As one of the alternative steel materials, ductile iron ball valves were discovered by humans in 1949 and quickly adopted by valve manufacturing enterprises. Steel with a carbon content of less than 0.3%, cast iron, and ductile iron with a carbon content of at least 3%. The existence of graphite layer structure without forming low-carbon content steelmaking as free carbon. Carbon is the natural form of free graphite flakes in iron. In ductile iron, it is transformed into small flakes of graphite balls through special treatment. This enables the ball to have better physical properties compared to the improved ratio of ductile cast iron and steel. This is the spherical microstructure of carbon, which has better ductility and impact resistance, and there is no table of ductility due to the cast iron on the inner side of the sheet.

 

Obtained from a ductile ferrite matrix, therefore, the load pressure of ductile iron parts is achieved during the intermediate annealing cycle of ferrite. The spherical structure within the toughness of cast iron can be easily eliminated by post-treatment, which can eliminate the phenomenon of internal cracks in ink sheets during the manufacturing of stone valves. In the microscopic photograph of ductile iron, it can be seen that the graphite balls terminate after the propagating cracks. In the ductile iron industry, these so-called graphite balls are the "crack terminators" because of their ability to prevent damage. Compared with cast iron, ductile iron has advantages in strength. The tensile strength of ductile iron is 60K, while the tensile strength of cast iron is only 31K. The yield strength of ductile iron is 40K, while iron does not show yield strength or fracture occurrence. The strength ductile iron has a much better cost ratio than cast iron.

 

Ductile iron ball valves should generally be installed horizontally in pipelines. Ball valves are divided into pneumatic ball valves, electric ball valves, and manual ball valves according to their driving methods.

 

Daily maintenance of ductile iron ball valves:

 

Having a long service life and maintenance free period will depend on the following factors: normal working conditions, maintaining a harmonious temperature/pressure ratio, and reasonable corrosion data

 

When the ball valve is in the closed state, there is still pressurized fluid inside the valve body

 

Before maintenance: Release the pipeline pressure and keep the valve in the open position; Disconnect the power or gas source; Detach the actuator from the bracket

 

It is necessary to confirm that the pressure in the upstream and downstream pipelines of the ball valve has been relieved before proceeding with disassembly and assembly operations

 

When disassembling and reassembling, care must be taken to prevent damage to the sealing surface of the parts, especially non-metallic parts. Special tools should be used when removing the O-ring

 

The bolts on the flange must be tightened symmetrically, gradually, and evenly during assembly

 

The cleaning agent should be compatible with the rubber parts, plastic parts, metal parts, and working media (such as gas) in the ball valve. When the working medium is gas, gasoline (GB484-89) can be used to clean metal parts. Clean non-metallic parts with pure water or alcohol

 

Non metallic parts should be immediately removed from the cleaning agent after cleaning and should not be soaked for a long time

 

After cleaning, it is necessary to wait for the wall cleaning agent to evaporate (which can be wiped with a silk cloth that has not been soaked in cleaning agent) before assembly, but it should not be left for a long time, otherwise it will rust and be contaminated by dust

 

New parts also need to be cleaned thoroughly before assembly

 

During assembly, metal debris, fibers, grease (excluding those specified for use), dust, and other impurities, foreign objects, etc. should not be allowed to contaminate, adhere or remain on the surface of the parts or enter the inner cavity. If there is slight leakage at the packing, the valve stem nut must be tightened again.

 

Attention: Do not lock it too tightly. Usually, lock it 1/4 turn to 1 turn again, and the leakage will stop.