FV For Vessel with direct pump connection.

[MohdYaseen2010]

Dears;

I had instructed our designer to consider FV for the vessel that directly delivering to pumps.
In my view, all vessels having pumps at its downstream (directly) or designed for flush-out (sand accumulation, etc.) shall be deigned for FV?
I am right? please correct me if am I wrong.

Mohd Yaseen

 

[LittleInch]

Fv = full vacuum? Please don't assume everyone uses the same abbreviations you do.

Well Full Vacuum is certainly a worst case scenario, but for many tanks it would increase costs by a factor of 10.

All vessels need to be protected from high or low pressures. How you do that is up to you looking at whether it increases costs to make it bullet proof or you find a different less costly path which does the same job, e.g vents or PV valves

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[RVAmeche]

Isn't there an old saying that anybody can design a bridge, but engineers can design a bridge that just barely works?

The same concept applies here. Yes, FV is the most conservative but as LI pointed out, its the most expensive. If the money isn't an object, great, go for it. If costs do matter, calculate the expected operating vacuum, design the vesesl to be a bit stronger, and install adequately sized PV/emergency venting.

 

[MJCronin]

https://www.eng-tips.com/viewthread.cfm?qid=366746

MJCronin
Sr. Process Engineer

 

[MohdYaseen2010]

Dear LI;

Thanks for highlights about abbreviation (will consider in future).

Dears;
Yes Full Vacuum will increase the cost much but regardless the cost view, I want to know its necessity, is it MUST or not on such case or not.
I have stated general configuration (vessel then pump) but in our case we have two types vessels didn't have PSV (or any further breathing device (Flare Knockout Drum) & vessel with PSV (Separator).

Dear MJ;

Thanks for the valuable post shared, I remembered I have passed through it before where I have concern about the concept of Half-Vacuum (I thinking its meaningless), either go for Full Vacuum or leave it at all.

Dears;

I want to point out also that for our case (also explained in the link shared by MJ) that some vessels having high Internal Design Pressure (2.2 MPa) so inherently will be FV protected.

Mohd Yaseen

 

[TiCl4]

I had instructed our designer to consider FV for the vessel that directly delivering to pumps.
In my view, all vessels having pumps at its downstream (directly) or designed for flush-out (sand accumulation, etc.) shall be deigned for FV?
"I want to know its necessity, is it MUST or not on such case or not."

Mohd,

To answer your question, it is NOT required to specify full-vacuum for vessels that are directly pumped out. It IS good practice that you consider the credible min/max pressure scenarios for each vessel and design for that scenario. For atmospheric or low pressure storage tanks, especially of a large diameter tanks, it will drastically increase costs (or may just not be feasible) to design the tank for full-vacuum rather than providing a vacuum breaker. There is a reason almost all large storage tanks I have seen have vacuum breakers and are not designed for full vacuum. I don't believe API 650 or 620 address a full-vacuum design - can anyone confirm?

For pressure vessels, it may add a lot, a little, or no cost at all to have full-vacuum, depending on the vessel dimensions and MAWP. To specify full-vacuum carte-blanche for all vessels that are pumped out of would not only be costly, but it would be lazy engineering as well.

Edit: Spelling

 

[MJCronin]

TiCl4 gives good advice ... I agree...He also states:

I don't believe API 650 or 620 address a full-vacuum design - can anyone confirm?


No, these two thin walled codes do not address FULL Vacuum design... However, many tanks are designed for a light partial Vacuum of between 0 and 7 inches of water.

If there was a chemical process reason to have full vacuum design for a large storage tank, then the plant design must change to use ASME-VIII style storage vessels (probably dished end vessels)

When there is a need for vacuum protection of API designed tanks, (sudden cold rainstorm causes condensation) robust and redundant Vacuum breakers must be included in the design

Also see....

https://www.cheresources.com/invision/topic/26830-full-vacuum-spec-for-api-620-or-api-650-tanks/

MJCronin
Sr. Process Engineer

 

[DieguitoI]

If liquid has vapor pressure higher than 1 atm at the min operating temperature I will not design the vessel for FV.