Design pressure & temperature for drains & air vents piping?
Design pressure & temperature for drains & air vents piping?
(OP)
Dear Sirs,
How we decided drain & air vent piping design pressure & temperature after 2nd isolation valve for boiler proper & non boiler external piping as per ASME B31.1?
As in my case we planned to collect all drains & vents in common drain & vent collectors. Please advice how to decide design parameters after 2nd isolation valve to common collectors.
How we decided drain & air vent piping design pressure & temperature after 2nd isolation valve for boiler proper & non boiler external piping as per ASME B31.1?
As in my case we planned to collect all drains & vents in common drain & vent collectors. Please advice how to decide design parameters after 2nd isolation valve to common collectors.





RE: Design pressure & temperature for drains & air vents piping?
Independent events are seldomly independent.
RE: Design pressure & temperature for drains & air vents piping?
This is often a key item when you HAZOP the system and needs to be looked at carefully as early as posisble as the design pressure and temeprature of vents and drains is often very low compared to the boiler. Getting it wrong is frequently a cause of failure and incident when a vent or drain is over pressuriseid and ruptures or is exposed to much lower or higheer temperatures than design. Just becasue it's "the vent" or "the drain", doesn't mean you can ignore the potential for over pressure. Equally having to change it later in the design is also a real pain.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Design pressure & temperature for drains & air vents piping?
Very very thanks.
As your reply, can i take drain & vent design pressure & temperature as vessel/main piping pressure & temperature.
Sir you have any ASME B.31.1 code reference for selecting these parameters.
RE: Design pressure & temperature for drains & air vents piping?
This is simply a matter of establishing your design parameters and looking at your system to see what design ratings are justified or not. If you have a free vent or drain pipe with no valves to atmosphere that can't get blocked then this can often be a lower pressure rating (sometimes much lower) than the vessel. It all depends on your design.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Design pressure & temperature for drains & air vents piping?
Thanks for reply.
I am not reaching to final decision for selecting these parameters. i will give you one example as following. if possible you are requested to tell me final value as your consideration.
1. I take 1 drain from the main steam piping having design pressure 171.0 Kg/Sq.cm(g), temperature 550Deg.C. For drain piping up to 2nd isolation valve i keep full pressure & temperature. now i want to know how i decide these parameters after isolation valve to common drain collector. (this length nearer 50m in length).
2. In other case i given one vent in piping having design pressure & temperature as 171.0 Kg/sq.cm (g) & 353 Deg.C. so please suggest design parameters after isolation valve to common vent collectors.
thanks in advance.
RE: Design pressure & temperature for drains & air vents piping?
Only you know the relative sizes of the drains, vents and header and other things venting into your common header. A vent and drain study when you have many items connected can be a major study to establish what the maximum pressure the system will see without being too conservative. I've not had direct experience of steam so cannot comment on what happens to the drain if you accidentally dump super heated water into it, but it sure isn't going to be pretty.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Design pressure & temperature for drains & air vents piping?
I need help from other forum member also if any one can do.
If any one have ASME B.31.1 code reference for selecting these parameters. please tell me.
RE: Design pressure & temperature for drains & air vents piping?
It can look a little bit odd having a pressure break at at tee, but has happened in the past for this exact reason, i.e. pressure in a small drain line can be a lot bigger than in a much bigger header.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way