6 replies to this topic

[fallah]

If thermal expansion is due to a heat source other than fire (with a lower heat input, e.g. solar radiation) would it be the case, normally, that a 3/4" - 1" TSV could be considered for vessel protection against overpressure?

For fire case, a PSV should be considered and to be sized such that it can handle each of three probable loads consisting of liquid relief (initial relief), two phase relief (after a little liquid is vaporized) and gas relief (after space created above liquid surface is considerable and also when all liquid is vaporized).

Largest calculated orifice size among above mentioned relief situations should be considered for PSV selection in fire case.

Vapor fraction depends on the liquid composition,operating pressure,wetted wall,....

[JoeWong]

"Thermal expansion" (due to solar heating as understood) and Fire heating case area, key parameter is the heat flux. Fire have higher heat flux than thermal expansion, so i believe it is governing in many event.

May be i did not put too much thinking into it. I believe LHV is determine by composition and component type in the fluid. Not sure how vapor fraction affect LHV. How you came across above statement ?

[sachindhopade]

hope u find this usefull
http://www.processcalculator.com/

[ankur2061]

hope u find this usefull
http://www.processcalculator.com/

Sachindhopade,

Are you an agent of the above mentioned website or just a plain idiot who doesn't know what he is talking about?

[Dacs]

Is it necessary to consider thermal expansion scenario for liquid filled vessels (eg. filters,hydrocyclones,etc) which contains cold liquid and getting expanded during fire case scenario.
My ambiguity is I suggested to calculate liquid flow rate for thermal expansion also by taking the heat input calculated for fire case. Finally, by calculating the PSV orifice area for both fire case and thermal expansion we can come to know the governing case for orifice selection.

Is it right method? Pls justify..

Will fire case be governing ever, or thermal expansion also be govering in above said method?

Also suggest me what vapor fraction shall be taken in Hysys to find LHV for fire case and thermal expansion scenario .

If you honestly feel that the thermal expansion scenario is worth investigating, then do so. I think it's just prudent for a process engineer to consider the worst possible scenario in every design that we do.

Usually however, 3/4"x1" size PSV usually suffices for thermal expansion. I would like to go out on a limb that the fire case would control the PSV size though.

May be i did not put too much thinking into it. I believe LHV is determine by composition and component type in the fluid. Not sure how vapor fraction affect LHV. How you came across above statement ?

By LHV we mean latent heat of vaporization, right? It can be confused with lower heating value which is quite odd in this analysis, unless we include flare analysis here

Anyways, my take is that maybe he's thinking that vapor generation during fire case changes the composition (and the latent heat) of the liquid under fire.