Questions regarding the hydraulic testing of tower equipment

The static pressure of a liquid column is related to the height of the water column; it decreases when the column is in a horizontal position compared to when it is vertical, which prevents it from rising. This value can be added after the calculated test pressure, and it’s easy to understand.

I know that lying down uses less energy than standing, but the question is why does it have to be included? For example, if the test pressure is calculated to be 3 MPa at a factor of 1.25, then why can’t I use these 3 MPa for the horizontal hydrostatic test? Fails to achieve the purpose of the hydrostatic test?

Because the hydrostatic test value is one that is calculated using your formulas, and this value is obtained after the tower-type equipment has been erected. During the horizontal hydrostatic test, it is impossible to verify that the vertical configuration can withstand all loads without taking into account the static pressure of the liquid column. Moreover, the drawings for tower-type equipment usually specify two test pressures; for horizontal and vertical types, these pressures take into account both the water pressure at the manufacturing plant and the water pressure after installation on-site.

You can take a look at the section on the hydrostatic pressure of the liquid column in GB/T150.1.

The horizontal test is a variant of the testing method. Pressure tests on normal tower equipment are always carried out vertically, which means it is necessary to take into account the hydrostatic pressure of the testing liquid (values below *% can be ignored). However, in practical applications, vertical pressure testing has many limitations and is not easy to implement. Therefore, whether in the manufacturing plant or on-site, horizontal pressure testing is used in place of vertical pressure testing; although the method has changed, the hydrostatic pressure cannot be ignored.

The design pressure is the pressure specified at the top of the container. For vertical containers, especially tower equipment, the pressure at the bottom is higher than that at the top; therefore, when performing a hydraulic test on a vertical container in a horizontal position, the actual hydraulic test pressure cannot be achieved without adding the static pressure of the liquid column.

I can’t understand this provision either. Firstly, the hydrostatic pressure of the liquid column in the medium while it is in use has already been taken into account when the design pressure is determined. The purpose of the hydrostatic test is to verify that all pressure-bearing components of the container can withstand a pressure equal to 1.25 times the design pressure. In the case of tower-type equipment when it is in an upright position, the static pressure of the liquid column must be taken into account; since the bottom reaches the test pressure, the top is at a lower pressure by the amount corresponding to the static pressure of the liquid column. Therefore, the actual pressure at the bottom should be the test pressure plus the static pressure of the liquid column. So by switching to a horizontal configuration, this problem no longer exists; each stressed section can reach 1.25 times the design pressure simultaneously. Then why is it still necessary to take into account the hydrostatic pressure of the vertical liquid column?

The hydrostatic pressure of the liquid column is not taken into account in the design pressure; it is only considered in the calculated pressure.

When a hydraulic test is conducted with the container in a horizontal position, if the static pressure of the liquid column is not taken into account, the test pressure at the bottom of the container, which was originally in an upright position, will be lower by the value of that static pressure; as a result, the purpose of the test is not fulfilled.

In SW6, the design pressure and the hydrostatic pressure of the liquid column are entered separately; the test pressure obtained after calculation is still based on the design pressure； What people don’t understand is why the test pressure still needs to be increased even though the values have been entered; that’s exactly why. Moreover, the hydrostatic pressure of that liquid column is used only for calculating the strength of the corresponding components. One can think further about this: the same principle applies to containers with jackets, as well, in order to determine the stress levels on each individual component. Illustration example!