Norwegian plant upgrades critical safety systems
06 August 2010
The Kårstø plant, located 30km north of Stavanger in Norway, already boasts an impressive safety record but site operator Gassco and its technical services provider Statoil were both keen to bring all systems in line with newer plants.
Enhancing safety at Kårstø is one of a number of projects collectively known as the Kårstø Expansion Project 2010 (KEP2010). The KEP2010 safety contract, which is worth in excess of £6m, was awarded to Hima-Sella.
Six Local Equipment Rooms (LERs) are to be fitted with new Emergency Shut-Down (ESD) systems, which Hima-Sella is building using HIMA’s rack-based HIQuad H51q programmable electronic systems (PES). Each PES has two dual (1002D) processor-based command modules.
Within each module, the two processors are continuously comparing their calculations. Any discrepancies will result in the module shutting down; but not resulting in loss of the ESD function.
Each PES has several racks containing input/output (I/O) modules which are hardwired to field devices. Each I/O is duplicated. On the I/O modules the individual I/O pins are continuously being toggled to test for any ‘stuck at’ conditions, and errors are flagged or a shutdown is automatically initiated depending on the device to which the modules are connected.
With this configuration of two dual (1002D) processor modules and the allocation of two I/O modules for each critical signal, the PES is affording what is known as ‘dual redundancy within a duplex system’; which provides high reliability whilst negating the need for a shutdown in the event of a localised fault. Moreover, in the event of a fault, any module can be ‘hot-swapped’, thus providing a rapid restoration to full availability.
Hima-Sella is also installing a Critical Action Panel (CAP). The CAP is essentially a curved control desk consisting of three key functions: ESD, fire & gas and telecommunications
The CAP features manual ESD functionality which, in the event of an emergency, allows the plant to be shut down in a safe and controlled manner.
There are about 300 safety-critical valves associated with gas processing and storage at Kårstø. These valves will all be protected by ESD functionality.
These valves will also be protected by a Process Shutdown (PSD) function; which is currently part of the current control system but KEP2010 will see PSD realised as a standalone safety feature - and not something which is tied in with a control system. The PSD signal will come from the modernised HMI; for which MW Kellogg is responsible.
Whilst having independent solenoids, the ESD and PSD systems will be interlinked. For example, in the event of a demand for shutdown the ESD solenoid will close the valve and send a signal to the PSD solenoid. This will feed back to the HMI. Upon the ESD being cleared it will be possible to reset the ESD solenoid locally, but the valve will not reopen until the PSD solenoid is also re-energised.
The ESD and PSD systems will include test functions – to be controlled from the upgraded HMI – which test the respective solenoids with a partial stroke.
A number of the plant’s valves will also be protected by High Integrity Pressure Protection Systems (HIPPS) - to ensure safety and to avoid unnecessary flaring.
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