Shell U.K. Limited has been operating an onshore telemetry wide area network in NE Scotland since the mid-1980s. The network, extending southwards from Shell
Annual operating costs were significant for the combination of private circuit and PSTN line rental, and unreliability of telecoms equipment was consuming an inappropriate level of manpower. Availability of the original solution was less than 99%.
The new network is based on a BT packet-switched service called ‘ISDNconnect’. This solution, capable of supporting TCP/IP, utilises spare capacity on BT’s ISDN2e channels, to provide a low bandwidth, always-on connection between terminal equipment and a central location. This type of service is used extensively in the financial services industry for ATM and card swipe authentication.
Up to 1,000 such connections can be made to a central ‘packet handler’. The connections are configured by BT as a closed user group thus providing the required security. A standard option for the service provides automatic failover to a standby packet handler, over a geographically separate link, in the event of link failure to the primary packet handler.
AdRem Consulting carried out the network design and managed implementation of the migration. Part of the migration required the existing telemetry, which was based upon serial Modbus communications, to be converted to Modbus TCP over TCP/IP for compatibility with the new packet-switched network.
Consequently AdRem Consulting needed to call upon an expert, to assist in the conversion of legacy Industrial serial devices onto TCP/IP. They approached specialist communications and automation supplier, M.A.C Solutions, for this service.
M.A.C Solutions provide a whole range of ‘open’, Ethernet communications equipment for such purposes and recommended its Ethernet, Industrial device server from Lantronix, which would enable all of the existing, serial telemetry equipment to be left in place, whilst utilizing the new packet-switched network. This would save time, money and minimize downtime for Shell. Around 80 device servers were required throughout the network.
Unlike the original serial Modbus network where only one master was permissible, the new device servers meant that multiple masters could potentially access data simultaneously. This allowed AdRem to completely bypass the original master/standby switch-over system, which was complex and costly, and to allow both redundant masters to access all slaves concurrently.
Andrew Willder of AdRem Consulting comments: “We found M.A.C Solutions over the Internet as a provider of Ethernet device servers. The reliability of the Lantronix device servers is excellent and the technical support provided by M.A.C Solutions was first class. We carried out a project at Shell first. Dave Hammond at M.A.C Solutions configured the first batch of device servers for us and kept us updated with firmware for the units.”
Standard network components from Cisco were also used throughout the network, with the exception of the packet handlers, which were supplied by AdRem Consulting. The packet handlers are required to interface with a European standard protocol that is not supported by Cisco or other mainstream data communications equipment suppliers, however, this requirement has been met by the use of a gateway device implemented in standard hardware and custom software with full ESCROW assurance. The gateways have run uninterrupted for more than two years without fault, and are implemented in a fully redundant configuration.
There are two, dual redundant ‘Arcom’ masters per slave. Since the device servers were installed, each slave can now communicate with multiple masters, so the master change-over unit (used to control which of the two masters could communicate with each slave) is no longer required.
One advantage of the ISDNconnect service is that there are no geographical charges, so the ISDN2e subscriber could be located anywhere within the UK. There are some small telephone exchanges that do not support the service, and a survey is therefore required to ensure first, that ISDN2e can be deployed to the required subscriber site, and also that the associated local exchange supports the ISDNconnect service.
A further advantage of the solution is that short term extra bandwidth can easily be provided on-demand to remote sites, e.g. for CCTV or PSTN calls, by means of the inherent ISDN2e B-channel service, which effectively operates over the public switched telephone service.
BT’s incremental charges for additional users, including the ISDN2e line rental, amount to under £1,000 per annum/user. A new user’s service can be set up or removed at relatively short notice.
As a result of this migration, Shell’s annual operating costs and support effort have been reduced, and system availability is well over 99.9%. The telemetry system is remotely managed by AdRem Consulting.
The service is ideal for centralising corporate UK telemetry operations, and provides a level of security and redundancy that should meet all Business Continuity Planning requirements.
Andrew Willder concludes: “Although the BT ISDNconnect service is being withdrawn in 2007, BT broadband-accessed VPN services are now available as replacements. This only has a minor impact on Shell’s telemetry network due to Shell’s adoption of Modbus TCP via the device servers which means that substitution of a WAN based on ISDNconnect with a WAN based on a broadband-accessed VPN will be straightforward. The use of TCP/IP across these WANs is effectively transparent, and migrating from one to the other simply involves some routing changes.”
- ENDS -
Note to Editors: M.A.C Solutions (UK) Ltd (www.mac-solutions.co.uk) is a UK-based maintenance, automation and control systems provider and technical service and support company that specialises in helping customers select and source appropriate systems to help leverage their production machine and process data from existing plant control and automation systems, up to enterprise business level systems.
With more than 10 years’ experience in the industry, M.A.C Solutions (UK) Ltd offers a range of industrial Ethernet ‘open connectivity’ solutions, as well as version control software, industrial Ethernet switches, web visualisation tools, alarm management software, connectivity devices for Siemens’ PLCs, Ethernet-enabled OPC servers, industrial monitors and PCs.
M.A.C Solutions’ clients include utility companies, food and beverage manufacturers, power generation, breweries, oil and gas, automotive, water treatment, wind farms, paper and print, electronics and pharmaceuticals.
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