Juan Carlos Ballesta from Krohne looks at how to choose the best Coriolis mass flowmeter according to the application
Coriolis meters come in different shapes and sizes. Selecting the best one for your application can be complex since each tube design has its strengths and weaknesses.
Coriolis meters seem ideal for a wide range of applications, but some models are suited to certain applications, while others excel with others. So how should an operator select the perfect meter for their requirements? They must consider the following factors: accuracy, flow rate, pressure drop, installation envelope, and, of course, price.
LOW MAINTENANCE
Compared with other technologies, the working principles of Coriolis meters offer several distinct advantages. With no moving parts that come in direct contact with the measured fluid, whether liquid or gas, they require little maintenance.
ACCURACY
Accuracy is often the main factor when selecting a Coriolis meter. They measure mass flow, density and temperature directly. The more basic meters typically offer an accuracy better than 0.2% when measuring liquids; the mid-range standard meters offer accuracies between 0.15% and 0.1%, while the premium ranges can offer 0.05%. Custody transfer options are typically offered in the premium accuracy ranges.
ASSESS THE PROCESS CONDITIONS BEFORE PURCHASING
Operators should size a Coriolis meter according to the process conditions. For example, just because a pipeline has a DN25 connection, doesn´t mean a DN25 meter is needed. It’s important to be smart regarding pressure drop too -. always ask your supplier what is included in the pressure drop calculation. The pressure drop in a straight tube will always be lower than in a bent tube if the internal diameters are equal. Make sure the sizing sheet accounts for the pressure drop across the entire meter, including the connections. This is the pressure drop measured at the entrance and at the end, near the meter, where there is pressure recovery. Don’t be fooled, some meters have a strangulation at the connection and open just before the flow splitter. The initial strangulation needs to be considered for the pressure drop, too. It is not realistic to consider only the pressure drop from the measuring tubes. It must also be recognised that connections are part of the meter. It is wise to question what is included in a pressure drop calculation.
APPLICATIONS FOR EVERY INDUSTRY
There are applications for Coriolis meters across every industry. It is possible to measure liquid, slurries or gases, but don’t forget that the concentration of two fluids with different densities – like Brix, Baume, NaOH, Plato, API oil standard, alcohol or general concentration – can also be calculated. This can be a suspension, an emulsion or a solution. Concentration measurement is the ‘hidden gem’ of a Coriolis meter, not everyone is aware that they can be used this way.
TUBE DESIGN
The tube design is of extreme importance. Straight tubes offer a more compact installation envelope and fit the pipeline perfectly. The pressure drop is that of a straight tube and won’t require elevating the entire pipeline or digging a hole in the ground. They are easy to clean and inspect. They can also handle abrasive fluids following the recommended guidelines. Single straight tube designs are available in many materials, such as Titanium, Hastelloy, Duplex, and Tantalum. The availability of these materials is especially important in the chemical industry, where various types of acids are handled. On the other hand, there are temperature limitations for straight tubes; typically, a customer will select a bent tube design above 130°C. The bent tube designs excel in applications up to 400°C or cryogenic down to -200°C.
Purchasing a Coriolis meter from a manufacturer that offers a wide range of designs will help customers find a suitable solution. This might be a single, double, four-tube, straight or bent design. Experience also matters. Krohne, for example, has 30 years experience in the field. The company also provides a free extended warranty to customers.
Juan Carlos Ballesta is International product manager mass flow at Krohne Limited
For more information visit: www.krohne.com
