What are Safety Integrity Levels and what do they mean for your process?

Safety Integrity Level (SIL) capability is becoming more common. Many people are familiar with hazardous area approvals such as ATEX, IECEx and CSA; however, a SIL capability is slightly different.

In simple terms, if a product has ATEX approval for use in Zone 0 hazardous areas, that means the product has been tested and proved to be safe to use in that type of area. This is the same for IECEx and CSA. SIL is different because it looks at risk reduction. Determining the appropriate level of risk is often site-specific. Operators must be able to identify an acceptable tolerance level and assess how that will impact on personnel and equipment.

SIL is defined by the International Electrotechnical Commission Standard IEC 61508 using two integrity categories: hardware safety and systematic safety. The requirements for both categories must be met for SIL certification to be awarded.

What is product SIL capability?

A product’s SIL capability defines its integrity as part of a complete safety system. The higher the SIL level capability, the higher the associated safety level. This in turn means a lower probability that a system will fail. SIL capability is determined by the following safety characteristics:

• The average probability of dangerous failure of a safety function in case of demand (PFDAvG)
• Hardware fault tolerance (HFT)
• Safe failure fraction (SFF)

There are four SIL levels:
SIL 1 - has the integrity to avoid minor incidents
SIL 2 - has the integrity to avoid more serious incidents that might lead to injury or death of one or more people
SIL 3 - has the integrity to avoid serious incidents leading to serious injury or death to a number of people
SIL 4 - has the integrity to avoid disastrous accidents

SIL-capable Oxygen Analyzer XTP601

The XTP601 Oxygen Analyzer for use in safe or hazardous areas is a linear device used for oxygen measurement within gases such as biogas, methane, hydrogen, nitrogen and carbon dioxide. The XTP601 meets the requirements of IEC 61508 (SIL2 capable), allowing the user to integrate the analyzer into their functional safety system.

Using thermo-paramagnetic technology, the XTP601 O2 Analyzer is robust and reliable at providing precise repeatable measurements of oxygen in process gases. It is a low maintenance unit, and therefore, a cost-effective option for long term monitoring with no consumables and no moving parts. This makes it less sensitive to vibration and movement and highly resistant to drift over a long period of time, compared to other sensing technologies. It offers increased protection against contamination.

The XTP601 is typically used in applications such as hydrocarbon storage tank or reactor blanketing, process control, natural gas monitoring and nitrogen/oxygen generator quality. It has a robust sensor with high sensitivity and stability. It can be factory calibrated in varying backgrounds to match the customer’s process gas. Together with the PS601 purpose-designed sampling system, the XTP601 O2 analyzer is able to operate in harsh conditions under various process and environmental conditions.

Meeting or exceeding BS EN50104:20 for detection and measurement of oxygen with safe area and worldwide hazardous area classification options, plus SIL2 capability, make the XTP601 the standard to meet for implementing a SIL solution for process oxygen measurement.

For more information, contact us.

Alternatively, check out our other SIL-capable products:
Compact SIL2 Capable Oxygen Analyzer - Ntron SIL-O2 (processsensing.com)