Pressure Gauge Requirements for Hydrotest of Pressure Vessel

Depends on the density of whatever's in the vessel.

What an odd pressure vessel.

Surely, given the greater pressure at the bottom due to the head of liquid, the lower gauge is the one that needs to be 'taken' for the assessment, Guv? What does the insurance company's Engineer/Surveyor have to say on the topic?

The difference in the two readings will equal the difference in head between top and bottom of liquid in the tank.

10 meters roughly equals 13 PSI at SG of 1.

No liquid in tank; both readings will be the same.

Whoops. I missed the Hydrotest part in the subject line. Disregard the comments below on hydrostatic level. I'm clueless on testing requirements. Iris

There's no reason to have a gauge at the top if the tank is vented, because if the tank is vented to atmosphere, the gauge at the top will always read zero.

If the tank is pressurized, the top gauge shows the blanket pressure. The gauge should be selected to show the blanket pressure, which is likely to be a different range than the lower gauge, which sees the much higher head pressure of the liquid AND the blanket pressure.

I suppose there are places where mechanical gauges are used, but the level is frequently read electronically with a 'differential pressure transmitter' that has two ports. One port is plumbed to the bottom, the other is plumbed to the top of a pressurized tank. Its output is difference between the upper and lower pressures, which provides a direct reading of head pressure. The units are typically distance (meter, millimeters) of water column.

If the medium in the tank is not water (with a specific gravity of one), then a compensation calculation is needed to get a level value, by dividing the head pressure by specific gravity of the medium.

lets put in this way that, for a hydrotest of any type of pressure vessel, the gauge at manifold and gauge on the vessel to measure the test pressure have to show same pressure or not. if not what could be the difference (toleance), is there any ref.?

can any body share me a copy of hydrotest procedure or ausrailian standard in this regard please.

Since "somebody is the source of your confusion here, why don't you ask "somebody" to help you with the standard. How did "somebody" arrive at 10%?

If you don't understand the requirements of the test, you'll need to hire a test person. I wouldn't hire "somebody" though, cause I'm not sure of their qualifications.

You should, at least, know the specification you are working to.

Good luck.

ok