Pressure pipelines and pressureless (gravity-flow) pipelines serve fundamentally different purposes in industrial and municipal systems. Pressure pipelines, constructed from materials like steel or high-grade PE/PVC, are designed to withstand internal fluid pressure for applications such as water supply, gas transmission, and chemical processing. In contrast, pressureless pipelines use lightweight
What is the difference between [pressure pipeline] and [pressureless pipeline]?
1. Definition
● Pressure pipeline:
Pressure pipeline refers to a pipeline system that bears a certain pressure inside the pipeline and is used to transport gas, liquid or steam. The design, manufacture, installation and operation of pressure pipelines need to consider the pressure of the fluid in the pipeline and ensure the safety of the pipeline under pressure.
● Pressureless pipeline:
Under normal working conditions, the fluid inside the pipeline does not bear or hardly bears internal pressure. Pressureless pipelines usually use gravity flow to transport fluids, and internal pressure is not considered during design.
2. Material
● Pressure pipeline:
The material of pressure pipelines must have sufficient strength, pressure resistance and corrosion resistance. Commonly used materials include steel (such as carbon steel, stainless steel), copper, aluminum alloy and high-performance plastics (such as PE, PVC, PP, etc.).
● Pressureless pipeline:
Since pressureless pipelines do not need to withstand high pressure, the pipe wall is thinner. The design mainly considers flow rate, flow rate and corrosion resistance. Usually, lighter and corrosion-resistant materials are used, such as plastics (PVC, PE), concrete, ceramics, etc.
3. Applicable fluids
● Pressure pipeline:
Applicable to the transportation of fluids that require a certain pressure to push, including gas (such as natural gas, compressed air), liquid (such as water, oil, chemicals), steam, etc. Fluids are usually transported in an environment higher than atmospheric pressure, suitable for industrial production, water supply, gas supply, heating and other scenarios.
● Non-pressure pipeline:
Mainly used to transport fluids that do not need to withstand internal pressure, usually gravity-driven liquids, such as rainwater, sewage, wastewater, etc., suitable for municipal engineering and infrastructure projects such as drainage systems, sewage treatment, and rainwater collection.
4. Design requirements
● Pressure pipeline:
Must be designed according to the maximum working pressure of the conveying medium to ensure safety and stability under pressure.
● Non-pressure pipeline:
Internal pressure is not considered during design, and the fluidity, gravity and slope design of the fluid are mainly considered.
5. Connection method
● Pressure pipeline:
Pressure pipelines are usually welded, flanged, hot-melt or electric-melt to ensure high sealing and pressure-bearing capacity, and adapt to high-pressure environments. Welding and flange connections are suitable for metal pipes with high pressure and high strength requirements, while hot melt and electric fusion connections are suitable for plastic pipes and can withstand medium and high pressure.
● Pressure-free pipes:
Pressure-free pipes are mainly connected by plug-in, bonding or threaded connection, and the design focuses on easy installation and economy. Plug-in and bonding are suitable for plastic pipes to handle pressure-free or low-pressure fluids, while threaded connections are used for small diameter or low-pressure pipes.
VI. Applicable scenarios
● Pressure pipes:
The fluid flows under high pressure, and the pipes can be arranged above or below the ground. The flow rate is high and the sealing requirements are strict. They are often used in tap water supply systems, industrial water supply systems, gas transmission, fire protection systems, etc.
● Pressure-free pipes:
It flows by gravity, is usually arranged underground, has a low flow rate, and has a small pipe design slope. It is used in municipal drainage, sewage treatment, rainwater collection, agricultural irrigation and other systems that do not need to withstand pressure.
VII. Inspection and testing
● Pressure pipeline:
Before construction and commissioning, strict pressure tests (such as water pressure test, air pressure test) and non-destructive testing (such as ultrasonic testing, X-ray testing) must be carried out to ensure the reliability of the pipeline under the design pressure.
● Non-pressure pipeline:
The inspection requirements are relatively simple, mainly appearance inspection, sealing test and flow test.
VIII. Installation and maintenance
● Pressure pipeline:
Due to the risks of rupture and leakage during the long-term operation of pressure pipelines, regular inspection and maintenance are required to ensure their safety, and the maintenance cost and technical requirements are high.
● Non-pressure pipeline:
Since it is not under pressure, the safety risk is low and maintenance is relatively simple. The main focus is on the patency of the pipeline and preventing blockage and corrosion.
In short, pressure pipelines have stricter requirements on safety and durability because they need to withstand the pressure of internal fluids. Therefore, they are widely used in systems that require continuous pressure, such as water supply, gas, and heating. Non-pressure pipelines are more suitable for occasions such as drainage and sewage discharge that do not bear internal pressure, and the design emphasizes economy and construction convenience.
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