LABORATORY TEST EQUIPMENT REQUIRED FOR CIVIL WORK AT THERMAL POWER SITES.

Till date we have discussed about the specific packages of civil work like MAIN Power House , CHP , AHP , Water System including NDCT ,CW etc. These packages are having high percentage of civil work than others in Thermal Power Station. We have left out following works which are comparatively less in volume and easy to execute. Those packages are Roads , drains ,culverts , Security Gate and watch Tower, enabling works ( The facilities to be created before actual execution of the project) , Quarters for staff and workers of the owners , other social obligation like School , Hospital , First Aid Centre etc. Different Small pump House , Transformer foundations , Storm water drainage system. All the above packages are permanent in nature and required at the Power Station Location at different times . One major job we have not discussed levelling and filling  of the land  .We have excluded Rail way lines , Merry Go Round System , sidings etc as those packages are executed by construction wing of Railway .

A common requirement of all projects are Quality System of the civil work . There are two distinct part . One is MQP ( Manufacturing Quality Plan) and other is FQP ( Field Quality Plan). Both the plan identifies the process points where checks to be done and if required the same will be recorded in a pre-determined protocol sheet. It also identifies the customer hold points at different stages . Construction people who are working in field needs FQP before start of their work. MQP will not be our part of discussion.

To start civil work at site we need to establish a civil laboratory to conduct routine test on different works . The following instruments are identified to be mobilised at site.

                                                                    Routine Test Lab.


      1.1 Vicat Apparatus     Cement Consistence     Penetration of Std. Needle          IS 5513
1.2 Lechatelier’s test
       Apparatus            Cement shrinkage Size    variation after curing of sample  IS 5514

 1.3 Mould (cement)
  (70.7x70.7x70.7mm)  Cement cubes      Cubes made of 1:3 cement: Sand  IS 10086

 1.4 Cement Mortar Mould
         Vibrator                Cube Compaction Vibration for fixed duration          IS 10078

 1.5 Concrete cube mould
        (150x150x150)mm  Concrete cubes                        --                          IS 10086

 1.6 Compressive strength
       Testing machine  Concrete cube test      Crushing strength of cube          IS 2505

 1.7 Concrete slump cone Workability check     Drop in cone height of concrete   IS 7320

 1.8 Coarse aggregate sieves    Sieve analysis                     Sieving                          IS 383

 1.9 Fine aggregate sieves        Sieve analysis                     Sieving                          IS 383

1.10 Sieve shaker                Mechanical sieving          --

1.11 Aggregate impact test
          machine                         Impact value of aggregate  --                         IS 9377

1.12 Compaction factor Apparatus       Workability of concrete Lab test
                     
        1.13 Abrasion and Attrition Testing Machines.
                     
        1.14 Proctor Density Testing Equipment with Mould
                     
        1.15 Thermometer
                     
        1.16 Measuring Cylinders

 PICTURES OF FEW LABORATORY TEST INSTRUMENTS ARE GIVEN BELOW.

COMMON WORK FOR ALL CIVIL JOBS IN THERMAL POWER STATION IRRESPECTIVE OF AREA.

PS: For further information on " ABC of thermal power" click on the adjacent

      advertisement

CONCRETE.

- All concrete works should conform IS:456 or Equivalent standards lik BS ,DIN etc.

- Mix design of concrete shall be used everywhere except for lean concrete and PCC.

- For lean concrete and PCC nominal /Volume mix is permitted.

- Design Mix should be carried out as per IS: 10262.

-Minimum Grade of  M 25 concreting to be done for all foundations including piling  .

- For Structural and other area M 20 grade of concreting can be done.

- For Underground and outdoor work M 25 concreting is to be carried out.

- Grade of concreting for critical foundations was already mentioned earlier. On enquiry same can again be furnished.

-Unless otherwise specified, 20 mm and down aggregates shall be used for all structural concrete works 

- 40mm and down aggregates may also be used under special conditions for mass concreting in foundation.

-All underground concrete structures like trenches, substructures of pump houses, all water retaining / carrying structures , etc., shall have super-plasticizer cum water proofing cement additive conforming to IS:9103. In addition, limit on permeability as given in IS:2645 shall also be met with.

-Sound and crushed stone aggregate shall be used for all concreting.

- All aggregate should be tested for alkali reaction. High percentage alkaline silica shall not be used.

- Lime stone aggregate shall no be used in general for machine foundations.

- The temperature of fresh concrete shall be maintained at about 25 deg. C . If necessary ICE cubes are

   generally used during casting to maintain the temperature.

-Plasticizer / super plasticizer / retarder  / pumping additive may be used as required and permitted by codes . The slump generally be kept in this range.

TG TOP DECK                                                                                 150   TO   200 mm

BFP /ID/FD/PA FANS /MILLS ETC                                               100    TO   150 mm

BLOCK  FOUNDATIONS                                                                100    TO   150 mm

COLUMN                                                                                          100     TO   150 mm  

-Plywood with film face form work shall be used for the top decks of all machine foundations and also for columns of TG foundation. Form work is the job which consume  number of man days in civil work

for fixing in position then using prop to support them all around . We have not come across any mechanical method to do it in faster way. Adjustment of support firmly behind the form work takes time. Sometime it disturbs the foundation bolts location to an unacceptable limit . Therefore bolt checking , shear pocket checking to be done only after form works. 

- Generally Portland cement  ( having specific gravity 3.15) can be used for all purposes. However there are two other cements are available in the market . Those are Portland - Blast furnace Slag cements and 

Portland - Pozzolan cement . The specific gravity of these cements varies from 2.85 to 2.94. These cements are also used widely.

- The mixes of grades M5 M10, M15, M20 ,M25 M30 etc correspond approximately to the mix proportions (1:4:8), (1:3:6), (1:2:4), (1:1.5:3) and (1:1:2) respectively. For concrete mixing ratio in all grades concrete, the mix has to be designed after testing all the materials including water in labs. For higher grade of concretes the mix has to be designed , it is the water to cement ratio plays a major part therefore the same has to be monitored. Therefore to achieve the grade conducting design mix is very important . Ratio arrives during design mix is to be followed for concreting.

- Base Raft and Top Deck of any any machine foundations shall be cast in single pour.

- Ultrasonic pulse velocity test shall be carried out for the top decks of all machine foundations and TG substructure to ascertain the homogeneity and integrity of concrete. In addition to that additional cubes are to be taken at a predetermined interval.

PICTURES GIVEN ABOVE ARE THE CEMENT MOULD USED FOR TAKINGS CUBES  DURING CONCRETING.

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

PUMP HOUSE ,AHP ,ASH DYKE SALIENT POINTS ON CIVIL WORK

Fuel oil pump house , pipe trestles etc major portion of the work is structural . The same will be discussed when we will discuss structural portion.

-600mm wide walkway is required along the trestles.

- RCC dyke wall of 1.2m clear height above finished ground level shall be constructed around LDO tank enclosing a minimum area of 17M x 17M.

-Overhead conveyor Gallery  of CHP ( Coal handling Plant) will have maximum span of 25 M.

- Double stream Gallery Should have one central and two side walkways having width of 1100 mm  and  800 mm respectively. For single stream Gallery two walkways having 1100 mm and 800 mm width   should be provided. Gallery should have anti skid chequered plate .

- Sliding PTFE bearing supports shall be provided at one end of the gallery for relieving forces due to temperature variation.

-Transfer Tower /Maintenance Building roof and subsequent floor will be RCC on structure.

-Ash handling plant /system ( for both wet and dry) shall comprises of  bottom ash and fly ash system.

 It also comprises Ash Slurry Pump House , Ash Water Pump House , Ash water Pipe line support to Ash dyke , Ash water re -circulation system  and Ash Dyke. All the civil jobs and structural jobs are

similar to other packages in execution however salient features are given below.

- Top line of Pipeline pedestal shall be 300 mm of FGL.

-The Capacity of the ash dyke shall be suitable for 25yrs of usage.

-Comprehensive seepage analysis to be done. Ash dyke to be deigned taking IS 7894 in to consideration.

- The ash storage area is divided into two storage lagoon and overflow lagoon.

- The water from storage lagoon goes to overflow storage area  through RCC well type structure.

- Embankment - the top width of embankment is to be 6 M and will have 3.75 M width WBM road.

- Free board will be minimum 1.5 M.

- Slide slope shall be minimum 2.5(H) to 1 (V). 3 M wide berms to be provided for all slopes at 6 M

   height interval.  

- 600 mm clay blanket is to be provided at the bottom of all the three lagoons.

- Internal drainage arrangement shall be given .

- Sand chimney of minimum 0.5 M thickness, upto 1.5 M below dyke top.

-Sand blanket of minimum 0.5 M depth

-Height of rock toe should be minimum 1.0 M

-The exit gradient shall not exceed about 0.14.

- When the annual rainfall is more than 200 cm, downstream slopes shall be protected by minimum 30cm thick stone pitching.

-On the upstream slope, stone pitching 30 cm thick shall be provided for the top portion.

  CW PIPES LAYING ERECTION INCLUDING ENCASING UNDER PROGRESS.

LAY OUT PLAN IS VISIBT LE. CHP GALLERY FROM DIFFERENT TRANSFER POINT IS ALSO VISIBLE.

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

NDCT CW SYSTEM CIVIL WORK IN SHORT FOR THERMAL POWER STATION.

Minimum test on concrete should be carried out as per codes and standard practise. However at least these tests are to be carried out.

1 Test for comprehensive strength - one cube per column.

2. Test for comprehensive strength - two cubes per climbing section of the shell.

Some of the cooling water construction is given below.

a) Shell wall centre line in horizontal plane measured radially at mid point on a 3m wide chord : +/- 15 mm.

b) Shell wall centre line in vertical plane measured over a height of 1m : +/- 10 mm

c)  Shell thickness : + 10 mm or- 5 mm

d) Horizontal radius of shell at any section other than shell base : +/- 50 mm.

e) Horizontal radius at shell base : +/- 40 mm

Beside chimney  and  NDCT the major civil work at thermal power is CW system comprising of  CW pump houses , CW ducts and CW channels etc.

- The Sub structures of all the pump houses , forebay etc will have RCC of M-30 concreting.

- Super structure building may have structural steel building .

- Sizing of Pumps , sizing of Forebays etc is to be decided by the model study . The model study will be conducted by reputed Hydraulic Research Institutes.

- Design of substructure  consist of two parts  1. Stability Analysis  2. Structural Analysis.

- Stability analysis is to be done for following load conditions.

Under operation stage :- Maximum load of super structure + equipment load + subs structure + earth pressure + ground water pressure etc.

2. Loads as above + Seismic Load.

3  Under construction stage loading and seismic load.

Following stability conditions to be checked on above load conditions .

a. Check for overturning.

b. Check for sliding.

c. Check for uplift.

Structural Analysis will be done in following areas.

1. Base slabs  2. Intermediate Piers 3.End Piers  4. Back Walls  5. Operating floor slabs .

Analysis will be done in different load conditions 

- CW ducts are made of steel liner and encased it concrete.

- Minimum thickness of the pipes is given below.

For pipes less than or equal to 2200 mm                                                       12mm

For Pipes more than 2200mm but less than or equal to 32oomm                  14mm.

For pipes greater than 3200mm                                                                     16mm.

Maximum velocity in the ducts should not exceed 2.2 M / sec.

These pipes are generally fabricated at site from steel plate and welded. After all pipes are manufactured , laid and welded hydraulic test was carried out  pressure. After successful Hydraulic test the pipes were encased. Special care should be taken during hydraulic test with an eye to venting about the system to avoid damage of the pipes.

Raw water Reservoir shall have net usable capacity of 17,76,000 cu m . Over and above evaporation loss is to be considered. To calculate the sizing of the reservoir  last 500mm depth is taken as dead storage for deposition of slits. Embankments will have side slope of 1(V) : 2 .5 (H).  Minimum top width of embankment will 6 M.

  

    NDCT SHELL

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

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