Rema Tip Top, established in 1923, is a global entity operating in over 150 countries. The company manufactures high quality conveyor products and delivers sustainable solutions in the industrial sector.
Clean conveyors will increase profits
As has been the case for decades, safety around conveyors, operational continuity and production remains in conflict. It has often been said that safety is non-negotiable and is, in fact, the one factor more important than production. In the same breath one needs to ask why safety is still suffering due to a lack of maintenance at materials handling facilities?
This article will not focus on maintenance as such but rather serves to highlight the risk of operating a non-maintained, dirty facility, where there are heaps of spillage, where there are high levels of air-borne dust particles, and where belt cleaning is not receiving the attention it deserves.
Why is spillage a potential risk to operations? There are many reasons. Firstly referring to a paper written by Shortt / Nel at Beltcon 8 in the 90’s, it can be seen that cleaning belts has economic and practical considerations.
Spillage costs money to clean, and even more so if not cleared. Piles of material may for instance restrict access for maintenance work. As spillage will likely create a hazardous environment, unless cleaned, maintenance personnel will not get to the conveyors, which in turn leads to a lack of maintenance, and subsequent equipment failure. Not only is the operation of the machine then compromised, but within the spillage itself lurks more risk.
Consider a simple heap of material underneath a conveyor carrying Platinum ore, say 600mm high, then one will find that the mass of such material could be as much as half a ton. Should there be several of these heaps of material, the integrity of the structure of the conveyor may be compromised, as the structure is simply not designed for the loads imposed on it.
Structural collapse due to material overload is not a new phenomenon and has occurred in the recent past. This begs the question, how serious are we really about safety?
Loss of product
Dirty conveyors will result in a direct loss of product. The same heap of material referred to earlier, with a volume of say 0.4 m3, and considering that to obtain one ounce of Platinum, one has to mine 10 tons (6.25 m3) of ore, could contain 1.8 g of Platinum at a value of around R810.00. It stands to reason that several of these heaps could amount to a very large amount of money, which effectively detracts from the profitability of the facility.
Damage to the conveyor equipment
Considering the conveyor itself, it has to be recognised that carry-back material not cleaned has the ability to damage the conveyor equipment. Idlers are normally the first to suffer, as ingress into the bearing will cause failure. Belt wear may increase and, given the cost of a decent belt in this day and age, this should be avoided at all costs. Spillage affects insulating drives or bearings which are likely to suffer an increased risk of failure due to not being cooled adequately. A common problem is spillage underneath take-up counterweight mass structures, which then does not allow the counterweight to travel to its intended destination.
Not only does this lead to belt slippage at the drive, as T2 tension cannot be properly applied, it could have disastrous consequences if the belt slips back over a pulley equipped with an anti-runback device. Incidents have been reported where the belt, while running back, attempts to drive the motor in reverse, this while the motor is winding down.
The coupling being driven from one side by the motor and from the other through the reducer, taking the reduction ratio into account, amounts to the coupling over-speeding, and the tender aluminium housing exploding. How safe is that?
Typical areas of spillage
There are two high risk areas for spillage. Firstly at the loading points, where due to poor chute design or poor maintenance, the material lands on the ground or somewhere other than the receiving conveyor. Uncontrolled loading, flood loading, or leakage of material underneath skirts may also be a contributing factor.
The second high risk area is at the discharge where due to poor design there could be material splashing. The biggest risk at the discharge is not cleaning the carry side of the belt, removing carry-back adhering to the belt. This is normally a result of no belt cleaning equipment or poorly adjusted equipment.
In many facilities, operators do not pay enough attention to the transfer techniques, and solutions are implemented that are not ideal for the material or the equipment in question. The value of correct transfer design, chute design and using the correct products for particular applications cannot be over-emphasised as this will contribute significantly to the wellbeing of the facility, reducing operating cost and increasing reliability of production and safety.
Types of belt scrapers
When transporting material, conveyor belts are likely to have a thin layer of material remaining on the carrier-side after the material discharge. If not cleaned there and then, the material remaining on the belt would dry and be loosened by the motion over the idlers and distributed along the course of the conveyor belt structure. Through the use of scraper systems at the discharge, the residual layer can be cleaned off to a large extent. For this, the choice of the correct type, the correct scraper material and the appropriate preload on the scraper tensioning unit is important.
The question has often been asked ‘Whose scrapers are the best?’ In reality, this question only has one answer. Graham Shortt used to refer to it as ‘Frikkie se Scraper’. That is, the unit could in reality be manufactured by anybody but is maintained by the mine and is continuously adjusted to the correct pressure and position. However, industry requires a range of belt cleaners to work with in order to select a suitable unit, to feel comfortable to install, operate and maintain, or even have a third party, such as the supplier of the belt cleaner, install and maintain the units.
Rema Tip Top offers a wide range of scraper systems, primary and secondary, for cleaning of the conveyor belt. The Rema scraper systems are available in rubber, polyurethane; rubber-ceramic, rubber-metal and hard metal versions.
The most important consideration with any scraper is the specific contact pressure. If it is too low, the scraper bar will not function correctly and an aquaplaning effect occurs rendering the scraper ineffective. If, on the other hand, the contact pressure is too high, the scraper system may damage the conveyor belt cover. All RemaClean scraper systems are modular and system carriers are the same for all belt widths. A change from one type of scraper to another is possible without having to modify structure.
The hardness of the scraper blade is equally important. If the blades are too soft, they are unable to scrape off fine or sticky material. In this case harder blades would be required. However, the harder the blade, the sharper the edge of the scraper blade will be, increasing the risk of cover damage.
For effective use, it is important to set the contact pressure in accordance with the manufacturer’s specifications for various types of scraper material. Apart from this, the condition of the conveyor belt and the type of joints also play a role in the selection of scraper bars or segments to be used.
Dr Paul Nel, www.rema-tiptop.co.za