MAIN CIVIL WORK PART VI OF THERMAL POWER PLANT.

In our last submission we have discussed few aspects of Chimney that a construction engineer should know it whether he is attached to Chimney job or not. A major aspect of Chimney erection is safety of the manpower engaged , safety of the manpower working below , safety of the equipment and machinery . While we will discuss the safety aspects as a whole afterwards but it should be prime important aspect of chimney construction. Safety norms stipulated in the contract to be followed strictly. Lapse in safety effort may cause havoc for the project and such incidents happened in recent past . It causes death , property loss and can bring doomsday for the company.

One more area which need utmost safety attention like Chimney is NDCT ( Natural Draught Cooling Towers ) which is used for cooling the Cooling water of the entire power plant. NDCT is major civil job in the thermal Power Plant. Its work principle etc will be discussed afterwards.

 -Specific weight of concrete shall be taken as 2.5 T /m3.

- Because of his height and specific parabolic shape wind load will be a significant factor . Reference 

  will be drawn from IS 875 code.

- Theoretical wind load is only valid if both the cooling towers is spaced more than ( 0.5x base dia.) M.

-  Wind pressure at different height has been calculated by taking reference of Vb= 47m/sec at 10M 

    height with risk co-efficient factor of 1.2.

-VGB-BTR KUHLTURME GERMAN SPECIFICATIONS is also used for wind load calculation.

- Seismic load as per IS and temperature load due to variation of ambient  temp ( 3deg C to 50 deg C).

- factor causing temporary loading during construction stage depends on the following

a. Barrowing of concrete b. Scaffolding and formwork . c. Hoist fixing . d. Temporary material kept

on scaffolding  e. Temporary access  f. Tower crane fixing g. Anchorage .

- Minimum load condition to be followed for designing of structure.

Dead load = D ; wind load = W; sesmic load = Se ; settlement load=S; Thermal load = T.

- i) D+W+S  II) D + Se  III)  D+T  IV) D+W+T+S  IV) D+Se+T+S V) 1.0D+1.5W.

-Permissible stress to be calculated as per IS codes.

- Shape formula generally used is H/D = 1.2 to 1.55 . D=diameter . H = the total tower height above

basin sill level; Hb/H =0.75 to 0.85  Hb is the vertical distance from the throat to basin sill level.

Critical dynamic Pressure ( wind pressure ) for Buckling of Cooling Towers is given below.
       
                                        0.07 Ec ( d )7/3
                             Pcr =   --------------------

                                                  rth

Pcr = Critical Dynamic Pressure ; Ec = Modulus of  elasticity of concrete  ; d =diameter of the shell

rth = Throat radius of the shell.

The buckling Safety Factor of the shell should not be less than 5 with D and W load.

The minimum shell thickness of the shell shall not be less than 200mm.

The minimum concrete grade to be followed for structural of NDCT.

Pre -cast and Pre stressed element                                         M-35

Entire Tower, Shell and Basin                                               M-30

PCC enchashment                                                                  M-20

Mud Mat PCC                                                                        M-10

Pile/Tower Foundations                                                         M-25

All other RCC                                                                        M-20

Add mixture is permitted to use as per IS Codes. 

P.S If  you are looking to earn few legitimate extra money from the comfort of your home then please click on the link given below

LINK 1 - PLEASE CLICK HERE 

LINK 2 - PLEASE CLICK HERE