ERECTION OF TURBINE GENERATOR PKG PART-VI, PEDESTAL, BASE PLATE ERECTION, INSTRUMENTS - ABC OF THERMAL POWER PLANT.

Part –VI

GROUTING OF PEDESTALS AND LP BASE PLATES

 Technical Requirements of Grout material used for turbine pedestal grouting.

Compressive Strength, Non-Shrink  - the compressive strength at 28 days must be not lower than 50 N/mm² .

The early compressive strength at 24 hours must not be lower than 24 N/mm²

- the grout may not shrink. In addition a certain swell-rate is desired (volume increase within 24 hours: atleast 0.2%; according to ASTM C 827-95a). The grout must be water and oil resistant.

The basis of the grout must be cement. It may not contain metallic components and added chloride or other admixtures that may corrode steel.

After adding of water the grout must be in fluid state .In order to improve the flow a high water content should be preferred within the admissible range specified by the manufacturer. The grout should be workable for approximately 45minutes and shall not segregate after grouting.

The specified range of suitable grouting heights must be considered for each application. In case of

a too wide grouting height cracks may occur due to strong heat development. If the grouting height

is too narrow the flow of the grout may be not sufficient and air pockets may form. Where grouting

heights cannot be complied with, a different grout type suitable for the grouting height shall

generally be used. In exceptional cases, a grout may be used for a larger-than-specified grouting


height if a stone aggregate (e.g. quartz) with a specified maximum grain size is

added. The manufacturer's instructions should be followed exactly. In our case

we generally keep the heights between 50 to 70 mm.

The processing instructions and specifications of the grout manufacturer must be complied with. Particularly with regard to the amount of water to be added, the processing temperature, the mixing process, as well as the permissible grouting height. Only drinking water may be used for adding to the grout. Concrete mixers shall be suitably sized .The duration and intensity of the mixing process must also be sufficient .No vibrator shall be used in pouring the grout. Grout should be free  flow (working into place) may be aided by manual.

Fill 3 to 8 mm washed Pea-gravel in all the anchor bolts sleeves. These gravel are necessary to give damping effect to the anchor bolts during operation of the machine.

Seal anchor bolts holes after filling of gravel to avoid any entry of grout metal.  Cap ,tapes etc may be used for sealing .Clean foundation with compressed air. Make shuttering of all the pedestal and LP base plates. Use thick polythene sheet inside the shuttering to give better finish and avoid moisture absorption by shuttering.

Shuttering should be made with maximum care to avoid any leakage of grout concrete. All sides of the shuttering are to be sealed either with some sealing compound or with thick mixture of grout material to avoid leakage of grout material.

Foundation are to be kept wet for about 6 hrs. before grouting.

Non shrinkage cement duly approved by turbine manufacturer is to be used for grouting of the pedestals and base plate. In India we generally use Pagel cement from Pidilite , Conbextra GP 2 from Fosroc , SIKA 214 (ACC) and Five star cement company.

Use fresh stock of the grouting material only and check the strength of the material before use. Every batch of the supply should be tested through cube test if the supply is not of same batch. No material ( grout cement) to be used without testing.

During grouting, the mixture has to be poured from one end only and it has to flow to opposite end to avoid any blockage of air pocket.

Water curing is to be carried out for about 10 days duration.

All anchor bolts are to be stretched minimum after 21 days of grouting.

HP, IP & LP module placement work can be taken up after 24 hours of grouting of the pedestal and base plates.

For individual pedestal and base plate, grout mixture should be poured in one lot only.

It is recommended that supplier representative (technical) is present during grouting of pedestal and LP Base plates and grouting is to be done under their technical supervision.

BRIEF TECHNICAL SPECIFICATION OF BHEL MAKE 500MW (TURBINE)

LOAD ( RATED)                                                                        500 MW

MAX. UNDER VALVE WIDE OPEN (VWO) CONDITION            524.2

THREE CYLINDER REHEAT CONDENSING TURBINE                 500 MW

SINGLE FLOW HP TURBINE WITH 17 REACTION STAGES

DOUBLE FLOW IP TURBINE WITH 12 REACTION STAGES PER FLOW

DOUBLE FLOW LP TURBINE WITH 6 REACTION STAGES PER FLOW

2 MAIN STOP AND CONTROL VALVES ( ESVs and HPCVs)

2 REHEAT STOP AND CONTROL VALVES (IVs and IPCVs)

1 SWING CHECK VALVE IN COLD REHEAT LINE

2 BYPASS STOP AND CONTROL VALVES

EXTRACTION SWING CHECK VALVES :

EXTRACTION-1                                                                               NO VALVE

EXTRACTION-2                              1 SWING CHECK VALVE WITH ACTUATOR

EXTRACTION-3         1 SWING CHECK VALVE WITH ACTUATOR & 1 SWING   

                                    CHECK VALVE WITHOUT ACTUATOR     

EXTRACTION-4.1       2 SWING CHECK VALVE WITH ACTUATOR

EXTRACTION-4.2       2 SWING CHECK VALVE WITH ACTUATOR

EXTRACTION-5

1 SWING CHECK VALVE WITH ACTUATOR & 1 SWING CHECK VALVE WITHOUT ACTUATOR

EXTRACTION-6                                                                         NO VALVE

SPEED (RATED SPEED)                                                             50.0 /S

RANGE                                                                 47.5 TO 51.5 /S

STEAM PRESSURES                                                                 RATED*

INITIAL STEAM                                                                        166.7   BAR

BEFORE 1st HP DRUM STAGE                                                154.4   BAR

HP CYLINDER EXHAUST                                                          44.9     BAR

IP CYLINDER STOP VALVE INLET                                          40.3     BAR

EXTRACTION 6                                                                        44.9          BAR

EXTRACTION 5                                                                        17.5     BAR

EXTRACTION 4                                                                        7.2       BAR

EXTRACTION 3                                                                        2.58      BAR

EXTRACTION 2                                                                        1.329   BAR

EXTRACTION 1                                                                        0.257   BAR

LP CYLINDER EXHAUST                                                          0.1013 BAR

PRESSURE IN SEAL STEAM HEADER (ABOVE ATMOSPHERIC)  35 MBAR

STEAM TEMPERATURES                                                                RATED

INITIAL STEAM                                                                                   536.0

IP CYLINDER STOP VALVE INLET                                                      536.0

HP CYLINDER EXHAUST                                                                    340.0

EXTRACTION 6                                                                                    340.0

EXTRACTION 5                                                                                    413.9

EXTRACTION 4                                                                                    292.1

EXTRACTION 3                                                                                    187.3

EXTRACTION 2                                                                                    128.3

EXTRACTION 1                                                                                    66.5

LP CYLINDER EXHAUST                                                                     46.1

CONTINUED TO PART -VII 

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