Processes & Operations
Manufacturing Units
Quench Tempered Process-made only from billets

TMT rebars (Thermo Mechanically Treated) are generally hot-rolled from steel billets and are subjected to a programmable logic controller (P.L.C.) for the thermo-mechanical treatment. The three major stages of conversion of steel billets into TMT rebars are:

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Quenching: When a hot rolled bar leaves the final mill stand (including roughing mill, intermediate mill, finishing mill, etc.), it is instantaneously quenched using a special water spray system in the quenching box. This is done to harden the surface while the core still remains hot and soft.

Self-tempering: After leaving the quenching box, the core continues to supply heat to the surface since it is relatively at a higher temperature. This causes the tempering of the outer martensitic layer into a structure called Tampered Martensite. The core stays austenitic at this stage also.

Atmospheric cooling: There are special cooling beds where the austenitic core gets transformed into a ductile ferrite-pearlite structure. The final structure, thus is a perfect combination of a strong outside layer (tempered martensite) with a ductile core (ferrite and pearlite).

PROCESS OF MANUFACTURING ERW WELDED STEEL TUBESre

The M.S. Steel Tubes & Pipes are made of from H.R Coils (Hot Rolled Strips) as per I.S. specification IS:1239 etc. in different sizes. The H.R Coils are slitted on slitting machine as per required thickness & width for different pipe sizes.

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After slitting the small slits/coil are transferred to Steel Tubes Manufacturing Mills. Coils are loaded on Pay off Reel and passed through looping cage then to the forming Mill which takes shape of open seam pipe through contact welding (H.F Welder). The top welded Flash removed with the help of Scarfing Tools, welded pipe passes through water cooling zone and cooled.

After that the pipe passes through sizing section where the outer dia is maintained & pipe straightened with the help of Turk Head.The required trimmed pipe is rolled out on conveyer & stopped by stopper at end of conveyer and ejected to the pipe collecting pockets. This is a continuous process.

After Rolling process over, the pipes are transferred to end facing machines where end Burr is removed. Each pipes is tested on Hydro Pipe Testing machine to check the leakage on welding seam. This pipe is called E.R.W. pipe.

GALVANIZING PROCESS

For the manufacturing of Galvanizing Pipes all end faced and Hydro tested pipes/tubes Galvanizing Plant.

There are five tanks filled with hydrochloric acid, running water and flux. First of all, ferrous oxide/rust of the pipes is cleaned by HCL Acid, when the rust is cleaned then the cleaned pipes are dipped in the running water tank for cleaning HCL Acid.

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After cleaning the pipes by running water, the pipes are dipped in flux tank. After this process the pipes are shifted to the bed of heating oven (for drying the wet pipes). The temperature of heating oven is 80’C to 100’C.

After dried pipes are dipped in Zinc bath (Molten Zinc Tank) by conveyor. The temperature of  Zinc tank is 440*C to 460*C, each galvanized pipes are lifted from Zinc tank by the help of tang to the extraction unit (conveyor) through an outer & inner air die for releasing the extra Zinc on/in the surface of pipes.

After this process each pipes are dipped in dichromate solution for cooling. When the pipes are dry then they shifted to the threading bed for threading (as per IS: 554-1999) & measurement. After the threading both the threaded ends are varnished & one end is assembled with PVC cap for protection of the thread and other end with sockets & then the pipes are measured, bundled and stocked.

PROCESS OF MANUFACTURING PVC PIPES

PVC uncompounded resin, unlike some other thermoplastics, is not suitable for direct processing. To confer the required processing and end instability, it is necessary to mix additives with the PVC resin. Following are some of the additives which are generally used for the manufacture of rigid PVC pipes.Plasticizers: The common plasticizer in use is DOP, DIOP, DBP, DOA, DEP,

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#Extrusion

Plasticizers: The common plasticizer in use are DOP, DIOP, DBP, DOA, DEP, Reoplast, Paraplex etc.Stabilizers: The common stabilizers are lead, barium, cadmium,

Stabilizers: The common stabilizers are lead, barium, cadmium, tin, stearate etc. Lubricants: Widely used lubricants are Buty-Stearate, Glycerol Moni-Stearate, Epoxidised Monoester of oleic acid, stearic acid etc. Fillers: Fillers are also used for producing

Fillers: Fillers are also used for producing the special quality product (e.g. calcined clay is used to improve the electrical properties of cable compounds).

# Sizing

The pipes coming out from the extruder is cooled in the sizing operation. There are basically two types of sizing used for manufacturing of pipes. They are (i) Pressure sizing & (ii) Vacuum sizing.

# Traction

The next operation needed after sizing is traction. The tube traction unit is required for continuous haulage of the pipes being extruded by the extruder. Cutting: The last operation needed is cutting. There are basically two cutting techniques for rigid PVC pipes viz. manual and automatic. The pipes are then tested for ISI marks and are ready for dispatching.

# Cutting

The last operation needed is cutting. There are basically two cutting techniques for rigid PVC pipes viz. manual and automatic. The pipes are then tested for ISI marks.

PAVCON

Mixing
  • The sand and gravel are stored outside in piles and are transferred into storage bins in the plant by a conveyor belt as they are needed. As a production run starts, the required amounts of sand, gravel, and cement are transferred by gravity or by mechanical means to a weigh batcher which measures the proper amounts of each material.

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  • 2The dry materials then flow into a stationary mixer where they are blended together for several minutes. After the dry materials are blended, a small amount of water is added to the mixer. If the plant is located in a climate subject to temperature extremes, the water may first pass through a heater or chiller to regulate its temperature. Admixture chemicals and coloring pigments may also be added at this time. The concrete is then mixed for six to eight minutes.
Molding
  • Once the load of concrete is thoroughly mixed, it is dumped into an inclined bucket conveyor and transported to an elevated hopper. The mixing cycle begins again for the next load.
  • The molds consist of an outer mold box containing several mold liners. The liners determine the outer shape of the block and the inner shape of the block cavities. As many as 15 blocks may be molded at one time.
  • When the molds are full, the concrete is compacted by the weight of the upper mold head coming down on the mold cavities. 8 The compacted blocks are pushed down and out of the molds onto a flat steel pallet. The pallet and blocks are pushed out of the machine and onto a chain conveyor. In some operations the blocks then pass under a rotating brush which removes loose material from the top of the blocks.
Curing

The pallets of blocks are conveyed to an automated stacker or loader which places them in a curing rack. Each rack holds several hundred blocks. When a rack is full, it is rolled onto a set of rails and moved into a curing kiln.

Standard weight blocks are usually cured at a temperature of 150-165°F (66-74°C), while lightweight blocks are cured at 170-185°F (77-85°C). When the curing temperature has been reached, the steam is shut off, and the blocks are allowed to soak in the hot, moist air for 12-18 hours.

Another type of kiln is the high-pressure steam kiln, sometimes called an autoclave. In this type, the temperature is raised to 300-375°F (149-191°C), and the pressure is raised to 80-185 psi (5.5-12.8 bar)

Cubing

The racks of cured blocks are rolled out of the kiln, and the pallets of blocks are unstacked and placed on a chain conveyor. The blocks are pushed off the steel pallets, and the empty pallets are fed back into the block machine to receive a new set of molded blocks.

The blocks pass through a cuber which aligns each block and then stacks them into a cube three blocks across by six blocks deep by three or four blocks high. These cubes are carried outside with a forklift and placed in storage.