Pipeline properties after the trap
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It is common in design to recover the condensate that forms behind the trap or to direct it into a drain. If recovery is carried out, the back pressure at the trap is usually around 50%-80%. In my case, the pressure before the trap is 10 kilograms, with a pressure drop of about 5 kilograms after the valve; the condensate ends up in a regular storage tank； So, is the pipeline downstream of the valve considered a pressure pipeline?
Low-pressure pipelines 0.1＜PN＜1.6 MPa
It shouldn’t be considered a pressure pipeline; it’s similar to the vent pipe downstream of the valve.
It mainly depends on the diameter. In the catalog of special equipment published by the new Quality Supervision Administration in October 2014, pressure pipelines are defined as tubular devices that use a certain pressure to transport gases or liquids. Such pipelines are those with a maximum operating pressure of 0.1 MPa (gauge pressure) or more, where the medium is a 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; furthermore, their nominal diameter must be 50 mm or more. Except for pipes 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 that form part of the equipment used for transporting non-toxic, non-flammable, and non-corrosive gases. Among them, the safety supervision and management of oil and gas pipelines shall also be carried out in accordance with laws and regulations such as the Work Safety Law and the Oil and Gas Pipeline Protection Law.
If classified as GC1, GC2, or GC3, it depends on the design pressure; since the design pressure is definitely above 0.1 MPa, I think it should still be included in the calculation
What is the basis for your so-called use of design pressure to determine whether it is a pressure pipeline? Many regulations and the provisions of the General Administration for Quality Supervision, Inspection and Quarantine define things in terms of operating pressure: The \"Regulations on Safety Supervision of Pressure Pipelines – Industrial Pipelines (TSG D0001-2009)\\" define pressure pipelines as those that meet both conditions of \"(1) the maximum operating pressure is greater than or equal to 0.1 MPa (gauge pressure, the same below)\\" ； (II) Those with a nominal diameter (Note 1) greater than 25 mm ； (III) When the medium being transported is a gas, steam, liquefied gas, a liquid with a maximum operating temperature equal to or higher than its standard boiling point, or a liquid that is flammable, explosive, toxic, or corrosive. ” However, this definition can also change, and the basis for that is the provision in the Safety Law of the People’s Republic of China on Special Equipment, which states that \"**special equipment is subject to catalog management.\" The catalog of special equipment is formulated by the department under the State Council responsible for the supervision and management of special equipment safety, and shall come into effect after being approved by the State Council. ”The catalog of special equipment published by the General Administration for Quality Supervision, Inspection and Quarantine in 2014 defines pressure pipelines as follows: Pressure pipelines refer to tubular devices that use a certain pressure to transport gases or liquids. They are defined as those with a maximum operating pressure of 0.1 MPa (gauge pressure) or more, whose medium is gas, liquefied gas, steam, or liquids that are flammable, explosive, toxic, corrosive, and have a maximum operating temperature equal to or higher than their standard boiling point; such pipelines also have a nominal diameter of 50 mm or more. Except for pipes 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 that form part of the equipment used for transporting non-toxic, non-flammable, and non-corrosive gases. Among them, the safety supervision and management of oil and gas pipelines shall also be carried out in accordance with laws and regulations such as the Work Safety Law and the Oil and Gas Pipeline Protection Law. ” According to this definition, if the operating pressure in the pipeline downstream of your trap valve is greater than 0.1 Mpa, it does not qualify as a pressure pipeline unless the pipe diameter is less than 150 mm
The pressure drop after the valve is 5 kilograms, but it is connected to the atmosphere
First of all, I have doubts about your question. The steam pressure in front of the steam trap is 10 kilograms; under normal circumstances, there is little pressure of water behind the steam trap. I’m not clear what you mean by a pressure drop of 5 kilograms
I think it should be considered as such, because after the desiccant trap, the condensate pressure drops from 10 bar to 5 bar; at this point flash vaporization occurs, generating steam at 5 bar. The fluid in the pipeline downstream of the valve is then a mixture of condensate and steam, which meets the definition of a pressurized pipeline.
I disagree with your statement. It is also incorrect to measure pressure pipelines based on operating pressure, as the standards define them according to the maximum working pressure. What you said later, that pipes with a diameter of less than 150 mm are not considered pressure pipes, is also incorrect; steam pipes are considered pressure pipes as long as their diameter is 50 mm or more.