Overcoming Signal Attenuation in Industrial Wireless Transmission

Wireless signals facilitate mobile and remote connections
of industrial process measurement and control equipment

Wireless connections for process measurement and control devices continue to grow in their application range and adoption. The ease with which remote, mobile, even nearby devices and equipment can be connected to monitoring and control stations keeps wireless connectivity a considered option for many facility modifications and additions.

How do you know if the wireless connection you intend to establish will work? It's not a question of whether the gear will function properly, but one of whether the signal will be able to find its way from point A to point B. Signal attenuation is the reduction in signal strength that occurs along the path between two points. Too much attenuation and the signal is not effective in delivering data to the destination. Two main elements contribute to signal attenuation.

Distance

Radio signals deteriorate over the distance traveled. This attenuating factor can be overcome by boosting transmission power, but regulatory limits are in place that disallow much in the way of increasing transmission power. Keeping in mind that signal attenuation at a level that renders a transmission indecipherable, just caused by distance alone, requires a very substantial distance. That said, there are several effective solutions that can be put in place. One involves increasing the height of the transmission antenna. Another is to install a repeater at a point along the transmission path. A repeater, properly placed, will effectively receive the signal from the transmitter, then transmit a new signal of greater strength that replicates the original received data. The use of repeaters can greatly extend the distance spanned by a wireless transmission.

Obstructions

Many are familiar with the objective of establishing "line of sight" transmission paths between transmitter and receiver. Physical structures and materials of all types should be considered detrimental to the transmission of wireless signals. A basic understanding of Fresnel zones is helpful in overcoming the barriers presented by physical obstructions. As with distance, antenna height or location can be a significant factor in dealing with the challenge of obstructions. Repeaters, described earlier, can be instrumental in getting your signal over or around otherwise impassable obstructions.

Routing wireless signals presents different, but no more complicated, challenges than routing cable. The tools are different, the medium is different, but you are still just trying to find a way from point A to point B. With experience, wireless signal propagation becomes is mundane is routing conduit.

Share your industrial wireless ideas and challenges with the experts at Analynk Wireless. Analynk Wireless manufactures equipment used to establish wireless process connections across the room, across the plant site, across the highway, and around the globe.

Industrial Wireless Application: Remote Equipment Monitoring

The A16000 Expansion Module increases the I/O
capacity of a standard wireless transmitter or receiver
Image Analynk Wireless, LLC

Imagine yourself a newly hired facilities manager, the go-to person responsible for the proper and continuous performance every machine on site. One machine in particular, you are informed, is a large walk-in refrigerator that houses the primary raw material for the production operation. There is a lot riding on that machine because the stored material is useless if not kept cold. Oh, and by the way, the plant site is bisected by a public street and the refrigerator is located across the street from the main building where the facilities office is housed. Your assessment of the equipment reveals that a lone temperature alarm device monitors refrigerator temperature and sounds a loud horn if the refrigerator temperature reaches a high limit setpoint. There are no existing wire pathways between the main building and the walk-in refrigerator that are available for your use.

Clearly, the level of risk associated with the refrigerator is high. It merits implementation of an improved strategy to monitor refrigerator performance. Things under consideration include some the following items.

• A real time display of the current refrigerator temperature in the facilities management office. 
• Analysis of the temperature data for an upward or downward trend that might indicate the beginning of a malfunction of the cooling system or controls.
• Monitoring of refrigeration compressor motor current, which can be related to the temperature data to confirm that the compressor is operating when it should.
• Real time display of refrigerant suction and discharge pressures.
• Analysis of refrigerant suction and discharge pressure to identify trends or conditions that may indicate service is needed or malfunction is imminent.
• Verify the door to the refrigerator is closed.
• Monitor evaporator fan motor current to verify that all fans are operating.

The greatest challenge in this application is not the gathering of the information, nor its analysis. The difficulty, as well as a substantial cost and time constraint, is delivering the information from the point of measurement to the point of use. Analog signals for real time temperature, refrigerant pressure, and motor current can be easily derived through the addition of sensors to the equipment. The only sensors likely to require intrusive work to install are those for refrigerant pressure. Routing the measurement signals to the facilities office across the road may prove difficult.

A wired connection between the measurement location to the facilities office will require either an underground or overhead routing of cable, traversing the public road. Permission from state, county, and/or local jurisdictions may be required and present potential barriers to timely completion of the project. The cost to install the cabling will be substantial. The distance may be long enough for signal attenuation to be a concern.

The best solution, in terms of initial cost and time to completion, is to establish a dedicated wireless connection between the walk-in refrigerator and the facilities office.

 A multi-input transmitter is installed at the walk-in refrigerator. The transmitter converts digital (switch) and analog input signals into encrypted digital data and transmits in the 900 MHz band to the receiver installed in the facilities office. The receiver decrypts the received data and mirrors the original analog and digital signals at its output terminals. Wireless overcomes the barriers presented by a wired installation, allowing completion in a timely manner at substantially reduced cost.

If you can operate a walkie-talkie, you can establish industrial wireless connections between remotely located, or mobile, equipment and central monitoring locations. Share your ideas and challenges with industrial wireless experts, leveraging your own knowledge and experience with their application expertise.

Remote Monitoring of Valve Position

Battery powered industrial wireless transmitter
factory installed in hazardous area rated enclosure
with hazardous area rated antenna.

The use of a centralized control or monitoring station is prevalent throughout many industrial applications. Employing a single location as collector and processor of all available information has operational advantages. 

Operations with control valves installed at remote locations face the challenge of determining whether the valve is responding properly to control commands or the demands of the process. Older systems, and some not so old systems as well, may have in-place valves that do not provide a confirmation signal of valve position. Many products are available for retrofitting this capability to a wide range of existing valves, but the challenge of delivering the valve position signal to the control center remains. It is unlikely that spare signal cable conductors were installed at the time of valve installation, so there are two clear options.

• Install signal cable from the valve position indicator to the control center.
• Install a wireless signal transmission system for the valve position indicator.

Unless the valve is located very close to the control center, the wireless option offers a more simple and cost effective method of connecting the valve position transmitter with the control center. Here are the basic tasks.

• Install transmitter at valve location in a suitable enclosure.
• Provide power to radio transmitter. Almost any power source can be accommodated. Power consumption is low enough to allow the use of a small solar panel and battery arrangement, if needed.
• Connect the valve position transmitter output to the radio transmitter input.
• Install a companion radio receiver at the control center, or where a wired signal can be routed easily to the control center. Provide a suitable enclosure.
• Provide power to the receiver, using any of the options available for the radio transmitter described previously.
• Connect the output of the radio receiver to an appropriate input on the central control system.
• Set the communications channels on the radio transmitter and receiver.
• Power up the system.

The transmitter digitizes and encrypts the input signal from the valve position indicator, then transmits the data via 900 MHz or 2.4 GHz to the receiver. The receiver decrypts the data and mirrors the signal that was delivered by the valve position indicator to the radio transmitter. 

This is a simplified illustration, but the implementation of a wireless connection between process components, even with all the details, is not difficult. Transmitters and receivers can be ordered pre-configured, wired, and installed in a specified enclosure, requiring comparatively little field labor. Analynk welcomes customized application challenges and your questions about how to utilize wireless connections in your operation. 

Analynk Wireless manufactures equipment used to establish wireless process connections across the room, across the plant site, across the highway, and around the globe.

Hazardous Area Enclosure for Aurba Access Point... and Others

AP623 Wireless access point enclosure
facilitates installation of commercial equipment
in hazardous industrial locations.

Analynk Wireless continues to expand its extensive line of wireless access point enclosures for hazardous industrial locations. The model AP623 is a recent addition, specially equipped to house the Aruba AP-314 dual band access point.

Analynk access point enclosures accommodate specific wireless access points from a range of manufacturers, facilitating easy installation. Every model includes UL listed explosion proof antennas, a mounting bracket custom tailored for the access point equipment, and RF cables to make the antenna connections. Enclosures have penetrations located to match up with the specified access point. Models are included to house a range of units from Symbol, Cisco, Meru, Aruba, HP, and Motorola, with more models added regularly to accommodate additional wireless access points.

Analynk Wireless specializes in industrial wireless communications. Your wireless communication challenges are welcome at Analynk, so make contact and share your requirements. Combining your process expertise with Analynk's product specialization will produce an effective solution.

The datasheet for the new model is provided below. You can see all the models and their companion access points on the Analynk site.

AP623 Hazardous Area Wireless Access Point Enclosure from Analynk Wireless, LLC

Product Options Match Wireless Equipment to Application

Analynk Wireless offers a broad range of accessories, options, and custom configuration and design services to complement their standard product offering of industrial wireless equipment. The specialty offerings can be used to extend the suitability of a standard product for a specific application, or to create a complete package with all necessary mounting brackets, antennas, cables, and other ancillary equipment needed for a complete installation. Analynk extends the same customizing capability throughout its Telmar line of process measurement and control products, as well.

The company welcomes all inquiries related to custom configuration, accessories, and turnkey system design. Share your wireless connectivity or process measurement and control challenges with the experts and Analynk, combining your process knowledge and experience with their design expertise to develop an effective solution.

Analynk Wireless Enclosure Options and More from Analynk Wireless, LLC

Rotary Vane Actuators for Quarter Turn Valve Automation

The inside of a rotary vane actuator
Image courtesy of Kinetrol

A rotary vane actuator is part of an automated valve assembly. Its role is to change the position of the valve trim, converting the motive force of fluid pressure in the actuator into torque at the valve stem.

Quarter turn valves are widely used in industrial fluid processes. Their application is primarily for operations requiring fully open or fully closed valve trim positions, although some do provide modulating service. A rotation of the valve stem through a 90 degree arc will reposition quarter turn valves between open and closed positions. A rotary vane actuator is well suited for driving this type of valve, with its own 90 degree arc of movement.

A rotary vane actuator is specific for application to quarter turn valves. A pressure tight housing contains a movable vane which is sealed to the sides of the pressure chamber by means of a low friction gasket. Inlets into the chamber on opposing sides of the vane allow a controller to produce a pressure differential across the vane. The vane will move, responding to the pressure differential, in either direction. A shaft is connected to the vane and the vane acts like a lever to rotate the shaft as the vane is moved by fluid pressure. The torque produced by the actuator assembly is primarily dependent upon the applied fluid pressure.

Hydraulic rotary vane actuators have the ability to handle large amounts of fluid and dynamic motions, exhibiting also qualities of durability and compactness. Pneumatic vane actuators use plant air pressure as the motive force. Both types generally have few moving parts and require little regular maintenance. A variety of typical automation accessories and options are available to customize a unit for a particular application.

Analynk Wireless manufactures wireless connectivity solutions for industrial applications and process control. Making cable free connections among process control equipment and instruments, across the room, across the property, across the globe.

Shell and Tube Heat Exchangers

View of the inside of a shell and tube heat exchanger shows
the tubes through which one of the transfer fluids passes.

Automobiles are part of the backbone of modern society, for both personal and commercial use. While being familiar everyday objects, they also contain systems which need to be constantly maintained and in-sequence to ensure the safety of both the machine and the driver. One of the most essential elements of car ownership is the understanding of how heat and temperature can impact a car’s operation. Likewise, regulating temperature in industrial operations, which is akin to controlling heat, is a key process control variable relating to both process operation and operator safety. Since temperature is a fundamental aspect of both industrial and consumer life, heat management must be accurate, consistent, and predictable. Many devices have been developed for the transfer of heat from one substance to another, with myriad applications throughout modern society.

A common design of heat exchangers used in the oil refining and chemical processing industries is the shell and tube heat exchanger. A pressure vessel, the shell, contains a bundle of tubes. One fluid flows within the tubes while another floods the shell and contacts the outer tube surface. Heat energy conducts through the tube wall from the warmer to the cooler substance, completing the transfer of heat between the two distinct substances. These fluids can either be liquids or gases. If a large heat transfer area is utilized, consisting of greater tube surface area, many tubes or circuits of tubes can be used concurrently in order to maximize the transfer of heat. There are many considerations to take into account in regards to the design of shell and tube heat exchangers, such as tube diameter, circuiting of the tubes, tube wall thickness, shell and tube operating pressure requirements, and more. In parallel fashion to a process control system, every decision made in reference to designing and practically applying the correct heat exchanger depends on the factors present in both the materials being regulated and the industrial purpose for which the exchanger is going to be used.

Schematic of shell and tube heat exchanger

The industrial and commercial applications of shell and tube heat exchangers are vast, ranging from small to very large capacities. They can serve as condensers, evaporators, heaters, or coolers. You will find them throughout almost every industry, and as a part of many large HVAC systems. Shell and tube heat exchangers, specifically, find applicability in many sub-industries related to food and beverage: brewery processes, juice, sauce, soup, syrup, oils, sugar, and others. Pure steam for WFI production is an application where special materials, like stainless steel, are employed for shell and tube units that transfer heat while maintaining isolation and purity of a highly controlled process fluid.

Shell and tube heat exchangers are rugged, efficient, and require little attention other than periodic inspection. Proper unit specification, selection, and installation contribute to longevity and solid performance.

Analynk Wireless manufactures wireless connectivity solutions for industrial applications and process control. Making cable free connections among process control equipment and instruments, across the room, across the property, across the globe.