Flowmeter Accessories
Alarms & Annunciators
Alarms are used to monitor flow, level, and pressure in processes. When the process conditions exceed limits set in the alarm unit, a signal is sent to activate horns, lights, and control room alarms so that corrective action can be taken.
Flow Controllers
Universal electric controllers are used to control process variables such as flow, level, pressure, and temperature in single or dual-loop operations. The controllers can take in 4-20mA analog input signals and RTDs, or thermocouples directly. The controller compares the input to a setpoint. As the input deviates from the setpoint, the controller sends an analog or digital signal to a device such as a control valve that operates to bring the measured unit back to the setpoint. Many controllers have RS-485 interface so they can be used with personal computers or larger systems.
Panel Meters & Rate Indicators
Precision Digital Panel meterPrecision Digital Panel meter
Panel meters and indicators are used to receive and display process measurements from Flow, Level, Pressure, Temperature Transmitters and other devices. In addition to displaying the measured process variable in engineering units, the panel meters are often used to display flow totals, level in multiple units like gallons and inches, and alarms when a process exceeds limits set by the user.
In addition to displaying process and alarm information, a retransmission of the process variable, usually a 4-20mA signal, and/or digital relay outputs can be used to send information to control rooms, distributed control systems, or to other devices like pump controls which provide single on/off or multi-pump alternation.
As their description indicates, panel meters and indicators are usually mounted in panels or enclosures where operating personnel can monitor them.
Flow Recorders
Industrial recorders provide data acquisition and recording by accepting analog voltage, RTD and other inputs which represent process variable conditions such as flow, level, pressure and temperature.
The results are printed on a paper chart or they are displayed on an LCD screen with paperless recorders. Recorders can also provide alarm relay outputs if inputs exceed user selected set points. The recorders can also retransmit a process variable via an analog 4-20mA output, and can perform totalizing functions. Some recorders can be used as controllers to provide outputs to control valves and other devices when process inputs differ from set points.
Some recorders can also be built with Ethernet connectivity with support for common protocols to provide net working to a local area network or the world wide web. For data export, a removable SD card or USB flash storage capabilities are available on some models.
Flow Strainers
The presence of foreign particles entering a control valve or other high precision controlling or monitoring device can seriously affect its accuracy and dependability. In extreme cases the internal parts can be completely destroyed.
Strainers are installed close to the inlet side of precision equipment to prevent pipe chips, scale, rust, welding slag and other harmful material from entering the equipment.
Strainers are built of various materials such as cast iron, carbon steel, aluminum bronze, stainless steel and other materials to withstand corrosive chemicals and salt water. They are built in various configurations such as Y, T, Basket, and duplex to accommodate pipe and process needs. The above image is a Mueller model 792BH, an example of a duplex strainer.
Flow Switches
Flow switches are often used when a simple economical, yet reliable, instrument is required to determine if air, gas, liquid, or solids are flowing in a pipe within a targeted flow range.
Flow switches are usually mounted directly in a pipeline. The most common types are paddle, piston, shuttle and thermal dispersion (no moving parts).
Normally flow switches send an electronic or electric contact output to a valve or other device to begin or end the flow in the line.
