Issues related to pipes and pressure pipelines in ethylene glycol aqueous solution media
Thread Content
Having worked on several projects related to ethylene glycol aqueous solutions, with design temperatures of (-15°C, -20°C, -25°C, -45°C, -80°C)； The corresponding design pressure is for low-pressure pipelines (primarily below 0.7 Mpa). Some project designs fall under the category of pressure pipelines, while others only require non-destructive testing. Many explanations were found, and they are rather confusing. Based on the above conditions, in conjunction with relevant standards, medium analysis, and the toxicity of the mixture. Everyone is welcome to join the discussion.
For pipelines and pressure pipes in an aqueous ethylene glycol solution medium, it is first necessary to determine the main design parameters for the pipelines, which include: operating temperature, design pressure, and the properties of the medium. Based on the operating conditions you provided, I’ve summarized the following points: 1. Design temperature and design pressure: The various design temperatures you mentioned (-15°C, -20°C, -25°C, -45°C, -80°C) cover a fairly wide temperature range. In this case, the selection of pipe materials and their thickness are crucial; it is necessary to ensure that they maintain good mechanical properties and an adequate safety factor even at the minimum operating temperature. 2. Whether a pipeline is classified as a pressure pipeline is usually determined based on its design pressure and diameter. According to GB 50251-2015 \"Code for Construction and Acceptance of Industrial Metal Piping\", pipes with a pressure of ≥0.1 MPa and a diameter of ≥DN25 shall be regarded as pressure pipes. You mentioned that the design pressure is generally below 0.7 Mpa; if it meets the aforementioned standards, it indeed falls within the category of pressure pipelines. 3. Regarding the properties of ethylene glycol aqueous solutions, such solutions are generally not highly toxic, but they can be corrosive under certain conditions; therefore, corrosion protection design for pipelines is also very important. 4. Toxicity and environmental impact of the mixture: Although ethylene glycol is relatively low in toxicity, high concentrations or long-term exposure can still have an impact on health. Furthermore, in low-temperature environments, the vapor pressure of ethylene glycol aqueous solutions is low, but leaks can cause the solution to come into direct contact with the skin or the environment, posing a safety risk. In summary, during the design and construction process, you should strictly follow relevant standards (such as GB 50316-2000 \"Code for Fire Protection Design of Chemical Enterprises\" and other similar standards) when selecting materials, carrying out construction, and conducting inspections. Especially under design conditions of low temperature and high pressure, additional safety factors need to be taken into account. At the same time, corresponding environmental protection and personnel safety measures are established based on the characteristics of the medium and potential environmental risks. I hope the above answers are helpful to you. .
Personally, I think it is still related to the content of ethylene glycol. In previous projects, a 20% aqueous solution of ethylene glycol was used, but it was not classified as a pressure pipeline.
Standard GB/T20801.1-2020: Pressure pipelines with a maximum operating pressure of 0.1 MPa (gauge pressure) or more, in which the medium is gas, liquefied gas, steam, or a liquid that is flammable, explosive, toxic, corrosive, and has a maximum operating temperature equal to or higher than its standard boiling point; such pipelines also have a nominal diameter of 50 mm or more. Excluding pipes used for transporting non-toxic, non-flammable, and non-corrosive gases with a nominal diameter of less than 150 mm and a maximum operating pressure of less than 1.6 MPa (gauge pressure), as well as the pipes forming part of the equipment itself. The key point is ‘flammable, explosive, toxic, corrosive liquids whose maximum operating temperature is higher than or equal to their standard boiling point’
I remember that for the projects I encountered, those operating at temperatures below -30°C were not considered pressure pipelines
Determining whether it is a pressure pipeline according to the \"Code for Construction and Acceptance of Industrial Metal Piping\" relies on an incorrect basis; even if the result is correct. Is it due to excessive pressure? The \"TSG D0001-2009 Safety Technical Inspection Regulations for Pressure Pipelines\" and other relevant standards and regulations should be applied ； The revised version of \"TSG D0001-2009 Regulations on Safety Supervision of Pressure Pipelines\" has not been officially released yet; therefore, classification can be carried out in accordance with GB/T 20801-2020.
There is no need to follow pressure pipeline design requirements. Experts from a city in Zhejiang reached a consensus.