Selection of vortex flowmeters
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Is there a DN50 vortex flow meter on site with a measurement range of 0–30 m3? It stops showing readings when the volume is below 2 m3! May I ask what model of Yokogawa vortex flow meter should be selected to ensure that the flow rate can be displayed when it is below 2 m3?
It is best to contact Yokogawa’s manufacturer or distributor to obtain a selection manual, or consult their technical staff.
1. A small-volume resection may have been performed, which is why the value is below 2 and not displayed. 2, 2:30 m3 – the range ratio is now 1:15. The measurement accuracy cannot be guaranteed. Either there is a problem with the design selection. Either the product selection is fine, but it’s due to adjustments you made to the operating conditions on site
1. Please indicate whether it is the DCS/PLC that does not display anything or the gauge heads that do not show any information. If the header information is not displayed on-site: check whether your vortex flow meter supports the HART protocol; if it does, use the handheld communicator to select it and see if the LOW CUT function is filtering out flow rates below 2 cubic units. If it is not displayed on the DCS/PLC, then you need to go to the configuration interface to check whether small-flow cutoff has been set up in the DCS system. Typically, the system and the header have low-flow cutoffs only at one end.
Even if it is displayed, the readings are inaccurate – they’re meaningless numbers. Either use two gauges, one large and one small, and switch between them depending on the operating conditions, or use a gauge with a larger range; vortex flow meters generally won’t work for this purpose.
Vortex flow meters require a certain flow velocity to generate vortices; when the flow rate drops to a certain level, no vortices are formed, and consequently no signal is produced.
No vortex flow meter is capable of measuring 0; all of them have a minimum measurement range. You can refer to this Siemens model for details. In the case of gases, the measurement depends on the flow velocity, as different media present different characteristics
It cannot be measured, unless a small-diameter vortex flow meter is used for the neck reduction
Vortex street meters have a lower measurement limit; the flow velocity must reach the minimum requirement for vortex formation.
Using water as the medium and taking the E+H product as an example, the measurement range for 50 is 1.5 to 62 cubic meters per hour. Looking at the range ratio, that of vortex flow meters is generally 5 to 40:1. This is taken into account along with the measurement principle of vortex flow meters. With a measurement range of 30, it’s practically impossible to measure 2. Finally, please check item 6.1.6 of hg20507: the normal flow rate should be between 50% and 70% of the full scale, which will help identify where the problem lies