Level Measurement Solutions for BlowdownAn important part of steam generation is the quality of the steam generated. Maintaining water quality in the boiler within design parameters ensures the highest quality steam possible while minimizing blowdown of the boiler, both of which improve energy and resource management.Continuous or manual blowdown of the boiler minimizes scale accumulation and corrosion resulting from impurities in the water. The blowdown provides a means of accommodating liquid and impurities from the boiler, with the latter facilitating energy recovery through the use of flash steam.Level Measurement ConsiderationsTaking advantage of a specific technology’s ability to reliably address the level measurement in either of these vessels, especially the blowdown flash tank, in a plug-and-play type installation and commissioning format is an easy way to ensure optimal performance. This forgoes calibration, external hardware or inputs.Estimates of up to 49 percent of the energy can be recovered through the use of flash steam routed to heat exchangers or the deaerator to preheat boiler makeup water or support the deaeration process, respectively. In addition, better level control technology at the boiler side eliminates energy losses resulting from unnecessary blowdown to prevent carryover conditions.The performance of any level technology relative to instrument induced errors, calibration nuances, and vulnerabilities to process dynamics can have an immediate and adverse impact on fuel consumption. Seamless response to changes in demand and reducing maintenance associated with the instrumentation or damage to hardware are residual benefits that have their own financial ramifications; these aspects should also be considered when implementing any technology.Level Measurement Solutions for DeaeratorsWith proper level control and instrumentation, every part of the steam generation cycle can be managed for optimal efficiency. Deaerator FunctionsThe deaerator serves as an “open” type heat exchanger with its primary function being the removal of oxygen and other corrosive gases from the boiler feedwater. This is accomplished using steam, which can give up about 970 Btu per pound, to support the deaeration process as well as preheat boiler feedwater.deaeratorsAny appreciable gain in boiler feedwater achieved through the process reduces the amount of energy (fuel) required at the boiler— in fact, every 10.8°F (6°C) rise in boiler feedwater amounts to a one percent savings in fuel cost. Inadequate level controls can inhibit the deaeration process (level too high) or reduce/shutdown feedwater flow to the boiler (level too low). The former affects hardware longevity and efficiency, while the latter risks production losses and possible damage to pumps.In addition to the “open” or deaerating feedwater heater, the more common shell and tube heat exchangers/condensers can be found in larger scale steam generation cycles where their costs are offset by gains in thermal efficiency. The effectiveness of a shell and tube heat exchanger in transferring energy is contingent, barring hardware anomalies, on accurate level control.Level Measurement SolutionsFor more accurate measurement in deaerators, magnetrol guided wave radar (GWR) is a preferred option. Since its performance and accuracy are not contingent on the specific gravity and/or inference, it can provide reliable measurements in all situations, including the difficult and turbulent process conditions of deaerators and feedwater heaters. In addition, GWR does not require external inputs or calibration to achieve specified performance. This effectively eliminates the introduction of errors during the calibration process or from external sources, i.e., pressure and temperature. With this high level of accuracy, operators can trust that their deaerators will be well controlled.
In an industrial factory, one of the most important level measurements is flow meter. Whether you do the in-house selection of flow meters or a seller or contractor does the selection for you, there are many variables to consider effectively.To select the right flow sensor or meter, you need to consider many important factors:Application Requirements:A clear and thorough knowledge of the demands of the specific implementation for which the flow sensor is designed is the foundation of a successful flow meter choice. Some of these criteria for implementation include:Evaluate the nature of the process fluid and the overall installationFlow rate information: is it continuous or totalized or bothIs the flow rate needed locally or remotely? If remotely, should the transmission be analog, digital or shared.Factors effect to Flowmeter Operation:We need to be able to analyze the properties and flow characteristics of the process fluid, the piping requirements that will accommodate the custom flow meter and many other operational factors in order to successfully select a flow meter that will be able to operate in the desired manner. These variables that should be closely regarded include:1. Flow characteristics:Nature of fluidLiquid or gas fluid or slurryIs the fluid is corrosive?Is the fluid conductive or not?Does the fluid contains slurry or large amount of solid substance.viscosity of the fluidfluid density or viscosity change2. Determine the required flow meter range. To accomplish this, identify the minimum and maximum flows (mass or volumetric depending on the application) that will be measured3. Consider the piping and the region of installation or location of the flow meter. Specify the direction, size, material, timetable, flange (stress rating), accessibility, up or down stream turns, valves, controllers, and accessible straight-pipe run lengths for flow meter piping.With regard to the region where the flow meter is installed, we must understand whether there are or are feasible vibration or magnetic fields, whether there is pneumatic or electrical power accessible, whether the area is categorized for explosion risks or if there are other unique conditions such as sanitary regulations.4. Accuracy:Determine the required flow measurement accuracy. Flow meter accuracy comes in different ways:Percentage of Flow Rate (% FR)Percentage of Calibrated Span (% CS)Percentage of Full Scale units (% FS)Percentage of Actual Reading (% AR)The accuracy specifications should be indicated individually at the minimum, normal and maximum flow rates regardless of the accuracy metrics. Failure to do so may compromise your flow meter’s efficiency across its full range.The absolute precision is highly essential in instances where the flow meter is used for business purposes (buying or selling). Repeatability may be far more essential than precision for other apps, so it is advisable to set up individually for each flow meter implementation for precision and repeatability requirements.Care should be taken to properly interpret the accuracy of the pneumatic flow meter. Flow meter accuracy can be inaccurate if misinterpreted. Meter accuracy in percentage flow rate, calibrated span of full-scale units all differ from minimum to maximum flow rate of the flow meterThe only proportion of real reading is the steady precision metric. Therefore, it is advisable to transform all cited error statements into the same percentage of real reading units in order to make a reasonable comparison in terms of precision between ranges of flow meter techniques in account for a specified implementation.It is also suggested that the customer compare facilities of flow meters based on the complete flow loop mistake. Total inaccuracy is calculated by taking at the required flow rates the root of the sum of the component squares inaccuracies.
There are distinct differences in functionality, accuracy, and certainly price. Ultrasonic sensors that accurately and non-invasively measure through commonly used tubing is an excellent multi-use option that is positioned on the higher end of the price scale. If low unit price is desirable without sacrificing accuracy, then single-use turbine type sensors are a good option particularly if working fluid is low viscosity. If higher viscosity working fluids are involved, the single-use flow through disposable ultrasonic sensors are the best fit.When selecting a flow meter consideration must be given to:Flow measurement type - momentum (velocity), volumetric or mass flow measurementAccuracy - required accuracy of the readingsEnvironmental considerations - special installation considerations such as hygienic installation, installing in to an ATEX zone or requiring tamper proof readingsMedia - type of media (liquid, gas or slurry) and any special condition such as particulates in the media and viscosity of the mediaMedia conditions - pressure and temperature of media and whether media conditions are likely to remain constant or varyFlow range - required flow range of mediaHere is an overview for some of the flowmeter options:Coriolis flowmeters offer true mass flow measurement through two designs: a single tube or two parallel tubes. They operate via an oscillation which is induced in the tube(s) at a reference frequency.Among the most accurate of technologies available, Coriolis flowmeters are suitable for a wide and growing range of gas and liquid applications. These devices provide multiparameter data on mass, density, and temperature. They are used in pharmaceutical manufacturing, wastewater treatment facilities, nuclear facilities, natural gas measurement and custody transfer.Ultrasonic flow meters offer more advanced technology and greater versatility than some other types. These designs measure the frequency shift of an ultrasonic signal that is sent through the fluid. Two types of ultrasonic meters are Doppler and transit-time. Doppler technologies utilize particles or aeration in the fluid as a reflective mechanism to gauge the velocity of the fluid. Transit-time technologies rely on a frequency difference in forward and reverse signals sent though a clean liquid to gauge the velocity of the fluid; the fluid must not have solids or aeration, as they will distort the sonic pulses. Because of their versatility and advantages of ultrasonic flow meter, ultrasonic flowmeters are used in a long list of industries, including facilities management, pulp and paper manufacturing, chemical manufacturing, and mining. Water/wastewater, petrochemical, and aquafarms also enlist this technology. Ultrasonic meters can be used to measure the corrosiveness of slurry fluid flow.Magnetic meters (or magmeters) are available in two design styles: insertion and full-bore. Coils in the meter produce a magnetic field. When a conductive fluid is passed through the field, a voltage is produced through an electrode in the meter wall or insertion probe; this generated voltage is proportional to the flow. Magmeters operate by measuring the electrical content of water or other fluids. The magnetic technology contains no moving parts, and the full-bore designs offer no intrusions into the flow stream. Magmeters are high end flow meters and are used in the food & beverage industry, water purification, pulp and paper manufacturing, mining, chemical manufacturing, and petrochemical industries. They should not be used with low conductivity fluids such as de-ionized water.Turbine meters contain a bladed rotor positioned along the centerline of the flow stream. The rotating component is designed to provide a pulse when passing either a magnetic or optical sensor. The frequency of the pulses is proportional to the velocity of the fluid. Some designs offer high levels of accuracy and can handle slightly higher viscosity fluids than basic propeller-type designs. Also, some turbine designs meet sanitary guidelines.Irrigation and water purification are two common applications for turbine flowmeters. They are also used in the oil and gas, utilities, and wastewater industries. When used with sanitary connections, turbine meters control flow in food & beverage applications.
What is a flow meter？Flow meters are devices that can be used to measure the amount of liquid, or gas which passes through it. It is an instrument which is used to conduct the flow instrument measurement. The flow rate of liquid and gases must be measured accurately for the better quality of the industrial process. Accurate measurement of gases is needed for the industrial process and it also does the control of flow rate. Flow meters measure the flow by two methods, some flow meters measure the flow as the amount of the liquid passes through the flowmeter during a period of time. While other flow meters measure the flow by measuring the total amount of fluid that has passed through the flow meter.How does a flow meter workFlowmeter consists of devices such as transducer and transmitter, the transducer will sense the fluid that passes through the primary device. The transmitter will receive a signal from the transducer, so the transducer changes this signal into a usable flow signal. So a flow meter can be considered as the combination of these physical devices.What are the factors that affect a flow meter selectionPipe size and accuracyRepeatability and costThe phase of the fluid-like gas, liquid, steamFlow conditions and flow range, flow conditions like clean, dirty, abrasive, viscous will affectProcess conditions like pressure and temperatureWhat are the types of flow meterFlow meters can be classified into differential pressure meters, variable area meter, positive displacement meters, magnetic, turbine, advantages of ultrasonic flow meter, vortex, and Coriolis. In differential pressure meters a restriction is used to create a pressure drop. So the flow rate can be determined by measuring the pressure drop across the restriction. In positive displacement meters, the measuring process takes place by precision-fitted rotors as flow measuring elements.Ultrasonic flow metersUltrasonic waves can propagate through any substances like solid, liquid, gases and this property of the wave is utilized to measure the fluid flow in a pipe the ultrasonic signal is sent to the pipe at an angle, and the time taken for the signal to reach from one side to another is measured. The difference between the transit time across the pipe and that of the signal traveling in the reverse direction is proportional to the flow rate.Vortex flowmeterThis flow meter is also known as oscillatory flow meters, it utilizes the natural phenomena when a liquid is allowed to flow in a bluff object. The frequency of the vortex shedding is directly proportional to the velocity of the liquid flowing through the r, this meter is widely used to measure the steam flow.Magnetic flow meterMagnetic flow meter depended on faraday’s law of electromagnetic induction, so it states that voltage will be induced when a conductor moves through a magnetic field. The liquid acts as the conductor and the magnetic field are created by energized coils outside the flow tube. The voltage produced is directly proportional to the flow rate, two electrodes are attached to the pipe wall to detect the voltage and it is measured by a secondary element. These flow meters can measure corrosive liquids and slurries