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5 Things to Remember While Choosing An Electromagnetic Flowmeter

Aug. 01, 2022

There are a variety of Flowmeters available to measure different types of fluids like liquid, gas, slurry, vapour, etc. The vital criterion for the selection of the right Flowmeter is to know its intended use - which application it is required for or what it is going to measure. An Electromagnetic Flowmeter is a volumetric Flowmeter that measures the flow velocity of a liquid through a pipe. The flow rate of this liquid is then calculated using the formula,

 

Q = V x A, where V is velocity of the liquid and A is the cross sectional area of the pipe.

 

1. Electromagnetic Flowmeters are widely used to measure liquids that are conductive in nature. Conductivity simply refers to the ability of a liquid to conduct electricity. Liquids with a minimum conductivity of 10 μS/cm are easily measured using an Electromagnetic Flowmeter. Typically, an Electromagnetic Flowmeter can measure water, wastewater, slurries, acids, alkalis, juices, fruit pulp, etc. which are electrically conductive. The pH also plays an important role here. If the pH is less than seven, it means the application is acidic. Chemical compatibility of a liquid becomes the basis for selection of the appropriate Electrode and Liner material for a Flowmeter that is suitable to a particular application. So, if the application is a conductive liquid, one can assuredly go in for an Electromagnetic Flowmeter. They are best suited for applications in slurries, which cannot be measured by many other types of Flowmeters. Additionally, the Electromagnetic Flowmeter can't be used to measure hydrocarbons and gases.

 

Electromagnetic flowmeter

 

2. The next important thing to know is the process parameters, which include working temperature, pressure and velocity. Temperature is an important parameter that one must know, as liner selection is based on this information. Liners in Electromagnetic Flowmeters provide insulation and resistance to corrosion and abrasion. Based on the temperature ratings, a suitable liner is selected. For example, for a working temperature up to 50 degree celsius, a Hard Rubber liner can be used, whereas for high temperature ratings up to 120 degree celsius, PTFE (Poly Tetra Fluoroethylene) is recommended by engineering professionals. Hard Rubber, PTFE, Neoprene, Polyurethane, PFA etc. are the types of liners that are available. Pressure ratings are necessary for selecting the flange standard. For the accurate sizing of the Flowmeter, velocity of the liquid, along with the minimum and maximum flow rate, should also be mentioned. Such an accurately sized Flowmeter will give the desired accuracy and better results.

 

3. The next question that one should ask is, what output one requires from the Flowmeter. The most widely used industrial output is 4 - 20 mA analogue current output. A 4 - 20 mA output is directly proportional to the flow rate of the liquid, which can be further communicated to the PLC for the purpose of control. To know the volume of liquid, there is an option of digital output i.e. pulse output. Say, for example, a Flowmeter generates one pulse for every 5 litres of liquid that flows through the pipe. If the total number of pulses recorded in a second are 10, then we can easily calculate the flow rate as (10 pulses x 5 litres) = 50 litres/sec. This can be easily converted into standard engineering units like m3/hr and gallons/min. Batching and dosing applications generally require a pulse output from the Flowmeter. Other commonly used outputs include RS-485 and RS-232, which are for serial communication.

Of both, RS-485 has a longer communication distance and the ability to connect to multiple nodes (or simply called devices) as compared to RS-232 and hence, it is more popular and most preferred nowadays. In general, applications that require billing of liquids go for RS-232 and RS-485 communications. Apart from these, GSM and GPRS communications are also popular for SCADA and Automation purposes. If one requires precise measurements and real-time data for one's specific application but the site is remotely located, then one can make use of the GSM or GPRS technologies. These technologies allow Flowmeter data to be sent to the user on his mobile via SMS or email, using a 2G, 3G or 4G network. However, these are application-based and totally depend on user requirements.

 

4. Another major factor for selecting the right Electromagnetic Flowmeter is power supply requirements. To power the Flowmeter on the field, one must check whether electric power is available or not. If the application requires a Flowmeter to be installed at a remote location where there is lack of electricity, then one can always choose the option of a battery. Battery-powered Electromagnetic Flowmeters easily solve power supply requirements and come with a typical battery life of 5-10 years, as per the manufacturer's specifications. If electric power is available, one can go in for a 24 V DC or 230 V AC power supply, depending on the specific application.

 

5. For some users, cost is the biggest criteria for Flowmeter selection, whereas for many, performance is important. One must know that one pays for the Flowmeter in order to get the exact measurements for flow of the liquid. For this, the selected Flowmeter should have good accuracy and reliability, so that one gets what one has paid for. Also, nobody likes a Flowmeter that requires frequent maintenance. An Electromagnetic Flowmeter does not contain any moving parts and requires very less maintenance. It can generally be used for any line size, with good accuracy and no pressure loss. Remember, for applications where accuracy is of utmost importance, in the range of 0.2% - 0.5%, one can surely go in for an Electromagnetic Flowmeter instead of other Flowmeter types.

As you must have noticed, there are loads of variables for selecting a suitable Electromagnetic Flowmeter. The simplest way to identify the proper meter is to start searching and involve an expert. Let Dongjin's expert team help you select an efficient Electromagnetic Flowmeter.

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