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Safety and Reliability Tutorial and Class Topics Chat Forum

Submitted by oseghale lucas… on

Lets discuss and analyse our mathematical topics and tutorial problems here by sharing our ideas together.

Mykola Mamykin

Regardless of the marks, the idea is great and we have to use it.

For example - in tutorial 2 question 4, tree valves with identical reliabilites of 0.9702 are placed in series. In this case, reliability of the system is supposed to be simple multiplication of all individual components reliabilities, which yields 0.913. Dr Tan's answer is 0,941.

What am I missing?

Wed, 10/24/2012 - 03:10 Permalink
Andy Reid

Hi,

Yeah this forum is an excellent idea! I'm reluctant to post a full answer as this may be frowned upon, but I believe you aren't considering the problem wholly.

If there are 3 valves in series, then they all need to open in order to allow flow, but only one needs to close in order to stop it. Therefore, the probabilities for failing to ALLOW flow and failing to STOP flow will be different.

You need to consider these two probabilities seperately and then combine them.

 

Andy

Wed, 10/24/2012 - 08:15 Permalink
Mykola Mamykin

Regardless of the marks, the idea is great and we have to use it.

For example - in tutorial 2 question 4, tree valves with identical reliabilites of 0.9702 are placed in series. In this case, reliability of the system is supposed to be simple multiplication of all individual components reliabilities, which yields 0.913. Dr Tan's answer is 0,941.

What am I missing?

Wed, 10/24/2012 - 03:11 Permalink
oseghale lucas…

Hi, mykola and Andy.....

I am happy we getting started on time over here.I would like to use

this medium to let every participants on this forum to know that this

chat forum is for contineous learning process. The idea of one mark to post

is left to the discretion of the course lecturer.

Also posting of the whole answer is not allowed as this is a thinking blog...

suggestion on how to solve is welcomed.

Back to mykola's question..

take a closer look at the question..you will notice that the 3valves

are statistically independent of each other and we are  interested on the reliability

of the system in terms of the additional two valves added only.

therefore calculating the probability of a complete cycle and raising the answer to power 2

gives you the answer..try it

thanks andy for contributing..................

Wed, 10/24/2012 - 22:37 Permalink
Mykola Mamykin

Hi.

1. Mykola is my first name. It is a general rule of politeness to spell it with capital "M" in front.

2. I believe the question goes: how does the presence of two additional valves affects reliability of the whole system, isn't it? I guess all three valves should be considered in the whole system. Raising component's reliability to the power of two gives the correct result, but then the question's meaning is vague to me. Do I make sence?

Thu, 10/25/2012 - 00:51 Permalink
Andy Reid

Mykola,

I understand your confusion but I think the question simply wants you to calculate the "system reliability" with one valve, then the "system reliability" with 3 valves. How the question is worded is slightly confusing but I believe in an exam situation that is the kind of point you could ask an invigilator to clarify.

 

Andy

Thu, 10/25/2012 - 07:58 Permalink
Andy Reid

Question 1 has me completely stumped. Can anyone point me in the right direction, even to a page in the notes where I can find the formulae I need to use.

When I set t=0 in the variable (1-t/t0)2 it inevitably cancels out the t0 term...?

 

 Andy

Thu, 10/25/2012 - 08:54 Permalink