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In industrial, commercial and municipal environments, the demand for safe, healthy and clean water is crucial. There are management standards for the use of certain equipment in these environments, which provide guidance and have legal effect in some jurisdictions.
Accurate control of pump flow is very important in drinking water application. The goal is to improve the efficiency by accurately tracking the amount of water in the water distribution system and identify potential performance problems. This requires effective water flow meter.
Background
Regulatory and legislative efforts to reduce the lead content in all pipeline-related products in contact with drinking water have increased. Federal and state agencies in the United States stipulate that the components of drinking water system must pass the standards established by NSF International, which is a non-profit non-governmental organization recognized for its expertise in health and environmental science, and must comply with the Safe Drinking Water Act (SDWA) of the US Environmental Protection Agency.
Standards for drinking water applications include National Science Foundation/American National Standards Association Standard 61: Components of Drinking Water System-Health Impact and National Science Foundation/American National Standards Association Standard 372: Components of Drinking Water System-Lead Content.
NSF Standard 61 is the certification of drinking water, while Standard 372 is the measurement method to determine the characteristics of "lead-free" (weighted average of 0.25% or less). Standards 61 and 372 are designed to ensure the health protection of products in contact with drinking water. This standard requires prefabricated household pump system to be certified as a whole system.
Understand pump performance
Manufacturers involved in food and beverage production and other sanitary processes, as well as operators of municipal water supply systems, need to use pumps conforming to SDWA standards. These pumps are made of stainless steel or other harmless materials and must be easy to disassemble and clean.
In this application, the accurate control of water flow rate of pump system is very important, which is usually characterized by intermittent low flow rate and reduced water consumption. Nowadays, the water conveyance system is characterized by large pipeline, low flow rate and low total flow rate.
The flow produced by the pump is essentially volume flow. The accuracy of any measurement depends largely on the properties of the fluid. The inaccuracy of ultrasonic flowmeter may be caused by process conditions, including temperature change, pressure change, air retention and component wear.
The data show that the water flow output of the pump may change significantly due to the degradation of pump components, environmental or system changes or the combination of these factors.
There are many reasons why the flow through the pump is measured:
1. Calculate the loss of the distribution system by subtracting the total readings from the total supply;
2. To optimize disinfection;
3. Treatment of corrosion;
4. Monitor the overall performance of the pump;
5. And determine the gross bill of custody transfer.
Most aspects of pump performance are related to the flow of pipeline liquid. Understanding pump performance involves basic knowledge of relevant specifications and performance curves.
Select metering technology
Industrial, commercial and municipal organizations can choose flow measurement technology to achieve accurate and safe water contact in pump control applications. All kinds of mechanical and electronic instruments can be used for liquid flow measurement.
The most commonly used options include turbine flowmeter with stainless steel wetted parts, electromagnetic flowmeter, plug-in ultrasonic flowmeter and external clamp ultrasonic flowmeter, all of which can be safely used for drinking water.
I. Turbine flowmeter
Turbine flowmeter is a mature technology and low-cost solution suitable for smaller pipeline sizes. They are famous for their high precision, wide adjustment range and repeatable measurement.
Turbine flowmeter produces high-resolution pulse rate output signal proportional to fluid velocity, and thus proportional to volume flow. These equipments are limited to clean liquid, and must be recalibrated and repaired regularly, otherwise the measured data will deviate greatly from the actual data.
Some turbine-based flowmeter designs use lead-free bronze alloy. They meet the requirements of lead-free drinking water and can pass the standard certification of National Science Foundation/American National Standards Association. All components of these lead-free alloy instruments constitute the certification system.
Since most drinking water processes involve conductive liquid, electromagnetic flowmeter is suitable for many related flow measurement tasks. These instruments help to meet the measurement accuracy goal, thus achieving more efficient pump operation at lower cost. They provide diagnostic capabilities to enhance reliability, process insight and reduce costs.
II. Electromagnetic flowmeter
The electromagnetic flowmeter adopts the non-invasive open flow tube design, which almost eliminates the pressure loss, but the subsequent maintenance and replacement is very troublesome.
Electromagnetic flowmeter is affected by velocity distribution. Under the condition of axisymmetric distribution, the flow signal is directly proportional to the average velocity. Therefore, there must be a certain length of straight pipe before and after the electromagnetic flowmeter. And the electromagnetic flowmeter is easily affected by external electromagnetic interference.
III. Ultrasonic flowmeter
Nowadays, many people choose the non-contact ultrasonic flowmeter, which essentially conforms to the regulations of the National Science Foundation of the United States, and will not interfere with or cut the pipeline when installed with external clamp. Modern ultrasonic flowmeter provides the same adjustment ratio as electromagnetic flowmeter, which is enhanced with the increase of power and sampling rate. The measurement accuracy of external clamp ultrasonic flowmeter like Xunsheng SUNCENT-X8 can be controlled within 0.5%.
And the fast-rising ultrasonic flowmeter uses the transit time method, which can measure and record the bidirectional velocity and flow. Ultrasonic waves propagate upstream and downstream through the pipe wall and the liquid flowing in the pipe. By measuring the difference in travel time and knowing the pipe size, the flowmeter can determine the speed and flow rate.
The external clamp ultrasonic flowmeter for transit time has no moving or wetting parts, will not suffer from pressure loss, and can provide maintenance-free operation. By measuring the sound velocity ratio of fluid, the change of fluid temperature and/or other characteristics can be obtained.
Clamp-on ultrasonic flowmeter can solve various flow problems, especially in pumps. These ultrasonic flowmeters are located outside the pipeline, and can be flexibly installed in various pipeline sizes, without contact with internal liquid or moving parts.
Insertion ultrasonic flowmeter can be installed under pressure without stopping production. Plug-in ultrasonic flowmeter does not need much maintenance after being installed correctly, and there is no pressure during quarterly inspection.
Ultrasonic flowmeter is a valuable tool to manage pump and system performance. Meters can provide baseline and load curve information needed to optimize system efficiency and reduce energy consumption and cost.
Using cloud-based data analysis, the latest flowmeter achieves higher visibility and control. The spacer data provides operational intelligence for optimizing water management. The cellular terminal broadcasts meter readings and event data to the system software. This helps identify leaks and other performance anomalies.
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