Low-capacity glass tube meters are used extensively in purge systems, where they are called purgemeters. The float moves up or down in the tube in proportion to the fluid flowrate and the annular area between the float and the tube wall. These do not require vertical mounting, but corrosive or erosive fluids can damage the spring and lead to reduced accuracy. The meter designer can shorten the flow range and lengthen the float travel to increase measurement accuracy to a degree unattainable with any other flow rate measuring instrument. These are usually manufactured in aluminum, brass or stainless steel. Glass tube rotameters are typically used for simple but reliable indication of flow rate with a high level of repeatability.
Its integral needle valve and constant-flow, differential pressure dp regulator are useful when it is used as a purgemeter. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. If you continue without changing your settings, we'll assume that you are happy to receive all cookies on this website. Small glass tube rotameters are suitable for working with pressures up to 500 psig, but the maximum operating pressure of a large 2-in diameter tube may be as low as 100 psig. To have your flow meter calibrated on one of the 0. In various configurations flow meters can be designed to withstand high pressures, corrosive fluids, high temperatures, and is completely independent of factors influencing electronic meters. This means that the flow rate can be read with the same degree of accuracy throughout the full range.
For example, large line size gas ultrasonic flowmeters for custody transfer applications need to be tested under high-pressure conditions with high speed flowing natural gas. This is done to reference the operating conditions to those at calibration of the rotameter. Please contact the closest to you for more details. Easily converted to measure different fluids. Some analyzers also require the introduction of modifying gases with the sample.
Rotameters are a subset of meters called variable area flow meters that measure the flow rate by allowing the fluid to travel through a tapered tube where the cross sectional area of the tube gradually becomes greater as the fluid travels through the tube. It reaches a constant position once the fluid and gravitational forces have equalized. . Safety-shielded glass tube rotameters are in general use throughout industry for measuring both liquids and gases. The flow rate inside the rotameter is measured using a float that is lifted by the fluid flow based on the buoyancy and velocity of the fluid opposing gravity pulling the float down. In general, there is a linear relationship between operating temperature and pressure.
The technique for measuring flow is accomplished by a freely moving float finding equilibrium in a tapered tube. Product Detail Process Connections Flange, threaded Process Temperature -200 C to + 370 Process Pressure 100 bar, higher pressures on request Ambient Temperature -40 C to 100 C Accuracy acc. Rotameter tubes for such safe applications as air or water can be made of glass, whereas if breakage would create an unsafe condition, they are provided with metal tubes. It is nature's strongest oxidizer and has a byproduct of pure oxygen. The air or gas supply pressure, however, must exceed the maximum line pressure by ~10 psi. The other dip tube, extending down to near the bottom of the vessel, thus can be a measure of head due to liquid level.
Programmability allows designers to specify the logic they want, instead of merely settling for what is available. Piston Prover Calibration Piston provers are a primary standard for flow calibration. The flow tube is traditionally placed in a vertical position and fluid enters from the bottom, forcing the float up in the tube until a sufficient annular opening exists between the float and tube to allow the total volume of fluid to flow past the float. It is simple to install and maintain. Two bubble tubes are immersed in a tank at different depths. Special Tests of Gas and Liquid Flows 18050S-18060S Special tests for gas and liquid flows are available. It can therefore measure fluid flows that no other type of meter will handle with continued success.
Principle of Operation The rotameter's operation is based on the variable area principle: fluid flow raises a float in a tapered tube, increasing the area for passage of the fluid. The plant operator will then be able to monitor the exact level in the tank. Master meters provide an uncertainty of 0. Handbook, Process Measurement and Analysis. A comprehensive set of approvals for use in hazardous areas is available for types with a local display and inductive limit switches as well as those with an electrical output signal 4.
One early design had slots, which caused the float to spin for stabilizing and centering purposes. Because this float rotated, the term rotameter was coined. General Correction Equations As you can see from these equations, a pressure increase of 50 psig will more than double the flow rate indicated by the float height in a rotameter. In the case of glass and plastic tubes you can simply view the float position to get a reliable reading of the flow rate. End fittings and connections of various materials and styles are available. For applications requiring a wide measurement range, a dual-ball rotameter can be used.
They are typically constructed of polycarbonate, with either metal or plastic end fittings. To find out more information about these cookies please. Dear Rich, Thank you for your favorable comments on my article. There are multiple methods of recalibrating a flowmeter. Floats typically are machined from glass, plastic, metal, or stainless steel for corrosion resistance. Our goal is to provide accurate testing, detailed reporting and quick turn-arounds.