If a Rotameter Is Not Level, Is the Reading It Provides Too High or Too Low? Why?

What are Rotameters? A rotameter is an industrial flowmeter used to measure the flowrate of liquids and gases. The rotameter consists of a tube and float. The float response to flowrate changes is linear, and a x-to-1 menstruation range or turndown is standard. In the case of OMEGA™ laboratory rotameters, far greater flexability is possible through the use of correlation equations. The rotameter is popular because it has a linear scale, a relatively long measurement range, and low pressure drop. It is simple to install and maintain. Principles of Operation The rotameter's operation is based on the variable expanse principle: fluid flow raises a float in a tapered tube, increasing the area for passage of the fluid. The greater the catamenia, the higher the bladder is raised. The height of the float is straight proportional to the flowrate. With liquids, the float is raised by a combination of the buoyancy of the liquid and the velocity caput of the fluid. With gases, buoyancy is negligible, and the bladder responds to the velocity head alone. The float moves up or down in the tube in proportion to the fluid flowrate and the annular area betwixt the float and the tube wall. The float reaches a stable position in the tube when the upward forcefulness exerted by the flowing fluid equals the downward gravitational force exerted by the weight of the float. A change in flowrate upsets this balance of forces. The float then moves up or downward, changing the annular area until information technology again reaches a position where the forces are in equilibrium. To satisfy the forcefulness equation, the rotameter float assumes a distinct position for every constant flowrate. Still, it is important to note that because the float position is gravity dependent, rotameters must be vertically oriented and mounted. Considerations - Rotameter Flowmeter Selection Primal questions which need to be answered before selecting a rotameter are: What is the minimum and maximum menses rate for the flow meter? What is the minimum and maximum process temperature? What is the size of the pipe? Would you similar a direct reading rotameter or is a expect up table adequate? What accuracy practise you need? Do yous crave a valve to regulate the catamenia? Will in that location be dorsum pressure level? What is the maximum procedure pressure?

Rotameter Designs Glass Tube Rotameters The basic rotameter is the drinking glass tube indicating-blazon. The tube is precision formed of borosilicate glass, and the float is precisely machined from metal, drinking glass or plastic. The metallic bladder is usually made of stainless steel to provide corrosion resistance. The bladder has a sharp metering edge where the reading is observed by ways of a scale mounted alongside the tube. Cease fittings and connections of various materials and styles are available. The important elements are the tube and bladder, frequently chosen the tube-and-bladder combination, considering it is this portion of the rotameter which provides the measurement. In fact, similar glass tube and stainless steel float combinations are more often than not bachelor, regardless of the type of case or end fittings the application tin demand, and then equally best to run into customer requirements. The scale of the rotameter can be calibrated for directly reading of air or water, or it may have a scale to read a percent of range or an arbitrary scale to exist used with conversion equations or charts. Safety-shielded glass tube rotameters are in general use throughout industry for measuring both liquids and gases. They provide flow capacities to about threescore GPM, and are manufactured with end fittings of metal or plastic to encounter the chemical characteristics of the fluid being metered. The only fluids for which these meters are not suited are those which attack glass metering tubes, such as water over 90�C (194�F), with its high pH which softens glass; wet steam, which has the same effect; caustic soda, which dissolves glass; and hydrofluoric acid, which etches glass. The primary limitations of general purpose rotameters are the force per unit area and temperature limits of the glass metering tube. Small-scale, six mm (ane/4") tubes are suitable for working pressures up to 500 psig, but the operating pressure for a big 51 mm (2") tube may exist as low every bit 100 psig. The practical temperature limit for glass rotameters is 204�C (400�F), although operation at such high temperatures substantially reduces the operating pressure of the meter. In full general, there is a linear relationship between the operating temperature and pressure. Metal Tube Flowmeters For higher pressures and temperatures across the practical range of glass tubes, metal tubes are used. These are usually manufactured in aluminim, brass or stainless steel. The position of the piston is determined by magnetic or mechanical followers that can exist read from the outside of the metal metering tube. Similar to glass tube rotameters, the spring-and-piston combination determines the flowrate, and the fittings and materials of structure must be chosen so as to satisfy the demands of the applications. These meters are used for services where high operating pressure level or temperature, water hammer, or other forces would impairment glass metering tubes. Spring and piston flowmeters can be used for most fluids, including corrosive liquids and gases. They are especially well suited for steam applications, where glass tubes are unacceptable. Plastic Tube Rotameters Plastic tubes are as well used in some rotameter designs due to their lower cost and high impact strength. They are typically synthetic of polycarbonate, with either metallic or plastic end fittings. With plastic end fittings, care must be taken in installation, not to misconstrue the threads. Rotameters with all plastic structure are available for applications where metallic wetted parts cannot be tolerated, such every bit with deionized water or corrosives.

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Source: https://cl.omega.com/prodinfo/rotameters.html

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