In large cities, the building site area is heavily congested. The plot of land may be surrounded by other structures, roads and heavy movement of people. Entry of heavy vehicles is often restricted in peak hours in some areas.
Almost the entire plot of land is excavated and very little working area is available. In this situation, the re-bar processing operation at sites creates major hurdles. The re-bars are supplied in 12 mts. long length or in U-shape and then straightened at site.
If one lorry load of 10 tons is kept in stock always, it will be in different diameter sizes, so the bars are spread out over a large area. Then, the site requires about 15 to 20 workers for this job. These people, along with the other workers have to be provided facilities on site for housing, water supply, electricity, canteen, security, sanitation, etc.
Then space is required for the cut and bent bars to be stocked, before they are lifted to the slab. The production and fitment never matches, and there is delay in the progress. The bars are kept anywhere and everywhere, people are walking over them, sometimes injuring somebody. Vehicles are passing over the bars, damaging them. Water, slush, debris, aggregates,etc. damages the bars, corrosion starts before the bars are placed in situ.
The accepted wastage of rebars on site is about 5% due to various reasons. Some bars are pilfered, some are used for other purposes. An Engineer is required permanently to supervise the re-bar work, account for the issue and use of the bars, make statements and reconcile the quantities.
A team of about 15 to 20 re-bar workers will produce about 2 to 3 tons per day. This team is also used to unload the lorry when the bars arrive at the site. This is a slow and painful task at site, if there is no crane available.
The SolutionIn the other option of a Centralized Re-bar plant, all the work is done under one shed, about 60 mts. x 20 mts. and with only about 10 skilled and 10 unskilled workers.
The output can be upto 100 ton per day, depending on the machine models and capacity with investment in machines of about Rs. 4 to 5 crores. If you are using 1000 tons of rebars per month in all your sites, cost @ Rs. 30,000/- per ton is Rs.300,00,000/- On this 5% wastage amounts to Rs. 15,00,000/ - per month or Rs. 180,00,000/- per year.
So, the cost of the plant is recovered in 2 to 3 years, only on the basis of steel savings plus you have other advantages of saving on manpower and time.
If 20 workers process 3000 kg per day, output per person is 150 kg.
If 20 workers process 100,000 kg per day, output per person is 5000 kg.
There is a huge shortage of skilled manpower at present, so mechanization definitely helps.
The present projects are with fast deadlines for completion under heavy competition, so innovation elps.
The MachinesThe Stirrup making machines can use coiled steel, One 8 mm, one ton coil is about 2500 mts long, There will be ZERO wastage of steel, as the machine is pulling only the required length.
It can produce stirrups upto 1800 pieces, about 600 kg. per hour with one operator and one worker.
The Shear line, with special software will cut optimum lengths, to avoid wastage in bigger dia bars, saving upto 5% of steel. It can process upto 5 tons per hour with 2 workers.
Bending station, with simultaneous double bending of bar in one action, computerized, with only one operator, output is 5 tons per hour.
If you don’t use steel in coils for making stirrups, you can use straight bars, upto 14 mts long, and produce about 1800 stirrups per hour with 2 workers. The feeding side has a 14 mts. long tray to hold the straight bars, which are fed in the machine. The savings in time and labor is enormous, the savings in steel cost is substantial about 5% overall.
The site receives factory-fresh re-bars, just in time to be lifted direct to the slab for fixing. No extra bars, all accurate in dimensions, all bundled and labeled, delivery to site can be in smaller trucks, the site pays for the exact tonnage it uses, no reconciliation of receipt and issue at site. The manpower is required only for tying of bars.
This is the way all fast-track projects all over the world are completed.