Fit Wireless Tech To Your Needs
EP Editorial Staff | April 25, 2019
Wireless technology used to move asset-performance data can determine what you analyze, reliability of results, and sensor life.
Much has been written about the Industrial Internet of Things (IIoT), asset-health monitoring, and predictive analytics, as well as the benefits these technologies offer. Discussions of those benefits, however, typically overshadow conversations about another important topic: how to reliably and securely transmit equipment-performance data to a central hub, portal, or cloud network for analysis by algorithms.
While it’s easy to get lost in the technical aspects of wireless data transfer, changes in the behind-the-scenes technologies that do this heavy lifting make the topic worthy of serious consideration. After all, the methods and technologies that organizations employ to transmit data will have a significant impact on how much information they can analyze, the reliability of their results, and how long their wireless sensors will last.
COLLECT, TRANSFER, ANALYZE
Although industrial operations may use different technologies to capture, transmit, and analyze equipment-performance data, their IIoT processes are usually similar.
Step 1: Interconnected wireless or wired sensors installed on pumps, seals, valves, and other equipment collect performance information. Data could include vibration, temperature, pressure, flow rates, torque, thrust, and other conditions. The breadth of data captured, though, depends on the types of sensors installed, battery life, and data-transfer limitations.
Step 2: Sensing instrumentation on an asset transmits data to a portal or on-site network for later retrieval. A variety of factors influence how the data gets from the equipment to the portal, specifically how much data is transmitted and how far the signal must travel.
Step 3: Once a central hub receives the data, advanced algorithms analyze it for patterns, trends, and signs of failure, and direct reliability engineers on how to address problems before they affect asset performance.
The following discussion focuses on the second step: how to reliably transmit data from the equipment to the central hub for analysis. For industrial operations, there are three standard methods of wirelessly transferring data. Each has advantages and limitations.
Most people are familiar with Wi-Fi, which allows them to wirelessly connect personal mobile devices to any number of peripherals. Maintenance crews can use this same technology to monitor critical assets in industrial operations. Because of wi-fi’s limited range, though, these crews can only wirelessly download equipment-performance data when they’re in close proximity to the equipment. After downloading, the data can be sent to vibration analysts, either on site or at a third-party service company, to review for anomalies. While wi-fi transmission greatly simplifies data downloading, the technology’s limited range still requires maintenance crews to physically walk around the plant to retrieve this information.
• Wi-fi is easy to install and use.
• It can leverage common Bluetooth technology.
• Mobile devices to download data are readily available.
• Cellular connectivity or VPN tunnels provide secure data transfer.
• Mobile devices must be within 50 ft. of sensors to download data.
• Wirelessly transmitting data with Bluetooth [see comment above] quickly drains sensor batteries.
• Wi-fi captures limited equipment data, and battery-life limitations prohibit full-spectrum analysis.
• Numerous teams are required to collect data at large facilities.
• Teams typically only collect equipment data once a month.
Another method uses a repeater to extend the 900-MHz wireless signal as much as a mile. The repeater eliminates the need for maintenance teams to walk throughout the facility, saving time and labor. The receiver sends the data to a cloud or onsite system for analysis.
As with traditional wireless, equipment sensors transmit by way of Bluetooth technology, which can drain sensor batteries over time. To save battery life, sensors only take a snapshot of equipment performance every 15 minutes. While this can include more than vibration data, it doesn’t capture a full-spectrum analysis on all assets. Personnel can, however, collect full-spectrum analysis on assets that trigger vibration alerts.
• Sensors can transmit information as much as a half-mile, eliminating the need to walk within 50 ft. of the equipment to collect data.
• Boosted wireless is scalable, with some repeaters capable of supporting 250 sensors and some receivers capable of supporting 300 sensors.
• Cellular connectivity or VPN tunnels provide secure data transfer.
• Because boosted wireless uses Bluetooth technology, sensor-battery drain is still a problem.
• Bandwidth and battery-life limitations prohibit full-spectrum analysis on all assets.
• Boosted wireless can be expensive, depending on the size of the plant and number of repeaters and receivers required.
• Supporting equipment requires a large footprint.
• Receivers require a line of sight with sensors, as obstructions can block or weaken wireless signals.
Mesh networks can be tricky to explain. In short, wi-fi and boosted wireless networks use a single line of communication to transmit data from a sensor to its final destination. In a mesh network, sensors placed across a facility serve as multiple access points, each communicating with other sensors across the network. If one sensor drops the signal, another one picks it up. It’s similar to a circuit: a wireless network is like a series circuit, where everything is wired together, and a mesh network is like a parallel circuit, where there are multiple paths for electricity to flow.
These types of networks hold significant potential for large facilities in that they can create a virtual blanket of connectivity over a plant, increase data-transfer speeds and allow engineers to collect more of the data required for 24/7 asset-health monitoring and predictive analytics.
The drawback of a mesh network is the potential for “hive collapse.” A collapse occurs when a sensor fails and all of the other sensors begin receiving the signals dumped when the first sensor stopped transmitting. Then more data gets transmitted to fewer sensors. As sensors become stressed by picking up additional signals, they too, can fail. This process continues until the volume of data is too much for the mesh network to handle and it shuts down.
• Mesh networks support long-distance transmission. Sensors can be placed as far as 164 ft. from each other.
• These networks are also capable of transmitting full-spectrum equipment data, including vibration, temperature, pressure, flow rates, torque, and thrust.
• Sensors automatically determine the most reliable path to send data, which means faster and more reliable data transmission.
• There are no line-of-sight requirements with equipment sensors.
• Less supporting equipment is required compared to wi-fi and other wireless networks, which translates as smaller footprints and lower setup costs.
• Since mesh networks operate at 2.4 GHz, there’s potential for interference from radio signals and other atmospheric conditions, leading to reliability concerns.
• Installing a mesh network requires detailed site mapping to ensure complete facility coverage.
• As more data is transmitted, a network can be strained, leading to hive collapse.
• The ability to transmit more data means more battery drain from wireless sensors.
New technology that offers the advantages of a mesh network while overcoming its disadvantages is emerging. LoRa, or long-range wide area network (WAN), transmits data at 900 MHz over distances as great as seven miles. This long-range ability eliminates the need to purchase receivers, repeaters, or the additional sensors that are required for other networks.
With LoRaWAN, equipment sensors connect directly to a gateway. Since LoRaWAN uses a single gateway to connect as many as 10,000 wireless sensors, facilities don’t have to worry about large network footprints, complicated installations, or high costs. LoRaWAN gateways are about the size of a conventional home router and can reduce the cost of hardware infrastructure by 50%.
LoRaWAN also enables two-way communication from the sensor to the gateway and allows personnel to connect to equipment sensors and check battery levels or change asset data parameters from anywhere in the world.
Perhaps the most exciting aspect of LoRaWAN is that it is based on an open-source protocol, so any manufacturer can develop sensors and other supporting equipment. More manufacturers in the space mean more innovation and lower costs. It also means end-users won’t be bound to technology from a specific device manufacturer.
One downside is that LoRaWAN isn’t built to transmit the amount of data required for full-spectrum analysis. Device manufacturers are already finding ways to overcome this limitation. As an example, instead of sending full-spectrum equipment data across the wireless network, OEMs are incorporating processors that perform the analytics in the sensors themselves. Since the data is analyzed within the sensor, only the analysis—not the data—is sent over the LoRaWAN.
Asset-health monitoring and predictive analytics require sensors to transmit data over long distances. Industrial operations have a variety of options for doing so. Each comes with advantages and disadvantages. New technology is on the horizon that could overcome many of the problems with existing networks, but they’ll require device manufacturers to reconsider how they capture and analyze performance data. EP
Information in this article is based on a whitepaper from Flowserve, Irving, TX. (flowserve.com).