Hot Oil (PetroTherm) system operating pressure vs end users operating pressure

[Ahmed Elarbagi]

Hello everyone.

If you have a hot oil (petrotherm for example) closed system with a direct fired heater heating a few end users, such as a condensate stabilizer for example. Is there a best practice in terms of the hot oil operating pressure being higher or lower than that of the end user?

Higher: If the hot oil system pressure is higher, you gain the benefit that if you have a tube rupture in the stabilizer, you will have the hot oil leaking into the condensate, not vice verse, as if the condensate leaks into the hot oil, it will flash and possibly affect the circulating pumps. It could also expand greatly, find its way to the expansion tank, pop a psv and go to a pop tank, and then into the atm, then possibly absorbed by the heater leading to an explosion.

Lower: However, having it higher is much more expensive, as this could change the HO system pressure from 20-30 psig to 200 psig. You're also risking the hot oil contaminating the condensate and no way to get it out.

Is there a standard you all see in terms of which is higher?

 

[georgeverghese]

Preferable to have HO pressure > end user pressure. This is to prevent process fluid from getting into the fired heater tubes in the event of a leak at end user HX tube, where it could reverse into fired heater and bung up the radiant section tubes with coke and a whole host of other nasties that may be in the condensate

 

[LittleInch]

I agree with George.

Also if your HO system is lower pressure then you need probably rupture discs to prevent rupture of the HO system in the event of tube failure in your heater.

Which then sprays Hot oil and condensate all over your plant....

Dealing with some contaminated condensate is much less of a problem.

 

[pierreick]

Hi,
Hazop or process safety review to take place.
I will not consider having hot oil spilled all over the plant. High risk of fire.
My 2 cents
Pierre

 

[GD2]

Hello everyone.

If you have a hot oil (petrotherm for example) closed system with a direct fired heater heating a few end users, such as a condensate stabilizer for example. Is there a best practice in terms of the hot oil operating pressure being higher or lower than that of the end user?

Higher: If the hot oil system pressure is higher, you gain the benefit that if you have a tube rupture in the stabilizer, you will have the hot oil leaking into the condensate, not vice verse, as if the condensate leaks into the hot oil, it will flash and possibly affect the circulating pumps. It could also expand greatly, find its way to the expansion tank, pop a psv and go to a pop tank, and then into the atm, then possibly absorbed by the heater leading to an explosion.

Lower: However, having it higher is much more expensive, as this could change the HO system pressure from 20-30 psig to 200 psig. You're also risking the hot oil contaminating the condensate and no way to get it out.

Is there a standard you all see in terms of which is higher?

You need to reframe the problem statement correctly.
Typically, hot oil HX are used to heat the condensate feed before it enters the stabilization tower. Condensate feeds are not directly heated due to its environment and safety concerns.
If you are talking about the feed heater HX, the system pressures will be determined based on the systems `-hot oil and condensate. Hot oil circuit will have its own system pressure and condensate it's own.
If you want to play with the hot oil system pressure, look at the entire system as a whole. You can't decide just by one component.