ESD valves are getting operate through ASCO make solenoid valve and SOV are continuous in energise condition. Solenoid coil supply is 24 VDC. These ESD maintenance can not taken due to service of plant main inlet gas line.
I have doubt regarding SOV coil life, because it is in continuous powered condition. SOV coil may weak after many hours and ESD will get close. Whole plant will get trip in case of ESD closes.
Please guide me about life of SOV coil so that we can plan for replacement as preventive by ESD taken on hand wheel.
It is common knowledge that heat kills electrical/electronic components.
ASCO's white paper
on power consumption and the heat it produces explains the impact of reducing power consumption:
"There is even a "ten degree C" rule of thumb, which suggests that a coil's thermal life approximately doubles for every ten degree Celsius reduction in operating temperature, all other things being equal.
This is based on Arrhenius' theory applied to a typical activation energy. If the current switching system mentioned above can reduce the output of conventional 11-watt solenoid coil by 2 watts, it would reduce coil temperature by about 40 degrees C, resulting in a lifetime increase of 2^(40/10), or 16, meaning that you could extend the service life of a solenoid coil from 5 years to 80 years." (page 4)
It isn't clear whether your particular ASCO valve is a one of the newer designs or not. But I suspect that the ASCO support people can help you out with figure for life expectancy for a continuously powered application.
I would suggest that you look into the ASCO Redundant Control System (RCS), which is a dual solenoid package with diagnostics, that can be configured in a 2oo2D or in a 1oo1S configuration. When the diagnostics are considered, which allows online testing of the solenoids, you get a good compromise of safety (ESD) and spurious trip protection. While not cheap, when the economic risk is considered due to a spurious trip of your plant, it would easily pay for itself if it prevents one spurious trip, e.g. a no brainer.
Triconex also has a redundant 2oo3 solenoid package which also provides safety reliability and spurious trip protection. It is also not cheap, but when the economic risk is concerned the cost is a minimal issue.
Actuating safety and other critical control valves with unmatched reliability Triconex TMR-SOV solenoid valve - Triconex Safety System, - Download Schneider: http://www.schneider-electric.com/en/download/document/PAS_63680_CPM16089/
ASCO states in the below document ("Solenoid Valves used in Safety Instrumented Systems") that the useful life of a solenoid is 3 to 10 years. The useful life can depend on many things (solenoid quality, selection, type, installation, ambient environment, electrical environment, etc.). exida states in their FMEDA report that for an ASCO 327 model solenoid, the useful life for the coil is 30,000 hours or about 3 years. You should check to see is there is an exida (www.exida.com<http://www.exida.com>) or TUV report for your model solenoid that gives the useful life of the solenoid.
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Solenoid Valves used in Safety Instrumented Systems http://www.asco.com/ASCO%20Asset%20Library/asco-pilot-Valve-operating-manual.pdf
I&M V9629R2 Solenoid Valves used in Safety Instrumented Systems Operating Manual in accordance with IEC 61508 ŠASCO Valve, Inc. 50 Hanover Road, Florham Park, New ...
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FS Eng. (TUV Rheinland)
SIS-TECH Solutions, LP
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The solenoid is "fail safe" in the sense that loss of power to the coil, or failure of the coil releases the actuator and switches the valve.
in all burner valving for example, the solenoid valve is only one issue as you also have redundant shut-off valves each with their own solenoids, and a vent or drain valve to depressurize the piping between the two block valves.
in some processes even that level of redundancy is insufficient! and you require a operator or manual trip plus manual block and bleed valves. At another level, the process enclosure it self has to be designed so has to fail safely as possible...
Safety, an unending pursuit...