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Petrol Alkylation Plant Upgrades ESD Systems

26 June 2009

Triplicated safety systems that have been used offshore for many years are now gradually being introduced into refineries as safety systems are upgraded to meet the latest regulations. To this end, K Controls says it has supplied a major UK refinery with 160 stainless steel position monitors for retrofitting to a variety of different rotary and linear valve actuators.

K Controls position monitor
K Controls position monitor

“The K Controls position monitors will be used in conjunction with special Triconex PLCs from Invensys,” explains David Yates, Joint Managing Director of K Controls. “It implements a two-out-of-three voting system prior to implementing any control changes.”

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K Control’s position monitor, housed in a stainless steel, Exd, IP67 enclosure, is shown here mounted on the left side of a large pneumatically actuated linear globe control valve in the petrol alkylation plant. The black armoured multi-core cable carries HART, 4-20 mA, and limit switch signals back to a Triconex PLC.
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Each position monitor contains both end of travel limit switches and a 4-20mA transmitter complete with the HART® protocol that allows it to be remotely calibrated. This enables the PLC to monitor valve and actuator performance throughout valve travel.

The valves are being partially stroked to an agreed schedule and in accordance with planned maintenance procedures, says Mr. Yates

The PLC monitors the movement and issues an alarm if the time taken exceeds a pre-defined limit.

Valve movement is also graphically displayed and any irregular patterns are investigated. “This process ensures the valves are in good working order and ready to react if a programmed shut down of the system is required in the event of an emergency,” says Mr. Yates.

He says his company was able to provide the contractor with SIL (safety integrity level) or life data for all the components used in the position monitor. The product was engineered to enable the PLC to perform short circuit and line break monitoring.

As the units are operating in a coastal environment, stainless steel IP67 enclosures were required together with hermetically sealed switches.

On quarter turn valve actuators, K Controls also provided polycarbonate position indicators and engineered and supplied all the valve actuator mounting kits needed for the retrofit. With linear valve actuators (as shown in the photo) the position can be determined by the position of the slotted drive lever.

The units are fully ATEX certified for use in intrinsically safe systems but where the necessary safety interfaces were not available, versions are certified flameproof Exd.

This particular plant in the UK, which is called a “petrol alkylation plant,” removes acid from petrol in order to make it suitable for vehicle use.



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