1 reply to this topic

[kybele39]

All,

I post my topic in a different forum. I saw this forum just now. SO copied my question here. If you give your inputs I will really appreciate it.

We are trying to come up with a sizing method for a PSV located on the shell of a water bath heater. Theater has a two process coil in it and one the coil heating medium has a really high pressure.

We assume the pin hole diameter is 0.25inches and we calculated the mass flow rate will pass through this hole. The process gas in the coil passing through into glycol water mix. The glycol-water temperature is 250F. And the shell is filled with this solution.

My questions are

1. What are the phenomena occuring at the pinhole and in the bath?

2. The process gas in the process coil is at the 1900psig pressure and at the 100F temp. The heater shell is pressurized at 40psig at 250F. When the gas starts leaking into bath fluid (glycol/water mix) is the process gas actually cooling? (at the pin hole, the gas temperature shows -77F at the 40psig bath pressure. )
3. If the gas is not cooling enough due to the bath temperature, then when the pressure equals to bath pressure and finally reaches the set pressure, the PSV will open?
4. Should the PSV sizing base on the bath fluid expansion due to pressure increase taking the reliving flow equal to gas mass flow that is calculated from the pin hole? Or should we base on the gas expansion due to the temperature increase from 100F to 260F?
5. How is the relief loads are calculated?
I will appreciate if you input with your expertise.

Thanks,
Kybele

[Bayo Alabi]

I posted  response to this topic in different forum. 

 

You do not need a pressure/vacuum relief device on the shell of the heater. I wrote the following in your previous post under different forum:

 

Water bath heaters do usually have an Expansion Tank with a Fill Hatch on the shell. This is usually the case. Check if you have this arrangement. If so, you do not need a pressure/vacuum protection in case of tube rupture as the gas is vented to the atmosphere. In addition, if there a contraction if liquid inside the shell, the same Expansion Tank/Fill Hatch will admit atmospheric gas into the shell for vacuum protection.