hi,
Can any body suggest me for the following:

Max. Operating liquid level from bottom of vessel is - 500 mm
vessel dia is 4500 mm (Horizontal vessel)

To determine the thk of the shell/dish. Pressure due to max operating liqiud should be taken or full liquid level should be taken since the vessel is to be hydrotested.

here thk variation is considerable when full liquid level is considered.

Does the CODE refers this when where?

Thanks & regards

gagilam

Hello Gagilam,

To know which loadings you have to consider for the calculation of the wall thickness for your pressure vessel you have to look into UG-22:

This means in your case you have to add 500 mmm static head to your MAWP to determine your (minimum) design pressure. Assuming your operating liquid has the density of water, e.g. 0,05 barg.
For the hydrostatic test you have to go to UG-99:

For example: When the MAWP of the vessel is 10 barg and the stress ratio test/design is 1, the minimum test pressure at the top of the vessel is 13 barg. The cylinder of your pressure vessel is subject to 13 barg + 0,45 barg (4500 mm) + water column from nozzles which are attached on the upper side. This means 13,45 + x barg.

Let´s assume for whatever reasons (customer specifications) the hydrostatic test pressure is 15 barg, you have to perform a calculation to show that your pv is adequately dimensioned for the test condition. Therefore run a second calculation with the test pressure and 0,9 yield strength as allowable stress value. As shown above the design pressure in this calculation is 15 barg + static head during the hydro.

Best regards
Michael

Hi,

I fully agree.

Just to clarify: there are many ways to comply with UG-22.

1) Many designers choose to add the hydrostatic head of the hydrotest condition to the MAWP stamped, and design the entire vessel for the full hydrostatic head. This is easy and simple.

2) As an alternative, the vessel can be designed for the operating condition(s) and the hydrotest condition separately. Tn the latter case, the alowable stress value for the hydrotest condition may be 0.9Sy, or 0.95Sy, or the stress value at test temperature. For hot design this gives an advantage.

3) Some designers choose to disregard the hydrostatic head of the test medium. This is not acceptable. Every Authorized Inspector should discover this Code violation during his design review.

Dirk

In what position is the plan for testing? (Vertical or horizontal?)

This is something to consider........ also.........the test position is required to be documented under Note no. 39 of App W .......as usual the inspector should be catching these issues........ here is what Note no. 39 states......


..........Indicate the type of test used (pneumatic, hydrostatic, or combination test, as applicable) and specify test pressure at the top of the vessel in the test position. Indicate under “Remarks” if the vessel was tested in the vertical position...............

Note: the "TOP" of vessel is relative based on vessel position during testing....

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