Double-sided expansion joints and single-sided expansion joints are key components in pipeline systems used to compensate for thermal expansion and contraction or mechanical displacement.
Single-side expansion joint (single-flange limit expansion joint)
Structural features
One end is connected to the pipe flange, and the other end is welded or socketed, usually with a limit device to prevent excessive stretching or compression.
Compensation direction
It can only absorb unilateral (axial) displacement (stretching, compression or a small amount of lateral offset).
Advantages
It has a simple structure and low cost, and is suitable for pipeline compensation on one side of the fixed support.
Disadvantage
The compensation capacity is limited, and attention should be paid to the directionality during installation.
Typical applications
In the straight pipe section, the position close to the fixed support; Scenarios where space is limited and only unilateral compensation is required.
2. Double-sided expansion joint (double-flange limit expansion joint)
Structural features
Both ends are connected by flanges and can extend and contract in both directions. Usually, limit rods are equipped to control the maximum displacement.
Compensation direction
It simultaneously absorbs the axial displacement of the pipes on both sides, allowing for greater expansion and contraction.
Advantages
It has a stronger compensation capacity, no restrictions on installation direction, and is suitable for complex pipeline layouts.
Disadvantage
It is large in size and high in cost.
Typical applications
The middle section of long-distance pipelines and situations requiring bidirectional compensation (such as both sides of pumps and valves, and pipe turning points).
3. Key differences
Comparison items: single-sided expansion joint, double-sided expansion joint
The connection method is a double flange connection with one end flange and the other end welded/socketed
Compensation directions: single-sided axial and double-sided axial
Installation flexibility requires directional installation without directional requirements
The cost is relatively low and relatively high
The applicable scenarios are simple straight pipelines, complex or long-distance pipelines

4. Selection suggestions
Choose one side: limited budget, simple compensation requirements, and one end of the pipeline is fixed.
Select both sides: When the thermal displacement of the pipeline is large, bidirectional compensation is required, or the installation direction is uncertain.
Notes
The thermal displacement of the pipeline needs to be calculated to ensure that the compensation range of the expansion joint is sufficient.
When installing, it is necessary to pre-stretch/compress as per the design requirements to avoid over-limit operation.
Regularly inspect the limit devices and sealing performance to prevent leakage or failure.
5. Other types of expansion joints
Sleeve type expansion joint: Suitable for high-pressure steam pipelines, but requires regular maintenance of the seal.
Bellows expansion joint: It can compensate in multiple directions and is used in vibration or complex displacement scenarios.