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The difference between pressure pipelines and non-pressure pipelines
2025/6/25
1. Definition and Working Principle
Pressure pipeline: It refers to a pipeline system that withstands a certain pressure inside the pipeline and is used for transporting gases, liquids or steam. Its working principle is to drive the fluid to flow in the pipeline through internal or external pressure. It is suitable for fluid transportation scenarios that require continuous pressure, such as industrial production, water supply, gas supply, heating and other systems.
Unpressurized pipeline: It refers to a pipeline system in which the fluid inside the pipeline does not bear or almost does not bear internal pressure under normal working conditions. It usually utilizes gravity flow for fluid transportation and is designed without considering internal pressure. It is suitable for municipal engineering and infrastructure projects such as drainage systems, sewage treatment, and rainwater collection.
2. Materials and Structure
Pressure pipelines: As they need to withstand relatively high internal pressure, their materials must have sufficient strength, pressure resistance and corrosion resistance. Common materials include steel (such as carbon steel, stainless steel), copper, aluminum alloy and high-performance plastics (such as PE, PVC, PP, etc.). Structurally, pressure pipelines are typically connected by welding, flange connection, hot-melt connection or electrofusion connection, etc., to ensure high sealing performance and pressure-bearing capacity.
Pressure-free pipes: As they do not need to withstand high pressure, their pipe walls are relatively thin. When designing, the main considerations are flow rate, flow velocity and corrosion resistance. Common materials include plastics (PVC, PE), concrete, ceramics, etc. In terms of connection methods, pressure-free pipes mainly use plug-in, adhesive or threaded connections, etc. The design focuses on easy installation and economy.
3. Fluid Characteristics and Transportation methods
Pressure pipelines: They are suitable for transporting fluids that require a certain pressure to drive, including gases (such as natural gas, compressed air), liquids (such as water, oil, chemicals), steam, etc. Fluids are usually conveyed under conditions higher than atmospheric pressure, with high flow rates and strict requirements for sealing.
Pressure-free pipes: Mainly used for transporting fluids that do not need to withstand internal pressure, usually gravity-driven liquids such as rainwater, sewage, and wastewater. Its flow velocity is relatively low, the slope of the pipeline design is small, and it flows by the force of gravity.
4. Safety and Maintenance
Pressure pipelines: Due to long-term exposure to internal pressure, there are risks such as rupture and leakage, so the safety requirements are relatively high. Regular inspection and maintenance are required to ensure its safety. The maintenance cost and technical requirements are also relatively high.
Pressure-free pipeline: As it does not bear pressure, its safety risk is relatively low and maintenance is relatively simple. The main focus is on the smoothness of the pipeline and the prevention of blockage and corrosion.
5. Application Scenarios
Pressure pipelines: Widely used in systems such as water supply, gas supply, heating, and fire protection that require continuous pressure.
Pressure-free pipes: They are more suitable for drainage, sewage discharge and other situations that do not bear internal pressure, such as municipal drainage, sewage treatment, rainwater collection, etc.
