Water treatment and distribution operations are inherently strict, including moving water from one place to another, increasing filtration pressure, injecting chemicals for water treatment, and distributing clean water to points of use.Accuracy and reliability are particularly important when using a controlled volume metering pump as part of a chemical and additive injection system in the water treatment process.The electromagnetic flowmeter can be an effective solution to verify the correct operation of the equipment to ensure the maximum efficiency of the chemical dosing process.Dedicated feed systems are used to supply chemicals for all stages of water and wastewater operations.The water treatment process requires optimal synthesis, so chemicals may need to be added to establish a favorable environment for biological growth.It is also necessary to obtain sufficient alkalinity to maintain the required pH operating range.
As part of chemical injection, it is usually necessary to add acid or caustic to control pH, add ferric chloride or alum to remove nutrients, or add supplementary carbon sources such as methanol, glycine or acetic acid for process development.When injecting expensive chemicals into the water treatment process, plant operators must ensure that the correct quantities are added to the process as part of quality control.Too much or too little use of chemicals can lead to high operating costs, increased corrosion rates, frequent equipment maintenance, and other adverse consequences.
Each chemical feed system is different, depending on the type of chemical to be pumped, its concentration, and the necessary feed rate.Metering pumps can be used as part of the process of injecting chemicals into the water treatment system.This is usually found in well water operations.A small feed rate will require a metered pump that can provide a specific dose of chemical to the receiving stream.
In many cases, the metering pump used in the water treatment plant is a positive displacement chemical metering device that can change the capacity manually or automatically according to the requirements of the process conditions.This type of pump provides a high level of repeatability and can pump a variety of chemicals, including acids, alkalis and corrosive substances or viscous liquids and slurries.
Water treatment plants are always looking for ways to optimize their operations by minimizing maintenance, downtime, breakdowns and other issues.Each factor affects efficiency and productivity.But when they are combined, they will seriously affect the factory’s production capacity and bottom line.The only way to know to inject the right amount of a given chemical into a water treatment process is to determine the actual dose rate maintained by the metering pump.The challenge is that many pumps for chemical injections do not allow the user to dial in absolute settings for a specific dose rate.Experience has shown that the use of flow meters for pump performance verification can provide valuable information about pump performance and the accuracy of the manufacturer’s specifications.It can also identify operational problems and reduced efficiency due to part wear or other conditions.By adding flow meters and valves between the pump and the process, users can obtain information to evaluate the performance of the actual equipment, highlight any differences, and adjust the speed of the pump when needed.
Many types of flow meters measure liquids, and some are more suitable for water and wastewater treatment environments than others.Some meters are more accurate and repeatable than others.Some require less or more complex maintenance, and some last longer than others.It is important to consider all the selection criteria and not just focus on one aspect, such as price.Considering the required performance and maintenance activities, low purchase prices are often a misleading indicator.A better criterion is the total cost of ownership (TCO), which considers not only the purchase price, but also the cost of installation, maintenance, and replacement of meters.
Considering cost, accuracy and service life, electromagnetic flowmeters can be an ideal choice for demanding water treatment applications.Electromagnetic measurement technology eliminates the need for moving parts, which can cause performance and maintenance issues when used in fluids with high solids content.The electromagnetic flowmeter can measure almost any conductive fluid, including process water and wastewater.These meters provide low pressure drop, extended turndown ratio and excellent repeatability.They are known for providing high accuracy rates at a reasonable cost.The electromagnetic flowmeter operates according to Faraday’s law of electromagnetic induction to measure the liquid velocity.The law states that when a conductor moves in a magnetic field, an electric signal is generated in the conductor, and the electric signal is proportional to the speed of water moving in the magnetic field.
Depending on the fluid medium and/or water quality, standard stainless steel (AISI 316) electrodes used in many electromagnetic flow meters may be sufficient.However, these electrodes are subject to pitting and cracking in corrosive environments, which may cause the accuracy of the flowmeter to change over time.Some instrument manufacturers have switched to Hastelloy C electrodes as standard materials to provide better corrosion resistance and longer service life.This superalloy has high resistance to localized corrosion, which is an advantage in chloride-containing environments at high temperatures.Due to the chromium and molybdenum content, it has a high level of all-round corrosion resistance.Chromium increases resistance to oxidizing conditions, and molybdenum increases resistance to reducing environments.
Some manufacturers use Teflon lining instead of hard rubber lining to provide a high temperature resistant material with strong chemical properties.Facts have proved that electromagnetic flowmeters are very suitable for critical chemical injection applications in water treatment facilities.They enable plant operators to accurately measure the volume of fluid passing through them.These meters can be used as part of a closed-loop system to send output to a programmable logic controller (PLC) to determine the chemical dose in any period of time.This information helps manage chemical costs and resolve applicable environmental regulations.They also provide important life cycle advantages for water treatment and distribution facilities.They are designed to achieve +0.25% accuracy under less than ideal fluid flow conditions.At the same time, the non-invasive, open flow tube configuration almost eliminates pressure loss.If specified correctly, the meter is relatively unaffected by viscosity, temperature, and pressure, and there are no moving parts that hinder flow, and maintenance and repairs are kept to a minimum.
In a demanding water treatment plant environment, even the best-sized metering pump may encounter operating conditions that differ from expectations.Over time, process adjustments can change the density, flow, pressure, temperature, and viscosity of the fluid that the pump must handle.Chris Sizemore is the technical sales manager for Badger Meter Flow Instrumentation.He joined the company in 2013 and has held positions in the technical support team.You can contact him at csizemore@badgermeter.com.For more information, please visit www.badgermeter.com.
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