Dual redundancy boosts fire and gas safety

A GE Fanuc Intelligent Platforms UK product story

Edited by the Engineeringtalk editorial team Apr 3, 2002

GE Fanuc Cimplicity HMI and GE Fanuc PLCs have been installed in a major control and monitoring upgrade for vital fire and gas safety at the main Snorre A oil and gas platform off the coast of Norway.

GE Fanuc's Cimplicity HMI and GE Fanuc PLCs have been installed in a major control and monitoring upgrade for vital fire and gas safety at the main Snorre A oil and gas platform off the coast of Norway.

The new system, with a Genius I/O distributed control system, is designed according to IEC 61508 standards thus ensuring ultrareliable protection for the installation and its workforce.

Located some 210km NW of Bergen, Snorre was the first major deepwater development in the Norwegian oilfields, starting production in 1992.

Snorre A is a steel-hulled tension leg platform, tethered to the sea-bed in 300m of water.

It fulfils the tasks of an integrated installation, including production, drilling and living quarters, with a sub-sea production facility some 6km away to the NE.

The Snorre B platform started production in June 2001 from its site about 7km to the north.

There are now 22 wells linked back to Snorre A and the underwater production system.

A further sub-sea production unit to the south west of Snorre A, the Vigdis, is operated remotely from the Snorre platform.

Currently eight wells utilise water injection to extract the oil which, when stabilised, is piped back to another platform for storage and export.

The oil and gas produced by Snorre A are piped back to another platform, Statfjord A, for final processing and loading into shuttle tankers.

Oil from Snorre B is piped for 45km to the sister platform, Statfjord B, for storage and transport, while the gas is stored in a reservoir or sent via a pipeline to Snorre A and thence into the Statpipe system.

When planning the upgrades for Snorre A, a number of requirements were specified.

These included improved system response times between PLCs and the HMI control system, as well as increased reliability and availability of the system.

There was also a desire to increase the amount of infrastructure status information available, in order to simplify service and maintenance.

As the platform was already fully operational it was also vital to cause a minimum of interruption to the operators.

To minimise downtime, system testing was carried out on-shore, and the existing infrastructure of cabinets and cabling was re-used as far as possible.

Cimplicity HMI was chosen as the control software with dual redundancy of servers, GE Fanuc 90-70 and 90-30 PLCs, and Genius I/O blocks.

The PC servers, running Cimplicity on a Windows NT platform, provide rapid two-way communication with the PLCs over an Ethernet network.

The Genius I/O blocks provide a localised distributed control system for the Scada infrastructure.

In the event of a server, PLC or DCS fault, the system automatically switches to the other back-up device without interruption to the overall control system.

Dual redundant PCs, running Cimplicity, act as Cimplicity Viewers in the control room, also ensuring continued access to the system.

One PC is also connected to the Ethernet network for maintenance purposes.

This can act either as a server or as a viewer.

A total of five pairs of 90-70 PLCs and one pair of 90-30 PLCs, all in redundant mode, handle 4500 I/Os for the fire and gas safety.

Of these I/Os, around 1000 are analogue inputs, detecting gas and flames, and around 1000 are digital alarm inputs including heat sensors, smoke detectors, and flame detectors.

Included in the outputs are activators for approximately 125 groups of fire dampers, with up to five dampers in each group, 29 deluge skids and eight sprinkler systems.

There are also fire alarm and other early warning alarm systems with 800 detectors linked to them.

The whole system comprises around 24000 PLC tags and 27000 HMI tags.

Historical data are archived to an MS Access database for later analysis.

According to Oystein Netland, marketing manager for Origo Engineering, and cosupervisor of the installation and verification of the new control system, "We have planned an investment in technology at Snorre for a 20 year lifetime.

We have every confidence in the robustness of the GE Fanuc equipment.

Benefiting from GE Fanuc's membership of the Microsoft Developers Network and the experience of GE Fanuc with critical applications, the HMI design and PLC programming has proved intuitive".