Paul:
Maybe you need to restate your question about creating P&ID's. Given a PFD and
knowledge of the process, somebody has to create the P&ID - and who better than
the engineer that knows what he intends to do, what he wants to monitor and
control, and what can go wrong. Agreed, you will have a number of "discussions"
with your instrumentation/automation person, unless you and he are the same guy.
But, from where I am, we start out with a flow diagram, possibly several listing optional flow paths or rates. Then we start putting in the valves to make the flow paths/rates/pressures happen. Then comes emergency isolation and blowdown valving. Next, what valves have to be controlled, where do you get the intelligence to control them, and what are the signals that have to be monitored. Before you know it, you are arguing over whether to use RTD's, thermocouples, local readouts....and VOILA! you created your P&ID. I would be really worried if it was created by an automation guy - they often know all about the transducers, PLC's and RTU's, but they don't really know the process. They will pick up the obvious valves to control, and conditions to report, but miss the finer points of what to monitor for the first signs of things going unstable. That's where we come in - you have to be in bed with the process to really control the "what if's".
So there - I've flung down the gauntlet, anyone want to throw rocks or roses??
George McKinney
Don't forget that a P&ID is also useful so that there is some sort of planning involved in what you want to do and which fluids you are expected to transmit. For those that are *really* good, all they need is a PFD and a pencil (and a lot of background knowledge). Even more brilliant are those people who come up with an innovative process related to fluids and design and build it all by themselves. A lot of these people are, um, "no longer with us" due to their lack of safety precautions.
Step one is learning how to read and understand a P&ID.
Which leads me to this question for the really experienced guys out there: based on a PFD and an understanding of the process, could you create a P&ID yourself? Does the computerized logic for plant/process control come from the computer programmers/IT department or the engineers?
A real tough question for this group, I'll bet.
Paul
> you mean to find out for discharge of the pipe.
> Generally pipes are designed for quantity of discharge.
> Discharge=area*velocity
> velocity will effect your friction inside the pipe(friction is
proportional
> to square the velocity of the fluid).If you want to go for less
velocity
> then you must choose large diameter pipes.
> once you decide your diameter for particular discharge then pressure
will
> decide your thickness of the pipe,means which schedule pipe you want
to use
> for particular case.
> all above considerations are primary.
> If you want to calculate exact diameter and thickness you must
consider all
> elbow,fittings ,contraction and expansion losses as well as work done
on
> the fluid for moving fluid from place to place then only you will get
exact
> dimensions of the pipes.
> hope this may help you.
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[Non-text portions of this message have been removed] Received on Thu Apr 01 07:50:00 2004
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