Sagta Engineering, a Shanghai, China, based engineering consulting company, is trying to introduce air cushion technology in conveyor systems in India. Frank Wang, General Manager, and U.K. Mullick, Chief Consultant of Sagta, say it is a maintenance free and environment friendly technology.
Material transportation equipment plays an important role cement plants. What are the innovative products you have?
Frank Wang (FW): Roller and tubular conveyor systems are well known among user. But both of them require a lot of maintenance because of friction they generate. We are in the process of introducing air cushion conveyor in India. Air cushion lifts up the rubber belt, removing friction in air cushion conveyors (ACC). It brings in several advantages - energy saving, environment-friendly and requiring minimal maintenance. We have introduced air cushion technology to Tata Steel, NTPC and MECON, an engineering and consulting company, etc., in India.
What are the key differences between belt and air cushion conveyor systems?
UK Mullick (UKM): In a conventional belt conveyor, where belt is running on rollers, a number of rollers appear along it. Basically the concept of ACC is very much similar to that of conventional belt conveyor, but the difference is there are no rollers in the new technology. Instead of rollers there are certain modules and on the surface of the modules there are a number of small holes through which pressurised air comes and keeps the belt afloat, so that the material loaded onto the conveyor belt moves on the airfill. A very thin airfill is generated due to high pressure air jet that comes from the module.
What are the advantages an air cushion conveyor user can expect?
UKM: The majority of power consumption of a conveyor is for overcoming the frictional resistance of number of rollers present in the system. If there are no rollers, then there is no friction due to which the power consumption will come down drastically. And this reduction is seen to be in the range of 20-70 per cent, which is really a great phenomenon- we are not only saving money, but also saving costly energy. Secondly, this 20-70 per cent saving depends on the length of the conveyor, longer the more.
FW: The lifespan of rubber belt in a conveyor is very important. Generally, due to friction the rubber belt lasts about three or four years and needs replacement. Sometimes it gets broken. There is a lot of downtime that goes into repairing the belt. Due to friction-free air cushion the lifetime of the rubber tends to be much longer. To our surprise, the rubber belt of our first project is still there even after 15 years, and no replacement needed anytime soon.
Is there any advantage in installation cost?
UKM: Cost is generally based on length of the conveyor - if it is less than a kilometre, the cost of ACC is slightly more compared to the conventional one. In a long distance conveyor, say 10-20 km, the installation cost is more or less the same. Simple reason is, say for a 15-km conventional conveyor's power installation needed is 4,200 kW, while for ACC technology the installed capacity required is 2,500 kW. That is a drastic difference due to absence of rollers. So, this is definitely an innovation so far not tried out in India and they are the way to go.
Are there any disadvantages or limitations for ACC when compared conventional conveyor...
UKM: If you ask me, is it possible to convey big boulders? The answer is simply "no." The maximum weight that can be conveyed by ACC is approximately 50 milli meters (mm). As for angle of inclination, it can take a very good angle of inclination up to 35-40 degrees. But one should be conscious about a thing - it cannot take right or left turn, and it has to be straight. As such this is very good for long distance material handling. For that purpose we have already approached JSW and they are planning to implement long distance conveyor and this technology is under their active consideration, subject to their visiting China and seeing it physically.
So it cannot be implemented in all terrains...
UKM: If the conveyor route has to pass through hills and mountains and have to take several twists and turns, you may need to install different types of conveyors û conventional conveyor for a portion of it, pipe conveyors where twists and turns are there, and ACC where the route is straight. Since Sagta Engineering is capable of supplying any kind of conveyors or a combination of all the three, it can offer the best solution to any terrain.
In India, the government follows L1 (least capital cost) method for choosing suppliers, though the trend is changing of late. How do you propose to pitch your product to them?
UKM: If you want to adopt any innovative technology, at that point of time one cannot compare the initial investment cost. If it can pay back the additional cost incurred in about three years, that is great.
Any more innovative products in pipeline...
UKM: Another innovative technology is friction-free coupling. Generally we have fixed coupling that is rigid coupling where bolts and nuts are used. Suppose if there is a little misalignment in drive and driven end, and if it is allowed to run at a very high speed, in no time the bolt or nut will shear and break, bringing the whole process/system to a standstill. Now for power transmission or stop transfers for motors of more than 30 kV we are using fluid coupling for different applications in power, mining, or cement sectors.
FW: But Sagta has come out with a new magnetic coupling which uses permanent magnet on either side - driver shaft side and driven shaft side. Suppose if the blower is installed, and between motor and blower if you put a magnetic coupling, and due to installation problem if there is some small misalignment, since these two items are not touching each other, (as they are held only by magnetic force), this is not going to hamper the driven or driven side operations. These particular couplings are available from 30 kW to 4500 kW. Friction-free coupling is also maintenance free and has a lifetime of 30 years, we can say. This product has been welcomed by the Chinese heavy industry, including steel plants.
Another product that is in the final stages of development is magnetic speed adjusting device used in motors and blowers. These can be used in the cement industry as well. It is also long lasting and maintenance-free.
- BS SRINIVASALU REDDY