We want to install some gas and flame detectors,

1- Does anyone have experience about F&G detectors which are SIL3?

2- If we only want to install some detectors (such gas detector or Flame detector) in the site for detection and monitoring, do we need to have a SIL 3 detector?

Thank you for your guidance

 

$IS (the dollar sign means expect to pay a LOT of money for the equipment and certifications involved in Safety Instrumented Systems) is something that is applied to the entire facility, not just to bits and pieces of a turbine island or production facility. If the entire facility doesn't have a $IL rating for the plant and for various processes in the plant, then it's pretty likely you don't need to purchase $IL-rated components for installation or replacement.

$IL ratings are based in part on estimations and calculations and some hard data, but it's more about achieving a "desired" level of safety and personnel protection. That's the problem I have with this whole initiative: It's about a desired level using estimations and calculations and some hard data.

In any case, I don't believe it can be applied to a single system unless your facility is migrating to a completely $IS/$IL-rated facility. The sensors and the devices the sensors are connected to would likely have to both be $IL-rated and integrated into the other systems at the plant. From your description, it doesn't sound like that's being done, but, that's only from the limited information provided in your description.

On the other hand, if your facility is already $IL-rated, then you should be referring to the relevant documentation for modifying or upgrading plant systems, and that is quite involved and generally not very specific, though that depends on who you ask. But, $afety Instrumented Systems, once implemented, have a very specific procedure for adding or changing components. I think you can refer to IEC-61508 and/or IEC-61511 for more information, or to the local laws and regulations in your nation or part of the world.

 

Honeywell's document 65-0312-1, Systematic Integrity: SIL3 Capable Rating for Select 7800 SERIES Controls and Flame Detectors claims SIL 3 rating

available here:
http://customer.honeywell.com/techlit/pdf/62-0000s/65-0312.pdf

(the forum sometimes inserts spaces into URLs, which must be removed for the URL to work)

 

You haven't given enough information to give you proper guidance. However, pl. note the following:

- SIL classification is the so far available best tool to determine the risk in industrial process. Design as per SIL standards (IEC 61508 &61511) ensures proper protection method to reduce the risk;

- IEC 61508/61511 doesn't call for SIL classification for the F&G system. Debate is still going on among professionals whether F&G system to be brought under SIL classification or not;

- Some countries/companies however insists that all loops in F&G system should fulfill SIL2 requirment. SIL3 is generally not a requirment for F&G system;

- If you want to design a F&G system with few detectors, you can take the safety PLC or F&G controller as SIL2 and design the overall loops complying to SIL2 requirment. This again depends on local regulation or your company policy;

- To design a SIL2/SIL3 loop you don't need SIL certified detectors. Ordinary detectors will do if you know how to design a SIL2/SIL3 loop. However, SIL2/SIL3 detectors are available. Pl. check the websites of F&G suppliers such as General Monitor, Honeywell, Detcon, Dettronics etc.

- Many countries/companies/local regulations still doesn't have any mandatory requirments for the SIL design in F&G system. However, this depends on your application and the gravity of risk you are facing. If common sense risk is high a SIL compliance design is preferable;

- If risk is not high from your perspective, just design a normal F&G system, that should be enough.