Darbus 321 stainless steel coiled plateHow to deal with technical service contracts

different directions

Attention shall be paid to the purchase of red copper pipe in order to study the distribution law of pipeline crack stress field under internal pressure. The simulation ysis and experimental verification are carried out for pipes with cracks of different shapes, different internal pressures and different sizes. The results show that the stress at the crack tip is much greater than that at the crack center. The crack shape has little effect on the stress. With the increase of the included angle between the crack direction and the pipe axis, the stress at the crack tip first increases and then decreases. With the increase of the pipe internal pressure, crack depth, and crack length the stress at the crack tip increases linearly. Among them, the effect of crack length on the stress at the crack tip is smaller than that of internal pressure and crack depth. During the construction and operation of long-distance pipeline, due to the influence of pipe manufacturing defects, welding defects, internal and external loads, stress concentration, corrosion defects and other factors, the pipeline will produce cracks and expand cracks, which is the most dangerous defect of long-distance pipeline and the main reason for pipeline failure. At present, pipeline cracks are mainly determined by internal testing and non-destructive testing after excavation. Among them, ultrasonic internal testing has a good identification rate for cracks with a length of more than 25 mm, a depth of more than 1 mm in the base metal or a depth of more than 2 mm in the weld; Magnetic flux leakage internal detection has a certain detection rate for cracks with opening more than 0.25mm, but it is difficult to identify and quantify. In NDT, magnetic particle, penetration, eddy current and radiographic methods have high detection and identification rate. The generation and propagation of cracks will cause local stress concentration in the pipeline, which is prone to brittle fracture, corrosion damage and other failure phenomena, seriously affecting the service performance and reliability of long-distance pipeline. In this paper, the influence of crack shape, direction and size on the stress at the crack tip is yzed by studying the stress field distribution law of copper pipe cracks, which provides a reference for the prevention and control of pipe cracks. What problems will be encountered in the production of copper tubes. The production of copper pipe includes four steps: welding, forming, inspection and pipe expansion.

However, for some important parts, it is also considered that the yield ratio should be smaller to improve their safety and reliability. However at this time, the utilization rate of materials is also low. Common sense: copper pipes for air conditioners are mainly used for conveying liquid, gas and steam; Boiler pipes and steam transmission pipes are used for the piping, structure and steam transmission of steam boilers, widely used in aviation, automobile, mainly used for oil and gas exploitation, such as casing, drill pipe and tubing, and pipe for petroleum refining and processing; Pipe for mechanical manufacturing, which is used to manufacture the race of ball bearing, the plunger, rotating shaft and body of air pump and hydraulic pump; High pressure vessel, used for manufacturing bottles, boilers, etc. At present, copper pipes for air conditioners are mainly used in three aspects in practical applications. First, medical copper pipes are widely used in industrial plants, high-rise civil buildings, municipal engineering, oil platforms, bridges, railway vehicles and other fields. Because of their good plasticity, high structural stability and strong resistance to natural disasters, they are particularly suitable for building structures in earthquake prone areas. Second, the air conditioning copper pipe has high tensile strength and toughness, high buildings, bridges and other steel structures have good cold bending performance and welding performance, and the section size and surface quality are well controlled, so it is widely used in vehicle manufacturing, large bridge construction, mechanical manufacturing, industrial plant components and many other industries. Third, air conditioning copper pipes are mainly used to make transmission line towers, microwave transfer station towers, elevator supports, etc. The idea is to use weather resistant steel when making iron towers to meet the service conditions of both normal temperature and low temperature. PPM pressure roll piercer used for air conditioning copper pipe tapping rolling is not replaced by inclined roll piercer used for square steel billet. The advantage of the conical piercer is that it has the consequence of rotary euphemism casting and the of restraining the shear deformation of the square circumference and the square back. Therefore, especially not for the reaming and fat wall perforation. When using a general piercer, the wall thickness/pitch diameter ratio (T/D limit is about 6%, while when using a square cone piercer the T/D limit can be 2%. Tianjin Precision Steel Tube Factory will give you a brief introduction.

Darbus . For small diameter pipes, when using filler metal, the length of filler metal is allowed to be equal to the diameter of the pipe which is enough to fill the weld crater. One of the five major application fields of red copper plate T2, accounting for more than half of the total consumption. Used for various cables and wires, motors and transformers, switches and printed circuit boards; In the manufacture of machinery and transport vehicles, it is used to manufacture industrial valves and accessories instruments, sliding bearings, molds, heat exchangers, pumps, etc.

It is still necessary to pay attention to the materials used for pipes and the hardness of materials, so as to comprehensively consider and avoid problems. The polymer is thermally copolymerized with the polymer to form the big data of the molecules connected by the ion bond of the co thermal polymerization. The thermal copolymerization is carried out according to the DA reverse reaction. The disadvantage of such materials depends on the fact that if simple heat treatment process is improved without additional metal catalyst, chemical formula or other unusual surface treatment of metal materials will lead to ionic bond in the area to be repaired and can open the gap several times. Copper tube concrete based textile materials. Self repairing concrete is a basic concept that mimics the automatic basic metabolism of some chemicals of the injured part by biological tissues, so as to make the injured part heal. Hollow glass fiber or liquid core optical fiber may damage the hollow bag of concrete raw materials, damage the hollow glass fiber or liquid core optical fiber, and flow the adhesive to the damaged part, so that the gap medical copper tube can be healed again. Cause of surface damage of copper tube. Copper tube is also a kind of material commonly used in engineering. The surface shall also be protected from scratches. The surface of the copper tube is also easy to be damaged, whether it is processed or stored in the warehouse.

.The selection of medical copper tube table, these problems are natural.

Plastic coated copper pipe is a kind of non-metallic material pipe with light weight, high strength and corrosion resistance. The plastic coated copper pipe is made of glass fiber with resin base weight, which is wound on the rotating hollow floor step by step according to the processing technology regulations, and the stone sand is laid on the ground evenly for a long distance in the middle of the chemical fiber as the intermediate weathering layer. The price quotations of plastic coated copper pipes with different thicknesses are also different. Here, we will explain the factors that determine the thickness of the plastic coated copper pipe design scheme. Appearance and specification of mpp cable duct 1 Color: generally orange red, other colors can be implemented according to the contract of both parties. 2 Appearance quality: The inner and outer walls of the pipe fittings shall be smooth, clean and even, and shall be free of steam bubbles, cracks, cracks, and obvious marks, dents, residues, dissolved discoloration lines and uneven colors. The inner holes of the pipe shall be laser cut and leveled and vertical to the pipe centerline. The inner holes shall be smooth and free of burrs. Specification: The length of pipe fittings is generally 6000 or 9000mm, which can also be negotiated by both parties. The specification error shall conform to dl/t801; The bending degree of the hose shall not exceed 1% of the nominal pressure. Some key points in the process of embedding plastic coated copper pipe: the embedding process of plastic coated copper pipe is very worthy of great attention. Although the actual operation in the process of embedding is relatively simple, In other words, if the road surface is seriously uneven, it is seriously affected by external forces. Relevant countermeasures must be taken, and fine sand and dirt should also be prohibited from seeping into the pipe during the burial process, so as to diligently maintain its compliance with the regulations during the burial process. The process of embedding the plastic coated copper pipe involves the problem of marking. In fact, it is only necessary to find matching marks for immediate maintenance. Number of layers of cloth stacking: all layers are made strictly according to the design scheme without additional construction, which increases the cost. 2 Resin: high temperature resistance, not easy to deform under stress. Plastic coated copper pipes are generally assembled from high-quality SMC water tank plates. Its characteristic is that it can select food grade stainless steel resin. Therefore in view of the good water body, clean up the natural environment and zero pollution,Darbus H65 brass plate, the commodity development trend has certain characteristics such as high compressive strength, light weight, corrosion resistance, beautiful and generous appearance design scheme, long service life, and more convenient management methods in maintenance. Cloth quality: the specification of cloth surface is the same, pure platinum cloth is thick, and it is thick with blended cloth or pure old coarse cloth. The thickness of fiberglass filament winding: our products are high-tech support points of fiberglass anti-corrosion ring, which ensures the bearing pressure of the products. In addition, if you must select the thickened type, you can yze the vertical cross type difficult winding when winding the winding machine, until the thickness and compressive strength of the thickened type are basically achieved.

In addition, quartz sand is used as sand intercalation layer on the long distance uniform pavement in the middle of chemical fiber. Its wall thickness and structure are reasonable, and the plastic coated copper pipe laying process stipulates that the plastic coated copper pipe is a non-metallic material pipe with light quality, high strength and corrosion resistance. The glass fiber with epoxy resin based weight relief is coiled on the rotating hollow floor step by step according to the processing technology. It can make full use of the efficacy of raw materials achieve the goal of applying compressive strength, improve the strength and stiffness, and ensure the reliability and stability of t2 copper tube. FRP sand pipe is accepted by many customers because of its excellent resistance to solvent erosion, light weight, high strength, non fouling, strong durability, long service life compared with ordinary seamless steel pipe, low comprehensive project cost, convenient installation, reliability and other advantages. Plastic coated copper pipe is used in: gray and black metallurgy industry, nonferrous plate metallurgy industry, power industry, coal engineering, petroleum industry, chemical industry, electromechanical engineering industry cotton textile, vehicle and motorcycle processing and manufacturing industry railway line for industrial production, shipbuilding, engineering construction, light industry, food industry, electronic industry, power, culture and art, sports culture and game entertainment, agriculture and animal husbandry, commercial services, Diagnosis, treatment and health and its national defense and civilian industries.

One of the classification of copper tubes. The common wave shape is a single copper tube. Hyperbolic means that two different arcs overlap on the same surface, that is, starting from different circle centers, draw arcs in two radii. The red copper tube is a module made of double curves designed according to the drawings. The red copper tube is light in weight, good in rigidity and high in strength. The shapes of the red copper tubes processed are different and can be processed into various geometric shapes such as arcs and spheres. It is beautiful, elegant and colorful. Let's talk about the two main methods of processing and forming the copper tube: The hot processing and forming method is to roll the copper tube to a roughly hyperbolic shape, then heat it, then place it on the mold prepared in advance then slowly beat it with a hammer, finally cut, weld, polish and polish it. The whole process needs to be very careful to ensure the surface quality of the copper tube. This forming method is very suitable for parts with small model and large arc change. When the model size is relatively large and complex, it can be considered to break it into small pieces for forming, and then splice it into large pieces. For such copper pipes, the cost is high and the production period is long. 2 Forming method of roll bending This method is to make some modifications on the roll bending machine, and change one of the shafts into a concave type and the other into a convex type. This method can form a regular copper tube like a sphere, with a small processing range, but it has great advantages for copper tubes with small radians. What problems should be paid attention to when designing the hyperboloid copper tube? Everyone knows that the design of the air conditioning copper tube is very important. To achieve the beautiful shape, exquisite workmanship and fashionable personality of the hyperboloid copper tube, first of all, the design is very critical. Some small copper tube companies are not mature enough in design and have not enough design experience, so they often have problems in design, Hyperbolic copper tube is very famous for preparing some details that we should pay attention to in the design. The sculpted copper tube is highly decorative, and the production and processing technology of hyperbolic shaped copper tube is relatively complex. Copper tube products with strong aesthetics. According to the design requirements, different shapes need to be molded for the sculpted copper tube, so the production process of sculpted aluminum veneer is relatively complex.

{2} The excellent performance of copper pipe The welded copper pipe has the characteristics of firmness and corrosion resistance, which makes it a suitable choice for modern contractors to install the water pipe, heating pipe and refrigeration pipe in all residential commercial houses.

In particular, it is an improved spray type passivation box for t2 copper pipe production line. The installation step of the connection structure 100 between t2 copper pipe and aluminum bar belongs to the improvement of the spray type passivation box structure for t2 copper pipe production line. The passivation solution spray box is set above the side of the passivation solution box, the passivation solution spray box with downward sloping bottom is connected with the inlet of the passivation solution box by the outlet set on the box wall at the bottom of the inclined bottom, the inlet of the passivation solution box is located on the box wall above the passivation solution box, the upper side of the passivation solution box is installed with a passivation pump, and the inlet pipe of the passivation pump is connected with the passivation solution box, The outlet pipe of the passivation pump is connected with the upper port of the passivation liquid spray box. With reasonable structure and convenient operation, it is convenient for operators to add passivation liquid to the passivation box, avoid equipment blockage, avoid crystals adhering to the zinc layer on the surface of galvanized pipe, and improve the surface quality of galvanized steel pipe.

Process inspection.I believe that after reading the above contents, all readers here have a clearer understanding of the automotive air conditioner copper tube. If you are interested in this product, please refer to more relevant contents. Suitable site and warehouse shall be selected for the storage of seamless air conditioning copper pipes: The site or warehouse for steel storage shall be located in a clean and well drained place away from factories and mines that produce harmful gas or dust. With the rapid development of economy, the number of cars is also fast. Nowadays, people can't live without cars. So we know what role the copper tube of automobile air conditioner plays in cars.

The material cost of medical copper tube will not be less than 40 yuan. The better the material is, the higher the price will be. It is called &one cent, one cent&. Moreover, in addition to the production and operation costs, etc., you must pay attention to the quotation below 45 yuan/square. Medical copper tubes are more and more widely used in the decoration of building exterior walls. In cold cities in the north, medical copper tubes can play a very good role in decoration and insulation. With the continuous progress of science and technology, the quality and firmness of medical copper tubes have been improved. However, as long as the decoration materials are used, they will inevitably crack during installation and construction. As time goes by, there will be aging to varying degrees in daily life. Next, Zhongsheng Thermal Insulation Technology will introduce how to prevent the cracking of medical copper tubes and how to prevent the aging of medical t2 copper tubes? Let's talk about these two issues. How to prevent cracking of medical copper pipes To avoid cracks, buildings should be fully insulated, including awnings and other components. Through the quality and construction methods of external medical copper pipes, the construction quality can reach By reducing the ratio of the linear expansion coefficient of external thermal insulation materials of the building structure to the linear expansion coefficient of materials such as external decoration leveling mortar and external decoration surface, gradual changes will occur between medical copper pipes layer by layer, and the stress can be flexibly released, To prevent cracking. How to prevent medical copper tube from aging? The insulation layer of high-rise buildings shall have fire resistance , and the surface shall not burst or collapse. Medical copper tube Medical copper tube is a new type of plate which is popular in China in recent years. It has many advantages, such as good heat preservation, fire insulation, sound insulation convenient construction, beautiful appearance, etc., and is deeply welcomed by the industry. The medical copper pipe may fall during use. In order to reduce the occurrence of this kind of phenomenon, Jinan Zhongsheng Thermal Insulation Technology made a detailed ysis. Next, we will introduce the reasons for the fall of the external wall of the medical copper pipe and how to protect the medical copper pipe during installation. Reasons for the fall of the external wall of the medical copper pipe The medical copper pipe was not firmly fixed and moved, forming a push-pull effect, causing local hollowing of the insulation layer, and long-term water seepage after cracks, leading to the fall of the insulation layer. 3 At the connection between the concrete beam column and the masonry, the medical copper pipe is easy to fall off due to the deformation of the masonry. 4 Scaffold holes are not solid, forming insulation layer, and local base course is not firm and damaged. 5 The surface load of the medical copper tube is too large, or the anti negative wind pressure measures are unreasonable.

Attention shall be paid to the purchase of red copper pipe in order to study the distribution law of pipeline crack stress field under internal pressure. The simulation ysis and experimental verification are carried out for pipes with cracks of different shapes, different directions, different internal pressures and different sizes. The results show that the stress at the crack tip is much greater than that at the crack center. The crack shape has little effect on the stress. With the increase of the included angle between the crack direction and the pipe axis, the stress at the crack tip first increases and then decreases. With the increase of the pipe internal pressure, crack depth, and crack length, the stress at the crack tip increases linearly. Among them, the effect of crack length on the stress at the crack tip is smaller than that of internal pressure and crack depth. During the construction and operation of long-distance pipeline due to the influence of pipe manufacturing defects, welding defects internal and external loads, stress concentration, corrosion defects and other factors, the pipeline will produce cracks and expand cracks, which is the most dangerous defect of long-distance pipeline and the main reason for pipeline failure. At present, pipeline cracks are mainly determined by internal testing and non-destructive testing after excavation. Among them, ultrasonic internal testing has a good identification rate for cracks with a length of more than 25 mm, a depth of more than 1 mm in the base metal or a depth of more than 2 mm in the weld; Magnetic flux leakage internal detection has a certain detection rate for cracks with opening more than 0.25mm, but it is difficult to identify and quantify. In NDT, magnetic particle, penetration, eddy current and radiographic methods have high detection and identification rate. The generation and propagation of cracks will cause local stress concentration in the pipeline, which is prone to brittle fracture, fatigue damage, corrosion damage and other failure phenomena, seriously affecting the service performance and reliability of long-distance pipeline. In this paper, the influence of crack shape, direction and size on the stress at the crack tip is yzed by studying the stress field distribution law of copper pipe cracks, which provides a reference for the prevention and control of pipe cracks. What problems will be encountered in the production of copper tubes. The production of copper pipe includes four steps: welding, inspection and pipe expansion.

Plastic coated copper pipe is one of the safe carbon fiber products. Its specific content is a new structural composite building decoration material that can be produced according to the development trend of production and manufacturing by using a glass fiber as the synergist and resin as the adhesive based on the application of full intelligent technical automatic control system equipment.

target.Some problems. For example, in the preliminary manufacturing of copper tubes for air conditioners for automobiles, the materials for air conditioners can be selected according to the actual size required by users, and then the copper tubes for air conditioners for automobiles can be manufactured, followed by pickling. The produced copper tubes for air conditioners are put into the pickling tank for pickling, and then stretched. Then the pickled copper tubes for air conditioners are stretched according to their size requirements.

As the domestic price of red copper in September was slightly adjusted up and down, the wait-and-see sentiment of foreign procurement was clearly reflected, which played a certain positive role in the export in October. Especially after the price fell at the end of September, some steel mills could talk about increasing space and the possibility of increasing the export volume in the future market was high. It is estimated that the domestic export volume in October will increase from August to September.In fact, the shutdown order is also for environmental protection. In addition, the 19th National Congress of the Communist of China in October also played a certain role in promoting. One is the inhibition of supply, and the other is the attack on demand. Both of them are in a weak state. We can only look at steel mills, mentality, periphery, etc. to support the current situation of the steel industry. So what I want to say here is why the middle and late period of the &Silver Decade& is an opportunity. There are the following two points: * * * *. The price is not high or low, which is a good time. At present, the billet is around 3500, which is close to 7-800 compared with the beginning of the year. The finished materials are mostly around 4000, which is close to 2-400 compared with July August. In addition, it is very difficult to say whether the billet will fall by about 3000, and the finished materials will fall to 3500-4000 across the board. Although the steel plant has profits, it will not decline rapidly. The cost is not allowed, and the steel industry will not agree; Large scale changes are not what the policy, manufacturers and supply and demand sides want to see.

The surface coating of medical copper tube is very important. Observe its thickness, how to prevent the aging of medical copper tube? How to select the foam density of medical copper tube Good medical copper tube and foam density are very high and hard. Check the quality of aluminum zinc coated color steel plate on the surface. As exterior wall thermal insulation decorative plate. Then use your hand to break it up and down to see if it is easy to deform. If you break it with force, which is not good. 3 See the price.

Darbus .Some problems. For example, in the preliminary manufacturing of copper tubes for air conditioners for automobiles, the materials for air conditioners can be selected according to the actual size required by users, followed by pickling. The produced copper tubes for air conditioners are put into the pickling tank for pickling, and then stretched. Then the pickled copper tubes for air conditioners are stretched according to their size requirements.

Use the medical copper tube table to eat. Because of the unique of the medical copper tube, when the oil drops on the table, it will only stick to the table, but not penetrate the table. Only with a slight wipe of the rag, the oil stains will be easily disappeared. In this case, when cleaning large canteens, the liquidators do not need to spend much effort but are relaxed. They just need to prepare a rag and a basin of clean water, and then carefully scrub it. t2 Medical Copper Tube Company thinks that the medical copper tube table is only made of the surface of the medical copper tube, and its exterior is not made of the medical copper tube. The price is cheaper than the wooden table, which is extremely suitable for a small amount of purchase. The medical copper tube has a natural bright and beautiful feeling. The color is extremely blended, and can stop the very good embellishment and reaction with the color in the surrounding situations. Now, let's understand some STEPs of the appearance processing of medical copper tubes. There are about five different methods for the appearance processing of medical copper tubes. Connect to t2 Medical Copper Tube Company and introduce them to the master. In addition, these methods can also stop the combined processing and create more medical copper tubes with different appearances. No matter which method is used, the following STEPs should be followed. First, before processing,Darbus Stainless steel plate, the agreement should be stopped with the manufacturer, and then a sample should be selected as the standard for future consumption. The second part, when using it, we should guarantee that the coils of the base we choose to use and the coils that are not yet used are the third of the same model and batch. If they are used in some construction, such as elevators, we should pay attention to the unexpected selection of materials. In some places with extraordinary contrast it is not appropriate to use the mirror t2 medical copper tubes. When processing, it is necessary to select the appropriate manufacturing process, such as weld grinding, pay attention to the bias, which is also called unidirectionality. For example, if the lines used are vertical rather than horizontal, it is not easy to apply the dirty residue on the appearance of t2 medical copper tubes. It is extremely easy when they are clean. When finishing, STEP of the process used should be added, so the cost also needs to be added. Therefore, when selecting the appearance of the processing, t2 Medical Copper Tube Company revealed that Panbo consumers should carefully select according to the situation and when selecting the planning and design staff, they should have a full understanding of the appearance of t2 Medical Copper Tube. Since the birth of medical copper tube, it has been widely used in food, chemical industry crude oil, machine manufacturing and other industries for its superior . It is precisely because of this kind of universal needs that people are increasingly demanding for medical copper tubes. Although this kind of situation is basically conducive to the development of the medical copper tube industry. Having said so much, the editor of this website will introduce the most popular technology in the medical copper tube industry -- the medical copper tube appearance fingerprint free disposal punishment technology. Mentioned here, I believe that many enemies have learned the greatest advantages of this kind of technology from the name. However, do you know that this is nothing more than a contrast of significant and abstract advantages. The most one-sided introduction is also my face. The medical copper tube after adopting this kind of technical treatment has a smooth appearance and soft hand feeling, and ordinary dust and impurities are not easy to adhere. Therefore, it is also extremely easy to clean. If the ordinary dust is probably dirt, just wipe it with a wet rag and you will lose the clean and smooth appearance. Because the implementation of this kind of craft is to use electroplating oil to shine the film on the red interior line, so it has the characteristics of being tough and not easily scratched. This prevents the possibility that some slight bumps may damage the medical copper tube. It also allows the medical copper tube to be used twice as quickly. Stop the fingerprint free disposal and punish the medical copper tube after the accident. It also loses great promotion in appearance. As the saying goes,Darbus 40Mn2 alloy steel plate, a superior appearance can always leave the best impression. Therefore, compared with the medical copper tube after the punishment and the medical copper tube without the punishment, it can often be welcomed by customers and enemies.Hot rolling and hot expansion. The main processing procedures include the blank sawing process, and the production process of the air conditioning copper pipe in the tower mainly includes cold drawing. Ring furnace heating process, piercing process, pipe rolling process, sizing process, cooling bed process, straightening process, pipe cutting soot blowing process, magnetic flux leakage detection process, length measurement and weighing to packaging and warehousing. Key points: yield strength limit: when the external force borne by the air conditioning copper tube sample exceeds the elastic limit of the material, although the stress no longer increases, the sample still has obvious plastic deformation. This phenomenon is called yield, that is, when the material bears an external force to a certain extent, its deformation is no longer in direct proportion to the external force, resulting in obvious plastic deformation. The stress when the air conditioning copper pipe yields is called the yield strength limit, and the corresponding S point in the tensile test curve is called the yield point. For air conditioning copper pipes with high plasticity, there will be an obvious yield point on the tensile curve, while for materials with low plasticity, there will be no obvious yield point, so it is difficult to calculate the yield limit according to the external force at the yield point. Therefore, in the tensile test method, it is usually specified that the stress when the gauge length on the specimen produces 0.2% plastic deformation is taken as the conditional yield limit, expressed as 0. The yield limit index can be used as the design basis for requiring that the parts do not produce obvious plastic deformation during operation.

In addition, the stress corrosion cracking inside the stainless steel plate will cause the transition film on the surface of the stainless steel plate. Therefore, the surface of plastic coated copper pipe shall be cleaned to a certain extent to ensure its service life. The oil cracking tube circuit breaker must be selected. The fracture of the plastic coated copper pipe shall be kept on a true circle, and the fracture line shall be inclined to the pivot of the plastic coated copper pipe. Too large is the reason for cutting plastic coated copper pipe into flat or oval shape, so moderate energy shall be used when cutting square steel pipe. What matters should be paid attention to when purchasing plastic coated copper tubes.