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Sunday, 14 July 2013

ELECTROSTATIC PRECIPITATORS FOR A THERMAL POWER STATION OVERVIEW, ERECTION PLAN & CONSTRUCTION FEATURE PART -II

There are many types of electrostatic precipitators but I will describe only

BHEL make ESP.

- ERECTION PLAN AND SEQUENCE.

- Check the foundation of ESP column .

- Mark the centre line .

- Check the distance between centre lines of ESP foundations.
  Tolerance +/- 10mm.

-Top elevation of ESP foundations to be measured.

- Spacing between its foundation and diagonal difference.

- Bolt to Bolt pitches distance and diagonal distance to be measured
  Tolerances for pitch +/-03mm and diagonal +/- 05 mm.

- Some of the foundation will have shear lugs also .All those measurement
  are to be taken.

Top of the elevation and dimension of shear lug pocket is very important

for carrying out the secondary grouting by Ready  Mix concrete like

conbextra , pagel , sikka , five star etc. Gap between foundation and  column

pedestal will determine the volume of RMC required. Generally GAP is

restricted to 30 mm to maximum 70 mm. Secondary grout can be done

by one grade higher concrete but the curing time and settling time will be

21 days where as the same value can be achieved within 3 days of  RMC

concreting. Cost of RMC is much more therefore optimum dimension should

be achieved during pre-concreting check of foundations.

Once all foundations are checked then we can start preparing for column

erection. For any 500MW ,600 MW or 660MW set either there will be

04 pass ESP or 06 pass ESP. The work involved in each pass will be the

same and repetitive. Erection should start from the centre pass of the ESP

then move out to outer side. This help us in optimisation of crane capacity

any deviation from this may attract the requirement of higher capacity crane

for erection of  wall , inlet nozzle , roof truss etc. Interface with boiler erection

CHP , AHP and Duct structure will obstruct ESP erection. Therefore careful

planning is required to erect ESP .

- Sweep and camber of the columns to be checked .

- After erection column to be vertical. Tolerance 1mm/M ,max 10 mm.

- Horizontal bracing and diagonal bracing to be erected.

- Checking of orientation of column is must before erection.

we donot erect all the digonal bracing  to allow movement of Hydra crane

between the columns . Otherwise same is not possible . Bracing are erected

when our requiremnent of Hydra crane reduces.

- After welding of all bracings etc bearing /slide supports are placed on the

 top of the column.Diagonal Distance are measured from the top of the fixed

foot column to other bearing top and recorded.










contd to part-3

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