It is simply not acceptable for anyone who must complete an instrument-based safety role at a certain SIL level to rely solely on the SIL level of each component. For example, it is critical to understand the probability of failure on demand (PFDavg) which, depending on the required SIL, must not exceed certain limits. To diagram and use a simple example of a non-redundant chain, you will use a bit more than your “PFD budget” each time you add equipment. Therefore, it is important to understand the PFD of each component.
Since PFDavg is directly proportional to the test interval, we need to understand this parameter as well. I will let you answer the following question: “Is it better to have a very good PFDavg at a weekly test interval or a slightly less favorable PFD, but from an annual test?”.
What we should note here is that not all SIL 2 detectors are the same and that a SIL 2 component working with another SIL 2 component doesn’t necessary result in a SIL 2 system.
The table below summarizes the reliability data of our gas systems and detectors. Please do not hesitate to contact us. We would be happy to assist you with the development of your gas and flame detection safety chain.
|Equipment||Type||SIL Level||Test interval||PFDavg||HFT|
|CEX 300/OLC 20/OLC 50||Catalytic (LIE)||SIL 2||3 months||5.53x10-3||0|
|OLC(T) 100||Catalytic (LIE)||SIL 2||3 months||8.3x10-4||0|
|OLCT 100||Infrared (LIE)||SIL 2||12 months||5.3x10-4||0|
|OLCT 100 O2||Electro-chemical||SIL 2||3 months||8.1x10-4||0|
|OLCT 100 CO||Electro-chemical||SIL 2||3 months||1.19x10-3||0|
|OLCT 100 H2S||Electro-chemical||SIL 2||3 months||3.26x10-3||0|
|OLCT 100 NH3||Electro-chemical||SIL 2||3 months||4.91x10-3||0|
|OLCT 100 CO2||Infrared||SIL 2||12 months||5.3x10-4||0|
|OLCT IR||Infrared (LIE)||SIL 2||12 months||1.6x10-3||0|
|MX52||16-channel system||SIL 2||12 months||2.19x10-3||0|
|MX62||64-channel system||SIL 2||36 months||1.56x10-3||0|
|-||SIL 2||12 months||5.24x10-4||0|
|MX62||64-channel system||SIL 3||36 months||8.89x10-5||1|
|-||SIL 3||12 months||2.95x10-5||1|
|Flame sensor 40/40I||IR3||SIL2||12 months||4.9x10-4||0|
|Flame sensor 40/40M||IR4||SIL2||12 months||3.6x10-4||0|
|Flame sensor 40/40LB||UV/IR||SIL2||12 months||1.9x10-4||0|
|Linear barrier 700||IR||SIL2||12 months||1.5x10-4||0|
OLDHAM has more than 100 years of experience in gas safety and detection. Our Research and Development department conducts its design and development in accordance with the very stringent IEC 61508 and IN 50402 functional safety standards and, in this regard, we undergo regular audits by certification entities. For more information on the products listed above, please see the products section where you may download all necessary information.
Global Director of Product Development