#White Papers
Process Industry Increasingly Goes Wireless
IHS Introduce Wireless Sensor
Process engineers and operators need to measure the conditions of operations to make quality products efficiently and safely. In the past, larger individual pieces of process equipment were fitted with sensors to help with this measurement. But missing was the ability to monitor the supporting equipment due to the high cost of installing and maintaining myriad wired sensors.
Conditions have changed with the introduction of more affordable wireless sensor systems. These systems give engineers and operators the ability to monitor more parameters of a process allowing the full process to be continuously analyzed and optimized.
One vendor in the space, Emerson Process Management, has coined the phrase ”pervasive sensing” to represent this notion of highly monitoring a process system to improve its overall efficiency. Pervasive sensing enables facilities such as refineries and chemical plants to acquire more and deeper data to enable their operations to run more smoothly and efficiently.
Vibration Monitoring
Wireless sensor systems were initially developed for the military for use in battlefield surveillance. The first civilian industrial wireless systems were developed for vibration sensing to monitor rotating equipment. Vibrations can be a sign of wear, misalignment or other out-of-balance conditions that would degrade equipment health. Identifying a baseline and subsequent changes in vibration allow for preventative maintenance to be scheduled to address issues before equipment fails. This approach can avert unplanned shutdowns and reduce inefficiency costs.
Manufacturers in recent years have developed a range of sensors that are compatible with wireless systems. These include temperature, pressure, proximity, flow, flame, gas and acoustic sensors, all of which perform essentially the same job: identifying performance issues. Measurements that formerly were difficult, expensive to perform or were done only when necessary now have become easier and optimized to be done on a continuous basis. At the same time, software applications have further improved aggregating and analyzing millions of data points into actionable information, enabling prompt response and offering better insight for decision-making.
A system of wireless sensors is known as a wireless sensor network (WSN). Sensors are equipped or connected to Wi-Fi transmitters that convert sensor signals into a radio transmission. More than one sensor can be connected to each transmitter and each transmitter (with its connected sensors, a microcontroller and antenna) are known as a node. The node receives power, either from a battery or from energy harvested from the process, and communicates with the Wi-Fi receiver. The cost of a sensor node is based on the quantity and complexity of the sensors; costs can range as high as hundreds of dollars. The radio signal is sent and interpreted by a receiver that then converts the wireless signal to a desired output, such as an analog current to be used by computer software.
Bi-directional Networks
More advanced networks are bi-directional, allowing control based on sensor activity. These networks use transceivers to communicate in both directions. Manufacturers have been developing wireless control devices such as valves, actuators and wireless controllers that not only identify operational issues, but also allow an operator to resolve or minimize those issues. Wireless sensor networks can be installed wherever needed and without wired infrastructure that would otherwise make the installation cost-prohibitive.
Applications for wireless sensor networks are almost limitless. Beyond sensor measurement characteristics, some key requirements should be considered. When selecting a wireless sensor system, accuracy, range, frequency and sensor types are all important. Most wireless sensors are as accurate as wired sensors, although typically they do not provide a continuous signal and transmit every few seconds to preserve battery power. This can be important in selecting the device, especially if uninterrupted measurement is necessary. The range of wireless systems varies widely depending on whether the application is indoors or outdoors, and the location of other obstacles that may lie between the transmitter and receiver. Some are designed for short-range indoor applications while others transmit to a receiver that may be located miles away.
Transmitting through obstacles such as machines and walls reduces indoor range capability while a transmitter broadcasting outside is capable of transmitting much farther. The frequency of radio transmission is determined by laws that vary by country and region. In the U.S., 900MHz, 2.4GHz (WiFi) are the major frequencies used as part of the unlicensed ISM (industrial, scientific and medical) band to transmit signals. Operating at 900 MHz yields almost twice the range of what is possible at 2.4 GHz, but is permissible in fewer countries. In Europe, wireless products typically operate on 868MHz or 2.4GHz.
Wireless Advantages
Wireless sensor technology can offer substantial advantages over traditional wired sensors. Adding remote sensors without the cost of laying cables or wires can result in up to 90% installation savings, as well as creating process improvements through improved monitoring and correction. Wireless sensors and controls can be used in locations that are remote and in locations that are dangerous to access due to extreme conditions such as temperature, pressure and moving mechanisms.
Employee productivity may increase, too, when operators no longer need to travel to obtain remote data. Continuous sensing implements condition-based maintenance, which allows for maintenance to be performed when needed and not on a time-based schedule.
Until recently, the cost and complexity of wired sensors often prevented engineers from achieving precise process monitoring. The reduction in the cost of deploying sensors with wireless technology means that engineers and plant operators are able to expand their sensor count and adopt pervasive sensing as a means to improve their operating efficiency and profitability.
