Sur elook like ther eis room for interpretation as this topics evolved but where i came from, a critaitcality assessment was done to eliminate this specific issue of "interpretation " and making sure that every player in the plant are on the same page...

So we use a simple database that look at specific criteria for each assets included in teh analysis. The criterai we choose were:

-Safety
-Environmental
-Sales
-Production
-Maintenance

For each of these criteria, we have 3-4 questions that relate to them and we then ask ourselves, what will be the impact of failure if this equipment fail ? yes i know that there is all kind of failure modes for all asset but we concentrate on, was looking at the design function of an equipment and use that as part of the analysis.

In my mind, what is really important is to be consistent throughout the analysis and rank all asset using the same approach. If one person is use to facilitate the process, the result are usually consistent and the assessment "means" something to the parties involve as long as everyone agrees on the objectives.....

The database was build in such a way that each asset end up with a "score" that range from 1000 (most critical) to 0. This value was then uploaded in the CMMS under each asset # and use for planning, scheduling and deciding what equipment we will do RCM first.

Some folks will call this prioritization, some others call it criticality, i called it criticality and it work for us !!!

Vee,

Which document contains the safety critical systems which are accepted by the HSE?

I have serach the HSE website and found UKOOA EHS04 Management of safety critical elements. Is this the source document that identifies the safety critical systems for oil & gas industry?

Josh,
I vant recall as it is some years since i worked with this subject. However UKOOA is the O&F industry representative and the document title sounds right. Have a look inside and it will probaly ring true.

Josh,

I am not too sure that is the document you are looking for. The HSE is an advisory / regulatory body and as such they are bound by rafts of legislation.

THis means there are layers and layers of definitions for almost anything you want to do.

For example: A safety element...

quote:

Safety Case Regulations Reg. 2 Definition of SCE - "safety-critical elements" means such parts of an installation and such of its plant (including computer programmes), or any part thereof:

a) the failure of which would cause or contribute substantially to; or

b) a purpose of which is to prevent or limit the effect of, a major accident.

Not all elements of a system are safety critical just because one of them is, and so on and so forth.

If memory serves correct a safety critical element is a different creature from a safety critical system.


Cheers

Vee,

Can the 13 safety critical system be the Electrical protection system integrity?

Josh,
Daryl is absolutely spot on when he differentiates between Safety Critical Systems and Safety Critical Elements.
Systems have many building blocks, which we call elements. As far as Offshore O&G industry, tehre are systems that are considered as critical. We do not do have to do an RCM to find out at failure mode level whether a Fire Protection System is critical.
Within Systems not considered safety critical, we may have a few elements such as relief valves which are critical.
While power generation is considered a Safety Critical System in the Offshore O&G industry, usually Distribution is not. I am not sure what you mean by electrical protection system. If you mean items like circuit breakers, they are elements.

This message has been edited. Last edited by: Vee,

I mean protective relays which forms the elctrical protetion system.

Josh,
Relays that perform a protective function have hidden failures. Depending on what they protect, they may be safety critical elements. If you did an IPF or RCM study, this will be highlighted. You can then assign a task to mitigate against this failure mode as you would for other failure modes.

Safety Critical Systems are ones that have the potential to pose a serious risk to the safe operation of the whole facility. If the whole system is not working, you should shut the facility down till it is rectified. For example in a fire protection system, a number of elements may cause this situation, e.g., Fire Pumps, Fire Water Piping, Deluge Valves, Sprinkler Heads etc. But if a sub-system does not work in one specific area, only that area needs a shutdown.
At the top level, it is the whole fire protection system that matters, so it must be analyzed using appropriate tools such as RCM. As we go down to sub-system level, we may look at, say, the deluge system. There may several blocks in the plant with such deluge systems. Let us look at one small geographical area like the sales gas compression area. The elements here are the deluge valve, the sprinkler piping, and the sprinkler heads. Each of these elements needs a detective task to assess its condition; sprinkler heads may be clogged with corrosion products or other debris, piping may be corroded or blocked by debris, deluge valve may fail to open on demand. Any one of these elements can cause the sub-system to fail in this local area. If the deluge valve is actuated electrically, the relay initiating the actuator movement is critical. If the power supply to the actuator is controlled by another relay, that is also critical.

All Safety Critical Systems should be analyzed using the appropriate risk based tool. All protective elements that are not part of a safety critical system also need analysis, e.g., a relief valve on an air reciever or a reverse-current relay on a transformaer.

This message has been edited. Last edited by: Vee,

I mean protective relays for MCC and switchboard.

Josh,

quote:

I mean protective relays for MCC and switchboard.

From the previous posts, you will see that these items may be safety critical elements depending on the risk they pose(i,e, probability x consequences of failure), but the power distribution system itself is unlikely to be a high risk one, since there will invariably be a high level of redundancy.
If these relays are known or shown to be critical, apply the appropriate maintenance task, following the RCM decision tree. or any other suitable method.