HIGH-RELIABILITY VORTEX FLOW METER WITH DUAL-COUPLED ULTRASONIC SENSORS |
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| Hiroshi Ohashi, Kuniyoshi Okamoto, Atsuro Sen, Hiroshi Yoshikura, Yutaka Inada |
- Abstract:
- Confirmation of measuring technology for flow rate of high pressurized gas is required. So, in order to build up measuring technology keeping ‘High Sensitiveness’, ‘Wide Rangeability’, ‘High Accuracy’, up to now, we have developed a vortex flow meter for gas with ‘one’ coupled ultrasonic sensors. And we confirmed this effectiveness by testing on an existing gas pipe line with high pressure. This type of vortex flow meter has a hole inside the bluff body situated in the flow, and the change of flow which are generated by vortexes lead to this hole. Ultrasonic sensors situated both side of this hole detect the change of flow in the hole.
This type of vortex flow meter has features as follows.
High sensitiveness (Min. Sensitiveness velocity 0.4 m/sec)
Anti-pipe-vibration characteristics (Max. 3 G)
High pressure capacity (Max. 7 MPa)
High accuracy (error +/-1%RD)
Explosion proof structure (Exd II BT4 equivalent)
This time we developed a new type vortex flow meter with ‘dual’ coupled ultrasonic sensors and two holes inside the bluff body for the purpose of improvement on robustness against pulsation change of pressure and temperature of gas and other purpose is to improve on reliability against electrical circuit troubles, and so on. The most remarkable structural feature of this meter is to have the bluff body with two holes and two pairs of ultrasonic sensors. This structure can get the advantages as follows.
1. The new vortex flow meter can eliminate noises such as pulsation change of pressure and temperature of gas.
The gas in the holes moves to opposite phase according to vortexes. The gas in the holes moves to the same phase according to various kinds of noise. Comparing each signals, same phase is canceled and opposite phase can be detected effectively. So it can eliminate noise and sensitiveness of vortexes is doubled in comparison with ‘one’ coupled ultrasonic sensors. It does not require some compensation circuit for pressure or temperature changes. It can keep stable measurement even in low flow rate.
2. The new vortex flow meter can measure if one of the ultrasonic sensors orcircuits has broken down or of a mal-function.
Ultrasonic sensors and some circuits are partially duplicated, if one of them has broken down or of a mal-function, another one can backup. So flow measurement signal does not suddenly stop. Self-diagnosis function provides us to indicate those trouble under operation.
We also designed fitting of ultrasonic sensors to the body with sonic insulation for the purpose to improve S/N ratio as is spread sensing range. Those opposite phase gas flow occurred by vortex in each hole in the bluff body should be sensed changing phase correctly. Transmitted signal is not only radiated in to the hole but also be conveyed in to the body of flow meter itself, this caused the error of phase. To eliminate those conveyed signal through the body is effective to spread the measuring range by improving minimum sensing flow rate.
The new type vortex flow meter can easily be used for not only gas pipe line but also pipe lines close to a compressor or a turbine in factories that caused strong pulsation change of pressure and temperature of gas, so conventional vortex flow meter could not measured steadily. - Keywords:
- ultrasonic, vortex, flow meter, sensor, buckup cancel
- Download:
- IMEKO-TC9-2000-052.pdf
- DOI:
- -
- Event details
- IMEKO TC:
- TC9
- Event name:
- FLOMEKO 2000
- Title:
- 10th Conference on Flow Measurement
- Place:
- Salvador, Bahia, BRAZIL
- Time:
- 04 June 2000 - 08 June 2000