitable range calibrated from a NABL accredited laboratory are to be used. One of

the gauges is mounted at drum floor/near and the other near pressure raising pump.

The least count of the gauge should preferably be 1Kg/cm².

 

DM water of quality specified below containing 200 PPM of hydrazine and

having pH between 9.5 and 10.0 by addition of adequate quantity of ammonia

shall be used for Hydraulic test.

 pH at 25 ⁰C                                                   :  7 + 0.2

 Conductivity                                               :   < 0.2 m mho/cm

Total hardness                                             :  Nil

Total Silica                                         :            < 0.02 ppm

Chloride                                             :            Nil

Sodium                                             : 0.003 ppm

During testing the temperature of water should be above 21⁰C but should not exceed 49 ⁰C.

Availability of reciprocating type pressurizing pump (H and Q of the pumps):

(a) 600 Kg/cm^2, 30 LPM  and (b) 600 Kg/cm²,  50 LPM.

Availability of  reciprocating type  chemical injecting pump of 600 Kg/cm² & 12 LPM.

Alternatively, hydro test pump can be utilized as chemical dozing pump.

Availability of Boiler fill pump.

Availability of power supply to the motors of these pumps.

Availability of Temporary tanks, Temporary fill pumps and dosing pumps.

Availability of flood lights and 24V hand lamps.

Availability of reliable communications system such as walkie-talkie sets, telephones etc.

Availability of Fire Tender and Ambulance near the test area.

Readiness of stair-cases, platforms, hand rails, approaches etc.,

Delivery line of pressurizing  pump should be high pressure seamless pipe to withstand

the required test pressure.

While raising the pressure for the first time no individual should be allowed to enter

the Boiler house when the pressure in the Boiler is above 25 Kg/cm².

Medical assistance should be readily available.

Erection of the Boiler pressure parts is complete as per drawing. All necessary

welding jobs are complete, stress relieved and x-rayed. All gamma plugs are seal

welded. All Quality checks as per approved Erection FQP are also complete.

No welding including attachment welding  or welding on tube will be allowed subsequently.

Filled & signed copies of FQPs and Erection Protocols with exceptions highlighted

are handed over to the commissioning group.

Effective communication facility is available between Drum floor, pressurizing pump

area and other operating areas.

Sky climbers / Scaffolding arrangements are provided inside the Boiler. 

 A cross functional team to be formed to identify leaks at different portion of the boiler.

  

Boiler drain is suitably connected to storm water drain / DM plant neutralizing pit.

All  debris shall be removed manually from all pressure parts, buckstays etc.

All manhole closure plates  and header handhole caps are closed  and  bolted  or welded tight.

Check that hydrostatic test plugs are installed where necessary and gags are fitted correctly.

Verify that locking arrangements for spring supports are provided when required for stress compensation.

Before filling the boiler with water, an air tightness test is to be performed to detect

leakages due to valve left in open condition, X-ray plug forgotten, any cuts etc. not

observed by visual inspection. This will reduce the DM water consumption and time as well.

The  air should be filtered and free from oil and dust prior to entering the unit. 

Boiler is  to be pressurized with air  up to 2 Kg/cm² (G).

Before admitting air, close manholes, isolating valves in drain lines, branching lines

and vent lines including the vent valves in SH link, economizer link and separator link,

drain and test valves in official pressure gauge etc.

Boiler is inspected. The pressure is raised up to 25 Kg/cm² and a thorough inspection of the

Boiler is done. For Stages IA & IB the pressure is raised in steps and held for 10 minutes at

100 & 200 Kg/cm². The rate of rise of pressure should not be more than 10 Kg/cm² per minute

up to approximately 80% of the test pressure and should be 1 to 2 Kg/cm² per minute beyond

that value. The required test pressure shall never be exceeded by more than 6%.

Hand tighten safety valve gags at 80% of pressure of lowest safety valve set pressure.

After reaching the test pressure the pressurizing pump is stopped immediately and power

supply to the pump is cut off.

Pr gauge showing the Hydro test Pressure 106 kg/cm2 ( Re  heater)

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