Requirements regarding the liquid temperature during pressure testing
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Clause a regarding the test temperature in 10.9.4.3 (page 129) of GB150-98 states: \"For hydraulic testing of carbon steel, 16MnR, and normalized 15MnVR steel vessels, the liquid temperature shall not be lower than 5\"℃； For other low-alloy steel containers, the liquid temperature during the hydrostatic test must not be lower than 15°C. If factors such as plate thickness cause an increase in the material’s ductile transition temperature, the testing temperature must be increased accordingly ； ” I have many doubts regarding this point: 1. The specified minimum test temperature is based on the concern of brittle fracture of the material at low temperatures; hydraulic testing evaluates the overall performance of the equipment after it has been manufactured. Does this comprehensive evaluation also include testing under harsh operating conditions? If it is included, then isn’t this minimum temperature set a bit high? 2. Is there a minimum test temperature requirement for the hydraulic testing of stainless steel containers? If so, what criteria are specified? 3. Besides the plate thickness factor, what other factors can cause an increase in the ductile-to-ductile transition temperature of a material? How much does plate thickness affect the increase in the temperature at which a material loses its ductility? 4. Should the temperature of the test liquid be increased accordingly? Is there any specific basis for this? For a pressure vessel made of 16MnR with a thickness of 95 mm, what should be the appropriate temperature of the testing liquid?
Hehe, if we have to take into account extreme operating conditions, then for low-temperature containers, only air pressure or saltwater can be used, as tap water will freeze at such low temperatures. Since stainless steel does not suffer from brittle fracture, there is no need to consider the ductile-brittle transition temperature. In addition to plate thickness, it is also related to the chemical composition of the material and the level of stress applied. According to relevant information, the determination of this tough-to-brittle transition temperature is generally done on a rough basis by considering the value of impact energy. You can check it out.
1. There are two types of pressure tests: one is hydraulic, the other is pneumatic; there is also a gas-tightness test. Hydraulic testing is generally the preferred method; if hydraulic testing is not possible, pneumatic testing is used instead. The temperature requirements for hydraulic testing take into account not only the material’s temperature at which plasticity ceases to occur at low temperatures, but also the solidification temperature of the liquid medium! The airtightness test is carried out after the hydraulic test is successful (the medium inside the container is highly hazardous). Hydraulic testing cannot be carried out in the following situations: 1. Trace amounts of residual liquid are not allowed inside the container; 2. The container may freeze and burst under extreme cold; 3. It is not possible to fill the container with liquid due to structural reasons; 4. The weight of the container with liquid in it exceeds the load capacity of the foundation. 2. Ordinary stainless steel needs only to meet the requirements specified in the drawings; for austenitic stainless steel, it is necessary to strictly control the chloride content in the water to below 25 ppm (in accordance with the \"Regulations on Safety Inspection of Pressure Vessels\"). 3. GB does not specify an exact increase in temperature; reference can be made to ASME standards. As the wall thickness increases, a Charpy impact test must be conducted. The temperature for this Charpy impact test should be about 20 degrees higher than the temperature used for the hydraulic test. Last edited by 263525689 on 2009-3-25 at 12:17