Wireless Communications has been widely used in the oil and gas industry since it is either impossible or cost prohibitive to run hard wire to many remote locations. Licensed radio communication (VHF and UHF) has been the predominant media used. The limited availability of RF frequencies, licensing delays, and annual licensing costs have been a bottleneck to more widespread use of wireless SCADA and Telemetry in the oil and gas industry.
Unlicensed radio communication offers a solution to this bottleneck. With no licensing delay, no annual licensing fees and channel availability, it opens up the opportunity for more widespread use of SCADA and Telemetry applications in the oil and gas industry.
What is Spread Spectrum Technology?
The FCC and Industry Canada have allocated sections of the RF spectrum for unlicensed communications systems. These include the 902-928 Mhz bands and the 2.4 Ghz bands. These bands are offered on a “no interference – no protection basis”. “No interference” means the RF equipment must not interfere with existing licensed users while “no protection” means that the RF equipment manufacturer is responsible for providing their own protection against other RF equipment operating in the band.
The 902-928 Mhz and 2.4 Ghz bands utilize 2 types of spread spectrum technology:
- Frequency Hopping – transceiver hop through a pseudo-random pattern of frequencies.
- Direct Sequence – transceiver simultaneously broadcast on multiple frequencies.
With these techniques, all transceivers in the same system would be assigned the same pseudo-random pattern or coding. Transceivers having the same code can communicate with each other but a transceiver with a different code could not communicate with any of these. This allows different systems to coexist without having to assign a unique licensed frequency to each system. The different pseudo-random patterns or codes effectively act to isolate one system from another.
Why use Spread Spectrum Technology?
The traditional approach to SCADA has been to package a Remote Terminal Unit (RTU) with a licensed radio or radiomodem. To implement a system, one would have to obtain radio frequency for the new sites or utilize the same radio channel as an existing field SCADA system.
A new radio frequency allocation may be difficult to obtain since the area may be highly congested with other existing radio systems. On the other hand, the option of putting the new system on the same frequencies as the existing SCADA systems may also not be desirable. The end result is that the system may be unnecessarily delayed or not implemented at all. With unlicensed radio communications, these problems don’t exist so the system can be implemented immediately.
What is the SCADALink 900-MB and how does it differ from other Spread Spectrum radiomodems?
Bentek Systems has incorporated 902-928 Mhz frequency hopping spread spectrum technology into its SCADALink 900-MB RTU / radiomodem.
Recognizing that there are many SCADA and Telemetry applications with limited I/O requirements that cannot justify a costly RTU and radiomodem system, Bentek Systems has integrated a small number of I/O with a license-free radiomodem into a single compact unit, the SCADALink 900-MB RTU / radiomodem. For applications with minimal I/O requirements, the SCADALink 900-MB is all that is needed. For larger applications, the SCADALink 900-MB’s onboard RS-232 and RS-485 ports allow license-free data communications to PLC’s, RTU’s, VFD’s or SCADA hosts.
If only a small number of I/O is initially required, a SCADALink 900-MB may be all that’s necessary. If in time more I/O must be added, the onboard RS-232 and RS-485 ports ensure easy future I/O expansion to PLC’s or RTU’s.
The 900-MB’s onboard I/O is addressable using industry standard Modbus protocol to facilitate ease of integration into existing Modbus systems (for more info and detailed specification go to the SCADALink 900-MB page. Bentek Systems offers solutions ranging from equipment to complete turnkey systems. To evaluate these options, go to Bentek System’s Products page.)
Typical Oil & Gas applications using the SCADALink 900-MB RTU / radiomodem
The following examples demonstrate typical oil and gas SCADA and Telemetry applications in which the SCADALink 900-MB provided a cost effective solution.
Application 1 – Solar powered SCADALink 900-MB RTU / radiomodem answers injection well problem
A major U.S. oil producer had a requirement to monitor the annulus pressures of water/CO2 injection wellheads to ensure proper injection.
Annulus pressure switches were monitored via underground cable that was buried during construction of the injection pipeline. In time,however, the environment and trenching had taken its toll on the cables.
Their requirement was to get these signals back to the PLC at the injection header. Burying new cable would have been cost prohibitive and the 900-MB was chosen as a cost effective wireline replacement. Bentek Systems supplied the client with solar powered SCADALink 900-MB RTU / radiomodem’s for this application.
License-free operation was important in this application since RF channel allocation was difficult to obtain in this high density oilfield area. The existing licensed radio channels to the SCADA host could not be used since communication was required to the PLC near the injection header and not to the SCADA host.
With the unlicensed system the customer could retain the existing system architecture, save on trenching costs and quickly implement the required communication link.
Application 2 – Compressor solution replaces hardwired monitor
An oil company monitored gas compressors using RTU systems connected by hard wire. Over the years, the hardwired system had been damaged by excavation for new construction and became increasingly unreliable. As the wiring deteriorated and communications to the RTU’s was degrading, there was a need to re-establish communications to these sites for status monitoring. The company was planning to replace the dated RTU systems with PLC’s and selected SCADALink 900-MB’s for this application since in addition to providing license-free wireless communications, it had I/O to which they could directly wire compressor alarms until they replaced the RTU’s with PLC’s.
Application 3 – Fast solution to alarm monitoring request
A U.S. oil producer had a gas locking problem in an oil pipeline which shut down production on high pressure. This required the site be continuously manned until it was rectified.
Bentek Systems was contacted at 5:30 PM Friday afternoon by one of the oil company personnel who had seen a demonstration of the license-free SCADALink 900-MB RTU / radiomodem. He felt that if the pressure switch alarm contact could be transmitted to an existing alarm callout at an oil battery seven miles away, then the site could be remotely monitored and unmanned. Bentek confirmed that the equipment would work for this application and shipped the equipment that evening for installation by the oil company. The system was installed the next day and the site could be unmanned. The license-free operation permitted immediate deployment.
The above are just a few examples of applications of the SCADALink 900-MB in the Oil & Gas Industry. For more applications go to SCADALink 900-MB Applications.