Go with the flow

Electromagnetic flowmeters are one of the most popular methods of flow measurement. Khrone’s Peter West offers a guide to the latest systems.

Most electromagnetic flowmeters (EMFs) available today boast an accuracy of greater than 0.2% of the actual flow rate with a repeatability of + 0.1%. Their unobstructed design, with an unimpeded tube cross-section, means there is no pressure drop to affect flow rates, while their lack of moving parts minimises maintenance requirements.

EMFs are also extremely versatile and can be installed in any position to measure the volumetric flow rate of liquids (with and without solids content), pulps, pastes and slurries (including highly abrasive slurries) in practically all industry sectors.

EMFs can be supplied as compact systems (primary head and signal converter supplied as a complete integrated unit) or as separate systems where the primary head is installed in the pipeline and the signal converter for signal processing is accommodated in a field housing or a 19′ rack plug-in unit. This is particularly useful in those instances where the EMF is to be installed in a remote or inaccessible location.

Today, EMF manufacturers produce a range of models to suit specific industry and environmental engineering duties. From low cost, simple, economic and flangeless models available with basic signal converters (with or without local indication), through to specific industry designed units. There are, for example, units available for the water & wastewater treatment sector incorporating industry approved liners. There are also special units designed to cater for the stringent demands of the food, beverage and pharmaceutical industry with industry approved linings, stainless steel housings, hygienic connectors and the ability to be integrated into CIP/SIP cleaning systems.

For the general processing industry, customers can choose from an array of models, some of which can be used in hazardous installations, with a choice of flange connections and a range of linings and electrode materials.

Where applications require extremely high measurement stability even under arduous operating conditions, these models can be supplied with smooth ceramic liners which offer a high resistance to acidic or alkali chemicals at high temperatures.

In addition to standard flow measurement applications, there are special designs of EMFs available, which cater for particular flow measurement duties, for example, measurement in partially filled pipes, batching/dosing and non-contact measurement. Manufacturers are also now taking EMF systems one step further with the introduction of two-wire versions for ease of integration into industries’ sophisticated process control systems with the promise of reductions in the cost of cabling, installation, engineering, and maintenance.

Apart from design considerations, it is also important for customers to develop partnerships with established manufacturers who have proven success in their particular field of industry. The chosen manufacturer should have acquired sufficient experience and expertise to be able to advise and assist in the correct selection of liner and electrode materials.

Krohne Tel: + 44 01933 408500