Analysis of the Bending Resistance and Design Requirements of Compensators

Release date:

2024-06-14

Direct‑buried bellows expansion joints are primarily designed for axial compensation and boast exceptional resistance to bending; therefore, they can be installed without accounting for pipeline settlement. Under the protection of the direct‑buried bellows housing and guide sleeve, they provide unrestricted expansion and contraction compensation, while their other performance characteristics remain identical to those of standard bellows expansion joints.

Installation precautions:

1. To ensure that the directly buried corrugated compensator performs its compensation function, fixed supports must be installed at both ends of the compensator to prevent the pipeline from shifting or stretching under the influence of internal pressure thrust.

2. For directly buried bellows expansion joints, one end (specifically, the dead end of a unidirectional expansion joint) shall be positioned close to the fixed support at that end, with the flexible section of the joint compensating for pipeline movement.

3. Determine the spacing between the two fixed supports based on the compensation capacity of the directly buried bellows expansion joint; typically, the compensation capacity does not exceed the pipe diameter.

4. During the pressure test, the directly buried bellows expansion joint shall not exhibit any tensile deformation.

Angular compensators are composed of Compensator It consists of a nozzle, a bellows, and a pair of hinges connected to the nozzle. It can only accommodate angular displacement in a single plane. When absorbing displacement, two or three angular compensators should be used in combination, while the hinges are capable of withstanding internal pressure thrust. The operating temperature is ≤420°C, and the fatigue life is 1,000 cycles.

Requirements for pipe rack design:

Angular compensators should be installed in pairs or triplets to accommodate lateral pipe displacements. Between the two fixed supports of Z‑shaped or L‑shaped pipe runs, only one lateral compensator or one set of angular compensators may be installed. In such cases, the axis of the planar hinge pin must be perpendicular to the plane defined by the bent pipe section (this restriction does not apply to universal‑hinge compensators). For pipe sections equipped with a set of hinged compensators, the clearance ε of the planar guide support may also be calculated using the aforementioned formula; however, the length L shall correspond to the distance between the hinge axes of the two compensators, and ΔX represents the total thermal expansion of the entire vertical pipe segment.