What are the classifications of compensators?

Release time:

2022-01-04

　　What are the classifications of compensators?

Compensator - Shaft Type.

　　It is primarily used to compensate for axial displacement. It can also compensate for lateral displacement or combined axial and lateral displacements. While it can compensate for angular displacement, generally compensators are not suitable for compensating angular displacement.

　　Compensator - Pipeline Rack Design Requirements:

　　1. Main fixed pipe supports must be installed at sections where axial compensators are installed, as well as at blind ends of pipelines, bends, sections with variable cross-sections equipped with shut-off valves or pressure-reducing valves, and at the inlets of lateral branches entering the main pipeline. The design of the main fixed pipe supports should take into account both the static hydrostatic thrust exerted by the bellows and the elastic restoring force resulting from its deformation. The formula for calculating the thrust is as follows: Fp = 100 × P × A, where Fp represents the axial pressure thrust on the compensator (N); A denotes the effective area corresponding to the average diameter of the bellows (cm²); and P stands for the pressure in this pipeline section (MPa). The calculation for the axial elastic force is as follows: Fx = f × Kx × X, where Fx represents the axial elastic force of the compensator (N); Kx denotes the axial stiffness of the compensator (N/mm); and f is a coefficient that equals 1/2 if there is “pre-deformation” (including a pre-deformation amount X = 0), and equals 1 otherwise. In addition to the supports located above the pipeline, intermediate fixed pipe supports may also be provided. These intermediate fixed pipe supports do not need to consider the effect of pressure thrust.

　　2. Only one axial compensator may be installed between two fixed pipe supports in a pipe section.

　　3. One end of the compensator should be positioned close to a fixed pipe support. If the length is excessive, guide supports should be installed according to the requirements for guide support placement. The spacing between other guide supports can be calculated as follows: LGmax—guide support spacing (m); E—elastic modulus of the pipe material (N/cm²); I—moment of inertia of the pipe cross-section (cm⁴); KX—axial stiffness of the compensator (N/mm); X0—positioning displacement of the compensation amount (mm). When the compensator undergoes compressive deformation, use the symbol “+”; when it undergoes tensile deformation, use the symbol “-”. If the pipe wall thickness is designed according to standard wall thickness, LGmax can be selected based on relevant standards.

　　2. Compensator – Lateral Type

　　It primarily absorbs lateral displacement and a small amount of axial displacement.

　　Compensator - Pipeline Rack Design Requirements:

　　1. The lateral compensator installed near the pipe bend is equipped with a high unidirectional support at each end, one of which is a planar guiding support. The upper and lower movement gaps are calculated as follows: - Movement gap (mm), as shown below: L—effective length of the compensator (mm); Y—thermal expansion of the Y-shaped pipe (mm); ΔL—thermal expansion of the vertical pipe section (mm), excluding the X-l length.

　　2. The guiding supports on both sides of the compensator should be positioned close to the compensator itself, and their design should ensure that the compensator maintains a defined direction. These supports consist of hinge pairs connected to the nozzle, bellows, and connecting pipe. They can only absorb angular displacement in a single plane. When absorbing displacement, two or three hinges work together within the compensator, and the hinges are capable of withstanding the thrust generated by internal pressure. The operating temperature is 420°C, and the fatigue life is 1,000 cycles.

　　Pipeline rack design requirements: Angle compensators should be used in sets of 2 to 3 to absorb lateral displacements in the pipeline. Between two fixed pipe frames in Z-shaped and L-shaped pipe sections, only one set of side compensators or angle compensators may be installed. In this case, the axis of the planar hinge pin must be perpendicular to the plane formed by the bent pipe section (universal hinge compensators are not subject to this restriction). For pipe sections equipped with a single set of hinge compensators, the clearance of the planar guides can also be calculated from bottom to top. However, L represents the distance between the axes of the two compensator pivots, while X denotes the total thermal expansion of the entire vertical segment.

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