Tips for ACSR cable fault location

The occurrence of ACSR Cable 336.4 MCM  faults is accompanied by the laying and use of cables. The location of cable faults varies with cable laying methods, and the difficulty in locating is gradually increasing. Among them, the positioning and searching of bridges, tunnels, and trenches are relatively simple, while the direct-buried method is the most difficult to locate. When the nature of the fault is simple, a dedicated cable fault location device can be used to locate the fault within tens of minutes. When the fault is special, it often takes 4-5 days or even longer to locate the fault.
When using the echo method to locate cable faults, sometimes through the transfer of faulty phases and wiring methods, complex faults are often transformed into simple faults, and the fault location can be quickly determined to gain time for on-site line repairs. This is important for power supply departments. Significant.

Low-voltage power cables are generally multi-core cables. After a fault occurs in continuous use after laying, they generally show two-core and multi-core phase-to-phase or relative-to-ground short-circuit faults. Sometimes when it is detected that the fault waveform collected by a certain core is not ideal, consider switching the wiring to other faulty cores for fault waveform detection. Unexpected effects will often occur, and the collected and detected waveforms will become More typical and regular, so you can quickly determine the specific location of the cable fault point.
In the long-term on-site measurement process of cable customers, it is found that after the failure of small cross-section copper core direct-buried power cables (35mm2 and below) and aluminum core cables, there may be short-circuit and disconnection faults at the same time. During on-site detection, according to the nature of the failure of each faulty core The difference between the short-circuit fault and the disconnection fault measurement will often get twice the result with half the effort.

For low-voltage cable and  direct-buried power cables with extruded armored inner lining, most of the faults are caused by external mechanical damage. When the insulated core fails, the inner lining may have been damaged. When encountering a special cable insulation fault, it is difficult to use a professional cable fault meter to collect waveforms. Consider using the acoustic measurement method to directly apply high-voltage pulses between the steel strip and the copper shielding layer of the cable, which will often quickly fix the point.
During the on-site measurement process, we also found that when the low-voltage cable fault point is determined by the acoustic measurement method, when the high-voltage wire and the ground wire are connected between the bad phase and the metal shield or armor, the insulation resistance of the two shows a low-resistance metallic connection. State, the sound is very small, the probe cannot be used to listen to the fixed point, and the effect is not ideal. Through the actual listening side many times, it was found that the distance between the discharge ball gaps was appropriately increased, and the high voltage and grounding wires were reconnected between the two phases where the fault occurred. Often the discharge sound will become louder, and the fault point will be quickly determined. .

There are many dangers of cable construction accidents in winter

When Low voltage cables and middle voltage Cables are constructed in winter, because the outdoor temperature is below minus 10 ℃, the low temperature polyvinyl chloride and cross-linked polyethylene insulation and sheath materials show hard and brittle characteristics, such as accidental accidents during the laying process If bumped, the insulated core and copper shield are easily damaged. Even if the on-site completion test can pass smoothly after the cable is laid, after the cable is continuously energized, partial discharge will occur after the capacitive current flows in the damaged part, accelerating the insulation aging, and leading to breakdown of the line. This situation is not prominent in low-voltage cables, but is prominent in medium-voltage cables. Sometimes there is no problem in the cable factory test. Because of the restrictions of various conditions, the cable is directly constructed in winter without any measures. After the cable is laid, the on-site completion test is all normal, but it appears after the power-on operation in a short period of time. Failure, anatomy of the failure point, there is no trace of mechanical damage in appearance, but serious breakdown and ablation occurred in the internal insulation.

In recent years, some newly laid medium-voltage 10kV and 35kV faulty cables have not been heated on site due to various conditions, and they have been directly constructed and installed at minus 10°C in winter. In a short period of time when the cable was energized and operated, there was a phase-to-phase and relative-to-ground insulation breakdown fault (the incident time was as short as 10 days, and the length was about 1 month). After the accident investigation, the cable production and factory tests showed no abnormalities. The completion test is also smooth (26/35kV power cable AC 52kV/1h passed). However, the failure occurred in a short period of time (as short as 10 days, and as long as 1 month) after power-on operation. This is undoubtedly related to the fact that the power cables were not heated during construction in0 winter.

Finding method for broken core of flame retardant cable

Power cables are known as the nerves of modern industry. Modern human life and production cannot do without the help of wires and cables. Since the founding of the People’s Republic of China, China has realized the important role of wires and cables in the future economic development, so it has spent a lot of manpower, material resources and financial resources. With investment in construction and research, China has become the world’s largest cable manufacturer.

In the past few decades, the productivity formed by my country’s cable manufacturing industry has made the world look at it with admiration. With the continuous expansion of my country’s power industry, rail transit industry, data communications industry, automobile industry, and mines, the demand for the cable market is also increasing. This is one reason why China’s wire and cable industry has developed so fast.
With the continuous improvement of people’s awareness of fire protection, in project construction, people increasingly prefer to use flame-retardant cables with fire-retardant properties. The market demand for flame-retardant cables is also increasing, but the cables may be used when they are in use. There will be some faults, such as cable breakdown, cable conductor damage, broken cores and other faults. The conductor of the flame-retardant cable has a small cross-sectional area and may be broken during the production of the cable or during the extrusion process. So how to check the disconnection of flame-retardant cables?

In the cable industry, there are usually three ways to check the broken core of flame-retardant cables. The first is the energized capacitance method, which uses continuous electricity to accurately determine the disconnection point of the cable. This method is extremely inefficient, and one is often checked. It takes several hours to break the line, so this inefficient method has been abandoned by many people.
There is also a method of combining capacitance method and induction method, which is to use the capacitance to find the approximate location of the disconnection, and then use the induced voltage to find the accurate disconnection point. This double combination method can locate faster than the pure capacitance method. The disconnection point has also become a more commonly used method in the industry.
Another method is the combination of constant current source and bridge method. This method is also often used. The principle is to burn and puncture the insulation at the broken core of the flame-retardant cable with a constant current source. Using the bridge method fault locator to locate, its efficiency is very high and accurate.

Analysis of Operation Failure of Armored Cable

At present, there are various on-site treatment methods for the armor layer of low-voltage direct-buried cables, including single-ended grounding and two-end grounding. There are also those that are not grounded at both ends. According to the different treatment methods of the steel tape armor at both ends of the field cable, after the cable fails, the appearance of the fault point will be different.
The steel strips at both ends of the cable are all suspended and not grounded. After a short-circuit fault occurs in the cable, the breakdown point may only be a burn-through hole in a local location of the cable line, which will not cause long-distance and large-area burning and carbonization. Because when the cable is partially damaged by accidental mechanical damage and the sheath insulation is damaged, the system may not immediately trip and power off. The damaged point will cause intermittent flashover discharge on the earth due to the action of moisture and moisture in the soil, which will eventually develop into Permanent grounding and short-circuit between phases cause a trip and power failure. Since the discharge current of the live wire to the ground is limited to the location of the damaged point of the cable, the discharge current does not form a branch circuit to the ground through the steel belt, so there is generally only one point in the entire cable after the cable fails. malfunction. However, the surface of the armor layer will be electrified at this time. In consideration of safe use of electricity, the armor layer exposed at both ends of the cable must be insulated and sealed.

The steel belt of the cable line adopts single-ended grounding or double-ended grounding. After a short-circuit fault occurs in the cable, the fault may be a section of the cable, and the local area of ​​the cable may have long-distance surface burnt and carbonized adhesion. Because after the steel belt adopts this connection method, when a single-phase ground fault occurs in the cable, a relatively large ground short-circuit current will flow in the steel belt of the cable; at the same time, the three-phase load current of the cable will also appear unbalanced. Eddy current may also occur in the belt. After the two currents flow through the steel belt, the steel belt will be like a high-power electric furnace, heating the cable sheath and insulation, and the customer’s switch selection is not appropriate, and the soil is localized. Poor heat dissipation, excessive thermal resistance, partial accumulation of cable coils, poor heat dissipation and other unfavorable reasons may cause long-distance and large-area burning and carbonization of the cable insulation and sheath. The burned area is relatively random. It may be near the fault point, or in another section. It is often the section with the most difficult heat dissipation and the section with the largest thermal resistance that burns the most. The system may not trip until the single-phase grounding develops into a two-phase short circuit and cannot be reclosed to transmit power.

For low-voltage cable armored cables, it is necessary to strengthen the real-time online detection and monitoring of the three-phase current of the cable. At the same time, after the armor layer is grounded, an armor layer current transformer should be installed to monitor the current of the steel strip from time to time. The single-phase grounding short-circuit fault of the cable should be detected and dealt with in advance to avoid the long-distance burning of the cable and cause unnecessary power economic loss, and to ensure the economy, reliability, stability and safety of the grid operation.
According to normal analysis, after a short-circuit fault occurs in a directly buried low-voltage cable, there should generally be only one fault point. However, during the actual field excavation and processing of cable fault points, it is found that low-voltage cable faults may have two or more fault points, and may also be accompanied by long-distance insulation sheath heating and burning and carbonization adhesion. The author believes that the difference in the failure of low-voltage armored cables may be related to the grounding or non-grounding of the cable armor, and the opinions and opinions may not be correct. It is hoped that professionals who have sincere insights into such phenomena can provide more scientific and authoritative analysis and opinions. To uncover the underlying cause of this phenomenon.

Matters needing attention in power cable installation

1. Keep a distance of 2m when the mine AAAC cable is installed in parallel with the thermal pipeline, and keep 0.5m when crossing.
2. When the cable is installed in parallel or across other pipes, a distance of 0.5m must be maintained.
3. When the cable is directly buried, the depth of the 1-35kV cable shall not be less than 0.7m.
4. When the cables of 10kV and below are installed in parallel, the mutual clear distance shall not be less than 0.1m, 10-35kV shall not be less than 0.25m, and the cross distance shall not be less than 0.5m.
5. The minimum bending radius of the cable must not be less than 15D for multi-core cables and 20D for single-core cables (D is the outer diameter of the cable).

6. Cable joints of 6kv and above.
A. When installing the cable terminal head, the semi-conductive shielding layer must be stripped off, and the insulation must not be damaged during operation. Knife marks and unevenness should be avoided, and sandpaper should be used if necessary. The shielding end should be flat and graphite The layer (carbon particles) is removed.
B. The copper shield and steel armor of the plastic insulated cable end must be well grounded. This principle should also be followed for short circuits to avoid induced electromotive force at the steel armor end during unbalanced operation of three-phase, or even “fire” and burn the sheath. Wait for the accident. The grounding lead wire should be tinned braided copper wire, and soldering iron should be used when connecting with the copper tape of the cable. It is not suitable to use a blowtorch to seal and solder, so as not to burn the insulation.
C. The three-phase copper shield should be connected to the ground wire separately. Note that the shield ground wire and the steel armor ground wire should be led out separately and insulated from each other. The position of the welding ground wire should be as low as possible.

7. The basic requirements for cable ends and intermediate joints: a. Good conductor connection; b. Reliable insulation, it is recommended to use radiation cross-linked heat-shrinkable silicone rubber insulating materials; c. Good sealing; d. Sufficient mechanical strength, Can adapt to various operating conditions.
8. The cable end must be waterproof and corroded by other corrosive materials to prevent breakdown due to aging of the insulation layer caused by water trees.
9. Cable loading and unloading must use cranes or forklifts. Horizontal transportation or laying flat is prohibited. When installing large cables, cable cars must be used to prevent cables from being damaged by external forces or scratching the insulation layer due to manual dragging.
10. If the cable cannot be laid in time for some reason, it should be stored in a dry place to prevent sun exposure and water ingress into the cable end.

What are the requirements for environmental protection cables

As the second largest manufacturing industry in China after automobile manufacturing, the wire and cable industry should also play a leading role in environmental protection. In recent years, environmentally friendly cables have become more and more popular in the market. In developed countries such as the European Union, non-environmental protection has been banned. Cables, China also attaches great importance to this aspect. China’s relevant laws and regulations explicitly require important buildings to prohibit the use of polyvinyl chloride wires and cables. Halogen-free and low-smoke cross-linked PVC wires and cables must be used to avoid a large amount of smoke and chlorine in the event of a fire. Casualties.
Environmental protection cables are the main direction of the future development of the cable industry, which can effectively enhance the competitiveness of cable companies. Because of the many excellent characteristics of environmental protection cables, they are also favored by more and more customers in the market.

Compared with ordinary cables, environmental protection cables have many excellent characteristics, such as no heavy metals, no halogens, no corrosive gas, no soil pollution, etc. If summed up, the requirements of environmental protection cables can be roughly divided into three aspects.
The first is that it does not contain heavy metals. Common PVC cables often contain heavy metals such as lead, cadmium and barium, which are harmful to the human body. Later, some countries stipulated that the content of eight types of heavy metals should not be higher than the specified value, and one of the main advantages of environmentally friendly cables It does not contain heavy metals, which is also its popular selling point in the market.
The second requirement of environmentally friendly cables is low-smoke and halogen-free. When ordinary cables are burnt, they will release a large amount of smoke and toxic gases, which will seriously pollute the air environment and cause harm to the human body. The low-smoke and halogen-free characteristics of environmentally friendly cables can not only protect the environment, but also It can help people evacuate and carry out fire rescue work when a fire occurs.

Secondly, it must be non-toxic. All component materials used in PVC formulations should be non-toxic. Cable material contains a lot of plasticizers, but non-toxic plasticizers must be used to make non-toxic materials. Therefore, this PVC material has higher requirements than lead-free and heavy metal-free materials, and the price is naturally more expensive.
Many countries have different requirements for environmental protection cables. For example, the European Union will restrict environmental protection cables containing asbestos. my country has not been as perfect as the EU in terms of related policy formulation and mandatory application. In this regard, China still has a long way to go. The way to go.

Difficulties in locating cable faults

Due to changes in the environment in which Power Cables are laid and the application of new materials for cables and their accessories in the cables, it is increasingly difficult to locate faults on the power cable site.
The difficulty of field cable fault location is mainly reflected in the fault location of directly buried power cable lines. At present, despite the relevant classic technical literature and advanced fault detectors, it is still available for high resistance faults in power cable lines. However, when using a professional cable fault locator to locate on site, sometimes you will encounter some special and difficult faults that cannot be located. For example, using a professional cable fault locator, part of the creepage flashover fault on the insulation surface of the medium voltage cross-linked power cable terminals and intermediate joints, and accurately determining the metal short-circuit fault, often appears powerless or powerless.

For common cable faults, you can use a cable fault locator purchased on the market to determine the location of the fault point within minutes or hours. However, when you encounter special difficult faults and the detection is not stable, you may need to call multiple cable fault detectors with different functions to repeat the test, and take turns to detect, locate, compare and confirm. The types of these fault devices mainly include various cable fault detectors designed, manufactured and developed based on the principles of bridging method and wave method. In this way, it may take several days or even longer to locate the fault. In this way, if you are lucky, you can determine the location of the fault point. If you are unlucky, the location of the fault point is still uncertain.
In northern China, the ground freezes in winter, and the directly buried cables fail at this time. The actual fault detection and handling process is actually a difficult task. First of all, the cable fault locator used must have high accuracy, and secondly, the corresponding personnel must have a clear understanding of the actual cable laying route. Although some cable fault detection instruments are now equipped with cable path testers, they must also be equipped with cable path testers. Only on-site personnel who understand the approximate laying path of the cable can cooperate to improve the positioning accuracy. The actual handling of cable faults sometimes depends on man-made three points and machine-made seven points.

At present, there are many manufacturers selling cable fault detection instruments on the market, and there are many types of detection instruments, but in fact, it is impossible to locate all cable faults. In actual use, the instrument usually can only effectively locate one or several types of faults, but still cannot do anything about some faults. The current electric power department hopes to spend a lot of money to purchase a universal cable fault tester with complete functions and high positioning accuracy (including rough and precise measurement points) to quickly and effectively solve all actual cable faults. But it’s actually hard to buy. There are various updated cable fault detectors on the market. However, the actual on-site inspection will still encounter some technical problems that cannot be located using the cable fault table. I think the reasons are mainly from two aspects: First, the various insulation, filling and wrapping materials used in the cable and its accessories are constantly being developed and updated, which leads to continuous changes in the types of cable failures. The other is that the market demand for cable fault detectors is limited, and related R&D personnel are scarce, resulting in a delay in the start of portable, high-precision, intelligent and multi-functional cable fault detectors. It is believed that with the advent of the smart grid era and the rapid development of Aerial Bundled Cable ASTM B231 Standard fault detection technology, the location of cable faults will become very simple and easy.

Comprehensive performance comparison of copper and copper clad aluminum wire

Copper-clad aluminum is formed by concentrically cladding a copper layer on the surface of aluminum or aluminum/steel alloy core material, and the thickness of the copper layer is 0.55mm or more. Due to the skin effect characteristics of high-frequency signal transmission on the conductor, the cable TV signal is transmitted on the surface of the copper layer above 0.008mm. The copper-clad aluminum inner conductor can fully meet the signal transmission requirements, and its signal transmission characteristics are the same as those of copper wires with the same diameter. The body is consistent.

Copper-clad aluminum and pure copper can be compared in the following three aspects:

Mechanical characteristics:

The strength and elongation of pure copper conductors are larger than copper-clad aluminum conductors, which means that pure copper is better than copper-clad aluminum in terms of mechanical properties. From the perspective of cable design, pure copper conductors have the advantage of better mechanical strength than copper-clad aluminum conductors, which are not necessarily required in the actual application process. Copper-clad aluminum conductors are much lighter than pure copper, so the overall weight of copper-clad aluminum cables is lighter than pure copper conductor cables, which will bring convenience to cable transportation and cable erection. In addition, copper-clad aluminum is a little softer than pure copper, and cables produced with copper-clad aluminum conductors are a little better than pure copper cables in terms of flexibility.

Electrical performance:

Because the conductivity of aluminum is worse than that of copper, the DC resistance of copper-clad aluminum conductors is larger than that of pure copper conductors. Does this affect the main 2014 high school entrance examination sprint comprehensive review guidance Beijing area test questions Guangdong area test questions Jiangsu area test questions to see if the cable will be damaged Using power supply, such as providing power to the amplifier, if it is used for power supply, the copper-clad aluminum conductor will cause additional power consumption, and the voltage will drop more. When the frequency exceeds 5MHz, there is no obvious difference in the AC resistance attenuation under these two different conductors. Of course, this is mainly due to the skin effect of high-frequency current. The higher the frequency, the closer the current flows to the surface of the conductor. The surface of the copper-clad aluminum conductor is actually pure copper. When the frequency is high, the entire current is plated. It flows in the copper material. In the case of 5MHz, the current flows in a thickness of about 0.025 mm near the surface, and the thickness of the copper layer of the copper-clad aluminum conductor is about twice this thickness. For coaxial cables, because the transmitted signal is above 5MHz, the transmission effect of copper-clad aluminum conductor and pure copper conductor is the same. The attenuation of the actual test cable can prove this point.

Copper-clad aluminum is softer than pure copper conductors, and it is easy to straighten during the production process. Therefore, to a certain extent, it can be said that cables with copper-clad aluminum have better return loss indicators than cables with pure copper conductors.


Copper-clad aluminum conductors are sold by weight, and pure copper conductors are also sold by weight. The price of copper-clad aluminum conductors is more expensive than pure copper conductors of the same weight. However, the copper clad aluminum of the same weight is much longer than the pure copper conductor, and the cable is calculated according to the length. The copper clad aluminum wire of the same weight is 2.5 times the length of the copper wire, and the price is only a few hundred yuan per ton. Taken together, copper-clad aluminum is very advantageous. Because the copper-clad aluminum cable is relatively light, the transportation cost and installation cost of the cable will be reduced, which will bring a certain degree of convenience to the construction.

Ease of maintenance:

The use of copper-clad aluminum can reduce network failures and prevent network personnel from “cutting the core in winter and cutting the skin in summer” during maintenance (aluminum strip longitudinal packaging or aluminum tube products). Due to the large difference in thermal expansion coefficient between the copper inner conductor and the aluminum outer conductor of the cable, in the hot summer, the aluminum outer conductor stretches greatly, and the copper inner conductor is relatively retracted, and cannot fully contact the elastic contact piece in the F header; in severe cold In winter, the aluminum outer conductor shrinks greatly, causing the shielding layer to fall off. When the coaxial cable uses a copper-clad aluminum inner conductor, the difference in thermal expansion coefficient between it and the aluminum outer conductor is small. When the temperature changes, the cable core-pulling failure is greatly reduced, which improves the transmission quality of the network.

In general, the overall performance of copper-clad aluminum conductors is better than pure copper conductors, which will save users’ costs.

Insiders believe that the use of copper-clad aluminum wire in the wire and cable industry is also a good way to relieve the current pressure on enterprises. The aluminum wire is covered with a layer of copper and made of bimetallic wire. It has the advantages of small specific gravity and good transmission performance. It is especially suitable for the inner conductor of radio frequency coaxial cable. Compared with pure copper wire, its density is About 40% pure copper. The transmission characteristics are better than pure copper wire, and it is the most ideal inner conductor of radio frequency coaxial cable branch line.

A big explanation of high-voltage cables

Power cables have become a necessity in human life and production, and play an important role in many fields and industries, including home appliances, automobiles, houses, engineering, transportation, and so on. The demand for high-voltage power cables has been increasing in recent years, and cable companies have also entered the market.

The main technology for the production of high-voltage cables is CV continuous vulcanization production. This production line converts polymers into high-performance insulating materials and wraps metal conductors to form cables. As far as China’s high-voltage cable market is currently in a state of overcapacity, Chinese cable companies have invested in building a large amount of production capacity, but demand cannot keep up with the substantial expansion of production capacity.

Statistics show that China’s high-voltage power cable production accounted for 40% of the world’s total in 2014. At present, there are more than 185 continuous vulcanization production lines in China that can theoretically produce conductors for high-voltage power cables, accounting for 50% of the global production of high-voltage cable CV continuous vulcanization production lines. Although many of these CV lines are not in production, or have not even obtained relevant approvals, China’s high-voltage cable production capacity still exceeds its demand by three times. Today, the output of high-voltage cables will continue to increase until 2021.
As the traditional high-voltage cable market is saturated with overcapacity and its competition is becoming increasingly fierce, some powerful cable companies have turned to high-voltage submarine cables. This field has higher requirements for technical thresholds. Only a few companies in China have Strong production, and with the construction of wind farm projects in many countries around the world, the demand for high-voltage submarine cables will increase in the future.

Rubber insulation of cables

1. Preparation of raw materials
The preparation of raw materials requires warm glue and glue cutting. The weighing of raw materials is a crucial process of preparation.
2. Plasticizing
Rubber has high elasticity at room temperature and is not easy to process. Therefore, it is necessary to change its high elasticity to make it have a certain degree of plasticity. The process of converting rubber from a highly elastic state to a plastic state is called plasticizing.
Factors affecting mastication; roll distance, temperature, mastication time, speed ratio and number of revolutions
Natural rubber must be masticated, while synthetic rubber may not be masticated.
Three, mixing
Mixing is to scoop all kinds of compounding agents into the rubber to make 2 rubber materials with a certain degree of plasticity. One strand is divided into open mixer mixing, internal mixer mixing, and continuous mixing.

Fourth, filter rubber
The requirements for the mixed rubber materials used for insulation and thin sheath products are relatively high. In the actual production process, various rubber materials inevitably contain impurities, and impurities will also be mixed in the transportation and mixing processes. The purpose is to eliminate the above-mentioned various impurities.
There are two methods for filtering rubber: raw rubber after plastic refining and rubber filtering during mixing. Under normal circumstances, raw rubber does not need to be filtered.
l Extrusion process and equipment
Extrusion is a process that uses a rubber extrusion machine to squeeze the insulation layer on the conductor or squeeze the rubber jacket layer on the cable core.
Extrusion process: warm glue, selection and adjustment of molds, control of extruding temperature, cold feed extrusion process
The equipment used to squeeze insulating rubber or sheath rubber has become the main extruder and is divided into eight types: 30.45, 60.90, 120, 150, 200, and 250.
The squeezing machine is composed of a main engine, a traction device, a take-up device, a meter counter, a cooling device and a transmission system, etc.
Main technical parameters: screw, outer diameter, screw length-to-diameter ratio, screw speed range, glue output per hour, main motor model power, equipment center height and overall dimensions

l Vulcanization process
Under heating conditions, the raw rubber in the rubber compound chemically reacts with the vulcanizing agent, so that the rubber is cross-linked from linear structure macromolecules into three-dimensional network structure macromolecules, resulting in a significant improvement in the physical and mechanical properties and other properties of the rubber compound. This process is called vulcanization.
The entire vulcanization process is divided into four stages: vulcanization induction stage (scorch), pre-vulcanization stage (low sulfur), normal vulcanization stage (normal sulfur), and over-bowling stage (over)
The scorch time refers to the time when the rubber begins to harden and the Men’s viscosity increases, and the thermoplastic flow cannot be carried out from then on. The stage between the scorch time and the positive vulcanization is called under-sulfur, which seriously affects the aging performance. Rubber should strictly control the lack of sulfur phenomenon: normal sulfur means that the degree of vulcanization cross-linking meets the process requirements, and the physical and mechanical properties meet the vulcanization time required by the use. The positive vulcanization time is called the vulcanization flat zone, and the vulcanization flatness refers to the wide area in the positive vulcanization zone. Flat vulcanization curve: Excessive sulfur indicates that the vulcanization crosslinking temperature is too high, at this time the tensile strength and fixed extension are reduced.
Vulcanization process: fixed vulcanization of vulcanized tube, continuous vulcanization
Vulcanization conditions include vulcanization temperature, vulcanization time, and vulcanization pressure. Correctly setting vulcanization conditions is a decisive factor to ensure quality.
The most basic principle of continuous vulcanization: use the method of increasing the temperature to speed up the vulcanization rate. According to the relationship between the vulcanization speed and the vulcanization temperature, it can be seen that for every 10 degrees increase in the vulcanization temperature, the vulcanization speed can be doubled on average, that is, the vulcanization time can be reduced by half.
According to the position of the vulcanizing tube, it can be divided into four types: horizontal, inclined, catenary and vertical. In addition to saturated steam, there are superheated steam, low melting point metal salts and infrared rays.
Continuous vulcanization has many advantages compared with tank line vulcanization: high production efficiency, good product quality, product length is not limited by equipment, easy to operate, continuous vulcanization has become the most important vulcanization method in the wire and cable industry, vulcanization tube vulcanization Be in a secondary position.