Hi to all,
PCV (pressure control valve) outlet 5m 18" line Sch 40 is going to silencer.My question to all is, should we consider ambient temperature after PCV outlet or as per line list.

PCV outlet line is going to silencer. Can any one suggest?

runner,
It's always better to talk to process guys in case you have any issues pertaining to temperature or any other process parameter. Line list may reflect a temperature that line could see for very short period of time.
But point is that you need to take into consideration all possible temperature profiles that line would see.

Dear RUNNER,

I am assuming you have a high pressure steam outgoing to steam silencer where pressure loss to atmospheric pressure results at high temperatures in upstream of PSV from high I mean (more than 250 deg C). In other words Steam silencer piping either Start=up vents or Safety valve vents.

NO you cannot use ambient temperature after PCV outlet. The temperature will be a bit less but not as much and it is utmost important for any designer to consider the Pressure loss (if any) but keep the temperatures at the outlet to silencer same as in upstream of PSV.

Remember there is not considerable heat exchange going on from PSV outlet to silencer inlet.

I have done CFDs and process simulations for Silencer design and related piping. Also designed Steam Absorptive type silencers so I'm pretty much sure temperature even in silencer decrease to just a 10-50 deg C from the inlet silencer temperature.(presure and temperature design limits apply ofcourse)

Rajinder, you are lucky to have such a process team which resolves such issues. In my case I wasn't so lucky.

Regards,
Salz

Salz,

As the PCV may not have continuous service, an operating scenario with ambient temperature after PCV outlet is possible also.

Best regards,

Dear danb,

It is nice of you to point out a possible scenario when PCV will not be operative and ambient temperature is the temperature of PCV downstream line BUT...we all are designers here and I'm sure you'll also agree that all piping is designed for worst case scenarios or maximum possible temperature or pressures it has to face at any point in its life. My intention is to design or comment on the basis of worst possible cases.

When PCV is operative what are the conditions at its downstream? must be greater than ambient!!! so this becomes our basis for design.

Regards,
Salz

Well, yes and no. Sometimes a combination of a part hot and part cold can be worse than all at maximum possible temperature (e.g. nitrogen purge connected to a very hot line or Pumps lines one operating one spare, or PSV lines one operating one spare). At least in terms of loads. Maybe here is not the case but as a designer you should first investigate all possible scenarios, then to retain only the worst.


Of course when PCV is operating, downstream is at operating temperature or close.



Best regards,

Thank you for your time in replying...

I I
I______I
10" (PCV) 18" l
--------IXI-------------------------l

Example: 10" line upstream then PCV which is connecting to 18" line then to silencer.
Material A335 P11
upstream design conditions
Design Temp: T1=450
Design Press: P1= 5600 Kpag
Hydro Press: H = 11860 Kpag.

DownSteam design condition

Design Temp: T1 = 300
Design press: P1 = xxx Kpag
Hydro press: H1 = 0.0 Kpag

My question to all is, should we consider ambient temperature after PCV outlet or as per line list.

Why I am so interested is...... If I compare existing piping as per ambient temperature loads are close to allowable limits as per vendor data, If I am considering as per line list, loads are not with in allowable limits, If I considering design condition loads are as high as unbelievable.

As you all know as per process operating conditions once in a while like upstream steam is vented thro silencer, were steam is expensive $ to vent it.

In your particular case, Salz was right.

You may think at re-routing or different supports.

Regards,