Silo Chimney & Cooling Tower

Overview

RCC Silo in Rourkela

Problem:

After putting to use, the silo reported major cracks due to construction error

Solution:

Steel supports were provided for supporting the hopper internally.
Cracked sections were rebuilt using thixotropic mortar.
Minor cracks were grouted with epoxy based chemical.
Silo was externally wrapped with alternate layers of vertical and Horizontal Light weight GFRP and CFRP wraps.

Overview

RCC Silo in Dala, Varanasi

Problem:

Poor workmanship during construction of 70.0 m high RCC Silo by slip form method
Bulging of Silo at few locations and out of plumb construction at certain location
Poor quality of Concrete
Bulging and eccentric construction causing excessive localized stress leading to minor cracks

Solution:

Finite element analysis was carried out to know nature and intensity of stress at critical locations
FE Model from level of 19m to 68m. Eccentricity was modeled based on the input data
It was found that several FRP overlays are required for retrofitting
Instead of conventional wrap system, factory made composite profiles were used and fixed at site by chemical adhesive and mechanical anchors
Exhaustive grouting with polymeric cement slurry and low viscosity monomer was carried out
Project was completed in 180 working days

Overview

RCC Chimney in Karnataka

Problem:

The 60m tall and 2.9m diameter RCC chimney at Goa minerals, Dharwad showed sway of 273mm due to construction error.
This resulted in excessive moments at different levels of chimney.

Solution:

Complete design build solution to take care of this additional moments of chimney.
A hybrid system of carbon laminates and wraps at bottom and helical GFRP wraps at top was designed and executed by Sanrachana Team
Cracked sections were rebuild using thixotropic mortar
Minor cracks were grouted with epoxy and silo was externally wrapped with alternate vertical and Horizontal GFRP and CFRP wraps.
Protective UV resistant Coating was applied on FRP System.

Overview

Chimney for Nirlon Ltd

Problem:

The 40m tall RCC chimney at Nirlon LTD, Goregaon old factory premises converted to an IT park, was damaged due to corrosion and concrete spalling was visible.
Tough non-functional chimney was to be retained to preserve the history of the area.

Solution:

Cracked concrete was removed and RCC structure was grouted with epoxy to improve microstructure.
Anti-corrosion treatment was given to rebars and additional reinforcement was added wherever required and coated with corrosion inhibitors.
Lost concrete section was rebuilt using Micro Concrete and Thixotropic repair mortar.
From durability aspect the whole structure was treated using vertical and horizontal CFRP wraps
Use of CFRP kept the dead weight low and helped to maintain the original cross section size
Protective UV resistant PU coating was applied on the chimney.

Overview

NTPC Cooling Tower, Faridabad

Problem:

RCC cooling tower requires regular maintenance because of severe exposure conditions
Top and bottom ring beams were damaged by corrosion of steel reinforcement
Work had to be completed as per the shutdown schedule of plant

Solution:

Anticorrosive treatment was done on exposed steel
Section was rebuilt using epoxy-latex mortar, followed by application of glass fiber wraps
Job was completed in 90 days in synergic manner without hampering plant schedule

“Sanrachana ensured timely completion and co-operated to adjust our shut down requirements. The job was executed as per contract specifications and by following stringent safety norms.” Engineer incharge, NTPC Faridabad.

Overview

NTPC Bhilai

Problem:

The cooling mechanism was enclosed in an aged building that required retrofitting
Corrosion effects such as spalling was visible in several locations.

Solution:

Anti-corrosion treatment was performed on all exposed steel bars
Polymer modified mortar was used to plaster over the treated portions
Fiber wrapping for confinement and additional strength
0.3 mm thick moisture protection coating for durability of the structure..

Overview

Masonry Chimney

Problem:

46m tall 6m diameter 60-year-old masonry chimney of industrial plant, had major vertical cracks which were over 12mm wide
Tension bolts of Hoop ring have been found to have failed
Chimney was designed only for gravity and wind loads. Adjoining structure constructed later, was imposing lateral thrust on it, for which it was not designed.

Solution:

Creating a separation between the chimney and adjoining structure.
Micro-fine cement grouts for filling cracks
Stitching of cracks using SRM-C wrap (carbon fiber wrap)
Additional confinement provided using glass fiber wrap (SRM-G Wrap)
Design-build solution offered by Sanrachana

Overview

REPAIRS FOR HOT INDUSTRIAL EXPOSURE

Problem:

Extensive micro-cracking and corrosion in 25-year-oldRCC coke oven structure of a steel plant due to constant exposure to 100°C temperature.

Diagnosis:

Repair system should be stable under sustained high temperature exposure. Conventional repair systems based on organic materials are unsuitable for this type of exposure.

Solution:

An inorganic repair system usingSRM Hot Wrap – FRCM (Fiber Reinforced Cement Matrix) was specially designed for this project and used.
172 RCC columns repaired in 30 days of shutdown
Accelerated temperature testing done successfully

Overview

RESTORING A POWER PLANT

Problem:

Extensive corrosion damage on columns, beams and coal stacking slab. Conventional jacketing not possible due to immovable service line network.

Diagnosis:

Corrosion damage needs to be rectified, low strength of existing concrete needs to be improved, without increasing cross section area.

Solution:

Rust removed,additional steel provided and anti-corrosion treatment done for spalled portions.
Pressure grouting done to improve micro-structure.
Sections rebuilt with PMM and micro-concrete.
Glass fiber wrapping for improving the strength by confinement, followed by sand pasting and plaster.

Overview

RETROFITTING A PRILLING TOWER

Problem:

Lift shaft wall showed cracks. Deflection and honey combing was noted. Staircase columns showed local buckling and sagging of beams.

Diagnosis:

Cracks on lift shaft wall was due to wind pressure. NDT showed that concrete quality was poorfrom 60m to 90m height. Major issue was improper handling of slipform formwork, which also explains the deflection of the tower.

Solution:

Single layer 600GSM CFRP was applied inside and outside lift shaft wall and on beam column junctions.
Treaded rods were drilled through walls with additional reinforcement and conventional jacketing was performed with micro-concrete to strengthen weak bottom portion.
Carbon fiber applied in beam column junctions was coated with UV resistant PU coat.
On exposed side of lift shaft wall, CFRP surface was roughened by sand pasting, followed by plastering and painting.