Thursday, April 19, 2018

Wireless Process Control Instrumentation

Wireless Process Control Instrumentation
Cost cutting is a fact of life for all industries. Whether it be for more efficient operations, or complying to current regulations, the need to build a better mouse trap is always present.

A very promising cost-cutting technology is wireless instrumentation. Wireless provides a compelling argument to change when you consider installation and overall cost effectiveness. Even more so when the application is located in a harsh environment, or where toxic or combustible situations exist. These robust devices provide critical performance data around the clock in the most inhospitable place in the plant, and operate through rain, wind, high temperatures and high humidity.

Untethered by cables and hard-wiring, wireless instrumentation is easier to deploy and monitor. Wireless transmitters are available for monitoring virtual all process variables such as pressure, temperature, level, flow, density, and acoustics. Networks of up to 100 (900 MHz) field devices can be created and then monitored by a single base radio or access point, with a typical communication range of over 1/2 mile. By communicating through the industry standard, Modbus, compatibility between device manufacturers is ensured.
Wireless Instrumentation
Wireless Instrumentation (Accutech and Foxboro)

The most obvious reason for choosing wireless over hard-wiring is the cost savings associated with running wires and cables. Savings estimates as high as 70% can be realized by deploying wireless field devices, compared to the same application using cables. Additional savings are realized when you consider that these devices use batteries and that the cost of adding to a network is borne only by the cost of the new device.

Wireless instruments also provide significant benefits in safety and compliance by keeping personnel out of hazardous areas. Areas that would require occasional human visitation can be safely monitored through remote monitoring.

So, what's the hold up? If the benefits are so clear, and the argument is so strong, why is there still reluctance to embrace wireless technology?

There are three main concerns:

Reliability
Wireless instrumentation must provide the same reliability (real and perceived) as traditional wired units. Every engineer, operator and maintenance person knows wires. Troubleshooting wires is easy, and understanding the failures of wires is basic - the wire is either cut or shorted. With wireless however, air is the communication medium and radio signals replace wires. Radio signals are more complicated than wires in terms of potential problems. For instance, signal strength, signal reflection and interference are all possible impediments to reliable links.

The good news is that radio frequency design is continuously improving, and the use of new and advanced technologies, such as frequency hopping receivers and high gain antennas, are enabling wireless devices to create highly reliable links.

Adapting to Existing Infrastructure
Wireless instrumentation networks have to adapt to the existing environment and the placement of structures and equipment. Most times it's just not practical to relocate equipment just to create a reliable wireless link. This can make it challenging to find the optimum location for a base radio or access point that is capable of providing a reliable communication link to your wireless instruments. Furthermore, accommodating the best strategy for one wireless device could negatively affect links with other devices on the same network.

The challenges of adaptability are being overcome by providing better frequency bands (such as 900 MHz). These bands provide longer range, the ability to pass through walls, and offer more saturating coverage. Other ways to overcome adaptability concerns are through the use of external, high gain antennas mounted as physically high as possible, and also by using base radios with improved receiving sensitivity.

Integration with Existing Communications
Engineers, operators, and maintenance crews are challenged by integrating wireless instrumentation networks with other, existing, field communications systems. The issues of having to manage and troubleshoot multiple networks adds levels of complexity to existing systems. This creates a conflict between the financial argument to adopt wireless instrumentation and the possible costs to increase the data gathering capabilities of an existing system. For instance, SCADA systems need to be able to handle the additional data input from wireless devices, but may not have the capacity. Adding the additional data capacity to the SCADA system can be expensive,  and therefore offset the wiring and cabling savings.

The financial argument for industry to adopt wireless instrumentation networks is persuasive, but its acceptance in the process control industry is slow. Reliability, acclimation, and integration are all challenges that must be overcome before widespread adoption occurs. Eventually though, the reality of dramatically reduced deployment and maintenance costs, increased safety, and improved environmental compliance will tip the scale and drive wireless as the standard deployment method.

Always consult with an experienced applications engineer before specifying or installing wireless instrumentation. Their experience and knowledge will save you time, cost, and provide another level of safety and security.

Thursday, April 12, 2018

Mead O'Brien: Problem Solver, Innovator, and Best Total Cost Provider

Mead O’Brien specializes in valves & valve automation, steam & hot water products and systems, instrumentation products, skid designs, field services, surveys, assessments, and consulting. The extensive product and application knowledge possessed by the Mead O'Brien sales force projects to all or part of ten states in the Midwest which includes Missouri, Kansas, Nebraska, Iowa, Oklahoma, Arkansas, Texas Panhandle, Southern Illinois, Western Kentucky, and Southwest Indiana.

Saturday, March 31, 2018

How Your Steam Trap Selection Affects Your Bottom Line Profits: Inverted Bucket Trap vs.Thermodynamic Trap

Steam Trap Selection
Below is a white paper, courtesy of Armstrong International, describing how steam trap selection affects profitability. This document compares Inverted Bucket Traps and Thermodynamic Traps.

The ability to monitor and maintain your facility’s steam trap population directly affects your bottom line. Armstrong’s Steam Testing and Monitoring Systems give you the means to achieve best practice steam system management by proactively monitoring your steam trap inventory.

For more information on Armstrong steam and hot water products, visit Mead O'Brien at https://meadobrien.com of call (800) 892-2769.


Monday, March 26, 2018

Process Instrumentation and Noise

Protect instrumentation from electrical noise.
Protect process instrumentation from
electrical noise.
Instrument noise, and eliminating instrument noise, is important to consider in process control instrumentation. Noise represents variations in process variable measurement that is not reflective of actual changes occurring in the process variable. Typically, electrical devices such as high voltage wiring, electric motors, relays, contactors, and radio transmitters are the primary sources of instrument noise.

No matter the cause for the process noise, the measurement signal in the process is being distorted and is not reflecting the true state of the process at a certain time. Accuracy and precision of process measurements are negatively affected by noise, and can also contribute to errors in control system. Controller output can reflect the noise affecting a process variable.

Grounding allows for the reduction of noise stemming from electrical systems. Shielded cabling and separating signal cabling from other wiring, as well as replacing and repairing sensors, allows for noise reduction. Low-pass filters are a way to compensate for noise, and much of the instrumentation used in process systems incorporates noise dampening features automatically. Determining the best kind of filter to use depends heavily on cut-off frequency, alpha value, or time constant.

The ideal low-pass filter would eliminate all frequencies above the cutoff frequency while allowing every frequency below the cut-off frequency to be unaffected. However, this ideal filter is only achievable mathematically, while real applications must approximate the ideal filter. They calculate a finite impulse response, and also must delay the signal for a bit of time. To achieve better filter accuracy, a longer delay is needed so that the filter computation “sees” a bit further into the future. The calibration of these filters heavily relies on the desired accuracy level of the process, while also taking specific steps in calibration to best fit a particular process.

Noise is important to mitigate because the noise observed while measuring the process variable can produce “chatter” in the final control element of a process. The resulting “chatter” increases the wear of mechanical control elements, such as valves, and will generate additional cost for the process as a whole. The filtered signal lagging behind the dynamic response of the unfiltered signal is a result of the filtered signal’s increased dead time, meaning that signal filters add a delay in sensing the true process state. The solution is to find a mid-point between signal smoothing and information delay, which allows for elimination of noise while not negatively affecting the speed by which information is delivered.

For question about any process control application, or challenge, visit https://meadobrien.com or call (800) 892-2769

Saturday, March 17, 2018

What Are Isolation Rings?

Isolation Rings
Isolation Rings (Ashcroft)
Isolation Rings are used for protection of sensitive and expensive pressure instrumentation, such as pressure switches, transmitters, and transducers. They isolate the instrument from an aggressive or viscous process. The Isolation Ring is mounted inline with process piping and fits between the process line pipe flanges, similar to wafer butterfly valves.

The ring design includes ring has a  flexible inner cylinder that prevents process media from collecting in the instrument, and therefore assuring reliable and continuous pressure measurement. An integrated needle valve allows for fast and easy removal for instrument repair, replacement, or calibration without interrupting the process media flow. The needle valve can also be used for pulsation dampening.

Watch the video below for a more in-depth understanding of how Isolation Rings are installed and operate.

For more information, contact Mead O'Brien by calling (800) 892-2769 or visiting https://meadobrien.com.

Tuesday, February 27, 2018

Commissioning a Glass Level Gauge with a Safety Ballcheck Valve

Safety ballcheck valves are intended to safely isolate boiler and tank level gauges from the process media. Jerguson, a premier manufacturer of safety ballcheck valves and liquid level gauges has put together this video to explain how to commission a glass level gauge with a safety ballcheck valve.

https://meadobrien.com
(800) 892-2769