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What is a SIL Certification - And does Your Level Application Require it?

SIL2 certified measurement
What is a SIL Certification and What Does It Do? 
When installing a SIL certified level sensor, the installation is certified regarding safety and process. These are defined in various standards, such as IEC 61508, that cover functional safety of electrical, electronic and programmable safety related systems. 

The SIL system simplified:
SIL1 – Lower level guarantee that the product will measure all the time
SIL2 – Low statistical risk of failure that you do not know about in the product
SIL3 – Redundant measurement capability – one of the primary differentiators between SIL2 and SIL3
SIL4 – Very few instruments available on the market, and extremely harsh demands to be certified for this. Used e.g. for railways electronics. 

Manufacturers can basically certify themselves by fulfilling the standards of SIL2 and the relevant IEC 61508 standards, but a true and objective evaluation of risk and performance is more reliable when performed by an external company or consultant doing the math. In this case the math is called FMEDA…

What is FMEDA? 
Failure Modes, Effects and Diagnostics Analysis is a thorough analysis that takes every individual component in consideration. The analysis compares the statistics from the individual component with all known failures from the installment base, failures due to product design, manufacturing and operating procedures such as ongoing maintenance.

By using external consultants for this analysis, the manufacturer achieves access to invaluable industrial statistics and numerous critical questions regarding the product. This might make the certification harder to achieve for the manufacturer, but at the same time, access to statistics and industrial knowledge only makes the certification more valuable. 

FMEDA Analysis simplified

The Value of a SIL2 Certified Level Sensor
A wide variety of level sensors are available on the market. Some of these level sensors are not certified at all, some are SIL1 certified and some of them are SIL2 certified. Typically, the price of a SIL2 certified level sensor is higher than the price of the SIL1 certified or non-certified versions, so when is it relevant to spend the extra money and choose a SIL1, or even a SIL2 certified level sensor?

Ask yourself these questions: What expenses can be calculated if a floating roof tank, a chemical tank or a stormflow construction tank experiences overflow? What number of working hours are spent on checking equipment that works? Have you experienced breakdowns due to level switch failure, and what were the costs? To lower the risk, increase safety and at the same time decrease hours spent on monitoring and verifying that the level sensors work correctly, a SIL certified level sensor is worth the value. In short, a SIL certified level sensor might be a bit pricier than a level sensor that is not SIL certified, but the extra money spent are earned in other areas.

For many process industry applications Engineers are familiar with hazardous area approvals. These are well known requirements ensuring the safe operation of electrical equipment in potentially explosive environments. For reliability and to ensure proper operation of your instrumentation, a SIL certified level sensor is an important step in securing the automation of the workflow. Furthermore, using a SIL2 certified level sensor ensures the quality of every individual component and holds this up against experience from an installed base of instruments. 

More than Technical Knowledge
Besides the thorough technical analysis, a SIL2 certification also demands an automatic product verification. This means that a level switch is capable of automatically running tests to electronically verify that the measuring instrument works as intended. If the test comes out with a negative result the auto-verify functionality will automatically alert the staff. This feature is especially beneficial on remote applications, or applications that are not easily monitored due to location. This functionality could be named a waste-protection – it protects from wasting working hours on checking equipment that works and allows the personnel a more efficient focus on a working day. 

Floating Roof Tank Spill Prevention System and Safety IntelliPoint SIL2 Certified

Drexelbrook and Safety
Due to Drexelbrook’s leading position on level measurement instruments and level switch alarms for the oil refining industry, safety have always been a quality stamp of the Drexelbrook level measurement instruments. Hazardous area approvals such as FM, ATEX or IECEX are commonly demanded to secure the working environment and are standard for most Drexelbrook products. Therefore, it has been a natural step to achieve the SIL2 certification for popular products such as the Safety IntelliPoint and Floating Roof Tank Spill Prevention System level sensor. SIL3 certification for this particular product can be obtained by the use of redundant switches. 

Ask your Drexelbrook consultant, how Drexelbrook can improve your safety and budget.