Fault Tree Analysis (FTA)

FTA is fault tree analysis, used for identifying causes required for a particular fault/event to take place.

This technique uses basic symbols of electronic & logic field. The Fundamental symbol used are AND & OR gate.

Truth table for AND & OR gates:

Input Output
A B AND OR
0 0 0 0
0 1 0 1
1 0 0 1
1 1 1 1

Symbols of AND & OR gates:

and or gates

The failure mode being studied is called head event.

The basic concept of this technique is to put all effecting events in a logical form.  Take a case of motor stoppage. The motor can be stopped due to following reasons:

  1. Power loss
  2. Overload
  3. Coil Damage
  4. Process interlock operated

Further power loss can occur if the incomer power supply fails & the emergency generator also fails at the same time. Over load can occur due to chocking in pipe line, or, the isolation valve is closed. Coil can damage due to over current or moisture ingress. Process interlock can be operated due to instrument malfunction or real high vibration.

The Logic tree can be built as follows:FTA

All the identified events can be given probability of failure depending upon MTBF calculated from past events. In case both events are required for resultant event to occur ie. AND gate, the probabilities are multiplied. In case, any one input can have the resultant impact ie. OR gate probabilities are added.

The FTA Analysis is done for finding out all probable faults possible. This enables us to attack on right cause for identify & eliminating the fault.

check some of these interesting posts of time management and of super organiser as well.
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Vanila ice cream stopped my car

Root Cause AnalysisSound crazy!!! Isn’t it.
Go through an amazing piece of case study of root cause analysis, how a Pontiac car owner surfaced an interesting issue which is hard to believe.

A complaint was received by the Pontiac Division of General Motors:
‘This is the second time I have written to you, and I don’t blame you for not answering me, because I sounded crazy, but it is a fact that we have a tradition in our family of Ice-Cream for dessert after dinner each night, but the kind of ice cream varies so, every night, after we’ve eaten, the whole family votes on which kind of ice cream we should have and I drive down to the store to get it. It’s also a fact that I recently purchased a new Pontiac and since then my trips to the store have created a problem….
You see, every time I buy a vanilla ice-cream, when I start back from the store my car won’t start. If I get any other kind of ice cream, the car starts just fine. I want you to know I’m serious about this question, no matter how silly it sounds “What is there about a Pontiac that makes it not start when I get vanilla ice cream, and easy to start whenever I get any other kind?” The Pontiac President was understandably sceptical about the letter, but sent an Engineer to check it out anyway.
The latter was surprised to be greeted by a successful, obviously well-educated man in a fine neighbourhood. He had arranged to meet the man just after dinner time, so the two hopped into the car and drove to the ice cream store. It was vanilla ice cream that night and, sure enough, after they came back to the car, it wouldn’t start.
The Engineer returned for three more nights. The first night, they got chocolate. The car started. The second night, he got strawberry. The car started. The third night he ordered vanilla. The car failed to start.

Now the engineer, being a logical man, refused to believe that this man’s car was allergic to vanilla ice cream. He arranged, therefore, to continue his visits for as long as it took to solve the problem. And toward this end he began to take notes: He jotted down all sorts of data: time of day, type of gas uses, time to drive back and forth etc.
In a short time, he had a clue: the man took less time to buy vanilla than any other flavor. Why? The answer was in the layout of the store. Vanilla, being the most popular flavor, was in a separate case at the front of the store for quick pick up. All the other flavors were kept in the back of the store at a different counter where it took considerably longer to check out the flavor.
Now, the question for the Engineer was why the car wouldn’t start when it took less time. Eureka – Time was now the problem – not the vanilla ice cream!!!! The engineer quickly came up with the answer: “vapor lock”.
It was happening every night; but the extra time taken to get the other flavors allowed the engine to cool down sufficiently to start. When the man got vanilla, the engine was still too hot for the vapor lock to dissipate.
The problems may sound crazy sometime. There is always a systematic approach for geting to the root cause. The engineer first off all, did believe that there is some technical reason behind the Pontiac getting stopped every time vanilla is bought. He collected every data. He tried to find pattern & found one. He then related the pattern with probable technical issue & reached root cause.
We in daily life, are facing such issues & had become use to it. Improvement start, if we do not accept these issues & work dedicatedly and systematically for digging out the root cause. After years of experience, numerous RCA (Root Cause Analysis) & reliability tools have been developed and are available openly.
We aim to provide expert solution for helping out our business partners for long term solution.
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