Nixon123,

You wrote:

......i need to know whether the questions i am asking is right or wrong, whether i am going in the right path or wrong path, whether my intention to learn about manual calculation behind code formulas is right or wrong.....

Some people posting above ARE answering your questions. You are also being asked to "do your homework" and READ the material that is being suggested. There is no such thing as a trivial question in the engineering field but when you receive answers from those you ask it is your responsibility to USE the suggestions ("do your homework"). With all due respect, if you have been working in piping engineering for one year and you (at this point) are asking questions about fundamental concepts, you have not learned much about piping engineering in your one year (are your working under a senior engineer?). Now (for the sake of other people's safety) you must study harder - READ THE BOOKS!!!

It took the mentors that post answers here many years of "doing their homework" to become competent piping engineers. There are no "shortcuts"; YOU must also be willing to study the material that is being suggested to you. Read and reread the suggested material and THINK about the concepts. THIS IS YOUR RESPONSIBILITY.

Read this:

http://www.eng-tips.com/viewthread.cfm?qid=189629&page=3

Respectfully, John.