Shell uses on-shore telemetry to cut costs at St Fergus Terminal

London - Shell UK Ltd operates an onshore telemetry wide-area network to monitor and control onshore pipeline operations across an area extending southwards from Shell’s St. Fergus Gas Terminal in north east Scotland. The network employs a BT packet-switched system, called ISDNconnect, which was selected for its ability to deliver savings in annual operating costs, improved reliability and network security.


ISDNconnect, which is designed to support 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 - a type of service that is used extensively in the financial services industry for ATM and card swipe authentication.


With the Shell network, 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.


The telemetry system is remotely managed by local company AdRem Consulting, which carried out the network design and managed implementation of the migration, part of which required the existing serial Modbus -based telemetry to be converted to Modbus TCP over TCP/IP for compatibility with the new packet-switched network. Communications and automation company MAC Solutions assisted in the work to convert the legacy Industrial serial devices onto TCP/IP.


MAC Solutions recommended its Ethernet, Industrial device server from Lantronix, to 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.


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 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. The service is suitable for centralising corporate UK telemetry operations, and provides a level of security and redundancy that should meet all business continuity planning requirements.


Although the BT ISDNconnect service has been withdrawn since last year, BT broadband-accessed VPN services are now available as replacements, according to Andrew Willder of AdRem . This, he said, 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."