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  • Users: Tom_H
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  1. Tom_H

    Venting toxic vapours

    Thanks for the replies. We ended up performing dispersion simulations showing that there was negligible probability of a toxic gas cloud impacting persons. Or indeed even reaching ground level. In other case, we would have considered an elevated vent as first alternative option before other choices.
  2. Tom_H

    Venting toxic vapours

    pennpiper, Thank you for your reply. The reason I did not specify the chemical composition is that it is a partly proprietary compound and I did not think it would have any meningful impact on the question to know the exact chemical composition for the purposes of general relief advise. I...
  3. Tom_H

    Venting toxic vapours

    Thanks for the reply. Yes, I agree, liquid seals are definitely not the preferred solution. There is no flare on site, so the alternative is a vent stack (i.e. open vent with some elevation). It could possibly serve many tanks. But it is of course a costly exercise unless truly needed...
  4. Tom_H

    Venting toxic vapours

    Hi, We have an older atmospheric tank currently only equipped with a lute pot for relief. It contains a flammable (flash point <20 C/68 F) and quite toxic liquid. It is nitrogen blanketed. It has been considered to equip the tank with a pressure/vacuum valve also sized for fire case. The...
  5. Tom_H

    Flammable mixture inside pump

    Thanks for all the responses. In response to the last post, the reason that air could be sucked in in our particular case is that a hatch is opened in the truck (container) in order to prevent underpressure. Thus, when all the liquid is pumped out, air could be pumped in until the pump is shut...
  6. Tom_H

    Flammable mixture inside pump

    A centrifugal pump is used for liquid transfer (filling) of a flammable and somewhat volatile liquid from a truck to a vessel. If the pump deadheads due to it continuing running despite the truck container being empty, is there then any risk of a flammable atmosphere occuring inside the pump...
  7. Tom_H

    Flame arrestor in arbitrary piping

    No, you are right, the tank kan only take a few mbar. This is a case that often occurs, where you get a somewhat strange HAZID finding that someone has dreamed up in a workshop, but you are not entirely sure how to quickly close it out even though it intuitively sounds very strange and not...
  8. Tom_H

    LOPA question

    Thank you, it makes sense when you word it that way and of course relates more to how probabilities work than blindly following a LOPA procedure. I.e. that the risk of course would be proportional to the number of operations and not time. Still, the CCPS LOPA report does state that it is always...
  9. Tom_H

    Flame arrestor in arbitrary piping

    Thank you very much for your insightful responses. The scenario seemed far-fetched and unrealistic. I see also that API 521 indeed designates this as a double jeopardy scenario (failure to purge segment after filling and simultaneous external fire). That of course relates to relief provisions...
  10. Tom_H

    Flame arrestor in arbitrary piping

    A question has been lifted in a HAZID regarding an external fire happening in a plant. The discussion then related to the risk of a line bursting due to this fire and the fire igniting the contents of the line and then the risk of flashback in to the atmospheric vessel to which the line is...
  11. Tom_H

    LOPA question

    There has been some internal debate following a LOPA that is being used to perform SIL allocation. One scenario in the LOPA is overpressuring of a tank during filling operation. Filling operations take place about 10 times per year. One initating cause for overpressure in the tank during...

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