In the second part of this post, Brigitte Pennington, Product Leader at Parker Conflow looks at methods of reducing the effects of Respirable Crystalline Silica (RCS) and how to implement a successful dust reduction programme.
One of the methods of reducing the effects of RCS is through wet dust suppression, which prevents fine dust particles becoming airborne by trapping it in water. Water sprays as part of dust suppression systems are one of the most effective ways of controlling RCS.
With dust suppression, the aim is to prevent dust escaping from its source, collect it and contain it - this is usually done through spraying mechanisms. Parker Conflow's dust suppression systems use water which is sprayed onto the source of the dust escaping and is usually done at the point of extraction or crushing. This ensures that the respirable sized particles are wetted and entrapped by the water droplets.
Alternatives to water are chemical suppression and solenoid valve dust suppression. Chemical dust suppression can be expensive and the dosage of chemical must be accurate at all times to be effective. This can add significantly to the overall overhead of a quarry.
A solenoid valve dust suppression system requires a power source and regular maintenance.
The Parker Conflow water dust suppression system is mechanical and requires no use of power and is therefore inexpensive to run.
The principle behind our dust suppression range is that the dust agglomerates with the water, causing it to fall under gravity. However, it is not just a question of providing a water spray. If the water droplets are too large then the airborne dust particles are just moved around in the resulting air currents and very little dust is removed from the air. Too much water also means a very soggy working environment. For the dust to be removed from the air, the water particles need to be of a similar size which means a collision between dust particle and water droplet is more likely.
Image 1. Spray control valve, code 100
The design of spray head is therefore of paramount importance in ensuring the right volume and size of water droplets is delivered. With dust suppression droplet size is less important.
Our engineers are continually working with quarries and equipment manufacturers to improve and develop new products to protect equipment and personnel from the harmful effects of airborne dust. Parker Conflow is in the process of working together with OEMs to provide a value added system to prevent and control dust. Environmental and Health and Safety legislation is becoming tighter and therefore these solutions are becoming more important. Not only does it make sense from an employee health point of view, but also commercially too – it means less equipment downtime, lower employee healthcare costs and better community relations. Dust suppression systems can be retrofitted to any existing installation and assuming there is an adequate supply of water, the system can be operational in a matter of a couple of hours.
The Parker Conflow Dust Suppression System can be installed where the primary and secondary crushers are located as well as alongside the conveyors. Rain systems can be placed around the stock piles and stackers for dust prevention.
Water suppression is often used to control dust from compressive crushers, which produce dust, providing that the moisture content of the product does not cause an issue at a later stage in the process.
Another area where dust issues can arise is on roadways within quarries, particularly during dry weather. Again this is an area where mechanical dust suppression can be used to reduce the issue of RCS.
For any dust reduction programme to be successful it requires:
Innovation in dust suppression systems means that quarry owners can reduce risks to workers and to a business and ensure they are fully compliant with Health and Safety regulations.
The first step is to evaluate and fully understand the requirements of what the dust suppression system needs to achieve, then we provide customers with a full site audit evaluation.
The evaluation means that our engineering team can determine the design of the system with the optimum number of spray bars and appropriate size of nozzles, which determines the size of the droplets that we need to disperse into the dust. It can also be designed into the system if a pump and a tank is required due to insufficient water pressure, as well as being low maintenance and very efficient.
Effective dust suppression makes sense both from a production and a health and safety point of view. It is an issue that no quarry can afford to ignore and is essential to being a responsible operator, reducing risks and remaining compliant.
Brigitte Pennington is Product Leader at Parker Conflow, Instrumentation Products Division Europe.