Siemens SITRANS LUT400 Pump Level Assist Routines

Siemens SITRANS LUT400

The Siemens SITRANS LUT400 series controllers are compact, single point, long-range ultrasonic controllers for continuous level, or volume measurement of liquids, slurries, and solids, and high accuracy monitoring of open channel flow.

The preconfigured pump routines in the SITRANS LUT 400 allow you to choose the best pump control scenario for your application. In the video below, you will see how the assist pump routines work.

The SITRANS LUT 400 has three assists pump routines available:

• Alternate duty assist
• Service ratio duty assist
• Fixed duty assist

The fixed duty assist routine mainly uses one pump to control the liquid level. In this example, pump 1 will always start before pump 2. When the liquid level reaches the pump 1 “on” set point, pump one will turn on. If the liquid level continues to rise while pump one is running, then pump 2 will start. Pump 2 will assist pump 1 to lower the liquid level. Both pumps we'll turn off when the liquid level reaches the “off” set point. This pump sequence is fixed. Pump 1 will always start first, then if necessary, pump 2 will assist pump 1.

The alternate duty assist routine rotates between both pumps to control the liquid level. Pump 1 will start first. If it cannot keep up with the inflow, then pump 2 will turn on and assist pump 1. Both pumps will run until the liquid level reaches the pump “off” set point. On the next cycle, pump 2 will be the first pump to start. Pump 1 will assist pump 2 if it is necessary. The starting pump will continue to alternate between pump 1 and pump 2 after each filling cycle.

The service ratio duty assist routine rotates between both pumps based on the defined service ratio. In this example the service ratio is split equally between both pumps. The SITRANS LUT will choose which pump starts first based on this ratio. Since pump 1 has the lowest runtime hours it starts first. Pump 2 will assist pump 1 if the level continues to increase.  On the next cycle, pump 2 to will start first. Pump 1 will assist pump 2 if necessary. The service duty ratio assist routine will continue to maintain the runtime ratio for each filling cycle.

The Basics of Continuous Emissions Monitoring (CES)

Continuous emission monitoring system
(courtesy of AMETEK Process Instruments)

Continuous emission monitoring systems, known as CEMs, are used by plants and facilities to assure compliance with the EPA’s requirement to limit the amount of certain gasses (such as CO2) into the air. A CEM samples, measures, collects data, records and reports the gas emissions information. CEM systems can also measure and report gas flow, gas opacity and moisture content.

CEMs are typically used to monitor flue gas emissions (the gas exiting to the atmosphere via a flue from an furnace, oven, or boiler).

CEM system are made up of a sampling probe, a filter, a sampling line, a means to condition the gas being sampled, a gas used for calibration, and a group of gas analyzers geared toward the gases being monitored.

The most common gases measured are: carbon dioxide, carbon monoxide, airborne particulate, sulfur dioxide, volatile organics, mercury, nitrogen oxides, hydrogen chloride, and oxygen.

Continuous emission monitoring systems operate by extracting a small diluted gas sample into the CEM via a sampling probe. The sample is diluted with air because of the hot, wet, and contaminant carrying nature of the stack gas. Once the sample gas is taken, the concentration of its components are calculated through a variety of technologies such as infrared and ultraviolet adsorption, chemiluminescence, fluorescence and beta ray absorption. After analysis, the sample gas exits the analyzer and is usually vented outdoors.

Another method of extracting a sample gas is called "hot dry" extraction or "direct CEMs". In this situation, the sample gas is not diluted with air, but instead the pure sample is carried through a heated line at high temperatures, filtered to remove contaminants, and dried to remove moisture. This method is preferred when O2 measurement is required because there is no additional oxygen being introduced via the air dilution as described in the above method.

The EPA requires a data acquisition and handling system to collect and report the data, so the CEM must operate continually and provide data on an hourly basis.

For more information about CEM systems, contact:

Ives Equipment Corporation
www.ivesequipment.com
(877) 768-1600

Vision Systems for Real Time Water System Analysis and Treatment

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:

Real Time Visual Analysis and Monitoring or Feed Waters for Optimization of Treatment Regimes from Ives Equipment

Industrial Temperature Sensors: Basics of 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).

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

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.

Series One Safety Transmitter, Pressure and Temperature Switch from Ives Equipment

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

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 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

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 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.

Basics of Differential Flow Devices

Orifice plate flow meter
(courtesy of Siemens)

The differential flow meter is the most common device for measuring fluid flow through pipes. Flow rates and pressure differential of fluids, such as gases vapors and liquids, are explored using the orifice plate flow meter in the video below.

The differential flow meter, whether Venturi tube, flow nozzle, or orifice plate style, is an in line instrument that is installed between two pipe flanges.

The orifice plate flow meter is comprised the circular metal disc with a specific hole diameter that reduces the fluid flow in the pipe. Pressure taps are added on each side at the orifice plate to measure the pressure differential.

According to the Laws of Conservation of Energy, the fluid entering the pipe must equal the mass leaving the pipe during the same period of time. The velocity of the fluid leaving the orifice is greater than the velocity of the fluid entering the orifice. Applying Bernoulli's principle, the increased fluid velocity results in a decrease in pressure.

As the fluid flow rate increases through the pipe, back pressure on the incoming side increases due to the restriction of flow created by the orifice plate.

The pressure of the fluid at the downstream side at the orifice plate is less than the incoming side due to the accelerated flow.

With a known differential pressure and velocity of the fluid, the volume metric flow rate can be determined. The flow rate “Q”, of a fluid through an orifice plate increases in proportion to the square root the pressure difference on each side multiplied by the K factor. For example if the differential pressure increases by 14 PSI with the K factor of one, the flow rate is increased by 3.74.