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Reduction of Loss of Water Supply Volume due to Insensitivity of Water Meter for Higher Economic Benefit |
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| ---Technical Features and Application of Ultrasonic Water Meter |
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Tangshan Huizhong Instrumentation Co., Ltd.
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Keywords: Meter-induced loss Minimum flowrate detectable Ultrasonic water meter |
Abstract: The water supply sector is currently using mechanical rotary-vane water meter for supply volume measurement. However, |
| the mechanical meter can only detect a higher initial flowrate and its use generally leads to higher pressure loss, causing the water supply |
| sector to suffer a noticeable economic loss due to the discrepancy between the actually supplied and measured water volumes, and higher |
| power consumption. Following an analysis of abovementioned problems, the paper presents a detailed description of the working principle |
| of the ultrasonic water meter and the technical performance of ultrasonic water meter in comparison with that of the mechanical version, and |
| the economic result that can be obtained through the use of the ultrasonic water meter. It proves that the use of this kind of meter provides an |
| optimal approach for the water supply sector to gain an improved economic result through reduction of meter-induced loss in water supply |
| volume. |
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| Introduction |
Meter-induced loss in water supply volume has remained an important factor affecting the economic performance of the water supply |
| sector. The loss thus induced is as high as 30 percent and even goes up to 40 percent in general cities of the country. This may be attributed |
| mainly to the reason that the mechanical rotary-vane meter (Hereinafter referred to as mechanical water meter) in current use is only sensitive |
| to a larger flowrate, and the water consumers tend to keep the water flow at the critical point or under the flowrate that can be detectable. |
| The higher power consumption of the water supply sector is another key factor jeopardizing the improvement of the sector＊s economic |
| result. The higher power consumption is due to the greater pressure loss caused by the use of mechanical waters. As the water and energy |
| resources are becoming increasingly short in demand, the water and power prices keep on the hike. The improvement of the two restricting |
| factors as described above is not only beneficial to the improvement of economic result, but also of far-reaching significance for saving both |
| water and energy resources. The 2 negative factors are resulted from the working principle of the mechanical water meter, and the key to the |
| solution of these problems lies in the making of breakthrough in the water flowrate measuring technology |
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| The ultrasonic flowrate meter developed by Tangshan Huizhong Instrumentation Co., Ltd. has thoroughly overcome the shortcomings of |
| the mechanical flow meter 每 less sensitive to a small flowrate, greater pressure loss, lower accuracy and shorter service life. The ultrasonic |
| flowrate meter can also perform wireless meter reading transmission and tariff management functions. Presented below is a brief introduction |
| to the meter＊s working principle, its technical performance in comparison with that of mechanical water meter and the practical application. |
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| Working Principle |
| When an ultrasonic signal produced by a transducer is made to propagate in the water, there exists an velocity difference which is in |
| proportion to the water flow velocity. The ultrasonic water meter is a meter which operates on the velocity-difference principle as illustrated in |
| the attached diagram. |
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| A, B 每 Ultrasonic transducer t1,t2-- Propagation time
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| D 每 Pipe diameter V 每 Water flow velocity in pipe |
C 每 Propagation velocity of ultrasonic wave in water |
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It can be inferred through a mathematic model that V ≦ fㄗt2-t1ㄘ. As C >>V*Sin r, the time difference is very small. However,the |
| ultrasonic water meter has a time detection resolution of less than 1ns. That is why the meter is highly sensitive to a very small flowrate. |
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| Ultrasonic meter vs. mechanical meter |
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Pressure Loss |
Power Consumption of Pump
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Fee Collection Mode |
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Wireless meter reading Transmission(Reliable)
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2m3/h |
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| With the use of ultrasonic water meter (DN200) the following favorable social and economic results are obtained |
| Water saving:The smallest flow rates that can be detected by the ultrasonic meter and the mechanical meter are 0.6m3/h and 2m3/h |
| respectively, with a difference of 1.4 m3/h. calculated on the basis that the time of water supply at a small flowrate (<2 m3/h) lasts for 3 hours |
| each day and an average water price of 4 yuan/ m3, a water supply enterprise will suffer from a big loss water supply volume as high as |
| 1533 m3 and an economic loss of about 6000 yuan per year. Such heavy losses should not be overlooked. |
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| Energy saving:At a normal water flow rate of 1m/s (113m3/h), the pressure loss due to the use of the mechanical meter is about 0.07 |
| MPa (7m water column) while that of the ultrasonic meter is almost zero. When calculated on the basis that the water supply time is 5000 hours |
| per year, with a pumping efficiency of 80 percent, and an electricity price of 0.8 yuan/kWh, a power save of about 13457 kWh and a cut-down of |
| cost by 10766 yuan can be expected a year. The calculation is made under the conditions as listed in the following Table. |
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Gravitational accelerationㄗNㄘ
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Loss of electrical energy(kWh)
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Electricity expense(yuan/yr.)
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9.8 |
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| Computational formula: Power Loss = Flowrate x Density x Gravitational acceleration x Pressure loss |
| Loss of Electricity Energy = Power loss / Pumping efficiency x Annual running time / 3600 |
| The above going analysis shows that after shifting to the use of ultrasonic water meter, the economic benefit that can be gained each year |
| through the reduction of loss in water supply and power consumption is estimated to reach a conservative figure of approximately 8000 yuan. |
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| Practical Applicationㄩ |
| Up to 2005.02, nearly 1000 ultrasonic water meter had found applications successively in 100-odd water supply enterprises, and those |
| where more such meters are used include Qingdao, Bengbu, Binzhou, Zhongshan, Zhangzhou, Zhanjiang, Chengde and Longhai water supply |
| companies. Some typical cases are cited here to demonstrate the remarkable performance of the meter in field application. |
| 1.A DN150 ultrasonic meter was fitted on experimental basis at Kaile Homeland by Qingdao Water Supply Co. for making a comparison with the |
| mechanical water meter. 45 days later, the water supply volume measured by the former was 3.86 percent more than that measured by the latter. |
| 2.A DN200 ultrasonic water meter was fitted by Nanjing Water Supply Co. in series with a mechanical water meter. The comparative test made |
| over a period of nearly one year showed that the water supply volume measured by the former was 3.98 percent more than that measured by the |
| latter. Moreover, along with the wear of the wear of the mechanical meter, the difference of the measured values showed the tendency to become |
| ever-increasingly larger. |
| 3.A DN150 ultrasonic water meter was mounted at Weihua bazaar in Tiexi District by Shenyang Water Supply Co. in series with a newly-calibrated |
| mechanical water meter. Through observation, it was found that during the normal business hours, there was no noticeable difference between |
| the 2 meters in measured values. However, during the period from 21:30 to 0:00, the water flowrate maintained predominantly at around 2m3/h. |
| In this case, the mechanical water meter worked intermittently yet the ultrasonic water meter could still maintain its proper measuring function. |
| At the small hours of 0:00~8:00, when the water flowrate was further reduced to less than 2m3/h, the mechanical water meter made no response |
| at all due to its low sensitivity, but the ultrasonic water meter which is sensitive to a flowrate as low as 0.3 m3/h, could still make proper |
| measurements. As evidenced by observation made over a period of 2 months, with the use of the ultrasonic water meter, over 10 percent of the |
| loss in water supply volume caused by low detection capacity of mechanical water meter had been retrieved. |
| 4.A DN150 ultrasonic water meter was installed in series with a mechanical water meter at the No. 2 College of Shenyang Medical University for |
| making a comparative test. At daytime, the flowrate was 2m3/h. Over a period of only one month (2004.10), the water supply volume measured |
| by the ultrasonic meter was 2077 m3, 150% higher than that by the mechanical meter which was only 833 m3. The well demonstrates that the |
| ultrasonic water meter can operates with a more remarkable performance at a lower water flowrate. |
| 5.Similar test was made by Chengdu Water Supply Co. at a residential quarter at Beixian County with DN150 and DN200 ultrasonic water meters, |
| mounted in series with mechanical meters. Over a period of 6 months, the water volumes recorded by DN150 and DN200 ultrasonic meters |
| were respectively 5 percent and 10 percent more than those measured by the mechanical meters. |
| 6.Two DN150 ultrasonic meters were respectively mounted by Tengzhou Water Supply Co. at its industrial park and brewery. According to the |
| feedback on the performance of the meters through one-year field operation, the meters all registered a water supply volume about 10 percent |
| higher than the values when mechanical water meters were used. |
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| Concluding Remarksㄩ |
| The debut of the ultrasonic water meter is a technological revolution in water flow measurement. The typical cases as cited above fully |
| demonstrate that the use of the ultrasonic meter can bring forth not only favorable economic benefit but also inestimable social benefit, |
| especially at the present time when the water and energy resources are increasingly in short supply. |
