Questions regarding the test pressure for containers
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Vertical container (about 3 meters), design pressure of 0.5 MPa, hydrostatic pressure of the liquid column of 0.03 MPa; the calculated pressure is therefore 0.53 MPa, while the test pressure is 0.625 MPa. Both the design pressure and test pressure are the pressures at the top of the vessel. Question: During a hydrostatic test, is it necessary to take into account the static pressure of the liquid column? How to determine whether the bottom of a container can withstand a pressure of 0.655 MPa?
During the hydrostatic test, the test pressure does not take into account the static pressure of the liquid column. To verify that the bottom shell can withstand the test pressure, it is sufficient that the maximum overall membrane stress σT ≤ 0.9Relφ; meeting this condition indicates that the bottom shell is capable of withstanding the test pressure.
If the tower is very tall, even in the case of a vertical test, is the static pressure of the liquid column not taken into account? That static pressure is also very high
Test pressure for hydraulic testing of the tower = 1.25 * design pressure * allowable stress at normal temperature / allowable stress at design temperature； Test pressure for hydraulic horizontal testing of the tower = 1.25 * design pressure * allowable stress at normal temperature / allowable stress at design temperature + hydrostatic pressure of the liquid column during hydraulic vertical testing.
Everything needs to be taken into consideration; it mainly depends on the proportion of the hydrostatic pressure of the liquid column. Do not confuse the hydrostatic pressure of the liquid column during design with that during experimentation. 1. When designing the container, you added 0.03; make sure that the container holds a liquid and is filled to the brim, so that this value of 0.03 applies. 2. Whether it is horizontal or vertical, hydraulic pressure always generates a hydrostatic pressure of the liquid column; this value should be included in the calculations. The only difference is that the hydrostatic pressure values for horizontal and vertical configurations are different.
If there is a hydrostatic pressure of 0.03 of a liquid column while the device is in operation, this value must be taken into account in the design, by increasing the calculated pressure. When checking the water pressure in the pressure testing process, the static pressure of the liquid column should be taken into account
The experienced technician told me that during vertical tests, it is also necessary to consider the test pressure in combination with the static pressure of the actual liquid column (using this as the calculated pressure) in order to identify the point at which the calculated pressure is highest. This is because there have been cases where towers were quite tall but had thin walls, resulting in failure during testing.
Why is the static pressure from liquid injection not taken into account when checking the pressure for vertical pressure tests? The hydrostatic pressure due to liquid injection only exists when the container is tested in an upright position. Since this pressure has not been verified, wouldn’t the test pressure at the bottom of the container during vertical testing be higher than the verified value?
That makes sense; maybe this is usually overlooked?
But generally, it seems that such verification has not been carried out either; the calculation sheet only provides a test pressure
There is indeed a static pressure, but the test pressure does not reflect this static pressure