External pressure single axial expansion joint
Product Introduction
1. Product Definition and Structure
The external pressure single type axial expansion joint is a type specially designed to absorb the temperature change or mechanical vibration caused by the pipeline systemAxial displacementA compensation device. Its core structure includes:
Bellows: Made of stainless steel (e.g. 304, 316L), elastic expansion and contraction through multi-wave design, is the core component for absorbing displacement.
Outer cylinder and inner cylinder: The outer cylinder is subjected to the external pressure of the medium, and the inner cylinder (guide cylinder) directs the fluid and protects the bellows from flushing.
limiting device: Such as guide rings and limit rods, which are used to limit radial displacement and ensure that the bellows moves only in the axial direction.
connecting component: Use flanged or welded joints for seamless butting with piping systems.
2. Working Principle
Bellows inExternal pressureIt works under the action of absorbing the thermal expansion and contraction deformation of the pipe through axial compression or tension. Because of the external pressure design, the bellows does not experience columnar instability and therefore can support a greater amount of compensation (compared to the internal pressure type).
3. Core Features
High compensation capacity: The multi-wave structure design can absorb a wide range of axial displacement and is suitable for long-distance pipelines.
Compressive and flexural resistance: The outer cylinder structure enhances the overall compressive strength, and the guide ring prevents radial deformation and improves stability.
Sealing performance: Use multi-layer bellows or special sealing materials (such as polytetrafluoroethylene), suitable for high-pressure, corrosive medium environment.
Low maintenance costs: The standardized design simplifies installation, and the discharge valve design can remove condensate water and reduce maintenance frequency.
4. Application Scenario
Heating system: Compensate for thermal displacement of steam or hot water pipes and prevent stress concentration.
Chemicals and Petroleum: Suitable for corrosive media (such as acid, alkali) or high pressure oil and gas pipelines.
Power and Metallurgy: Used for boiler flue, cooling water system, withstand high temperature (-196℃ ~600℃).
Direct buried pipeline: The external pressure type design is suitable for trench or direct burial laying, and should be used with inspection wells.
5. Installation and Maintenance Points
Alignment and support: Make sure the pipe axis is aligned and install guide brackets to disperse external loads and avoid eccentric stresses.
Limit adjustment: Set the limit rod according to the design compensation amount to prevent structural damage caused by expansion and contraction beyond the range.
Stress testing: After installation, a sealing test is required to check whether the flange or weld is leaking.
Periodic inspection: Monitor corrosion and fatigue crack of bellows, and replace aging parts in time.
6. Model and Standard
Common models:WZ type(external pressure single type axial type),YXWA type(with bending sleeve), etc.
Implementation criteria: MeetGB/T12777General Technical Specifications for Expansion Joints of Metal Bellows.
7. Advantage Comparison
| characteristic | External pressure single type axial type | Internal pressure axial type |
|---|---|---|
| Resistance to column instability | Strong (external pressure suppresses instability) | Weak (limit device required) |
| Compensation amount | Large (multi-wave design) | smaller |
| Applicable pressure | Medium and high pressure (external pressure bearing) | Medium and low pressure |
| Maintenance Ease | Sewage design reduces maintenance difficulty | The inside of the bellows needs to be cleaned regularly |
More technical parameters and customization requirements can be referred to.
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