Estimation of bearing capacity of bellows tubular compensators
Currently 22.1 km of gas pipelines in the Ukraine are located in the areas of coal mines influence and this amount is constantly increasing. Therefore, the justification of its safety operation is an important problem.
The investigation deals with the estimation of the load carrying capacity of the bellow compensator Dn100, made of stainless steel AISI 304, which is supposed to be used for providing the necessary level of deformability of main buried gas pipelines in the mining production areas.
As the result of the experimental researches it is determined that compensator has strength margin relatively to the operating internal pressure and compensating capacity margin both in terms of cycles number and displacements amplitude.
For bellow simulation under the conditions of long excavated section of the gas pipeline the compensating capacity from operating pressure which is 1.7 times greater than the working stroke guaranteed by the manufacturer is determined. The given estimation is approximate since it is obtained after experimental testing of the nominal cyclic durability. In this case, the macrocracks occurred in the bellow upper layer resulting in the compensator carrying capacity loss in tightness and static strength.
The deformation amplitudes in each layer are determined by means of the compensator finite element modeling. It is shown that the bellow external layer (as is proved by experiment) is the most loaded. It is defined according to the amplitude of von Mises deformations and fatigue curve of the bellow material that the bellow cyclic durability for tension-compression ±75 mm is up to 32 cycles.
The results of experimental and numerical-analytical investigations prove the possibility of bellow compensator Dn100 use for compensation of axial displacements on the gas pipeline sections in mining areas for maximum 15 mine workings.