9 replies to this topic

[Process1990]

Hi everyone 

If anyone can help me with this example in API 14E (EXAMPLE A2 PUMP SUCTION PIPING DESIGN)

I had highlighted the part i can not understand (hf & the number 0.433 where did it come from) .

 

 

Thanks

 

 

Attached Files

•  Doc1.pdf   382.56KB   42 downloads

[Bobby Strain]

The formula simply converts the pressure drop in psi to feet of liquid. Were you asleep in class when this was discussed?

 

Bobby

[Napo]

Process1990,

 

Bobby has reason, is a simple conversion, I attached you the factor.

 

Napo.

Attached Files

•  Conversion.pdf   252.7KB   38 downloads

[Process1990]

Bobby,

If you just bothered to calculate the final result 0.09 you'll find it will be 0.128 not 0.09 .

So please tell me about that .

Napo, 

Many thanks to you .

 

 

Regards 

[MTumack]

It would appear that the specific gravity has been taken into account on the numerator in lieu of the denominator (or proper order of operations was not preformed) of the calculation in that version of the text.

 

0.046 * 0.825 / 0.433 = 0.0876 =~ 0.09

 

Not sure if it is correct in my copy, but seems like an arithmetic error.

[Saml]

Hey Process.

Take it easy.

Bobby is like the Grouchy Smurf in this village. He has a very good heart and is one of the most valuable contributors to this forum.

And yes. It appears that you stumbled into an error in the standard.  However it is not what you asked in your first question.

 

Cheers.

[Process1990]

Smal,

Do not worry . Bobby is an old man and we all have to respect him.  

 

MTumack,

Thanks . But I agree with Smal that it's an error . 

 

 

Best Regards

[Bobby Strain]

You will soon learn that I don't do calculations or check any work. I just offer advice.

 

Bobby

[Art Montemayor]

Process1990:

 

These comments are not meant as a criticism or put down to your query, but rather to address your comment to Bobby Strain and to let all know that I’m moving this thread to the Student Forum, since you are clearly a student and this topic is clearly also not related to Chemical Process Simulation.

 

Although Bobby’s response may not be sufficiently detailed to you, it is nevertheless completely rational and correct with respect to answering the basic query:

 

The math displayed is nothing more than a conversion of fluid density per foot of fluid height to obtain a static head.  We know the fluid gravity, so we need the water density per foot of height.  This is simply done, as Bobby indicates, as follows:

 

Water density/foot = (62.4 lb/ft³) / (144 in²/ft²) = 0.4333 lb/in²-ft

 

That should answer your specific query.  Bobby deserves some rightful respect.  As the old Spanish saying goes, "Mas sabe el diablo por viejo que por diablo".

 

The next key learning for you - and for any other young ChE student is that you should never take any API (or other “sacred” document) for granted when reading or studying the related math.  ALWAYS check the math and the rational reasoning.  This is not the first - and ONLY mistake in the API documents and standards.  They are human also (and sometimes dumb).  As an engineer you are always challenged to use your intelligence and common sense.  You are well advised to always check and/or challenge given standards and calculations carefully and thoroughly - especially if you are involved in process design.

 

I hope these comments help you out and give you some insight into API documentation.

[Process1990]

Art Montemayor,

Thank you for your detailed answer but you all must know I respect Bobby a lot that's why I tagged him .

His experience is obvious in his answers .

 

 

Regards