What is considered "critical component"?

[hchiutx]

I've been looking for a definition or a guide on what constitutes a critical component to be included in the Critical Components List for the Technical Construction File. I have not had too much success. My intuition tells me that it has to be based on safety (i.e. all components on the safety circuit, if any) and components that the machine cannot function without.

The danger is to go overboard and include everything! My customer suggested that I include the monitor and keyboard and mouse too which didn't make too much sense to me - you can grab one at any store as a replacement and the equipment doesn't even need these to function (they are good for diagnostics in case of failure). However there aren't any guides I can use to convince my customer otherwise. Any suggestions? Thanks.

 

[andym]

In electrical items, the critical components are those that their failure could lead to a breach of electrical safety. Not enough info. but in a computer system it will be a power supply and in the power supplies it will be usually, Mains fuses, fuse holders, IEC mains connectors, components on the mains side (Y1, X1 caps etc.).
Transformers, High voltage capacitors (energy hazard), any components that cross the primary-secondary boundary - optocouplers etc.

Your applicable safety standard should guide you on the list and Creepage and Clearance which catches most people.

A good book is "Electrical Product Safety" A step-by-step guide to LVD self-assesment by Tzimenakis & Holland - published by Newnes.

For IT equipment, the applicable safety standard is IEC 950 or EN 60950 if in Europe. Always take professional advice when selecting the correct safety standard.

 

[ccaserta]

If the enduser changes devices on you without your approval or does not have you update your TCF it violates your D of C and your company is not responsible.

The ponit of listing you critical components is to support your Declaration of Conformance for the system for CE Certification or Licensing. By collecting the documents you prove all applicable test have been performed on components that are critical to the system.

Christopher Caserta
ccaserta@us.tuv.com
Ph:904-225-0360

 

[Jbones878]

There are a number of reliability standards that attempt to define critical components. They include operations and cost, in addition to safety. What is more important are critical failure modes; these you must design out or compensate for.

If you have further interest, please send a note and I can send some reliability references. It all comes down to reliability engineering, not taught in college.

 

[Jbones878]

Typically, for something like a PC, there are few if any critical components. The whole PC costs less than $2000; what's critical is the information. That you simply backup. So if anything, I would vote for the hard drive in a critical application. (What is the application?)