What Is Burst Pressure?

Bursting pressure refers to the maximum pressure value that a container can withstand when a container bursts. It is generally calculated by Faupel's formula.

Burst pressure is the pressure value when a pressure load is applied to a pressure vessel to rupture it. Can be based on the material

The commonly used formula is the famous Faupel formula. The lower limit of the burst pressure is

Similarly, the upper limit of the burst pressure is

The actual blasting force of a general container is between

Japanese style

Between the two, and varies linearly with the yield ratio v of the material, so there is

or

make

, Then

Becomes

For the convenience of research, the formula

Divided into two parts, namely

such,

Obviously represents the ultimate pressure of an ideal plastic material;

It indicates the influence of the material's yield ratio on the ultimate pressure. because

, So

. This explains why the ultimate pressure (burst pressure) of a cylindrical shell made of a non-ideal plastic material is greater than the ultimate pressure of a cylindrical shell made of a modeled ideal plastic material.

In recent years, when using the Faubel formula, the calculation results also have error problems. Especially after testing high-pressure steel vessels of medium strength, it is found that the error of this formula exceeds 15% to 20%, sometimes as high as 30%. Some people use a ratio formula

A more simplified but more accurate calculation of the maximum pressure:

It is said that the error of this formula is about 8%. ^[2]

Welding gas cylinders are mobile pressure vessels that can be filled repeatedly with low-pressure liquefied gases such as liquid ammonia, liquid chlorine, cyclopropane, and liquefied petroleum gas, as well as dissolved acetylene gas, without insulation. It is widely used, large in quantity, large in fluidity, dispersed in management, and poor in use environment. Most of the filling media are flammable, explosive, highly toxic, and highly corrosive. Therefore, while cylinders contribute to economic development, there are also some hidden safety hazards. In recent years, there have been cases in which the overdue unchecked gas cylinders and overdue serviced gas cylinders have been supplied to the market. The hidden safety hazards are very prominent, and gas cylinder explosion accidents often occur.

After the accident, during the analysis of the cause of the accident, it is necessary to simulate the accident process and calculate the burst pressure. There are many simulation studies on the static burst pressure of gas cylinders. In 1957, COOPER published a paper on predicting the static burst pressure of gas cylinders, and proposed an analytical equation to predict the static explosion pressure of steel cylinders made of isotropic plastic materials. This equation gives the relationship between the ideal explosion pressure, material properties, original dimensions, and ultimate tensile strength of the material. Subsequently, successively based on the elastic theory, elasto-plastic theory, and plastic theory, the static burst pressure models of cylinders applicable to different conditions such as thin-walled, thick-walled, single-layered, multi-layered, and corrosion defects on the inner and outer walls were established.

Static blasting is often used to simulate and analyze the water pressure or air pressure blasting of gas cylinders. The blasting form is still very different from gas cylinder explosions. Due to the slower pressure rise of water pressure or air pressure blasting, the cylinder is subjected to a long load and the strain rate is low, which can be regarded as a static or quasi-static process. Divided by strain rate, when the strain rate is lower than

When it is called static deformation;

Quasi-static deformation

This is called dynamic deformation.

Generally, as the strain rate increases, the yield strength and tensile strength of the material increase, the elongation decreases, and yield lag and fracture lag appear. To study the explosion process of gas cylinders, it is necessary to grasp the dynamic mechanical behavior of the gas cylinder materials, because the relevant dynamic performance data will provide more accurate boundary conditions for the use of dynamic models to simulate the explosion process and improve the accuracy of simulation results Sex.

Obtained through experiments, the cylinder burst pressures at different loading rates were predicted, and compared with the results calculated by the revised empirical formula, the following conclusions were obtained:

(1) As the tensile rate increases (from 0.05 to 200 mm / s), the tensile strength and yield strength increase (from 469.2 to 517.9 MPa, from 332.2 to 392 MPa).

(2) Finite element cylinder burst dynamic simulation analysis results show that the cylinder and the head are deformed when the cylinder is loaded, and finally the cylinder is broken. With the increase of the loading rate, the plastic deformation of the cylinder during blasting decreases, the stress increases, the blasting time decreases, and the blasting pressure increases.

(3) With the increase of the loading rate, the burst pressure obtained from the finite element simulation analysis is gradually approaching the burst pressure estimated using the modified Barlow formula, so under dynamic fast loading conditions, this formula can be used to predict the burst pressure. ^[3]