Design service life of pressure vessels

If others who designed it dared to write it in that way, it must be because they took multiple factors into consideration. . This was already an expected value. .

HG/T20580, Page P22, Item 8 – Design life: The recommended design life for containers is as follows: 1) Ordinary containers and heat exchangers: 10 years; 2) Fractionating towers, reactors, and high-pressure heat exchangers: 20 years; 3) Spherical containers: 25 years; 4) Important reaction vessels (such as thick-walled hydrogenation reactors, ammonia synthesis towers, etc.): 30 years

The design service life of pressure vessels depends to a large extent on the corrosion resistance of their materials. The corrosion rate is an indicator of a material’s uniform corrosion resistance, and the corrosion data available in various literature sources serve merely as a guide for estimating the service life of pressure vessels during their design. There are also the factors of material aging, low-cycle fatigue during use, temperature fluctuations, and start-up and shutdown effects. . . It’s too complicated. The heat exchangers designed for us have a lifespan of only 10 years, while the usual lifespan is 15 years. . . I’m not sure what the right amount is?

The design life recommended by standard specifications represents the most economical outcome resulting from a comprehensive consideration of various factors; of course, this is not a rigid rule and can be overridden. As long as it is a proper design.

This is determined based on the corrosion rate. The actual number of years it can be used depends on many factors; various accidents can occur, and specifying a longer number of years isn’t useful at all – it’s only meant to deceive those who don’t understand

It doesn’t hold much significance; during use, there are needs for year-end inspections and regular checks. The special inspection agency conducts thickness measurements during these regular inspections, reviews the design documents, and makes a comprehensive assessment of the safety level to determine whether it is advisable to scrap the item.

Pure liquefied petroleum gas does not cause corrosion to carbon steel and low-alloy steel. However, liquefied petroleum gas inevitably contains impurities; for example, hydrogen sulfide can cause stress corrosion and chemical corrosion in steel. If no strict requirements are imposed on the components of liquefied petroleum gas, a corrosion margin of 1 mm is too small after 20 years. If problems occur during the design service life, the designer will bear corresponding responsibility. Although our country’s legal system is imperfect, it is clearly stated in writing, and the risks are evident. There must be a source for indicating the design service life. It can be calculated based on the corrosion rate, and this should be specified in the design documents. If there is no reliable data, refer to HG/T20580 for determination; it can at least serve as a basis. For property owners, if they decide to choose the option with the most attractive pricing parameters without further consideration, they still have to bear the associated risks; not having knowledge does not relieve them of their responsibilities.

Pressure vessels are generally maintained through regular inspections in normal use; if corrosion is severe, they may need to be retired ahead of schedule. Can such vessels still continue to be in service beyond their intended lifespan due to corrosion? The design life is only for reference.

The design life is a reference value; the actual service life of pressure vessels should be determined based on their usage conditions

The regulations clearly state that the design service life must be indicated on the equipment layout diagram! This is very important: on the one hand, it protects the designer, and on the other hand, it provides data for the expiration detection by users. The design life is merely a reference value.