Thursday, December 31, 2015

Vision Systems for Real Time Water System Analysis and Treatment

canty particulate analysis
Image courtesy of JM Canty
Effective monitoring of intake and effluent flows presents a difficult challenge to the water treatment industry in many ways. Real time knowledge of water condition can inform downstream or upstream processes how to change treatment regimes to affect a consistent, positive outcome in relation to standards. FOG’s are a constant headache in wastewater treatment. Particulate can build in pipelines causing significant flow reductions and overflows.

Water drawn from rivers, lakes and shed areas for human and industrial uses can become laden with particulate due to weather or other natural events which can overload filtering capacities intended to purify the water prior to use. Invasive species such as the zebra mussel can collect at intake and outlet pipes and reduce volume flows. Vision technology can provide real time monitoring solutions and, in addition to providing a visual verification of process conditions, has resolved the longstanding fouling issues instruments have generally had in extreme processes. 

Analysis of particulate based on size, shape and percent solids can indicate varying conditions of feed water to operators who can then optimize treatment or close intakes while the upset conditions prevail, thereby preserving water quality. This technology also provides the user with visual verification of process conditions and together with Ethernet transmission protocol, view and analysis can be provided at any point throughout local or wide area networks.

Read, or download, the full research paper (courtesy of Canty Process Technology) below:

Tuesday, December 29, 2015

Industrial Temperature Sensors: Basics of Thermocouples

industrial thermocouples
Industrial thermocouples
(courtesy of Applied Sensor Technology)
Thermocouples are the most widely used industrial temperature sensor found in industrial processes today. They are rugged, relatively inexpensive to manufacture, and provide fairly good accuracy.

Thermocouples operate on the "Seebeck Effect", which is the phenomena whereby two dissimilar metal conductors (wires), joined at two points, with one point kept at a known constant temperature, produce a measurable voltage difference between the two conductors.

Thermocouple types - such a type J, type K, type R, and type S - refer to the alloy combinations used for the conductors and are based on standardized color designations. 

Thermocouples are used widely in industrial processes in industries such as power generation, primary metals, pulp and paper, petro-chemical, and OEM equipment. They can be fabricated in protective wells, and can be housed in general purpose, water-tight, or explosion-proof housings.

The following video provides a basic visual understanding of thermocouple wire, how a T/C junction is determined, and also discusses thermocouple connectors, polarity and some aspects of construction (such as grounded vs. ungrounded vs. open tip).

Wednesday, December 16, 2015

Pressure and Temperature Transmitters/Switches - Safety Right Out of the Box

safety transmitter
UEC Safety Transmitter
Many process safety experts are looking for sustainable ways to help their personnel improve their safety critical loops, do it in the most cost-effective way possible, and with a minimum of complexity. The problem is the traditional approaches to deploying a full blown safety system are expensive and very complex, and still may not deliver the needed risk reduction for some safety critical systems and loops.

In the sensor subsystem for example, United Electric’s certified safety transmitter for pressure or temperature has opened up a new, less costly, less complex path for designers, I&C engineers, and maintenance personnel. It has something very unique. In addition to a 4-20 mA output, is has an embedded programmable high-capacity relay which exida has certified as a safety variable output. Now you have a device that provides designers the option of a hard wired trip in less than 100 milliseconds, with a tenth of a percent repeatability, while still providing the monitoring functions of a traditional continuous analog output.

For equipment under control, like pumps and compressors that require protection, or processes where rapid excursions can initiate dangerous events, this unique pressure and temperature transmitter, (certified for use in SIL2 safety instrumented functions, with SIL3 capability)  is addressing process safety time constraints, coupling issues with PLC and DCS’s, and adding diversity to the safety instrumented function.

The safety transmitter has a safe area fraction of 98.6% with breakthrough, automatic, self diagnostics and is one-third the cost of typical certified process transmitters.


Tuesday, December 15, 2015

An Introduction to Industrial Pressure, Differential Pressure, and Temperature Switches

pressure switch
Pressure switch with large diaphragm
Most industrial applications require the monitoring of pressure and temperature of a process. Pressure and temperature measurement can be accomplished either by transmitters, gauges or by switches.
This post will provide a quick introduction of industrial electromechanical pressure switches and temperature switches.

An industrial pressure and temperature switch is made up of the three main components: 1) the sensor, 2) the housing and 3) the switching element.

The correct combination of each component assures proper application of the device for its intended use.

Sensor

The sensor is located above the pressure port and process connection. For pressure and differential pressure switches, there are several varieties of pressure sensors to choose.  The most common types of pressure sensors are:

Metal Bellows - an accordion-like device that provides linear expansion and contraction based upon the application of pressure or vacuum. Bellows are excellent sensors because they provide good overall pressure range and are fairly sensitive to small changes in pressure.

Piston - A rod and o-ring combination that moves linearly in direct response to applied pressure. Piston sensors are normally only applied to only very high pressure ranges. They have very small surface areas and wide deadbands (the change in pressure required to change the position of the switch output).

pressure switch
Pressure switch with piston sensor
Diaphragm - A thin, elastomer or metallic membrane, often with a rolled lip that allows for greater movement. The diaphragm has a large surface area and provides the most sensitivity to pressure change, making it ideal for low to mid-range pressure sensing.

Housing

Housings are classified and selected based on the atmosphere in which they’ll be used. Housing ratings are classified by several national and international agencies such as NEMA and CENELEC. Very generally put, housings can be rated as general purpose, dust & water resistant, water tight, corrosion resistant and hazardous (explosive) environments. Proper selection of the housing is important to the operation and life expectancy of the device. In hazardous environments, proper selection is absolutely critical. If unsure about the housing classification, consultation with an applications expert is required.

Switching Element

The switching element refers to the signaling device inside the enclosure that responds to the movement of the sensor. It can be either electrical or pneumatic, and provides an on-off signal (as opposed to an analog, or proportional signal produced by transmitters).

differential pressure switch
Differential pressure switch
The switching element is most times a “micro” type single pole, double throw (SPDT) electrical switch. These microswitches come in many configurations and electrical ratings, such as double pole, double throw (DPDT), 120/240 VAC, 12VDC, 24VDC, and hermetically sealed.

For the switching element and the sensor, it is very important to know the cycling rate (number of on vs. off times over a period of time) the instrument will see. Since both of these elements are mechanical, they will eventually wear out and need to be replaced. Switches are an economical and strong performing choice for low to medium cycle rates. For extremely high cycle rates, the use of solid state transmitters are a better choice.

temperature switch
Temperature switch
Temperature Switches

An electromechanical temperature switch (sometimes called a thermostat) is, for the most part, a piston type pressure switch connected to an oil filled capillary and bulb sensing element. The thermal expansion of the oil inside the bulb and capillary creates the pressure and linear movement upon the piston sensor of the switch. The bulb and capillary elements can be supplied in copper or stainless steel, and at various lengths.

There are many more details to selecting and applying electromechanical pressure and temperature switches. This post is only intended to provide a very general introduction. It is always suggested to discuss your application with a qualified applications engineer so that you are assured to get the longest lasting, most economical and safest instrument possible.