Float-type flowmeters are approved for hazardous areas
28 January 2009
Yokogawa has enhanced its Rotameter family of float-type flowmeters with the introduction of a patented float-blocking indication system. The RAMC flowmeter automatically detects any problems with the free movement of the float and is approved for hazardous areas.
Float-type flowmeters are approved for hazardous areas
Flowmeters based on the rotating-float principle offer simplicity, minimal energy consumption, low cost and robustness. However, foreign particles in the medium being measured can cause the float to jam.
Modern flowmeters have the float rising and falling in a metal tube, with the float’s position transmitted by magnetic coupling to the indicator. Although this leads to a more robust instrument, it becomes inherently more difficult to check the working condition of the flowmeter.
The patented float blocking indication system is based on the fact that the float oscillates slightly when there is a flow. Software is incorporated in the transmitter to detect whether this basic movement is present. If the oscillation is absent, the software triggers an error signal and the output current is adjusted to fault-current level. Remote diagnostics then indicate that the instrument is no longer working correctly.
The Yokogawa Rotameter Series RAMC and RAKD flowmeters are housed in stainless steel 1.4301 enclosures with the casting sealed to IP protection class IP66/67. The instruments carry hazardous area approvals for available including ATEX, FM, SAA and NEPSI, and the RAMC also complies with the SIL1 and SIL2 requirements.
In addition to providing a 4-20 mA analogue signal for flow indication, minimum and maximum switching signals are available. Hart and Profibus PA are also available as interfaces for digital communication.
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