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Mechanised sweepers

It is no longer uncommon to see a massive road sweeping machine rumble down the arterial road of a city, or down a highway in the middle of the night. While India has begun to slowly awaken to the merits of mechanised sweepers, the uptake has been slow, despite no lack of machines designed to suit specific needs.

M Krishna, MD – Kam Avida Enviro Engineers Pvt Ltd and Ruediger Schroeder, CEO – Challenger Sweepers Ltd tell us about the critical difference between indoor and outdoor sweepers, why one cannot be used in place of other, why imported machines may not be suited for Indian conditions and why the procurement process derails the mission of mechanised road sweeping:

Indoor sweeping

When one needs to sweep a covered area – say, a factory shop floor – one has to sweep the aisles and gangways. Usually, one doesn’t sweep around the machines. Walk-behind, push-behind, and rideon sweepers have been designed to perform just this function. However, these are not all-weather machines, and cannot be used to sweep city streets, since they cannot deal with the sun and the rain.

Since indoor sweeping is done for a definite area, the performance of the machines is typically measured in square feet or square metres swept per hour or shift. Hence, while estimating requirements, breadth as well as length need to be known. Coal and cement processing plants – which generate a tremendous amount of dust – may require a particular configuration of machine, while automobile plants have entirely different requirements.

“Very often, people believe that the same sweepers used to sweep indoor areas can also be deployed outdoors”, said Krishna. “This is a misconception, which will almost inevitably lead to failure. Buying the same machine for indoor and outdoor sweeping just does not work.”

Outdoor sweeping

While any large industrial area will definitely bank on sweeping machines for its outdoor areas, let us focus on road sweepers for now. By definition, they need to be all-weather machines; if it suddenly starts raining, they still need to be able to work. In major cities, since road sweeping is done typically at night, the machines may need to be mounted with lights.

Krishna explained the mechanics of road sweeping: “Roads are convex by design, which is why rainwater flows to the curbs. When a vehicle passes, its air draft pushes dust and debris to the side of the road, where there may be a road shoulder/ footpath, or to the median in the middle of the road. Hence, when sweeping a road, one typically focuses only on the side of the road, and the area near the median, where there may be accumulation of litter.”

Hence, machine requirements and performance are measured in kilometres, and not in terms of area. For example, a 10 km stretch of highway may require a machine to pass up one side of the road, down the median, up the median and then up the other side of the road; the total distance it will cover is 40 km. Hence, a machine’s performance depends upon the number of passes it has to make.

Cities have both narrow and main roads. Bigger, truck-mounted machines with larger capacities are used on main roads. Why? Once capacity is reached, the truck needs to be sent to the landfill to empty the debris, which wastes both time and money. By deploying a bigger machine, one saves on cost.

However, these gigantic machines won’t even be able to enter smaller lanes, leave alone negotiate them. While 6-8 ton machines are needed for main roads, smaller-width 2-3 ton machines may be needed here.

Why imported machines don’t work in India

In Europe, rain ensures an almost constant covering of grass on fallow land, which binds the topsoil layer to the layers beneath and prevents soil particles from flying around. Prolonged periods of no rain in India have deprived it of green cover and topsoil in many parts, because of which dust is free to fly into the air. European machines are designed to pick up only litter and horticulture waste. “As an importer of foreign machines, it took me 10 years to realise that machines used in India need to collect fine dust, which foreign machines are not designed to do”, said Krishna.

When picked up, this fine dust enters the machine but also tends to exit through the blower at the back, covering the people walking behind with dust. Some machines have sprayers at the front to make dust heavier and settle on the ground, but in India, there is so much dust that spraying water on it just ends up making it into a paste.

“Very often, people believe that the same sweepers used to sweep indoor areas can also be deployed outdoors. This is a misconception, which will almost inevitably lead to failure”.
-M Krishna

A homegrown machine for Indian needs
Kam Avida has developed a PM 2.5 compliant machine whose spray also has a mist creator, which pushes airborne particles onto the ground, without making a paste out of them with just a spray. More importantly, a polyethylene filter placed before the blower prevents collected dust from being blown back into the atmosphere. Hence, it can work in both wet and dry environments.

These filters tend to get choked over time, which will prevent air from passing through them and out of the blower. This is averted by an inbuilt pulse jet cleaning system, in which reverse air is blown into the filter to clear it of dust, so that required porosity is maintained. This jet blown dust is collected in filter bags, which are cleaned by jetting 5% air from the inside.

Mechanical vs manual sweeping

According to government rules, three people are needed to clean every 1 km of a main road. Krishna laid out an example: “For a 40 km stretch, 120 people will be required. However, a machine can sweep the same 40 km in a single shift with just two people operating the machine”. The savings on paying for manual labour are incalculable. According to Krishna, a machine can recover its CAPEX cost in just one year.

When a human being is asked to perform a mundane task like sweeping day after day, he cannot perform it with the same consistency daily. While a sweeping machine can remove as much as six tons of debris in six hours (or one shift), a whole team of sweepers may struggle to collect even one ton in a shift. The debris that they sweep tend to be collected in heaps on the side of the road, from which it is transferred to a wheelbarrow; the slightest gust of wind can blow it all back onto the road again.

“Mechanical sweepers are more suitable for Indian roads as they are different from those in Europe and America. Also, the dust and dirt on the roads are different”.
-Ruediger Schroeder

Purchasing process

Large industries are likely to buy their own outdoor sweeping machines based on past experience or references. However, the story is very different for urban local bodies. Here, even though the actual sweeping process is outsourced to a contractor, the latter has no influence over which machine is procured.

Since it is public money being spent by government officials, civic bodies tend to opt for the cheapest machine, regardless of technical specifications and reliability. These break down easily and often, after which they are abandoned for days at a stretch, which convinces decision-makers that they are just white elephants which drain money. Budgeting for and awarding the O&M contract to the manufacturer is critical to protect the longevity of the machine.

For Schroeder, large cleaning contractors are the target market. “While some FM companies will buy their own machines, most will outsource road sweeping to another vendor.” Government tenders for road sweeping machines often end up being worded in such a way that only some companies of a certain size qualify, while the smaller ones – which may just be as reliable – are left out in the cold.

At present, only a miniscule fraction of India’s roads is cleaned by road sweeping machines. Their benefits are proven and their costeffectiveness is undeniable; all we need is officials and decision-makers who will take the time to understand the technology in front of their eyes, realise that a one-time investment will save them much more money, and opt for mechanised road sweeping over inefficient, age-old manual sweeping.

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