Sending vapor line to liquid line

[Chem2020]

I am currently working on a design of storage vessel pressurized with nitrogen. My team decided to send the vent Line to liquid line at the discharge of pump. I have never seen vent line connected to liquid line. I appreciate if anyone can explain if this is a good or bad design.

 

[Latexman]

Let you send us a P&ID attachment. The few words above are most likely not the full picture.

Good luck,
Latexman

 

[TD2K]

As Latexman said, the devil is in the details. It's not a usual design but it's not one I would automatically rule out though it's also not likely something I would pick for my first option.

I would want to look at where the vapor is going to go, obviously the destination has to be able to handle it. A floating roof tank wouldn't be a good destination. How much vapor do you plan to send to the line, is it going to affect the hydraulics adversely? What if the pump isn't running, the pump is going to start up the next time with perhaps a line with a lot of vapor. Any pressure concerns or different pipe spec issues from connecting these two systems together? Any production specification issues? Just a few things I would want to think about.

 

[sshep]

Is it possible that this is just an equalizing line to vent vapors back to the vessel when priming the pump?
Just a thought,
sshep

 

[SNORGY]

Or nitrogen purge scheme...?

 

[786392]

Still as Latexman said P&ID is a must.

To correctly analyze,guide/attempt for problem resolution with particular details e.g.

Where is the subject liquid pipeline's routing/final termination point i.e. going through some vaporiser to flare system or elsewhere??

Best Regards
Qalander(Chem)

 

[Latexman]

The OP should provide more data, like a sketch, PFD, P&ID (preferred), and/or detailed description; or, we can keep polishing this turd until the server is full.

Good luck,
Latexman

 

[Chem2020]

I had to do hand sketch. The idea is to collect suction pump strainer liquid in a horizantal vessel. All wastes will be captured in the filter. Operators will clean strainer, and open the manual gate valve and send all liquid to the horizantal vessel. It is necesary to have the container because the filters are huge as a result high volume and very hot (560 F). The collecctor is blanket with nitrogen. We do not want to waste any of the liquid so liquid in the container will be reciculate back to the suction line downstream of the filter. As you can see on the sketch the vent is connected to the discharge of a pump. This pump will run continously and never stops. Only during a manintance. I was more concern with sending vapor to liquid line which is already sized for liquid and not two phase flow. If there is two phase flow in the line then the line needs to be sized for two phase. The Liquid is Heat Transfer Fluid. Thank you and sorry for the lack of information. This is all I know at this moment. operating pressure and temprature is written on the line.

 

[SNORGY]

I think sshep's guess looks pretty close to what my interpretation of the sketch would be.

It looks like the recirculation line ties in *upstream* of the pump filter...

Maybe its just me, but from the sketch, there isn't enough information for me to piece together what they are trying to do. If the pump at the bottom of the page runs continuously then, depending on the N2 pressure on the vessel (is it higher than 206 psi?) the intent might be to blowcase the collected drained liquid into the downstream tank where, presumably, the blanket N2 pressure is much lower.

Given the temperatures and the fluid (heat transfer fluid?) involved, part of me, at least, thinks that a corrollary intent might be to make sure that N2 is in the system in preference over air in order to stay below a lower flammability limit.

 

[Latexman]

I see a flow arrow on the line from the horizontal tank to the pump discharge, but I see no check valve. Is a check valve there or not? If not, the line could be used to dilute the filter drainings with fluid from the tank. Maybe this would lower contamination and decrease viscosity or some other adverse property of the filter drainings?

Good luck,
Latexman

 

[dcasto]

You have a blowcase that will push heat transfer fluid back into the system. The blowcase is used to capture the heat transfer fluid when you drain the filter.

You want to to take the N2 used to run the blowcase and vent it into the tank. Wow, talk about anal, what the heck is in that heat transfer fluid that a few ppm when vented into the air will harm anything? If it is that bad, it will vent out of the top of the tank eventually.

You do realize if the tank (the storage tank) is full, you may only be able to vent the blowcase down to say 15 psig and you will have to vent that to the atmosphere.