Safety Critical
Safety Critical
(OP)
In many project, I've met the word "Safety-critical equipment".
And experienced that some particular systems such as flare system, fire fighting system, ESD systems etc. have been considered as "safety-critical equipment".
It is generally agreed but hard to define clearly.
Are there any specific definitions on international standards(eg, BS, API, NFPA etc.)? or text or articles?
And experienced that some particular systems such as flare system, fire fighting system, ESD systems etc. have been considered as "safety-critical equipment".
It is generally agreed but hard to define clearly.
Are there any specific definitions on international standards(eg, BS, API, NFPA etc.)? or text or articles?





RE: Safety Critical
Yep, I guess there must be internation standards that describe things in detail, no doubt somebody can tell you exactly which ones.
RE: Safety Critical
There is a lot of work done on safety. The safety categories are typically broken down interms of the consequences to human life and equipment or cost to repair or replace. Often, but not always risk is defined interms of single item failures. There are key differences between industries e.g. process chemical vs aero-industry.
The general definitions are frequently included in handbooks on process safety, but you can even find excerpts from the various standards in vendor literature.
Good luck
RE: Safety Critical
When coupled with the probability of occurrence, this develops the overall risks for the system that are to be mitigated. In many instances, simple design modifications can prevent certain effects from occurring. In others, auxiliary equipment become critical because you depend on them to prevent certain classes of injury or damage.
TTFN
RE: Safety Critical
Through the all posted, I can figure out the definition of SC as;
1. Independent from the process.
2. Can be identified during the risk analysis e.g. FMECA, QRA, Consequence Analysis, Fire Protection Analysis..
3. Provided to prevent certain level of equipment damage, personal injury or death.
Firstly, fire fighting, emergency shutdown/depressuring, flare system comes to my mind. is it right? or what else can be safey critical equipments or systems?
RE: Safety Critical
Monitors, gauges, alarms, fail-safes, built-in-test, etc., are what can potentially prevent or warning of an impending safety problem.
TTFN
RE: Safety Critical
But I'm still curious.
Monitors, gauges, alarms can prevent safety problem also process upsets.
But can it be the last line of defence?
In my opinion, alarms and indicators can not prevent escalation of crisis when it already happen.
I feel that fail-safes or fire and gas detections rather can be the safety-critical items.
SweetMoon
RE: Safety Critical
RE: Safety Critical
Your ability to receive an overtemp warning in a reactor is MUCH preferrable to only rely on a containment vessel after the fact. If you study ANSI Z136.1-2000, which is the ANSI laser safety standard, you'll see that much of the safety infrastructure is about procedures, training, warning lights, interlocks, safety glasses, warning labels and shields. It's much preferrable to have prevented your eye from getting zapped than to know that you've got a medicine cabinet handy for healing the burn.
Fire sprinklers are indeed the last line of defense against fires, but if that's the only line of defense, you're going to lose. That's why smoke detectors are so prevalent, because, in many instances, it can warn you about an impending fire that could be easily controlled or extinguished, rather than waiting for the fire to get so large than you have to depend on your sprinkler system.
As an industry expert puts it, "Only you can PREVENT forest fires."
TTFN
RE: Safety Critical
Some good comments here, especially from IRstuff. A bit more of a help might be to check out two things. One is IEC61508 (or IEC61511, which applies to the chemical industry). This sets out semi-quantitative methods for assessing "safety critical" systems, using a fault tree type diagram. Others also want to use the LOPA (Layers of Protection Analysis) which means that you have many layers that are "safety critical" because many layers must fail, so 'normal operation' might still have "safety critical" elements integrated into it.
pandora