Converting serial networks to Ethernet communications
Hybrid systems? Hybrid protocols is more like it: Legacy endures, Ethernet enters
By Jim Gardner and Dean Weber
Today, many oil and gas producers and pipeline companies find themselves in an awkward position.
They have invested millions of dollars in legacy serial communications systems and, in most cases, millions more in older SCADA remote terminal units (RTUs) and electronic flowmeters (EFMs).
Driven by IT organizations, there is a desire by most of the industry to convert these systems to Ethernet. The Ethernet protocol offers advantages over the older serial communications in terms of peer-to-peer communication, faster polling cycles, as well as the ability to poll multiple devices at the same time.
With the price of oil and gas at record levels, many companies are scrambling to expand their fields through drilling and/or acquisition. This compounds the problem even more because the number of EFMs or RTUs is constantly growing.
The larger the field gets, the longer the polling cycles become. What should companies be installing on new wells? New Ethernet based systems? Or stick with the same proven technology that already is in place for using existing standard tools and standard practices?
Is there a bridge between these two choices? The answer likely depends on the balance of specific objectives for information frequency, maintenance budgets (e.g. power consumption), construction costs, and most important, security.
New technology advances
New communications technologies have emerged that provide high-speed wireless Ethernet communications to field applications.
Like all new technologies, there are many products that are capable, yet few that actually are applicable to the rigorous field conditions or even many industrial applications. It is important when looking for new technology and definitely before deploying any that you insure they meet your installation’s temperature requirements.
For example, they should be tested from -30°C to +60°C minimally and designed for very low power draw, since most oil and gas systems run on solar and battery power systems.
Another evaluation criterion for these new technologies is the operating range. Many of the WiFi devices on the market are not industrial grade and, as such, have limited range. Always look for a radio with a proven range that exceeds your requirements. Are 20+ miles of operating range and the ability to store and forward data (repeat) in a single radio required to insure complete and reliable coverage of the field?
Thus, the decision criteria are:
Temperature specifications -30°C to +60°C
Low power consumption
20+ mile range with line of sight
Store and forward (repeat) in one radio
Many of these devices are for use in an office environment where AC power is available and temperatures always are consistent and moderate.
With the wide range of new Ethernet-based products available, it is a daunting task to find which are best suited to your needs. Often it is best to stick with manufacturers who have a proven record of accomplishment in the oil and gas industry, simply because they design for the environmental extremes that we have all come to understand as being a part of our life in this industry.
Some of these communications companies have designed new products that actually allow operators to leave their legacy serial networks in place and add new Ethernet backbones. The backbones are a broadband (high-throughput) Ethernet series of repeaters that run through the field and connect to the serial radios and serial EFMs.
In this piece, we will consider any radio with over-the-air throughput of 800 kbps or greater to be a high-throughput communications device. By installing a few of these high-throughput Ethernet repeater sites, the company can speed up polling times exponentially and provide Ethernet data back to the network—and even enable mobile connectivity from the technician’s truck in the field back to the network.
Examples of deployment
In an existing field with EFMs and communications already established, the operator can upgrade by simply changing out the master radio and the repeaters to high-speed Ethernet radios. The serial master now connects to the Ethernet radio and provides a seamless connection between the two protocols.
Some of these new high-throughput (high-bandwidth) radios come with built-in terminal servers. A terminal server allows the user to plug a serial device into the radio and convert the data to Ethernet protocol. This ability to convert serial to Ethernet creates “hybrid systems” that are part serial and part Ethernet.
Now, the user can continue to maximize the use of his or her investment in serial EFMs and existing serial radio networks, and accomplish the goals of faster polling times and Ethernet data delivery.
By utilizing the Ethernet “backbone” concept, an IP addressable system exists. Each Ethernet radio can have an IP address, and each “port” can have a separate port address. Some of these radios have multiple ports. In some installations, a radio may have three communications ports. Two are serial ports that can configure in any combination of RS-232 or RS-485, and one is an Ethernet port that can connect by using a CAT-5 cable with a RJ-45 jack.
Faster polling times
After having deployed an Ethernet backbone, the user can start to create a unique “hybrid network.” For instance, imagine the user has deployed one Ethernet radio and two serial radios at each repeater. The Ethernet radio works as a repeater, and the serial radios are operating as “masters.” These masters each have a family or network of serial “slave” radios that report to them. Each serial master connects to one of the serial ports on the Ethernet radio. Therefore, it has its own unique IP address and port address.
The network master (at the host computer) can call multiple serial master radios at the same time because they each have an IP address. If there are four repeater sites in a network and each has two serial masters, the host can poll eight masters at the same time, thus cutting the polling time to one-eighth of what it would have been with only a serial network.
Say, for instance, a serial network of 400 serial radios with a serial backbone has a polling time of 90 minutes. A high-speed Ethernet backbone network of 400 serial radios with eight masters reduces the polling time to 11 minutes.
One of the great advantages to this system is you do not have to stay with a single manufacturer’s systems and equipment. With the implementation of a high-throughput backbone, you can tie RTUs, PLCs, or EFMs from different manufacturers into one communication system.
By using the addressable communication ports on the radios, you can tie one manufacturer’s equipment to another’s communications port with a dedicated master polling of that particular brand of equipment and then install a second master on the second communications port polling a different manufacturer’s equipment. All of the data comes back through the same “big pipe” Ethernet backbone.
The communication system now resembles a gas gathering system. Starting at the wellhead, the radios connect to EFMs that typically are serial devices with low baud rates (i.e. 9,600 or 19,200 kbps), comparable to a two-inch gathering line coming from the wellhead.
Next, the “slave” radio at the wellhead connects to a master serial radio at a repeater or backbone site. The serial master connects through the addressable serial port on the high-throughput radio similar to a compressor station in a gathering system.
The high-throughput radio now sends the data back to the host at eight times the speed of the serial radio system. This is comparable to the gathering system connecting an eight- or 10-inch pipeline.
A small subset of radios
By deploying such a fast system, we have opened the door to many new “outside the box” ideas that were not feasible with serial radios. Some of these ideas include video.
Many operators are looking at video for security and safety. Typical examples of video are mounting web cameras at compressor sites to allow the operator to scan the area visually before doing a remote start on a compressor.
Another common practice is intrusion alarms. The operator will set a web camera to trigger when a door or gate opens in an unmanned location. The camera will provide 10 or 15 seconds of streaming video that allows the operator to know who has entered the location.
Another novel use is leveraging web access from the field. With a high-throughput radio backbone in place, field technicians have the ability to access the network from their trucks. By installing a high-throughput radio in the truck, the technician can access the network anywhere he has “line of sight” (unobstructed view of the repeater up to 20 miles away) to any of the backbone locations. This means he can poll the system from his truck, access the web from his truck, or do anything he would be able to do if he were at his desk in the office.
These advances in communications technology remind me of a favorite quote by philosopher and mathematician Alfred North Whitehead in 1911: “Civilization advances by extending the number of important operations which we can perform without thinking about them.”
High-throughput Ethernet technology is changing the way field data collection is done. It will improve our ability to rapidly access information and share that information among users.
Seldom does a new technology breakthrough come with so little requirement for implementation. In the case of FreeWave HT+ backbones, an example of the technology we have discussed here, all that is required is a small additional subset of radios at the repeater sites.
ABOUT THE AUTHORS
Jim Gardner (Jgardner@freewave.com) is an ISA member and is manager for strategic development at FreeWave Technologies. He has 30 years experience in the oil & gas industry. Dean Weber is measurement coordinator at the South Rockies Business Unit of EnCana Oil & Gas.
Backbone is a high-speed line (or a series of connections) that forms a major pathway within a network.
Repeater: In telecommunications, this device boosts network signals transmitted over a long span.
RTU is a remote terminal unit, an industrial data collection device typically located at a remote location and that communicates data to a host system by using telemetry—radio, dial-up telephone, or leased lines.
Ethernet is a family of computer networking technologies that operate at many speeds for local area networks. The name comes from the physical concept of the ether. It is standard IEEE 802.3.
Serial communications refers to any data transmission scheme in which data is sent one symbol, one bit at one time, sequentially over a communications channel.
RS-232, 422, 423, and others refer to a recommended standard (RS) pertaining to plug and socket configurations, voltages, signaling rate, distances, and other electronic configuration characteristics.
IP address: Each machine connected to the Internet has an address known as an Internet Protocol address (IP address). The IP address takes the form of four numbers separated by dots, like 22.214.171.1240.