Redundancy

HI EXPERTS
IN SAFETY ASPECT CAN ANYBODY EXPLAIN TO ME WHAT IS REDUNDANCY AND PERHAPS WITH A SIMPLE EXAMPLE
THANKS EXPERTS

There are many levels, or types, of redundancy.

Some Redundant Systems go as far as having multiple PLC's and multiple field devices. The more critical the situation, the greater the need for redundancy. The Space Shuttle has multiple redundant Systems.

You asked for a "simple" example. An E-Stop typically has 1-contact dedicated to the power circuit (it might also have another contact dedicated to an indicator for that E-Stop).

You can increase the reliability*** of the E-Stop Function even if the contact is fused closed. You do this by adding more contacts onto the E-Stop. If you have three contacts, wired in series, instead of one, the E-Stop Function becomes more reliable.

*** This really only increases the reliablility of the contacts and therefore the Function... HOWEVER... there is still a chance that the E-Stop itself can malfunction. In that case, having 20 contacts on the E-Stop wouldn't make a difference!

You only have to go so far before your redundancy starts to become redundant!

Terry gave a good explanation.

redundancy:Electronics. Duplication or repetition of elements in electronic equipment to provide alternative functional channels in case of failure

A simple example is when using dual contactors on a system in series, the controller monitors the auxillary contacts on the contactors. IF for any reason either contactor doesnt close OR open (when they should) then the system will go into alarm mode. The use of 2 contactors and auxillary contacts is redundant.

I looked up redundant in the dictionary

You only have to go so far before your redundancy starts to become redundant

Click to expand...

I looked up redundant in the dictionary. It told me to see redundant. [Robin Williams]

Redundant system.

At many locations I would install a PLC to take place of a relay logic system. Most all cases the relay logic system had became in bad repair and something had to be done and some inovative young tech had convinced the upper management to install a PLC. Not only did I install a PLC I had to recondition the relay logic system for REDUNDANCY, they didn't trust the PLC, they insisted on the redundant system.


Roger

Redundently Redundent

When I worked an a famous Nuclear power plant all of our critical systems had a 100% identical backup system. A and B. Each of these systems had two emergency safeguard activation systems (ESAS) monitoring them. System A had ESAS A&C monitoring it. System B had ESAS B&D monitoring it. Then the ESAS system had a two out of three logic scheme monitoring it. All of this was designed and built before the advent of PLC's.

All system there also used what I would call passive redundancy. every wire, relay, bolt, etc was de-rated. #10 wire could be loaded to 15A, etc.

So I guess the question of how much redundancy do I need depends on how ugly thing could get if the primary system fails.

Hello !
That's a tricky question(big area), you could read something about it from these pages:
https://mall.ad.siemens.com/de/gues...063-993-745-744-743-1-746-752-751-&jumpto=746

(you can select the areas from the left side)

It gives you an idea what redundancy/failsafe is all about ?

b.r
nicke

Was that TMI?

KMG said:

When I worked an a famous Nuclear power plant all of our critical systems had a 100% identical backup system. A and B. Each of these systems had two emergency safeguard activation systems (ESAS) monitoring them. System A had ESAS A&C monitoring it. System B had ESAS B&D monitoring it. Then the ESAS system had a two out of three logic scheme monitoring it. All of this was designed and built before the advent of PLC's.

All system there also used what I would call passive redundancy. every wire, relay, bolt, etc was de-rated. #10 wire could be loaded to 15A, etc.

So I guess the question of how much redundancy do I need depends on how ugly thing could get if the primary system fails.

Click to expand...

In that case the redundant human controllers failed.

Peter, You are correct! That was the major failure.

I now understand the relevance of KMG's Avatar.

We use rdundancy for PLC's as well, 2 PLC's with the same program if one crash the other take the relay!!