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Hot Dip Galvanized Pipe

Hot dipped galvanized steel pipe is in manufacturing process using steel pipes of removed rust dipped into zinc liquid of 500℃ temperatures, and making steel surface attached zinc layer so as to achieve the purpose of anti-corrosion.

Galvanized Steel Pipes are used in a variety of settings. Until about 30 years ago, galvanized steel was utilized for water supply pipes in construction. It is used in outdoor applications wherever the strength of steel is desired, such as fence posts and rails, scaffolding and as protective railings.

Hot-dip galvanized (galvanizing)

Hot-dip galvanized (galvanizing), also known as hot-dip galvanized, it is an effective anti-corrosion of the metal, mainly used in various sectors of the metal structure facilities.

The rust steel immersed in liquid zinc melt around 500 ℃, steel members attached to the surface of the zinc layer, which play the purpose of anti-corrosion.

Hot-dip galvanizing process

finished of Pickling – washing – plus help the bath – drying – hanging plating – cooling – Pharmaceutical – cleaning – polishing – completion of the hot-dip galvanizing, hot dip galvanized by the ancient method of hot-dipped development come since 1836, France had been used in industrial hot dip galvanized, has a history of 140 years. However, the hot-dip galvanizing industry the past three decades along with the rapid development and large-scale development of the cold-rolled steel strip.

With the discovery of the industrial, hot dip galvanized products have been applied to many areas, hot-dip galvanized advantage of the anti-corrosion service life for a long time, to adapt to the the antiseptic treatment method widely been very popular. Been widely used in power tower, communication tower, railway, road protection, light poles, marine components, construction steel structure components, substation ancillary facilities, light industry.


hot dip galvanized iron pieces cleaned, and then the solvent treatment, drying after immersion in liquid zinc, iron, and the reaction of molten zinc alloyed zinc layer, its processes: the skim – washing – pickling – the fluxing – drying – hot-dip galvanized – separation – cooling passivation.

Galvanizing alloy layer mainly depends on the thickness of the silicon content of the steel chemical composition, the rough degree of the size of the cross-sectional area of ​​the steel surface of the steel, the temperature of the zinc pot, the zinc immersion time, the cooling speed, and the cold deformation.

Hot-galvanized advantages

  • low-cost processing: hot-dip galvanized anti-rust lower cost than the cost of other paint coating;
  • Durable: standard hot dip galvanized rust thickness can be kept for 50 years or more in the rural environment, without having to patch; standard hot dip galvanized rust layer can be maintained for 20 years in the urban areas or offshore area, without having to patch;
  • good reliability: galvanized layer with steel is metallurgically bonded to become a part of the surface of the steel, and therefore more reliable coating persistent;
  • the toughness of the coating: zinc coating to form a special metallurgical structure, this structure can withstand transportation and use of mechanical damage;
  • full protective: plated parts each part can be plated with zinc, even in the recesses, sharp corners and hiding places can be fully protected;
  • saving time and effort: the the galvanizing process faster than other coating construction method, and can avoid the the brushing time required on site after installation.


A hot-dip galvanized coating is relatively easier and cheaper to specify than an organic paint coating of equivalent corrosion protection performance. The British, European and International standard for hot-dip galvanizing is BS EN ISO 1461 which specifies a minimum coating thickness to be applied to steel in relation to the steels section thickness e.g. a steel fabrication with a section size thicker than 6 mm shall have a minimum galvanized coating thickness of 85 µm.

Hot-dip galvanizing (HDG), as referenced is the process of dipping fabricated steel into a kettle or vat of molten zinc.

Galvanizing is one of the most widely used to methods for protecting metal from corrosion. It involves applying a thin coating of zinc to a thicker base metal, helping to shield it from the surrounding environment. The next time you are in your car, take a look at the street signs and lamp posts you pass. A large number of them will have a mute, silver color on them. That “silver” is actually the coating of zinc.

Quite simply, galvanizing a metal gives it anti-corrosion properties. Without the protective zinc coating, the metal would remain exposed to the elements and potentially oxidize and corrode much faster. Galvanized Steel is a cost effective alternative to using materials such as austenitic stainless steel or aluminum in order to prevent corrosion.

Galvanized pipe process characteristics

Zinc sulfate biggest advantage is the current efficiency of up to 100%, the deposition rate, which is the other galvanizing process unparalleled.

Galvanized pipe process characteristics:

1 zinc sulfate optimization

As the crystalline coating is not detailed enough, dispersing ability and poor throwing power, and thus is only suitable for simple geometries such as pipe and wire plating. Sulfate galvanized iron alloy craft of traditional sulfate galvanizing process optimization, leaving only the main zinc sulfate salt, and the remaining components are discarded. In the process of forming a new recipe and adding the right amount of iron, so that the original single-plated zinc alloy metal plating layer is formed. Reorganization process, not only to carry forward the original process high current efficiency, fast deposition rate advantages, but also the dispersion ability and throwing ability has been greatly improved in the past can not be plated complex parts, simple and complex parts can now plated and protective properties increased by 3 to 5 times faster than a single metal. Practice has proved that for wire, pipe continuous plating, coating the grain is more refined than the original, more bright, fast deposition rate. Within 2 ~ 3 min coating thickness to meet the requirements.

2 Zinc sulfate conversion

Sulfate zinc sulfate zinc alloy to retain only the primary zinc sulfate salt, the remaining components such as aluminum sulfate, alum (potassium aluminum sulfate), etc. can be processed in the bath, was added sodium hydroxide so as to precipitate an insoluble removal; organic additives, then add powdered activated carbon adsorption removed. Tests showed that aluminum sulfate and aluminum potassium sulfate is difficult to completely remove the one-time, affect the brightness of the coating, but not serious, may be accompanied by the consumption, the brightness can be restored at this time plating solution through the processing, according to new techniques additional ingredients required,to complete the conversion.

3 deposition rate, excellent protection performance

Sulfate galvanized iron alloy craft up to 100% current efficiency, fast deposition rate is unmatched in any galvanizing process, speed fine tube 8 ~ 12 m / min, the average coating thickness 2m/min, it is difficult to continuous galvanizing achieved. Bright coating delicate eye. According to national standards GB/T10125 “test in artificial atmospheres – Salt spray test” method of testing, 72 h, plating intact, unchanged; 96 h, coating the surface of a small amount of white rust.

4 unique clean production

Galvanized pipe with galvanized iron alloy sulfate process lies between the trough and the trough are perforated production straight out and no solution or overflow. Each step of the production process from the circulation system components, i.e. the alkali solution tank solution, plating solution, and the passivation fluid, light, not only by the outer loop back leakage or discharge system, located only 5 line cleaning tank, cyclic reuse periodic emissions, especially after the production process without passivation without cleaning the wastewater generated.

5 Particularity of electroplating equipment

Electroplated galvanized pipe with wire plating, as are all continuous plating, but different plating equipment. Wire with its characteristic elongated strip designed plating tank, the tank is long and wide but shallow. Electroplating wire from the hole piercing, showing a shape in the liquid started to keep distance from each other. Unlike wire and galvanized pipe but has its unique slot equipment is more complex.

The tank by the upper and lower parts, the upper part of the plating tank, the lower part of the storage solution circulation tank, the narrow width forming a shape similar to the trapezoidal grooves in the plating bath has a channel running plated galvanized pipe, There are two holes in the bottom of the storage tank is connected to the lower, and the formation of the bath round robin system and sump pump. Therefore, galvanized pipe with wire plating as plating are dynamic in nature, with the difference between the wire plating, plating bath galvanized pipe is dynamic nature.

The technical requirements of galvanized steel pipe

The technical requirements galvanized steel pipe should reach.

Steel mechanical properties is an important index to ensure that the steel eventually use performance, it depends on the chemical composition of the steel and heat treatment system

  • Grades and chemical composition. Galvanized steel grades and chemical composition shall comply with the stipulated GB3092 standard of black steel pipe steel.
  • the manufacture method: the manufacturing method of black steel pipe (furnace or electric welding) should be selected by the factory. Galvanized by hot dip galvanizing.
  • thread and pipe joint
    1. delivery of galvanized steel pipe with screws, screw thread should be done after galvanizing. And the thread should comply with the provisions of the YB822.
    2. steel pipe joint shall comply with the terms of YB238; Malleable iron pipe fittings shall comply with the terms of YB230.
  • the mechanics properties: the mechanical properties of steel tube before galvanized should comply with the provisions of the GB3092.
  • the uniformity of the galvanized layer: the galvanized steel pipe should be carried out galvanized layer uniformity test. Steel tube specimens in the copper sulfate solution dipping 5 consecutive shall not become red (copper plating color).
  • the nominal diameter of cold bending test no greater than 50 mm galvanized steel pipe should carry out cold bending test. Bending angle is 90°, bending radius is 8 times the diameter. Without padding when testing, sample welds should be placed in the bending direction of the lateral or upper. After the testing, the sample should not have cracks and zinc layer peeling off with the elephant.
  • hydrostatic test: water pressure test should be performed in the black steel pipe, eddy current flaw detection can also take place of hydrostatic test. Test pressure or eddy current inspection shall comply with the terms of GB3092 contrast sample size.

In the steel tube standard, according to different application requirements, the tensile strength, yield strength or yield point, elongation and hardness, toughness index are all stimulated, and even the user’s high, low temperature performance, etc.

Galvanized steel pipe welding technology

Galvanized steel welding characteristics:

Galvanized steel is generally in the low-carbon steel outer layer of zinc-plated, galvanized layer is generally in the 20um thick. Melting point of zinc in 419 °C, bp 908 °C or so. In welding, the zinc melted into the liquid floating on the surface or in the root of the weld pool position. Zinc has a greater degree of solid solution of iron, zinc, liquid etching along the grain boundary deep weld metal, low melting point of zinc to form a “liquid metal embrittlement.” Meanwhile, zinc and iron can form brittle intermetallic compound phase of the weld metal of these brittle plastic reduction in the tensile stress and cracks. If the welding fillet welds, especially T-joint fillet most prone to penetrate the cracks. When welding galvanized steel, bevel edge surface and a zinc layer under the action of the arc heat, oxidation, melting, evaporation and even volatile white smoke and steam, can easily cause weld porosity. Due to oxidation and the formation of ZnO, the high melting point of about 1800 °C or more, if the welding process parameter is too small, will cause slag ZnO, simultaneously. Since Zn as a deoxidizer. Produce FeO-MnO or FeO-MnO-SiO2 slag melting oxides. Second, because the evaporation of zinc, a large amount of white smoke evaporation, stimulate the human body, harmful effects, therefore, necessary to weld galvanized layer of polishing off.

Galvanized welding process control:

Galvanized steel welding preparation and the general low-carbon steel is the same, you need to pay attention is to seriously handle groove size and the nearby zinc coating. To weld penetration, beveling size should be appropriate, generally 60 ~ 65 °, to leave a certain gap, is generally 1.5 ~ 2.5mm; zinc in order to reduce the penetration of the weld, the weld before, the groove may be galvanized layer clear later welding. In actual supervision, using a centralized hit groove, leaving a blunt edge technology for centralized control, two welding process, reducing the possibility of lack of penetration. Welding galvanized steel pipe should be based on a matrix material selection, general ease of low carbon steel due consideration, the choice of J422 is more common.

Welding techniques: the first layer of multi-layer welding weld seam, try to make it melt the zinc layer vaporization, evaporation and escape the weld, which can greatly reduce the liquid zinc remain in the weld. In fillet welding, the same as in the first layer and make the molten zinc vaporization, evaporation and escape the weld, which is shifted forward end portion of the first electrode of about about 5 ~ 7mm, when the zinc layer melted and then continue to move back to its original position welding. Horizontal and vertical welding again, if use short-slag welding, such as J427, tend to be small undercut; roundtrip transportation if the front and rear of technology, but also can be non-defective weld quality.

Galvanized steel hardness

Galvanized Steel are those steel that has been covered with a layer of zinc metal.

Galvanized steel in terms of hardness test is a Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, micro-hardness and high-temperature hardness, etc.,

which can be divided into a variety, most of the manufacturers or using a Buchner,Rockwell, Vickers hardness of these three methods.

Brinell hardness measurement principle is the test force F (N) with a certain size, the diameter D (mm) of hardened steel balls or carbide ball pressed into the surface of the metal under test, to maintain a predetermined time after the drop test force, the the indentation average diameter d (mm) measured with a reading microscope, and then the equation Brinell hardness HB value, or the value d from the prepared Brinell hardness table to detect HB Brinell hardness measurement method is suitable for cast iron, non-alloy, annealing and quenching and tempering steel, the determination should not be too hard, too small, too thin and the surface does not allow the larger indentation specimen or workpiece.

Rockwell hardness test when the sample is too small or Brinell hardness (HB) is greater than 450, to switch to a Rockwell hardness measurement. The test method is an apex angle of 120 degrees with a diamond cone or the diameter 1.59mm/3.18mm the ball, pressed into the surface of the material under a certain load, the hardness of the material by the indentation depth obtained.

The Vickers hardness means a standard of the hardness of the material. Vickers hardness there is a small negative Vickers hardness test load 1.961 <49.03N, it applies to a thinner workpiece, the tool surface or coating hardness measurement; micro-Vickers hardness test load <1.961N applicable to the metal foil, , of the ultra-thin surface layer hardness measurement.

How Does It Work?

Galvanizing can protect metal is a number of ways. Firstly, it creates a protective coating that shields the metal from the surrounding environment. The layer of zinc prevents water and moisture and other elements in the air from corroding the steel underneath. Should the zinc coating be scratched deep enough, the metal would become exposed and susceptible to corrosion.

Galvanizing can also protect metal through a process called “galvanic corrosion”. Galvanic corrosion occurs when two metals of a different electrochemical make up are placed into contact with one another with an electrolyte present, such as salty water. Depending on the atomic structure of the two metals, one metal is the anode and the other is the cathode. The anode corrodes more rapidly than it would by itself and the cathode corrodes at a slower pace than it would by itself. The reason zinc is used for galvanizing is because it has an affinity towards being the anode when in contact with many different types of metals. Since the zinc coating in contact with the base metal is usually the anode, it slows the corrosion of the base metal, or the cathode.

Difference hot-dip galvanizing and cold galvanizing

Hot-dip galvanizing, it is at high temperatures the zinc ingots melt, being placed in the auxiliary material, then the metal structure is immersed in a zinc plating bath, so that the metal member attached to a layer on the zinc layer.

The hot galvanized advantage depend on its preservative ability, the better the adhesion and hardness of the galvanized layer.

Cold galvanizing is a zinc salt solution by electrolysis, to the plating on the coating, in general, which do not have heating, the amount of zinc rarely encountered humid environment is very easy to fall off. The cold galvanizing physical treatment, just in the surface brush a layer of zinc, zinc coating so easy to fall off the use of hot-dip galvanized construction.

Process of hot-dip galvanizing and cold galvanizing

Hot dip galvanized is immersed in liquid zinc dissolved workpiece degreasing, pickling, dipping, drying a certain period of time and put forward.

Cold galvanizing, also called electro-galvanized, is the use of electrolysis device to the workpiece into the composition of the zinc salt solution, after degreasing, pickling, and connecting the negative electrode of the electrolytic device; zinc plate placed at the opposite side of the workpiece is connected in the electrolytic device the positive electrode, the power is turned on, a current from the positive electrode to the negative directional movement, it will be deposited on the workpiece with a layer of zinc.

Appearance of hot-dip galvanizing and cold galvanizing

Cold galvanizing looks more smooth, bright, color passivation process plating layer is yellow-green in color, was colorful. Plating layer was bluish-white or white with white passivation process was green, white coating passivation process and the sun was significant Colorful angle. The complex workpiece angular edges parts prone to “electrical burning” from gloomy, the parts of the zinc layer thick. Yin corner site is easy to form a current dead undercurrent gray area and the area zinc layer is thinner. The workpiece overall zinc tumor, caking phenomenon.

Hot dip galvanized look a little rough compared to the electro-galvanized, silvery white, look prone process waterlines and a few drops of tumor is more obvious, especially in the one end of the workpiece. Hot dip galvanized zinc layer than a few times of the electro-galvanized thick corrosion protection is several times that of the electro-galvanized.

Difference between plastic coated pipe and galvanized steel pipe

Galvanized coating has a number of characteristics that make it a well-suited corrosion protective coating for iron and steel products in most environments.

Th excellent field performance of Galvanized coating results from its ability to form dense, adherent corrosion product films of corrosion considerably below that of ferrous materials (some 10 to 100 times slower depending upon the environment). While a fresh zinc surface is quite reactive when exposed to the atmosphere, a thin film of corrosion products develops rapidly, greatly reducing the rate of further corrosion. In addition to creating a barrier between steel and the environment, zinc also has the ability to cathodically protect the base metal. Zinc, which is anodic to iron and steel, will preferentially corrode and protect the iron or steel against rusting when the coating is damaged.

Many different types of zinc and each has unique characteristics. These characteristics not only affect applicability but also the relative economics and expected service life.The method of processing, adhesion to the base metal, protection aff orded at corners, edges, and threads, hardness, coating density, and thickness can vary greatly among the diff erent coatings.This is practical aid discusses each of the major types of zinc coatings, applied by batch hot-dip galvanizing, continuous sheet galvanizing,electro galvanizing, zinc plating, mechanical plating, zinc spraying, and zinc painting, to help specialists assess and select zinc coatings for corrosion protection.

After deciding to use a Galvanized coating for corrosion protection, some factors must be considered to ensure the proper coating is selected for the intended application and service environment. Obviously, zinc coating processes which are limited to small parts, and operations limited to continuous lines in steel mills (i.e. continuous galvanizing and electrogalvanizing) cannot be considered for the protective coating of structural steel members. Each Galvanized coating reviewed provides various degrees of corrosion protection.

Anticorrosion performance of galvanized mild steel pipe

Galvanized mild steel pipe is cheap and anticorrosive performance is relatively better related stainless steel pipes. 

Galvanized pipe in the design and production of an important form of full use of the standard design, galvanized mild steel pipe is generally pipe joints, mainly for low domestic water pipes, low cost, good corrosion resistance, connections are made using British Elbow, tee, short sections to achieve, and generally do not have the means to connect welding, welding will destroy the zinc coating, welding slag prone plus, porosity phenomenon and the impact of anti-corrosion effect.

Galvanized mild steel pipe is to use the principle of electrochemical corrosion, cathodic protection and consumed mainly in the steel and zinc anode contact, carbon steel a cathode, zinc as the anode, thus ensuring that the steel from corrosion. Generally used for process instrumentation or process water piping is threaded connections for multi-temperature low-pressure pipeline medium without danger. Galvanized mild steel pipe are generally after surface treatment on its surface coated with a layer of protective film, with hot dip and cold-plated to prevent corrosion.

Galvanized mild steel pipe because of high potential than iron, zinc corrosion first, so it protected the iron pipe, and if not threaded connection, you can also use welding methods, welding room ventilation must be good, because zinc oxide is toxic to humans with acid electrode J422 can be welded.

Advantage of galvanized spiral pipe welding process

Galvanized pipe welding processes can be divided into spiral welded and straight seam welded, and galvanized spiral welding process is relatively wider number of applications, but also more complex.

Galvanized spiral pipe welding method is first out of the forward end portion of the electrode about 5 ~ 7mm, without leaving a blunt edge technology for centralized control to ease the industry needs to pay attention to seriously handle groove dimensions and near-plated zinc layer.

For penetration, undercut the tendency will be very small, If the front and rear of the round-trip transportation technology is used, generally 1.5 ~ 2.5mm; to reduce zinc weld penetration, with a focus on playing groove industry downturn, such as the use of short welding slag such as J427, to leave some space sector is expected to greatly reduce the liquid zinc remain in the weld, when welding fillet welds, you can get no defects of welding quality.

Advantages of galvanized spriral welding: the welding precision can not be compared for the straight seam welding, large diameter pipes or some special pipes are all used the spiral welded pipe, because spiral welding welding density is big, welding up is very flexible, welded together can form a variety of changes.

But straight seam welding can only weld one line, the curve of straight seam welding completely couldn’t play the advantages, therefore, The use of spiral welded is the best choice.

Different Methods of Galvanizing

There are several different processes for galvanizing metal:


As the name implies, this method involves dipping the base metal into a molten pool of zinc. First, the base metal must be cleaned either mechanically, chemically, or both to assure a quality bond can be made between the base metal and the zinc coating. Once cleaned, the base metal is then fluxed to rid it of any residual oxides that might remain after the cleaning process. The base metal is then dipped into a liquid bath of heated zinc and a metallurgical bond is formed.

The advantages of this method are that it is economical; it can be performed quickly and to complex shapes. However, the final coating can be inconsistent relative to other galvanizing processes.


This method is very similar to hot-dip galvanizing but is performed at the steel mill, usually on materials that already have a specific shape. Pre-galvanizing involves rolling metal sheet through a similar cleaning process to that of the hot-dip galvanizing process. The metal is then passed through a pool of hot, liquid zinc and then recoiled.

An advantage of this method is that large coils of steel sheet can be rapidly galvanized with a more uniform coating compared to hot-dip galvanizing. A disadvantage is that once fabrication of the pre-galvanized metal begins, exposed, uncoated areas will become present. This means that when a long coil of sheet is cut into smaller sizes, the edges where the metal is cut are left exposed.


Unlike the previous processes, electrogalvanizing does not use a molten bath of zinc. Instead, this process utilizes an electrical current in an electrolyte solution to transfer zinc ions onto the base metal. This involves electrically reducing positively charged zinc ions to zinc metal which are then deposited on the positively charged material. Grain refiners can also be added which helps to ensure a smooth zinc coating on the steel. Similar to the pre-galvanizing process, electrogalvanizing is typically applied continuously to a roll of sheet metal.

Some advantages of this process are a uniform coating and precise coating thickness. However, the coating is typically thinner than the coating of zinc achieved by the hot-dip galvanizing method which can result in reduced corrosion protection.

Galvanized steel clamp connection technology applications

Galvanized pipe is protected by zinc, so it is not easy to rust, galvanized steel pipe is lighter than seamless steel pipe, if it is used in the balcony, the best light with galvanized pipe, because seamless steel pipe is heavy with thick wall thickness, and the cost of seamless steel pipe is higher than galvanized steel pipe, as well as galvanized steel is durable, useful life is much more than a seamless pipe.

If the quality is excellent, using twenty years should not be an issue. Surface coated or hot dip galvanized welded steel pipe can enhance corrosion resistance and prolong life.

Galvanized steel pipe with corrosion-resistant, not easy to pollution the transmission medium, which is widely used in domestic water supply systems, fire water systems, heating systems and gas delivery systems. In order to ensure the transmission medium process requirements and corrosion requirements, galvanized steel connection technology, the most widely used method is threaded connection. Clamp connection method for large diameter pipe connected to the system with easy maintenance construction, fast, able to meet higher working pressure requirements for piping systems, piping installation of high quality, low requirements of the construction team, the small number of requirements, equipment and simple, the disadvantage is the cost of using a clamp connection fittings slight increase.

Threaded connection clamp connection technology and process shortcomings compare

  1. during installation in pipe, a higher quality threaded threaded connection requirements, is more difficult threaded processing. After more than DN50 galvanized steel pipe specifications, especially for DN100, DN125, DN150 and other large-sized pipes, even to have the construction experience, high-level team of construction, installation and construction are more difficult, and this clamp connection method can overcome these difficult because only a pipe clamp connection butt, butt clamps, tighten the nut.
  2. threaded connections, requiring high pressure piping systems is difficult to meet the requirements. In practice, for the operating pressure exceeds 1MPa piping system, using threaded connection, it is difficult to ensure that no leakage, but with clamp connection method can meet the installation requirements are relatively higher operating pressure piping systems.
  3. threaded process connection pressure test of the entire system installed, or use, pipeline leak occurred after maintenance more difficult. Either a large area removal, replacement pipe fittings, pipes, or cut off the pipeline, with the welding tool repair. The former because a lot of demolished normal channels, thus greatly increasing the amount of maintenance work, while the latter uses a construction maintenance method specification is not allowed because of galvanized steel by welding, heat destroys the galvanized layer, so that the pipe joints at the long-term use may affect water quality, and even leaking, especially the fire sprinkler system. And for such shortcomings, clamp connection technology embodies a greater advantage. Such as certain pipe or a pipe leakage, simply connect the pipes, fittings at both ends of the clamp nut open, you can replace, very convenient, can greatly reduce installation engineering rework engineering, but also normal use can reduce the amount of maintenance work.
  4. threaded pipe connections requiring high quality, especially for higher working pressure fire pipeline system, does not allow the tube trachoma, burrs and other defects threaded tolerance with the bad, but in the actual installation works, often due to pipe fittings amount of maintenance and rework caused by unqualified installation is very large, such as the use of this clamp connection technology, the entire piping system can significantly improve the quality of the installation.
  5. install the necessary equipment and tools, threaded connection requires large-sized pipe wrench, chain wrench and twist wire machine, but you only need to pipe clamp connection technology equipment and general machining grooves end wrench to operate, relatively speaking , is much simpler.
  6. the construction team technical quality requirements, threaded connection when applied to large diameter, high pressure piping systems, high technical level of construction workers, construction experience demands to meet the higher number, but with clamp connection technology, for the number of technical quality requirements of the construction workers are much lower, requiring less fit.
  7. using a clamp connection pipe threaded connection time investment than the slightly more than the threaded connection clamp connection because in addition to the normal pipe clamps more than a cost, but reduces rework maintenance costs, so the total project cost to said little effect.

British Standard (BS1387-85) Thin thickness pipe specification

ND Outside Diameter (mm) W.T. Weight of Black Pipe (kg/m)
Nominal Size (DN) Screw Identifiers Maximum Minimum Thickness Plain end pipe Threaded and With Coupler
15 1/2 21.4 21.0 2.0 0.947 0.956
20 3/4 26.9 26.4 2.3 1.38 1.39
25 1 33.8 33.2 2.6 1.98 2.00
32 11/4 42.5 41.9 2.6 2.54 2.57
40 11/2 48.4 47.8 2.9 3.23 3.27
50 2 60.2 59.6 2.9 4.08 4.15
65 21/2 76.0 75.2 3.2 5.71 5.83
80 3 88.7 87.9 3.2 6.72 6.89
100 4 113.9 113.0 3.6 9.75 10.0

Normal steel pipe size

ND Outside Diameter (mm) W.T. Weight of Black Pipe (kg/m)
Nominal Size ( DN) Screw Identifiers Maximum Minimum Thickness Plain end pipe Threaded and With Coupler
15 1/2 21.7 21.1 2.6 1.21 1.22
20 3/4 27.2 26.6 2.6 1.56 1.57
25 1 34.2 33.4 3.2 2.41 2.43
32 11/4 42.9 42.1 3.2 3.10 3.13
40 11/2 48.8 48.0 3.2 3.57 3.61
50 2 60.8 59.8 3.6 5.03 5.10
65 21/2 76.6 75.4 3.6 6.43 6.55
80 3 89.5 88.1 4.0 8.37 8.54
100 4 114.9 113.3 4.5 12.2 12.5
125 5 140.6 138.7 5.0 16.6 17.1
150 6 166.1 164.1 5.0 19.7 20.3

Pre-galvanized steel pipes are used in the following fields, steel structure, build structure, guard rail, fence, metal furniture etc. our products are exported to about 50 countries in the world, we get a lot of recognition from many customers since our good quality and service.

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