PROCESS PLANT HIGH POINTS/LOW POINTS AND FREE DRAINING

[FRANCISPIPER]

Hi,

I am a freelance piping designer and in the past few years I have been working on either pharm. jobs or equipment modeling etc and have been limited in my actual pipe design during this time and so my memory is not was it was ! I have recently returned to oil and gas design...

I get confused when talking about high and low points and free draining and when a pipe can or can not have a low point.

It is my understanding that the P&ID will always indicate when a slope or free draining is required ...

A pipe run from a relief set will always slope to the knock-out drum with NO POCKETS & MUST FREE DRAIN - Is this correct ?

A line containing either gas or liquid can have a high point or low point as long as either a drain or vent (where required) is present and approved by process..... ie. no liquid build up in the gas line...

I ask this as after a recent site vist where a propane line had a complex run but was informed it was ok as the line had been through a small knock out pot and was "dry"....

What I am trying to get to is when is it ok to have a high and low point in the pipe design ...

It hasn't helped working on pharm jobs recently where everything has to slope !!!!

I really appreicate any help here ..

Many thanks

Kevin

 

[knapee]

Dear Francispiper

Since no one would like to give you comment on this issue, I

would post my suggestion here. (I hope it may fit your topic).

The slope marked on P&Id is depended on the process requirement.

Ex. fire header pipe should be marked a slope at least 0.2%

downward to knock drum to prevent the liquid accumulation.

And,pocket and trap installation is not allowable in piping.


Thanks.