Using Orifice Plates to Measure Flow

The orifice plate is the simplest of the flowpath restrictions used in flow detection, as well as the most economical. Orifice plates are flat plates 1/16 to 1/4 inch thick. They are normally mounted between a pair of flanges and are installed in a straight run of smooth pipe to avoid disturbance of flow patterns from fittings and valves.

Three kinds of orifice plates are used: concentric, eccentric, and segmental (as shown in Figure 1).

orifice plate
Fig. 1 - Orifice plates (click for larger view)
The concentric orifice plate is the most common of the three types. As shown, the orifice is equidistant (concentric) to the inside diameter of the pipe. Flow through a sharp-edged orifice plate is characterized by a change in velocity. As the fluid passes through the orifice, the fluid converges, and the velocity of the fluid increases to a maximum value. At this point, the pressure is at a minimum value. As the fluid diverges to fill the entire pipe area, the velocity decreases back to the original value. The pressure increases to about 60% to 80% of the original input value. The pressure loss is irrecoverable; therefore, the output pressure will always be less than the input pressure. The pressures on both sides of the orifice are measured, resulting in a differential pressure which is proportional to the flow rate.
Orifice plate flow pattern
Orifice plate flow pattern (click for larger view)

Differential Pressure Transmitter
Differential pressure
transmitter used to
calculate flow.
Segmental and eccentric orifice plates are functionally identical to the concentric orifice. The circular section of the segmental orifice is concentric with the pipe. The segmental portion of the orifice eliminates damming of foreign materials on the upstream side of the orifice when mounted in a horizontal pipe. Depending on the type of fluid, the segmental section is placed on either the top or bottom of the horizontal pipe to increase the accuracy of the measurement.

Eccentric orifice plates shift the edge of the orifice to the inside of the pipe wall. This design also prevents upstream damming and is used in the same way as the segmental orifice plate.

Orifice plates have two distinct disadvantages; they cause a high permanent pressure drop (outlet pressure will be 60% to 80% of inlet pressure), and they are subject to erosion, which will eventually cause inaccuracies in the measured differential pressure.

Contact Power Specialties with any process flow question or requirement. You can find them by visiting or by calling (816) 353-6550.

Chino IRMA Analyzer Re-Zeroing Calibration Procedure

The Chino IM series is an on-line multi IR wavelength analyzer utilizing the infrared absorption technology for measuring product constituent and/or thickness. Watch the video below for instructions on re-zeroing the IRMA calibration. 
(816) 353-6550

Easily Select a Fox Thermal Gas Mass Flow Meter with Help from this Tool

Saving time and being accurate. Two very important elements to every engineer's workday. Anytime a tool comes along to provide both, it needs to be featured.

Fox Thermal, the manufacturer of thermal gas mass flowmeters, has an excellent Web-based configurator that's easy to use and provides accurate, detailed output.

After a quick registration process, anyone interested in applying a thermal gas mass flowmeter will be guided through a meter section process. The app will help you select the correct model, and then begin asking more specific application questions.

Finally, the application presents a summary of your requirements, and then checks if you want to have the Fox Thermal sales department provide a quotation.

Check out this video for a tutorial on how the gas mass flow meter configurator works.

Courtesy of Power Specialties
(816) 353-6550

Yokogawa Model GX10/GX20/GP10/GP20 Paperless Recorder First Step Guide

Yokogawa Model GX10/GX20/GP10/GP20 Paperless Recorder
Yokogawa Model GX10/GX20/GP10/GP20 Paperless Recorders
The Yokogawa GP series is an industry-first multi-point touch panel, to improve intuitive and smart operator control. Users can scroll, pan, zoom historical data, and even write freehand messages on its dust-proof and water-proof display. It delivers industry leading reliability and measurement accuracy. The GP series is ideally suited for monitoring or troubleshooting long term physical or electrical trends.

The GX series is an industry-first multi-point touch panel, to improve intuitive and smart operator control. Users can scroll, pan, zoom historical data, and even write freehand messages on its dust-proof and water-proof display. The Yokogawa GX series delivers industry leading reliability and measurement accuracy. Its custom graphics accommodates application or process-specific displays, while a wide range of communication protocols guarantee compatibility with your network architecture. It's simple for operators to view and retrieve past data with automatic email and FTP notifications.

Below in the embedded document is the First Step Guide for your review.