4 replies to this topic

[Iris_T]

I'm currently doing a review of the installed venting capacity for our tankage. Looking through past documentations and calculation sheets from our tank designer, I'm pretty much confused at the moment as it seems everyone has their own views when it comes to which venting devices to take when it comes to calculation of the installed venting capacity available for normal venting. For example, our naphtha tank (floating roof tank) has the following venting devices installed:
-One Rim Vent (PVV)
-One automatic bleeder vent
-Six breather valves (PVV)


Questions:
1) For normal venting, can the capacity of the automatic bleeder vent be credited as part of installed venting capacity available, i.e. Installed venting capacity=Capacity(Rim vent+breather valves+automatic bleeder vent)?

2) For sizing of the automatic bleeder vent specification is the calculation the same as normal venting requirement? The document I have here says that " The purchaser should specify the maximum pumping rates for the tank manufacturer to determine the number and size of automatic bleeder vents".

To me, it means only the maximum flow for the loading pump would be sufficient for sizing of the automatic vent i.e. the maximum capacity of the loading pump = min capacity of the automatic bleeder vent required? Is that true?

3) When comparing required venting capacity versus installed venting capacity, is there a rule of thumb when we say the installed venting capacity is inadequate (i.e. installed venting capacity must be at least 10% greater than the required venting capacity, else it is considered inadequate)? I have an example here:

Capacity of 6" PVV= 950 m3/hr
Number of 6" PVV installed = 2
Calculated required inbreathing capacity=1832 m3/hr
extra inbreathing capacity (installed-required)=68m3/hr [only 3.7% ( extra capacity/required capacity)extra capacity available. Is this ok?]

4) If the tank is protected for vapour breakthrough conditions (There is a LZA on the column located upstream of the tank), can this condition be eliminated during the sizing of the PVV, i.e. inbreathing= max flow from rundown+thermal requirement?

Thank you for the help.

[breizh]

Hi IRIS,

GO to the safety device forum, you will find a lot of information, including a workbook issued by Mr Montemayor.

Hope it helps.
Regards
Breizh

[quelareine]

thanks for the reply!


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quelareine

Thanks for sharing your idea here. I appreciate your idea, very excellent .


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[AudreyGarcia]

This is indeed a very interesting topic as I am planning to install devices on our tank.

Thank you.


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