Diff b/w ASME test pressure horizontal (shop) and test pressure (vert) 1

[fizzy]

Hi all,

I'm designing a vertical vessel to ASME VIII and my client wants me to include both the test pressure vertical (site) and the test pressure horizontal (shop). Can someone pls advice me on which one is 1.3xDesign pressure and how to determine the other one.
Thanks in advance.

 

[eyec]

if memory serves me, 1.3X is for air test when conditions prevent using a hydro.

hydro is usually @ 1.5X

Steven C
Senior Member
ThirdPartyInspections.com

 

[vesselfab]

new code says 1.3 X mawp (which can be design pressure)

vertical water static load must be added to the design of components.

Test pressure and design pressure is at top of vessel

 

[fizzy]

Thanks Vesselfab,

This means that the test pressure at the top of a vertical vessel will be higher than when place horizontally due to the hydrostatic head.

Pls is there a formular used in determining any of these cases?

 

[vesselfab]

no, it means the test pressure at the top will be your calculated test pressure. the actual pressure at bottom of vessel will be higher.

0.433 psi per foot of height

 

[fizzy]

Yeah, so it means i'll have different values for both vertical and horizontal pressures.

Because i have a calculated pressure of 14.6Barg for 2m x 12m high vessel.

I'm being asked for both vertical(site) and horizontal(shop) values.

 

[dig1]

Fizzy,

Is your client asking for or has mentioned something like the following?

"If the vessel is tested in the horizontal position, the test pressure shall be at least as great at all locations as if the vessel was tested in the vertical position full of water."

I have seen this before. This means that the test pressure in the horizontal position is much greater than that in the vertical position to account for the hydrostatic head differences between being tested vertically and horizontally.

Reading between the lines, it appears this is may be what they are trying to find out.

 

[jehan17718]

Fizzy,

For vertical vessels hydrotested if tested in VERTICAL position position at shop (based on the design pressure; to simplify matters).

Pressure at top (i.e. highest point)=(1.3 X Design presure X Stress ratio) .... (1)

....and.....

Pressure at bottom (i.e. lowest point)=(1.3 X Design presure X Stress ratio)+ Static water head acting at bottom (i.e. low point) .... (2)

..However, if the same vertical vessels hydrotested if tested in HORIZONTAL position position at shop, in order to hydrotest the stress the bottom as per eqn (2) above, the hydrotest pressure to be adopted=1.3 X Design presure X Stress ratio)+ (static head corrsponding to the difference in TL-TL and ID of the vessel)

Hope things are now clear. Note that the above is really speaking a common enginnering practise and the CODE does not explicitly prescribe the above procedure.

-jehan