Discussion on the hydrostatic testing issues of CAESAR II
Thread Content
When performing calculations for steam stress, some people include a parameter for hydrostatic testing (1.5P); among the available options is W+HP – does this refer to the stress resulting from a single application of pressure, or to cold loads? Also, during the hydrostatic test, the spring pins are not removed, and no stress is allowed either? Or maybe a hydrostatic test isn’t necessary in CAESAR? Because versions prior to 4.4 didn’t seem to have this hydrostatic test requirement. Please share your suggestions and feedback. This post was last edited by visavis on 2009-3-27 09:19.]
Some people say that a hydrostatic test is mainly used to determine the yield limit, and the stresses applied in the first and second stages don’t require consideration of water pressure. Others say that when conducting a hydrostatic test, it’s necessary to use water as the medium, and then calculate the strength of the supports under those conditions! Well, without a teacher, it’s really impossible to do this properly.
1) The hydrostatic test is used to determine the yield limit. 2) As for calculating the strength of the supports during the hydrostatic test, in reality it’s not possible to know where exactly pressure will be applied at the site; therefore, this can only serve as a reference.
The current version 5.1 includes an option to enable or disable the hydrostatic test.
What are the main things that a hydrostatic test is used to check, how should one interpret the results, and could you explain in detail?
The loads on the supports of steam pipes in the cold state and during operation do not include the weight of the medium (the mass of steam can be ignored). If the support loads are calculated based only on these two conditions, they will be too low. Since the pipes are filled with water during hydrotesting, it is necessary to use this condition to assess the stresses in the pipes under hydrotesting conditions, in order to determine whether temporary supports are needed and where they should be placed. An automatic hydrotesting load case (WW+HP, HYD stress type, with spring hangers locked) is generated when there is a non-zero HP value. During hydrotesting, the springs are in a locked state in CII; you can see that the spring setting is “rigid” in the condition editor). That is, WW+HP is less than Sy!
For hydrotest stress: Enter the yield stress in the Caesar spreadsheet along with the factor (for example, 0.9; according to ASME B31, this factor can be 1.0), and Caesar will calculate the stress for you.
The calculation for the hydrostatic test should take WW+HP into account; the pressure level used for this test likely varies from company to company
Hydraulic testing is generally used to check whether the strength of the supports is sufficient during such testing, and to determine whether temporary supports are needed while conducting the hydraulic test