Direct buried (fully buried) type expansion joint

Product Introduction

        1. Definition and Use

Directly buried (fully buried) type expansion joint, also known as directly buried corrugated compensator or underground telescopic device, is an axial compensation device specially designed for directly buried pipelines, which is mainly used to absorb the displacement of pipelines due to temperature change, geological settlement, etc. Its core features areStrong bending resistanceIt can adapt to pipeline sinking or soil pressure, and is suitable for the thermal compensation demand of directly buried pipelines such as heating pipe network, petrochemical industry and municipal engineering.

        2. Structural and design features

• Multi-layer protective structure: It is composed of bellows, shell, guide sleeve and limit device. The bellows adopts integral forming without reinforced U-shape or reinforced U-shape design. The shell and guide sleeve provide compression protection to prevent external loads directly acting on the bellows.

• Balanced design: It is divided into free type (unbalanced type) and balanced type, the latter offsets axial thrust and reduces the load on the fixed bracket by pull rod, hinge or internal pressure self-balancing technology.

• Sealing and guiding: Self-sealing structure is adopted, and some models are equipped with exhaust check valves or air pipes to ensure the sealing performance for long-term buried use.

3. Technical Parameters

• Pressure range: 0.1 – 6.0 MPa (special design for higher pressures).

• Temperature range: -200℃ to 1300℃, covering extreme operating requirements.

• Path Range: DN32 – DN8000, supports various pipe specifications.

• Compensation amount: Axial compensation 30 – 500 mm, some models can absorb lateral or angular displacement.

        4. Core Strengths

• Long life and maintenance-free: Double protection of housing and guide sleeve, bellows avoids direct contact with external corrosive media, design life can reach more than 30 years, no regular maintenance is required.

• Cost efficient: Allow multiple compensators to be set in the main fixed bracket, reduce the number of fixed brackets for segmented compensation and reduce the construction cost.

• Resistance to environmental interference: Bending resistance can counteract soil subsidence or vehicle load effects without additional reinforcement.

• Easy to install: There is no need to set up an inspection well, and it is directly backfilled after direct burial, which simplifies the construction process.

        5. Implementation of standards and certifications

• Design and manufacture standard: GB/T12777-2008 (replacing the old GB/T12777-1999), referring to American EJMA standard.

• Inspection specification: Pass the pressure test of pressure-bearing weld (1.5 times the design pressure), coaxiality test (tolerance ≤1% nominal diameter) and other strict tests.

        6. Typical application scenarios

• Central heating pipe network: Compensate the axial thermal expansion of the thermal pipeline, and adapt to the direct buried laying environment.

• Oil and Gas Transmission: Used for displacement compensation of long-distance pipelines, resistant to high pressure and corrosive media.

• Municipal water supply and drainage: Absorb settlement deformation in buried pipeline system and reduce pipeline stress.

        7. Installation and Precautions

• Embedding requirements: Fill the pipeline with a sand layer with particle size

• guide bracket: Guide brackets should be set on both sides of the compensator to ensure the degree of freedom of axial displacement and avoid torsion.

• Welding protection: It is prohibited to splash welding slag to the surface of the bellows, and the transportation fixture shall be removed after the pipeline is installed.

Summary

Direct buried (fully buried) expansion joint is an ideal compensation scheme for buried pipeline system due to its high compensation capacity, bending resistance and long life. Its design takes into account both safety and economy, is suitable for complex geological conditions and severe working conditions, and is a key component in municipal, energy, chemical industry and other fields.