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Liquid flow rate measurement with Parshall flumes
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MEASURING SET DESIGN
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-> Parshall flume
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-> FLOWBOX Flow meter
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* FLOWBOX Flow meter = M1600 Transducer + Ultrasonic level sensor
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ASSUMPTIONS
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The liquid flow rate measurement with Parshall flume and water rise method in rectangular channels is based on the actual liquid level measured by the ultrasonic sensor (radar sensor, optional) at the hydraulic structure converted into the value of flow ratio by the measuring transducer.
The basic condition to apply the method is to provide free, undisturbed outflow of liquid from the measuring flume.
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LEGAL BASIS
Currently, the list of instruments subject to metrological inspection in accordance with article 8 of the regulation of 11 May 2001 „Trade Metrology Act” (Dziennik Ustaw of 2004 No. 243, item 2441 as amended) is specified in the regulation of the Minister of Economy of 27 December 2007 establishing the types of measuring instruments subject to legal metrological inspection and the scope of metrological inspection (Dziennik Ustaw of 2008 No. 3, item 13). The regulation does not establish the duty of metrological inspection of liquid meters in open channels, and the certification body informs that the liquid meters in open channels are not subject to metrological inspection and no approval or verification process is
anticipated.
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PARSHALL FLUME
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APPLICATION: Parshall flumes in accordance with ISO 9826 data sheet are intended for measurement of volumetric flow rate in rectangular channels with gravity flow. The flumes are made of stainless steel or PVC sheets and enable measurements within the range specified in the table below.
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The flume is embedded in concrete in a rectangular channel with subcritical flow. The conditions can be obtained by maintaining a specific gradient and minimum inlet and outlet channel length. The measurement in lower range for a specific flume type will be encumbered with a significant error.
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THE FAMILY OF PARSHALL FLUMES (dimensions in cm)
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| Typ zwężki
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Q [m³/h] |
A |
X |
C |
D |
L |
Y |
E |
F |
G |
| P1 |
1-20 |
2,54 |
30 |
9,29 |
16,75 |
63,5 |
5 |
23,0 |
24,8 |
30,7 |
| P2 |
2-48 |
5,08 |
34 |
13,49 |
21,35 |
77,5 |
5 |
26,4 |
28,6 |
35,35 |
| P3 |
3-151 |
7,62 |
39 |
17,80 |
25,88 |
91,5 |
5 |
46,7 |
49,2 |
39,9 |
| P4 |
5-470 |
15,24 |
53 |
39,40 |
39,69 |
152,4 |
10 |
62,0 |
69,6 |
54,0 |
| P5 |
9-907 |
22,86 |
75 |
48,10 |
57,47 |
162,6 |
10 |
80,0 |
87,6 |
80,0 |
| P6 |
11-1640 |
30,48 |
120 |
61,00 |
84,46 |
287,7 |
10 |
92,5 |
100,1 |
100,0 |
| P7 |
15-2509 |
45,70 |
130 |
76,20 |
102,6 |
294,3 |
15 |
92,5 |
100,1 |
120,0 |
| P8 |
43-3373 |
61,00 |
135 |
91,44 |
120,7 |
301,9 |
20 |
92,5 |
100,1 |
140,0 |
| P9 |
61-5137 |
91,40 |
150 |
121,9 |
157,2 |
316,9 |
20 |
92,5 |
100,1 |
180,0 |
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| Example installations:
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FLOWBOX FLOW METER
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The FLOWBOX Flow meter is intended for measurement of liquid level and volume in vessels and flow rate measurement in open channels. The ultrasonic method eliminates sensor contact with aggressive (acids, bases) or contaminated (wastewater) medium. The measuring set includes M1600 Microprocessor Transducer, ultrasonic level sensor and connecting cable.
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METHOD OF OPERATION
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The flow meter measures ultrasonic beam passage time between the sensor and the surface of measured liquid. The distance to medium surface is measured. The value can be used to read the liquid level or with a formula for over 20 flumes and weirs to determine the liquid flow rate.
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FLOWBOX FLOW METER FEATURES
-> Level / volume measurement
- determined for various vessel shapes
- or with a 32-point characteristic curve
-> Flow measurement in open channels with:
- Palmer-Bowlus flume
- Venturi flume
- Parshall flume
- measuring weirs
- general flow equation
-> Code protected flow meter access (optional).
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SPECIFICATION OF MEASURING TRANSDUCERS
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-> Readout: instantaneous flow rate, total flow rate
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-> Current outputs:
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- 0-20mA
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- 4-20mA for instantaneous flow rate
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-> Impulse output - adder (optional)
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-> Accuracy: ± 0.1% of range
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-> Supply: ~230 V, 50 Hz or battery supply
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-> Power input <10 VA
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-> Ambient temperature: -10 °C to +55 °C
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-> Housing protection rating: IP65
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-> Housing material: ABS
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-> Weight: ~1.5 kg
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SPECIFICATION OF ULTRASONIC SENSORS
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-> Narrow ultrasonic beam
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-> Measuring range: 0-1.8 m
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-> Accuracy: ± 0.25% of measuring range
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-> Ambient temperature: -30 °C to +60 °C
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-> Automatic temperature compensation
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-> Sensor material: PVC
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-> Protection rating: IP65 (IP67 on request)
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RECOMMENDED INSTALLATION
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-> Cabinet
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-> Rack for transducer or cabinet
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