MechChem Africa September-October 2023

Filter monitoring: a crucial component for energy-efficient operation This article by Jürgen Arndt of WIKA outlines how continuous filter monitoring crucially influences the energy efficiency of a system and supports operators in complying with legal requirements.

must be introduced to compensate for the restriction in the filter.

Energy-related vs cost-based considerations

From an energy perspective, a lightly soiled filter should be replaced straight away. This conflicts with the fact that the exchange itself generates material and labour costs. In addition, the exchange can only take place in the absence of both pressure and flow, and thus the machine or the process must be stopped. Based on these considerations, it is also clear that an exchange after a fixed period of use, as we are familiar with during annual services on cars, for example, is not an optimal solution. Cost elements for filter changes • New filter element costs. • Seals and sealing. • Disposal of the old filter element. • Maintenance hours. • Production shutdown costs. The compromise is to identify an accept able level of contamination specified via a maximum allowable differential pressure across the filter. Normal limit values for the differential pressure (ΔP) of hydraulic filters are between 1.0 and 5.0 bar. In ventilation systems, the limit values are between 50 and 5 000 Pa (0.5 to 50 mbar). Regular monitoring of the pressure drop saves on operating costs, since changing

In hydraulic circuits, increasing contamination of the filter element causes an increasing pressure drop.

I f the careful use of energy resources used to be for cost reasons, today, increased environmental awareness plays a role, and is becoming mandatory thanks to legal requirements and the quality of the technology. Whether with air filters in ventilation and air-conditioning systems or oil filters in hydraulic circuits, increasing contamination of the filter element causes an increasing pressure drop. To keep the flow of the medium (air or oil) constant, the fan or the pump must apply more power, so the energy consumption increases. Filter monitoring signals the increasing pressure drop across a contaminated filter element. Replacing a fouled filter ensures the flow of the medium and thus prevents the energy consumption of the fan or the pump from increasing. Legal bases With the adoption of the Kyoto Protocol in 1997, the European Union committed to reducing CO 2 emissions. To reach this climate goal, in 2005 it adopted the EuP (Energy using Products) Directive. This was renamed the ErP Directive (Energy-related Products directive) – also known as the Eco design directive, in 2009. The directive aims to reduce energy use and other negative environmental impacts throughout the life cycle of products pow ered by electricity fossil or renewable fuels.

The Directive means manufacturers must consider energy use and other environ mental factors in product design and both manufacturers and importers are directly affected.

High resistance – high energy consumption

It is easy to understand that a contaminated filter element is more resistant to the flow of a medium than a new, clean element. Physically, the pressure in the filter inlet increases – which can be monitored very easily using a pressure measuring instru ment – and this reduces the flow rate. Since the required flow is specified, more energy

A contaminated filter element is more resistant to flow than a new, clean element, so more energy must be introduced to compensate for the restriction in the filter.

34 ¦ MechChem Africa • September-October 2023