Liquid Flow Switches, Volumetric Information on GlobalSpec

Liquid flow switches, volumetric are devices with a switch output used for measuring the flow or quantity of a moving fluid in terms of a unit of volume per unit time, such as liters per minute. The basis of good flow switch selection is a clear understanding of the requirements of the particular application. Measuring the flow of liquids is a critical need in many industrial plants. In some operations, the ability to conduct accurate flow measurements is so important that it can make the difference between making a profit and taking a loss. In other cases, inaccurate flow measurements or failure to take measurements can cause serious (or even disastrous) results.

With most liquid flow measurement instruments, the flow rate is determined inferentially by measuring the liquid's velocity or the change in kinetic energy. Velocity depends on the pressure differential that is forcing the liquid through a pipe or conduit. Because the pipe's cross-sectional area is known and remains constant, the average velocity is an indication of the flow rate.

The basic relationship for determining the liquid's flow rate in such cases is:

Q= V x A; where Q = liquid flow through the pipe V = average velocity of the flow A = cross-sectional area of the pipe.

Other methods of flow rate determination include positive displacement, velocity meters, and true mass flow meters. Other factors that affect liquid flow rate include the liquid's viscosity and density. Specific applications should be discussed with a flow switch manufacturer before purchasing to ensure proper fit, form and function. A volumetric liquid flow switch’s performance can be determined by the switch’s turndown ratio. Turndown ratio is the effective dynamic or operating range of the flow switch. For example: If the 500 GPM flow rate device has a turndown ratio of 50:1 it will effectively operate and resolve flow down to 10 GPM. If the same device has a turndown of 100:1 it will effectively resolve to 5 GPM. The operating pressure is the maximum head pressure of the process media the switch can withstand. The maximum temperature of the media that can be monitored is usually dependent on construction and liner materials.

Volumetric liquid flow switches can have an electro-mechanical or solid-state switch construction. The normal state can be normally open (NO), or normally closed (NC). Liquid flow switches, volumetric can have single poles (SP), double poles (DP), and more than two poles. The throw type on volumetric liquid flow switches can be single throw (ST) or double throw (DT). Mounting options for volumetric liquid flow switches include insertion types, in-line flanged, in-line threaded, and in-line clamp. Insertion flow switches are inserted perpendicular to flow path. They usually require a threaded hole in the process pipe or other means of access. In-line flanged flow switches are inserted parallel to the flow path, usually inserted between two pieces of existing flanged process pipes. In-line threaded flow switches are inserted parallel to the flow path, and threaded into two existing process pipes. NPT is the most common thread type. In-line clamp flow switches are inserted parallel to the flow path, and clamped between two existing process pipes. Common interface types include serial and parallel.

More >>

Products & Services Related to Liquid Flow Switches, Volumetric

Flow Meters

Flow meters (flowmeters) and flow sensors are devices used for measuring the flow rate or quantity of a moving fluid or gas.

Flow Transmitters

Flow transmitters provide electrical outputs that are proportional to flow inputs. They use flow meters to measure the flow of liquids and gases.

Paddlewheel Flow Meters

Paddlewheel flow meters have a paddle wheel that is perpendicular to the flow path. The rotor axis is positioned to limit contact between the paddles and the flowing media.

Positive Displacement Flow Meters

Positive displacement flow meters measure the volume or flow rate of a moving fluid or gas by dividing the media into fixed, metered volumes. These devices consist of a chamber that obstructs the media flow and a rotating or reciprocating mechanism that allows the passage of fixed-volume amounts.

Rotameters

Rotameters are typically tapered glass tubes positioned vertically in the fluid flow. A float within the tube rides upward in relation to the amount of flow.

Turbine Flow Meters

Turbine flow meters measure the rate of flow in a pipe or process line via a rotor that spins as the media passes through its blades.

Vortex Flow Meters

Vortex flow meters are flow sensors that detect the frequency of vortices shed by a bluff body placed in a flow stream. The frequency of the vortices is proportional to the flow velocity.

Engineering Web: Liquid Flow Switches Volumetric - TechBriefs

Pages: 1 - 3 of 270

Flow Meters \| Mass Flow Controllers, Air Flow Meters, Oxygen... Sierra Instruments manufacturers high performance mass flow meters and mass flow controllers for nearly any gas, liquid, or steam application. See Sierra Instruments, Inc. Profile & Catalog
Liquid crystal display - Wikipedia, the free encyclopedia Liquid crystal display From Wikipedia, the free encyclopedia Reflective twisted nematic liquid crystal display.
MITSUBISHI ELECTRIC RESEARCH LABORATORIES http://www.merl.com... MITSUBISHI ELECTRIC RESEARCH LABORATORIES http://www.merl.com Wireless Liquid Level Sensing for Restaurant Applications TR2002-21 April 2002 Abstract See Mitsubishi Electric Research Labs Information

More >>