API 650, EXTERNAL PRESSURE

<...6.9 kpa...> is around the same as the variation in ambient pressure between a warm, pleasant sunny day and a stormy night.

<...is there any provision to measure such pressure through pressure guage?...>

How about one of these:

?

There are now several threads running on the topic of <...API 650...>.

<...6.9 kpa...> is around 8in water gauge, which is probably the difference in levels on a water seal on a vapour lock lute attached to the tank somewhere, though, again, it is impossible to see what is going on from here without a P&ID document!

6.9 kPa = 69 mbar ~ 690 mm = 27.2 in water gauge.

OK. So one uses a taller lute.

Most of this has been covered in the earlier threads.

2) How process engineer decide external pressure value? how to decide external pressure? Depends on the plant details, which we don't have. It might be specified in API 650, or it might be determined by other kit connected to the tank.

<...it might be determined by other kit connected to the tank...>

That's exactly why the P&ID is important.

_{Why it has not been disclosed to the forum might remain an mystery for ever more...}

GA

Agreed, but I think we've given the OP all the help we can with information provided. It's up to him to consider the plant as a whole, and what implications it has for the tank design.

Quite.

<unsubscribes>