what is the Vulcanization and Types

VULCANIZATION

The insulation of the conductor or the sheathing of rubber cables are operated continuously by means of an extruder (pump) provided with a forming head, which is the first component of the equipment, even if it is materially not part of it.

The equipment has the function to treat the insulation or rubber sheathing (in other words, we are talking about a tube coating the conductor or cable) processed continuously, so to induce those chemical-physical modifications, known under the name of "vulcanization", highlighting mechanical resistance and elasticity under different temperatures. Vulcanizing systems can be divided into three main groups, that are :

1. Salt melts vulcanizing systems without air pressure
2. Salt melts air pressure vulcanizing systems
3. Steam / Nitrogen vulcanizing systems

Salt melts vulcanizing systems without air pressure

Atmosphere vulcanizing furnace length 15÷30 meters. It is composed by a tank containing salts, at a temperature of 230 deg. C. Multiple passes of the cable through the tank (60÷90 meters) will speed up the process.
- Washing unit, it has the function to remove the salt from the vulcanized cable.
- Water cooling unit (and additional washing), whether needed.
- Distillers for recovery of salt melted in water.

Salt melts air pressure vulcanizing systems

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Telescopic section, It actually is a tube sliding into another tube which has larger diameter. Sliding of the tube can be operated either by pneumatic or by hydraulic cylinders. Suitable sealing devices are located between the fixed tube and the sliding one, as well as between the sliding tube and the extrusion head. A proper device connects the extrusion head to the vulcanizing unit, through the telescopic section.

Air pressure vulcanizing furnace length 15÷40 meters (one or two stages). It is composed by a large diameter tube (DN300 min.). At the inside, the cable immersed in the salt melts goes through a channel, which is located on the upper part of the tube. A centrifugal pump keeps circulating the salt melts. The lower part of the tube acts as a tank for the salt melts. Pressure (compressed air or nitrogen) : up to 10 bar and more.
Vulcanizzazione

Dividing sections and rough removal of the salts from the cable. Dividing sections are located between the vulcanizing unit and the cooling unit.

Cooling section. The diameter of the cooling section is about a quarter of the vulcanizing unit diameter. Length 6÷12 meters and more. Cooling by counterpressure.



Pressure chamber with bi-conical seal. Once vulcanized and cooled, the cable goes through a ring shaped rubber seal, which is thicker at the center than at the outside. The hole which the cable goes through is provided with circular chambers, enabling the seal to shape the hole according to the cable diameters. It is clear that the chamber is not properly watertight, because the water overflows due to cooling by counterpressure. This must not be considered as a malfunction, on the contrary, the water flow acts as a lubricant between the cable and the seal. Moreover, the water continously flowing helps maintaining the end section of the equipment at a low temperature. The seal can be adjusted by means of a manual screw drive or, occasionally, by a servomotor. It has a wide adjustment range and, usually, it is possible producing cables without replacing the seal, even when diameters are a little different. Anyway, different size rubber seals are available for the same pressure chamber

Steam – Nitrogen vulcanizing systems



Telescopic section. , It actually is a tube sliding into another tube which has larger diameter. Sliding of the tube can be operated either by pneumatic or by hydraulic cylinders. Suitable sealing devices are located between the fixed tube and the sliding one, as well as between the sliding tube and the extrusion head. A proper device connects the extrusion head to the vulcanizing unit, through the telescopic section.
Vulcanizzazione

Main vulcanizing and cooling units. Vulcanizing unit is composed by a section which the cable goes through and which can be more or less curvilinear and more or less inclined. In case of steam vulcanizing systems, saturated steam is placed at a pressure between 16 and 24 bar, providing heating in the same way. On demand and with the suitable equipment, it will be possible having both procedures on the same unit. The cable goes through the vulcanizing section first and then through the cooling section, which is by counterpressure type. Length is about 80 to 140 meters and more.


Pressure chamber with bi-conical seal. Once vulcanized and cooled, the cable goes through a ring shaped rubber seal, which is thicker at the center than at the outside. The hole which the cable goes through is provided with circular chambers, enabling the seal to shape the hole according to the cable diameters. It is clear that the chamber is not properly watertight, because the water overflows due to cooling by counterpressure. This must not be considered as a malfunction, on the contrary, the water flow acts as a lubricant between the cable and the seal. Moreover, the water continously flowing helps maintaining the end section of the equipment at a low temperature.


The seal can be adjusted by means of a manual screw drive or, occasionally, by a servomotor. It has a wide adjustment range and, usually, it is possible producing cables without replacing the seal, even when diameters are a little different. Anyway, different size rubber seals are available for the same pressure chamber.

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Steam or nitrogen CV line vulcanization




Salt melts air pressure vulcanizing system




Salt melts air pressure vulcanizing system