About the Hydrostatic Test

it sounds like they want the vessel to be tested in the shop before you send it to the job site.

further they are looking for some pressure above design to account for the difference in vertical.

thanks for your help,but i need more details about this content,maybe this technics requirement specified the vertical vessel need when test horizentally the static head and 1.25 design pressure , because it will reperform hydrostatic test on site when the vessel operated some years later.but what is the corroded condition?is it corrosion resistant part or else? because when the vessel operated ,corrosion resistant part will corroded by the fuild.

how about the second question,"the nameplate and the general arrangement drawing shall state "Test Horizontally" alongside the shop test pressure figure. what is the meaning of the "underline content"?

Calculate the test pressure for the vessel in the vertical condition. Add the static head that the bottom of the vessel would see to that pressure and that becomes your est pressure.

When you make the nameplate, stamp this pressure on the same line that you write that it must be "tested horizontally". (Alongside = next to)

In the case of a vertical vessel tested horizontally in the shop,the test pressure shall relate to the design pressure adjusted for static head when the unit is in the vertical position.It must be ensured that no part of the vessel will be subject to a higher stress when tested vertically at site in its corroded condition,than it experiences during its initial test.

In your manufacturing works, assuming you are going to test the vessel in horizontal condition, rather than in the actual operating configuration (vertical) then you have to ensure that

The test pressure = required test pressure (which as the previous post said =1.25 times the design pressure, as per API as well as other standards)

+ The extra pressure due to the static head of the process fluid - which will put an extra pressure on bottom portion of the vessel/tank . This can be calculated based on the length (or height) and the density.

You have to also ensure that due to corrosion, as the wall of the vessel wears out (to the maximum value corresponding to the relevant codes), the increased stress on the vessel must be used to calculate the design test pressure. Ie the design pressure should be the design pressure of maximum permissible corroded vessel.

So the process will be

Take the design pressure value (or the actual pressure along with the factor of safety) (say 5 bar)

Calculate the stress on corroded vessel on this pressure.

Equate the stress on un-corroded vessel.

calculate the new vessel design pressure (say 7 bar)

Add the fluid additional pressure due to the vessel height and the fluid density, so say if you have water as fluid and the vessel is 10mt then you must add 1 bar extra to the previous step.

Do the testing. (at 7+1 = 8 bar)

In the name plate punch

"TEST HORIZONTALLY AT 8 BARS"