BOILER FEED PUMP ERECTION AND COMMISSIONING PART-II ABC OF THERMAL POWER PLANT

        Typical  data of BHEL make Boiler Feed Pump and its motor is given below briefly.

A.  Booster  Feed Pump

a. Direction of rotation                                         Anticlockwise  (viewed on NDE)

b. Suction temperature ; C                                                           161.8 deg c

c. Suction pressure                                                                          8.43 ata

d.Discharge Pressure                                                                     25.65 ata

e.Flow rate, m³/hr                                                                          1143.7 

f. Efficiency  %                                                                                   81

g.Speed rev/m                                                                                  1494

h.Power absorbed, KW                                                                  662

i.  Driver/Pump flexible coupling                                            Euroflex, India

B. Boiler Feed Pump

a.  Suction Flow                                                                                894960 kg/hr

b. Suction pressure                                                                         26.85  ata

c.  Discharge Pressure                                                                    209.19 ata

d.  Speed rpm                                                                                    5465

e. Power consumption KW                                                          6233

f. Efficiency                                                                                        81%

g.  Normal recirculation flow                                                       250  m³/hr.    

C. Hydraulic  Coupling

a.  Manufacturer                                                                               VOITH

c.  Rotation seen in direction of power flow                         CCW

              

d.  Motor Speed rpm                                                                      1494

f.  Primary Speed ‘rpm’                                                                 5089

g.  Full load slip                                                                                 2.24%

i. Max. output speed ‘rpm’                                                          5820 

k. Oil tank filling                                                                             2500 litres.

Auxiliary  oil Pump

     Power                                                                                         30 KW

     Rated speed                                                                            2945 rpm

     Voltage                                                                                     415 V

     Frequency                                                                                 50 Hz

     Protection                                                                                  IP 55

The details above are for 500 MW units . It is prudent to verify with OEM ( original equipment Manufacturer specification during working .

Activities related to Boiler feed pump erection and commissioning (MD)

Preparation of foundation for  PUMP ,MOTOR and HYDRAULIC  COUPLING ( i.e checking of center line with respect to known co-ordinates , checking of  pocket dimensions , Level of the foundations etc .Also check the foundation of coolers .Also record the data in protocol for further decision

Placement of motor and hydraulic coupling on the foundation .

Grouting of motors & HC with ready mix grout ( conbextra GP 2 , SIKKA etc)

Motor winding RTDs( Resistence Temperature detector), Instrumentation checking completion  

Motor cooling waters lines completion

Alignment of motor & hydraulic. Coupling

Hydraulic coupling instrumentation completion

Mounting of scoop tube actuator

Checking and clearance setting of motor bearings.

continued to PART _III

TIPS ON CONDENSER ERECTION AND START BOILER FEED PUMP ERECTION --PART -I

I received mails for not delivering any dispatch since long. My PC became out of order and remain out  of

order since then. In between I had an operation on my left shoulder for infected cyst removal . I am still 

recovering from it. 

condenser.

-The joining plates between the water chambers should be welded and checked before lowering of condenser intervals.

-The corners of the neck joint with LP turbine should be checked to ensure completeness.

-The welding of the stiffeners with the main tube plate should be done only after welding  of all support plates with the shell and stiffness has been completed.

-Welding sequence should be reversed for every layers of welding.

-During pre-assembly of bottom plates / side walls & dome walls it is advisable to put a packer below the joint so that during welding the plates straighten out.

-Not more than four welders should be deployed during the welding of the internals. Adequate supervision should be exercised to ensure proper welding sequence.

-It is desirable that after 50% of the welding of internals has been completed the alignment of the tube plates is rechecked. Subsequent welding sequence should be decided based on the observation made.

-During tubing in case the tube is not going freely the holes of the tubes support plates may be reamed suitably.

HYDRAULIC TEST OF WATER BOXES

The condensers are subjected to a hydraulic pressure test on the cw side. For this purpose, the cw inlet and outlet pipes must be blanked using suitable hydro-test flanges and the manholes using the original covers. The water box covers must be mounted ready for operation and a protective coating must have been applied to the water boxes.

The hydro-test can also be done by closing the butterfly valves in the inlet and outlet of condensers. This apart from also ensuring the tightness of B.F. valves and expansion joints, reduce the time cycle as the temporary test flanges need not be erected.

After the hydro test, drain the cw.

BOILER FEED PUMP

There are  3x50% Boiler feed pumps in a major power station  i.e. 500MW and above  with 02 number  Turbine Driven and one number motor driven. Motor driven pump is located in between operating floor and zero meter floor (8.5m) . Turbine driven pumps are located on operating floor ( near B row column). Motor (10 MW  approx) squirrel cage  constant speed  with Hydraulic coupling for variable speed is coupled in between main pump and booster pump. Around 10 MW capacity single cylinder variable speed turbine  is used turbo driven BFP.

Details of specification will be available with OEM’s O&M manual and erection manual. I will give a very short description of these pumps which may get overlooked during erection and commissioning.

- Main pump will have butt weld discharge connection. Suction connection can be butt weld or  flanged connection.

- Booster pump will have flanged connection both in suction and discharge.

-One pump can handle approx 65% of  unit rated  load flow and head  .

-Trip speed of steam turbine will be 10% above the design speed of boiler feed pump.

-Minimum recirculation of booster pump and main pump is around 25% of design flow.

- All pumps and accessories of MDBFP and TDBFPs are interchangeable.

- Fabricated base plates are used for booster pump , gear box ,main pump, hydraulic coupling  etc

- During parallel operation of MDBFP and TDBFP the difference of flow in any one pump should be less than 5%.

continued to part -ii
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CONDENSER - AUXILIARIES OF STG SETS CONCLUDING PART -ABC OF THERMAL POWER PLANT

   Following checks are made  during the course of erection of condenser.

- Welding checks as per welding manual  consist of welder test, consumables selection and processes as per OEM. This is very relevant as condenser is having huge quantity of welding jobs at different stages of erection. Therefore all the details of welding specially sequence of welding is very important or there will be distortion in forming the box. OEM specify the sequence in their manual.

- Level Position of hot well w.r.t. Transverse and longitudinal axes of turbine as well as front & rear water box ends of condenser and Bottom plate openings and alignment of bottom plates w.r.t. to Turbine axis.

- Level and alignment of bottom plate relative to turbine axes within  ½  degree slope.

-Sag checking of tube plates and also flange checking of water box and chamber.

-Length in between Tube Plate at locations, covering full area of tube plates.

-Distance between sidewalls and height & verticality of Sidewalls.
- Position of Support Plates. Hole alignment of tube plates and tube support plates.
- Verticality of hinge door assembly. Tolerence should be as per drawing.
- Verticality of hinge door assembly.
Location of spring units and setting of condenser slope.
Alignment of L.P Cylinder opening with Condenser.
-Dimensions of the dome walls from turbine longitudinal and transverse axes.
-Nozzle orientations as per drawing.
-Orientation of condensate spray nozzle.
-Check position, level and alignment of heater.
- Mock up test on separate tube plate including air leak test on mock up set up.
- Setting of expander for required tube thinning as per the procedure given by OEM.

  Condenser Tubing under progress

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CONDENSER - AUXILIARIES OF STG SETS PART II-ABC OF THERMAL POWER PLANT

Depending on site conditions, the preassembly of the plate will be done.If the foundation and 

approach is ready then it would be directly assembled on the foundation. However, if the foundations 

are not ready it would be assembled separately outside. The bottom plateis in four parts and two of them will be pre-assembled outside. On each half the hot well and the spring supports will be welded/tacked. As the opening on the foundation is big enough the preassembled bottom plate can be lowered flat without any risk  by EOT crane .However fixing of lug plate for mounting D-Shakle should be carefully done considering the weight of the plates and accessories.

 Both sidewalls are carrying in four parts. Two joints would be welded outside the foundation.

Each dome wall, both upper and lower is in two parts. These would be assembled together before erection.

DOME SHIFTING STRUCTURE

The central portion of the structure shall be assembled outside.

 CLEANING OF COMPONENTS

 The cleaning of components shall be done either by sand blasting using low-pressure air (2.5 kg) or by alkali and hot water.

 TUBING  

The tubing of the condenser shall be carried out from the end of the condenser. The opening in “A” 

row    in front   of the condenser is not to be closed till tubing is complete. Tubes shall be transported 

on a long bed trailer so that the overhang is not more than 1.5mm either side. In case a small crane 

and space is available the tube boxes shall be unloaded near “A” row columns. However, in normal 

cases the boxes shall be unloaded inside the TG hall by EOT crane and shifted   to position   

manually. However when site is  ready with A_row civil work then tubing should be done from A –Row side. The Platform for tubing to be made flexible and can be  lifted time to time after completion of certain height of tubing. Therefore total platform should be held by eight  chain pulley block with adequate capacity. Rough  weight calculation to be done before finalising the pulley block. At present all vendors brought specialised gang to do this job therefore time is considerably reduced .  

 WATER BOX HANDLING DEVICE

This would be erected when the welding of internals is in the progress.  In case this is not available it would be better to have suitable openings   on TG Floor and oil canal from where the slings can be inserted   to handle the water boxes when they are opened for tube inspection.

Check the foundation for dimensional accuracy in accordance with the plate foundation drawings. Set the support plates in mortar and align with the positions in which the spring elements will be mounted.

Tack the base plates to the spring elements. Lower hot well below and place it on the ground. Lower 

the sections making up the bottom plate onto the support plates of the condenser foundation.  

Assemble and align the sections which have been lowered onto the foundation.  Weld bottom plate 

as per sequence. Lift hot well and weld with bottom plate. Align the bottom plate to the turbine axis 

in zero elevation. Raise bottom plate in axial direction and into zero elevation, taking care that when 

condenser is finally tilted, its center line would match with turbine axis.  When the bottom plate is at 

zero elevation, shim assembly of the water boxes and condenser shell internals, the support bolts of 

all the spring elements must be in their uppermost positions before the work is commenced.    Detach 

the tack welded base plates from the spring elements and eliminate the weld spotsplates under all 

spring elements.  In order to avoid displacement of the bottom plate during  assembly of the water 

boxes and condenser shell internals, the support bolts of all the spring elements must be in their 

uppermost positions before the work is commenced.    Detach the tack welded base plates from the 

spring elements and eliminate the weld spots.

Typical pre-assembly bay of condensed on urbine floor. Very first work done which is not listed in

OEM manual is jointing of stiffenr rod of condenser. Please note tonnes of welding rod is necessarry

to complete the job which is time consuming and labour oriented. Some of the TSP are lying for 

cleaning and checking.

An opening of LP turbine is visible when A Row civil work is not ready but EOT crane is ready then

hotwell , bottom  plate and other material goes through this route. It is experienced that the area 

between paddle flange and condenser foundation takes considerable time to complete because of 

water accumulation..

continued to part-iii.


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TCONDENSER - AUXILIARIES OF STG SETS -ABC OF THERMAL POWER PLAN

Till last dispatch I have given an outline of  Turbine ,Generator erection including some   detail of integral piping specially  Lube oil ,control oil , drain lines ,seal steam  lines etc. From today onwards   I will describe the major auxiliaries likes Condenser , pumps and their drive turbines , heaters and other items . I receive number of mails from supervisors and young engineers for auxiliaries erection details therefore  I will try to answer all their queries in my subsequent dispatches. 

In my working time I have come across two distinct type of set one is Russian and other is German. For a given capacity like 200 MW set Russian condenser work is very less compare to German condenser. Russian condensers are pre- fabricated  up to tube supporting plate and box has to inserted and assembled . However for German design set like KWU /Siemens every item needs to be assembled i.e. starting from base assembly to the making of the box therefore time  taken for condenser erection is more than Russian set. I have never worked in Chinese sets therefore feedback is not available with me. I request readers to enlighten me in this regard. One more recent development in 660MW Siemens deign the base plate is tilled half a degree and instead of spring support bearings are provided below the base plate. There may be some other changes but not that significant during erection.

I will outline my discussion based on BHEL make 500MW. However I will use photographs of 660 MW set so readers should not get confused about the size.

   
  The condenser is a box type construction with divided water box design double flow; two pass 

which facilitates the operation of one half of the condenser while other half is under maintenance. 

The steam space is of rectangular cross-section with integral air-cooling  section from where air and non–condensable gases are drawn out with the help of air evacuation equipment.

The surface condenser is mounted on spring supports. The condenser is welded with   the exhaust hood of the low-pressure turbine. The tube plates are welded with the water chambers. Condensers are provided with domed shape water box. The condenser tubes are supported within the condenser shell by tube support plates. The condenser is installed in such a way that all condenser tubes are drained automatically into the condenser water Condition has been provided with an extension suitably to connect it to the turbine exhaust opening. Adequate internal clearance is provided. The rigid construction results in a sound-condenser combination for trouble free operation.  

The water boxes of the condenser have been designed for smooth entry and uniform distribution of cooling water to all the tubes. The water boxes are removable type and have been provided with necessary hinged manholes for easy access to the interior for inspection. Each water box has been provided with a vent and drain connection. The circulating water connections of adequate size have been provided with water boxes. The condensate produced in the condenser & drains entering through flash vessels collect in the hot well from where the pass to the condensate pumps.

CONTINUED PART -II

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TURBINE AUXILIARIES (CONTROL OIL SEAL STEAM ,DRAIN SYSTEM ) PIPING ABC OF THERMAL POWER PLANT

OTHER IMPORTANT MISC. INTEGRAL PIPING SYSTEM IN TURBINE ISLAND

A. Control Oil system.

In 500 MW Units, fire Resistant Fluid (FRF) used for the control systems and LP Bypass system mainly to 

avoid fire accident in case of leakage of working fluid over high temperature parts of turbine.

This system consists of following equipment.

a. A FRF tank with pumps mounted .

b. Oil vapour exhausters. 

c.  Filters  and FRF coolers.

The process pertains to FRF system is similar to TG lube oil system. 

However Piping size of control oil system is small bore piping with some 

exception.

The fluid circulated in the system is divided for different purposes. Such as control fluid,

secondary fluid, Trip fluid and start up fluid etc. Control oil transmits signal from

Governing Rack ,LP Bypass rack , Spray water racks etc to equipments like Control

valves ,IPCV , Extraction valaves , LP Bypass valves etc.

Precaution needed during erection stage for small bore piping.

A. Control oil piping is small bore piping that includes pipes , gasket , different size “ O –

ring” , fastners and other assorted fittings  for sealing purpose. Therefore it is requested to

make a check list of each line and supervisor should monitor the completion by using proper

material at proper place. This will reduce time during HT of the line and also save time and

money during flushing. Please remember FRF is very costly fluid.

B. Piping erected as ascending radient should have minimum 67 mm(1:15) slope.

C. Descending gradient should have minimum 175 mm slope.

E. Maintain gradient as far as possible if high point is unavoidable then provide venting

provision with orifice.

SEAL STEAM SYSTEM

Seal steam system comprises of following sub systems :

  

Seal Steam Lines, valve Stem Steam Leak-Off Lines and Seal Ring Steam Leak-Off Lines.

In laying these lines, provide sufficient compensation for thermal expansion. The service

temperature for all lines can be assumed to be approximately 450 degC. These pipes expand

by approximately 6 mm/m between the cold state (initial temperature 20 degC) and the hot

state.

Seal pipelines to be connected to the cylinder only after full assembly.

Seal and leak off steam pressure is very very low therefore impulse line for pressure

measurement should carefully laid to avoid pulsation of signal.

DRAIN SYSTEM

One of the important integral piping system contains small bore to large bore piping

including numerous motorised valves , manual valves and pipe fittings. Insulation of the

line is also an important criteria for  drain piping.

 All drain lines shall have as steep a gradient as possible, an all cases at least 20

mm/m.

 In erecting these lines, provide sufficient compensation for thermal expansion. The

service temperature in plant can be assumed to be approximately 450 deg C.

 These pipes expand by approximately 6mm/m between the cold state (initial

temperature 20 OC) and the hot state.

 On drain lines made from thick-wall piping, ensure straight pipe sections at least 500 mm

long between the drain sockets (on casings and pipes) and the first bend in the pipe.

A few PID diagrams of different system ( of BHEL make set) are attached .

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TURBINE AUXILIARIES (OIL SYSTEM -LUBE ) PART-II ABC OF THERMAL POWER PLANT

PART-II

OIL SUPPLY DATA FOR A TYPICAL 500MW SET MANUFACTURED BY 

BHEL

MAIN OIL TANK, RATED CAPACITY:                       25/40             Cu . M

Ist OIL FILLING (ESTIMATED):                                   47.5                Cu . M

FLUSHING OIL QUANTITY (ESTIMATED):               28.5              Cu . M

OIL TEMP. AT COOLER OUTLET,                               38 TO 45 DEG C.

TEMP. RISE OF OIL IN BEARINGS                              20 TO 25 DEG C

OIL PUMPS

M.O. PUMP     A.O. PUMP       E.O. PUMP                         J.O.PUMP

      1                      2                          1                                  AC : 2             DC : 1

                                        

                                             CAPACITY (RATED)

      

    75                     89.25                     30                                    1.53              dm3/s

                                               

                                   DISCHARGE PRESSURE (GAUGE)

       

    8.6                     6.2                        2.3                                   178                 BAR

                                                           

                                                       SPEED

    50                   24.75                       24.3                                49.42                         /s

A Few erection points need to be remembered during erection of Lube line of turbine

1. Lube system includes jacking oil line. Jacking oil is used to lift rotor from bearing 

during starting .

2. As these lines requires lot of small items including fastners , o-ring , gasket, small 

bore pipes , prefabricated pipes, valves ,supports  etc a systematic material 

management is required to reduce the time cycle. No pipes to be kept open at the end. 

All pipes to be cleaned by compressed air before erection.

3. To start the work oil canal and oil room front availability is must.

4. All the pipelines joints small bore / large diameter should be tig welded in root.

5. Temporary pipes required for oil flushing to be made during erection itself so that 

last minute fabrication is not necessary.

6. Match up, weld and examine the prefabricated connecting pieces of the discharge 

and suction nozzles prior to the final erection of the first bearing pedestal.

7. Other matching and welding work to be done when the bearing pedestal is full 

assembled.

8. The direction of flow of the oil temperature control valve should be ensured as 

indicated by markings on the valve itself.

Jacking Oil Lines

9. Once the line has been welded to the bearing pedestal, fit a protection plate to 

protect the line in this area.

10. Ensure that oil vapor extraction lines are laid with a gradient descending constancy 

towards the main oil tank without low points. A drain loop at the lower end of this line 

upstream from the blowers return drains to the oil tank.

11. To avoid fire hazards, do not route oil lines near lines or components at high 

temperature.

Oil tank with pump motor on the top.

Typcal 500MW lub oil scheme is given above ( BHEL make sets) 

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