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The new $55 million Darwin Industry Fuel Terminal, which opened upin Sept. 2005, stores up to 113million litres of jet fuel, aviationgas, petrol, and diesel for three oil companies. The scale of the project is impressive, with 23km of internal fuel pipes planned for the terminal.
Fuel is pumped from ships at the wharvesinto 11 major fuel tanks, with another 25 tanks providing for productslike additives. From there, fuel is transferred to the fleet ofbulk tankers supplying distributors and petrol stations.
The terminal operator selected a highly specified Pilz Programmable SafetySystem (PSS) to oversee the emergency stop system.
In the eventof a spill or other emergency shutdown, a Pilz Programmable Safety System (sometimes referred to as a 'safety PLC') with fibre-optic SafetyBUS p safe fieldbus takes control. According to Pilz Safe Automation Australia electrical engineer and state manager, Raju Kotecha, fibre-optic cabling is important in such a hazardous area to avoid the risk ofsparks associated with copper wiring.
Once triggered by a safety breach, the PSS/SafetyBUS p combination shuts down the entire plant, de-energises all machinery and communicates with the plant's standard operations programmable logic controller (PLC).
Three types of switches
Three types of emergency switches are monitored by the PSS network: the traditional emergency stop button, tank-mounted high-level sensors and emergency-release couplings at the wharf.
In total, there are 80 digital inputs and 48 outputs, including a set of monitored redundant relays for each pump, managed by the PSS. Diagnostics are fed through to a Citect Supervisory Control and Data Acquisition (SCADA) system for display.
The safety-conscious terminal operator specified that any safety system should match the calibre of IEC61508 SIL 3 approved Pilz PSS with SafetyBUS p.
An open technology based on the CAN fieldbus system, SafetyBUS p enables users to incorporate field modules from other manufacturers and network programmable safety systems for more than 1000 I/O over 3.5km, which can then be bridged to multiply the total I/O and bus length.
From a designer's perspective, the Pilz PSS also offers significant configurationand operational benefits over conventional safety relays with its TUV -approved standard function blocks and diagnostic tools. In fact, Pilzhas developed a software package specifically for tank farm installations, which includes the evaluation of emergency stop devices, deadmanswitches, level monitoring, gas detection, plus the monitoring and control of flaps and valves.
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