Case Study - Shell Leman Uptime

Leman Uptime For Shell (One Gas) Ltd - Project Value £1,350,000

 

Leman is an offshore gas production facility situated off the Norfolk coastline. Shell required new low voltage switchgear to replace the existing obsolete equipment whilst minimising the shutdown of one of the largest gas producing platforms in the North Sea. Three contracts were awarded consecutively to Blackburn Starling over a four year period following competitive tenders and extensive negotiations with the client.

The initial contract was for the replacement of the main low voltage switchboard which had to mirror the existing footprint wherever possible to enable the utilisation of the existing cabling.  This required extensive modification of Blackburn Starling’s standard designs in order to accommodate the client’s requirements. The 2000A (50kA for 1 second) switchboard is a combination of incoming and outgoing air circuit breakers fed by the existing plant generators and includes various starters and distribution feeders. The footprint of the switchboard is an “F” shape with the glanding being at the rear and suitable for both top and bottom entry.

Based on an extremely onerous programme the project was completed on time and to budget with gas production being re-instated on target. This included the installation and modification of the existing control systems by Blackburn Starling offshore engineers.

A further replacement low voltage switchboard was required which again had to mirror the existing footprint. The contract for this 1600A (50kA for 1 second) switchboard had similar constraints to the previous project and was successfully completed to budget within the client’s required timescale.

 The largest of the three contracts was the replacement of the Uptime low voltage switchboard and the associated extensive offshore modifications.

A new 440V low voltage switchboard was required to fit into an existing room with access restrictions and limitations. The switchboard was for the power distribution from three generators to the main and two satellite platforms. This was designed as a back to back unit with front top and bottom access to accommodate cable entries of the existing equipment. The project was further complicated as the switchboard design also had to take into account the floor structural reinforcement and cable transits.

The 3200A switchboard (80kA for 1second) built to BS EN 60439-1:1999, has incoming circuits utilising 3200A air circuit breakers. The outgoing feeders are a mixture of fuse switches, air circuit breakers and motor starter units.

Several meetings were held with the customer to ensure that the switchboard and modular modifications were integrated. The switchboard design had to accommodate three new generators being installed whilst operating in conjunction with the existing generators. Temporary controls between the new and existing were therefore required.

Following the meetings a detailed design was developed that ensured the existing control systems could be operated whilst the new generators were brought on line systematically. A new control, power monitoring and load shedding system was to be installed to ensure that the available generators (new and old) were not overloaded during the change out phase.

The customer, Shell (One Gas) Ltd, requested a collaborative approach between all parties to ensure that the installation and commissioning would be achieved within the allocated timeframe to minimise the shutdown of the gas field.  Based on these instructions all subcontractors worked together to ensure that all interfaces were seamless. All aspects of Blackburn Starling’s design, manufacture and structural floor requirements were available at an early stage of the overall process.

Once the installation phase was completed, a detailed commissioning programme was implemented between all vendors to ensure that the commissioning phase was achieved within the required timescale. The restrictions on this were primarily due to the availability of suitable offshore accommodation and manpower restrictions. The site installation and modifications to the existing switchboards on the platform were undertaken over a six week period and required up to six engineers to be present at any one time.

The overall emphasis of the project was for the main partners to work together to achieve the goals of the client and maintain the programme due to the prospect of one of the UK’s largest gas fields being shutdown.