The contradiction regarding the hydraulic test temperature
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The specification states that the test temperature refers to the average metal wall temperature of the shell； Paragraph 11.4.9.3 in GB150.4 refers to the “liquid temperature” during the hydraulic test. How to understand it.
During the hydraulic test, the temperature of the liquid is transferred to the housing, eventually causing the housing temperature to approach that of the liquid.
There is no contradiction; the test temperature refers to the metal temperature of the housing, but the temperature of the test liquid is controlled for ease of measurement. There is a statement in GB/T150.4 stating that pressure can be increased slowly to the design pressure only when the metal temperature of the test vessel wall is close to the temperature of the liquid.
Is it more convenient to measure liquids? The inspection staff in the factory use temperature guns to measure the metal temperature by pointing them directly at the surface of the casing. On the contrary, measuring water temperature is not easy either. I think this concept is intended to apply to the temperature of the metal; even if the temperature of the liquid is very low, it doesn’t matter as long as the temperature of the metal in the housing meets the requirements. However, GB150 specifies a liquid temperature, which can lead to misunderstandings.
Before the experiment, it is necessary to ensure the temperature of the liquid used in the test first. As for the concept, Part 1 of the standard has already clarified it.