Bringing Ethernet networking to existing outstations

Transco has used a powerful and cost-effective Industrial Ethernet Device Server from MAC Solutions to provide communications between existing serial-based outstations and the new Transco Satellite-based Wide Area Network (WAN)

Transco is the UK's largest utility company, responsible for gas transfer across a network of 200,000 miles of pipeline which serves more than 20 million commercial, industrial and domestic consumers. As a UK-wide provider, Transco inherited a mixture of existing automation equipment that uses a variety of technologies. Many of these are neither inter-operable or compatible.

Transco decided to develop a complete new generation of telemetry and control for its gas network. The main aim of this project was to enhance existing communications and control structures and provide sufficient flexibility to meet the future needs of Britain's gas market. A careful review of issues within Transco concluded that a new network should be developed based on the Internet Protocol (IP), which seemed the natural choice for a new industrial network. Many of Transco's sites are in remote locations so a satellite-based WAN (Wide Area Network) was chosen as the ideal way to carry IP traffic. This avoided the high ongoing costs and inflexibility associated with leased-line telephone systems.

TCP/IP and Ethernet has been adopted as a de-facto networking standard by industrial companies and utilities alike as it offers distinct advantages over traditional serial or other proprietary communications methods. There is better hardware and software platform interoperability, high transmission efficiency, and the ability to add new devices to a network without disrupting operations. On the factory floor and within utility companies IP networks also open up new opportunities to integrate widely dispersed locations into a company-wide intranet, and can also be used for voice-over-IP and video-over-IP applications across and between sites.

Legacy equipment Outstation sites to be connected to the new IP-based network had a large number of serial-based control and communications devices that had already been installed. There was no reason to replace this equipment as it was working perfectly, just as in factories there are existing PLC and control systems that do not need to be replaced. Basic problems with existing outstation equipment which had to be solved were: how to integrate serial-based equipment with no Ethernet connection; and how to integrate equipment that was not IP protocol compatible.

Transco worked to solve these problems with MAC Solutions, a UK Industrial Ethernet specialist with experience of industrial applications as diverse as food processing and offshore oil and gas production. MAC uses various techniques for evolving serial industrial and automation systems onto Ethernet TCP/IP including one that uses Industrial Device Servers.

Engineers concluded that the existing serial protocol supported by the outstations was not ideal for reliable transmission across an IP-based network. For Transco it was vital to have rapid and reliable communications because of the safety implications of delayed or inaccurate responses to system requests.

So that a more IP-compatible protocol could be used, an intermediate communications device was developed by telemetry engineers at Transco which would translate between the proprietary serial protocol used by legacy outstations and IP, the new protocol. MAC Solutions uses various types of Industrial Device Servers, from those embedded within a PCB to DIN-Rail mounted models. This project used a matchbox-sized, embedded version of the Lantronix Industrial Device Server (Micro IAP).

Micro IAP incorporates an IP stack, serial-buffering and a Web-server, so there was no need for Transco's telemetry engineers to be involved with the development of a TCP/IP interface for their IP-based satellite system. This unit is simply plugged onto a connector designed for the device PCB and provides it with TCP/IP connectivity at a stroke. Firmware is pre-loaded so that the Micro IAP also translates between the serial protocol used inside the Transco unit, and the IP network protocol used externally to interface over the a satellite IP infrastructure.

Faultless trials After Transco engineers had thoroughly tested a prototype device with legacy outstations using the proposed protocol, Micro IAP was used to Ethernet-enable a unit which could then be connected onto satellite WAN. In trials which sent over 100,000 messages over via satellite WAN to old outstations to legacy Transco devices fitted with a new Micro IAP device server, there were no failures and the customer was more than satisfied with the result. Transco is now using this technique throughout the UK, and is considering other legacy installations which might benefit from a similar approach.

The use of Ethernet and TCP/IP does not mean that existing, non-networked or non-Ethernet connectible equipment has to be made obsolete. By working with Industrial Ethernet specialist MAC Solutions, Transco has been able to retain existing equipment for use in conjunction with a new IP network. A lot of engineering time and expense has been saved, and from the customer's point of view, existing capital investment has been protected.

MAC Solutions
m105@industrialnetworking.co.uk