Case Studies

Triplex pumps for misting duties

Odour control within the landfill and waste treatment industries is largely achieved by the installation of a misting system, whereby a very fine spray of water is released into the atmosphere either adjacent to or above the affected area. Fine water droplets prevent the release of obnoxious odours to the wider environment. It is a proven technology and there are very many types of systems available on the world market.

Where an application only requires a small misting system, typically between one and 100 misting nozzles, a relatively small water flow rate is needed. Technically, it is very difficult to produce a pump to deliver such low flows at the high pressures required to produce a sufficiently fine mist. However, it is a difficulty that is easily overcome by the Cat Pumps positive displacement principle. Because there is virtually no slippage in the pumphead, the pumps remain highly efficient even at very low flows.

Cat Pumps offer a range of purpose-designed pumps for smaller misting systems and models come in many sizes. Their very popular mist cooling and temperature control units use the 2DX pumps. These triplex pumps deliver from 0.5 -8.5 litres/minute and offer the compact profile needed for this installation. These direct drive positive displacement plunger pumps are capable of delivering pressures up to 140 bar (2000psi) and contain specially formulated hi-pressure seals together with concentrically ground ceramic plungers in order to ensure maximum seal life.

For larger, continuous-duty applications, the Company’s ‘traditional’ pumps are suitable for supplying water to several hundreds of misting nozzles for applications such as perimeter odour control at landfill and water treatment plants, evaporative cooling at large open spaces and re-humidification, as well as dust suppression.

Many methods are in use for controlling industrial waste odour, but none are as effective or easy to use as those which use a Cat Pump for the high pressure misting concept. The triplex pump employs three synchronised plungers, which give it the ability to deliver a predictable and constant flow. This flow is far smoother than that of simplex and duplex pumps. The benefit is that flow pulsations in the discharge line are reduced enormously and the much smoother flow greatly reduces the possibility of system failures caused by excessive pulsation.

As the majority of pumps in the marketplace use a roto-dynamic pumping principle, it is necessary for potential users to change their mindset when it considering reciprocating pumps. The advantages of Positive Displacement Plunger (PDP) pumps for misting applications lie in their high efficiency, their ability to generate high pressure and to produce constant volumetric flow irrespective of the back pressure. Because of that, where an application demands a controlled variable flow, they are eminently suited to using variable speed drives as the output is a linear function of the rpm, so removing the requirement for a complex algorithm to run the variable speed drive.

With greater emphasis now being placed on life-cycle costs, using a Cat Pumps triplex pump with a variable speed drive can provide very high efficiencies in a pumped system across a wide range of flow rates and pressures. When roto-dynamic pumps are operated away from their Best Efficiency Point (BEP), then there is a dramatic drop in efficiency. In variable flow installations a triplex pump should be high on your shortlist as it is safe to say that this pump type will always operate at greater than 85% energy efficiency and can be as high as 95%, depending on the pump selected and how it has been installed. Furthermore, using the latest designs and component materials, Cat Pumps products are built to last, with the target being to run a system total maintenance-free for more than one year.

To get the full benefits of a positive displacement pump for misting applications, it is not necessary for the user to understand the complexity of the system. Engineering personnel at Cat Pumps (UK) Limited are highly experienced in selecting the best pump for any application and are more than happy to provide full advice and consultancy in system design and installation.