Metal hose is not suitable for liquid sulfur delivery pipeline

Liquid sulfur is transported to the wharf by ship and then pumped into the storage tank in the installation area. To overcome the fluctuation of the river and the sloshing of the barge, a metal hose is selected for the liquid sulfur pipeline between the dock Zhanqiao and the riverbank.
The liquid sulphur is shipped to the dock and then pumped into the storage tank of the installation area. In order to overcome the fluctuation of the river and the barge of the pontoon, the metal hose is selected for the liquid sulfur transportation pipeline between the pier Zhanqiao and the river bank. The metal hose soon cracked due to liquid sulfur leakage. To this end. The causes of breakage were analyzed, and communication with suppliers and manufacturers was made, and suggestions for improvement were put forward.
The design parameters of the metal hose are: the jacket is accompanied by the tube DN125, the outer tube DN200, the length is 10 m, the material is 304 stainless steel, the wall thickness is 0.8 mln, and the design pressure is 1 MPa. The operation conditions are as follows: the liquid sulfur intermittent transportation, the internal liquid sulfur working pressure is 0.6 MPa, the temperature is 135 oC, the outer layer steam pressure is 0.5 MPa, the temperature is 140 degrees Celsius.
It is found that the leakage position is on the first wave peak of the bellows of the inner hose close to the pipe joint, and the crack is distributed in the circumference, and the opening of the inner surface of the crack is larger than the outer surface. It is inferred that the crack extends from the inside to the outside.
The liquid sulfur itself has a certain acidity. In the process of loading and unloading, liquid sulfur is unavoidable to contain a small amount of water and oxygen, and oxidize to a certain acidity. Therefore, the acidity of liquid sulfur is further increased; on the other hand, the solid solution treatment is improper in the production and processing of the metal hose material, the carbide is not fully dissolved and the material itself has carbide precipitation, which greatly reduces the 30 4 the corrosion resistance of stainless steel itself, in acidic conditions, first appeared micro electrochemical reaction at these locations, resulting in corrosion.
The fracture area of the metal hose is located on the upper side of the first peak. Because the hose is too long, the curvature of the fracture is too large and the stress concentration is concentrated. In addition, the interstitial fluid is used during the operation. When it is not transported, the steam is stopped and the liquid is solidified in the hose, so that the hose is turned into a rigid tube and can not absorb the stress generated by the displacement of the barge. Under the combined action of the above two stresses, the metal hose is cracked by stress corrosion.