Part 3 - Calculating LOF - Flow Induced Vibration

Welcome.

Glad you made it to the 3rd series.

(Refer Part 2 for Kinetic Energy Classification)

Today we are going to calculate the flow Induced Vibration Factor (Fv)

In order to do just that, we will need to determine the current support arrangement of the piping system.

To do that, we will need to check the ISOmetric Drawing and determine the Lspan (the length between two supports)

Let us say that the length between two support arrangment is 12m (Lspan = 12m), lets determine wheather the Lspan is categorized as;

1. Stiff

2. Medium Stiff

3. Medium

4. Flexible.

How do we do that? By using the formula given by Energy Institute (Premium Subscriber, please ask me for the details of the document, i will share)

The diameter of the pipe is DN 500, therefore Dext is 508mm, pipe thickness is 5.54mm (you can check this details in pipedata apps)

Plug in the formula and Lspan, 12m is at Medium Stiff.

Therefore, we will be using the Medium Stiff formula to determine Fv.

Plug in the formula to get alpha and beta.

Alpha is 471881 and Beta is -0.8119

Fv is 12038.7

FVF is 1 for multiphase.

LOF = (5424.6 / 12038.7) x 1

= 0.451

Ok, the likelihood of failure is 0.451, what does it mean?

Well we dont like this number, we prefer for it to be below 0.3.

I will conclude at Part 4

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