criticality Rating for valves

Hi all,
How do we assign criticality Rating for different types of valves. Do we have a standards which discusses it. What is the logic for assigning criticallity rating.
Does criticallity rating and level of inspection has any connection or is it specific to the process or project.
For example PSV's have criticality rating of 1 so it has to have a higher level of inspection of 1 which means a resident inspector at suppliers premises.
Can we say small bore manual valve is less critical than PSV when it is placed in a critical position in the plant. In this case do we need to assign a higher inspection level for this valve.

How can we assure the quality of custom made valves of special size or design.
Are certan valves more important than others.If it is so what is the order of importance.

I think I have confused you all a bit because i am also bit confused.

Please give some thoughts on this topic.Thanks in advance.

regards
Deepu

Hi Jop,

Thanks for the reply.
The procurement of pipe fittings valves(especially custom made valves which may have a long lead time) etc from different countries creates a situation where we need assurace regarding quality.One way of acheiving this is to ensure the extend of QC monitoring attributed to each items is consistent with the complexity and application of these items in relation to their design fabrication and process operating requirements.
I will reproduce from the project procedure document for criticallity and inspection levels

1.For level 1 criticality rating and inspection level 1
Resident inspector or regular presence /High visibility of inspector at supplier and /or Subcontractors premises

2.For level 2 criticality rating and inspection level 2
Attend hold and witness points as specified in supplier ITP's

3.For level 3 criticality rating and inspection level 3
Witness Factory Accepted testing(FAT) or Site Acceptance Testing(SAT)

4.For level 1 criticality rating and inspection level 4
Receipt inspection only

I think if we procure an item which takes high lead time it needs to have a high QC inspections during their manufacture especially if it is manufactured and procured directly from a distant country.
In my question I was looking for assigning criticallity rating for different valves viz.large bore actuated ball valves(Top/side/side&top entry-flanged and welded),Small bore manual ball valves(side entry),small bore check valves,small bore globe valves,Double block and bleed valves,pressure regulators and pressure safety valves.

Criticallity is determined by a rating criteria of personal safety,hazard to environment,fluid characteristics,economics in case of an operational failure,Economics in relation to design or manufacturing failure or rework,design complexity and availability of proven design,complexity of manufacture,complexity of maintanence after failure and material traceability and identification.
we give different points to each criteria and if the total valve comes between a particular range it will be rated level 1,2,3 or 4.
I would like to know what is the order of complexity for different types of valves based on experience.

Any thoughts are welcome.


Thanks
Deepu