Category: pipe fitting Knowledge

Grooves too wide or too small
Reason: a pressure wheel assembly and pipe size do not match. On the pressure wheel and knurling wheel relative position is not adjusted to the specified value.
Solution: 1. Replace the pressure slot corresponding to the tube wheel. Release sliding fastening bolt, adjust the bolt so that the pressure wheel and knurling wheel on the good slot and seal width value.

Notching
Reason: pipe end and pipe center is not perpendicular.
Solution: Fix the end face of the tube.

Excessive groove depth deviation
Reason: The pipe is oval, the pressure speed is uneven.
Solution: the use of circular tubes, uniform pressure speed, each rotation more than a week deep pressure, the thicker the more slowly, gradually.

Pipe port is too large
Reason: a tube offset angle is too large Boluo tube back end too high or too low Left and right deflection serious 4 processing speed
Solution: 1. Adjust the offset angle, the height of the back end and the right and left skewness; 2. Slowly and evenly increase the pressure depth speed

Pipe detaching during machining
Reason: 1. the pipe axis offset is serious; the processing speed is too fast; the active knurling wheel is worn out
Solution: 1. To correct the angle and reduce the processing speed. 3. Brush with steel wire to remove dirt or replace the driving wheel.

Pipe is skidding and not turning
Reason: 1. Speed too fast. Limit is not allowed.
Solution: 1. Slow down and adjust the limit.

End fracture of grooved seal
Reason: 1 on the pressure wheel and knurling wheel do not match. On pressure wheel is not on the knurled wheel slot and pressure slot is too deep.
Solution: 1. Make pressure pulley matching. 2. Adjust the pressure on the wheel is knurling groove control.
Second, the effect of too deep groove on the installation quality

If the groove is too deep, the pipe will appear a relatively large arc, which not only reduces the pressure allowance after the pipe is installed, and is easy to leak, but also easy to get out of the pipe when the pipe has a certain pressure.

If the groove is too deep, the strength of the end of the pipe will be affected, the cracks are easy to appear on the weld, and the zinc layer is easy to be damaged.

If the groove is too deep, the diameter of the bell will increase and the installation quality will be affected.

Grooves too deep easy to cause radial dislocation pipe, prone to leakage.
The influence of shallow grooves on the installation quality

Grooves too shallow will make the pipe card interface gap, medium pressure increases, rubber ring diameter easy to bulge out, affecting the sealing performance. Medium pressure to a certain extent, in the place where the apron drum tear easily cause water leakage accident.

Groove is too shallow, the pipe clamp installed to reduce the tightening margin leakage.

If the groove is too shallow, the clearance between the middle diameter and the outer diameter of the pipe clamp exceeds the permitted range, The outer side of the aprons lip is squeezed into the gap under the action of the medium pressure, which causes the rubber ring to be damaged. In serious cases, the apron will break in the high medium pressure and reduce the sealing performance of the apron.

Originally a flexible joint, because the groove is too shallow, will lose the characteristics of flexible joints, became a rigid joint.

Easy to cause the pipe to fall off.
Three points to ensure the safe use of fire trench pipe fittings

First of all, the time of purchase, the need to buy a variety of products to check whether there are cracks or broken seal;

The connection of various parts should also be checked whether it is tight, the screw nut is matched and the size of the seal ring is appropriate;

A very important point is the fire trench pipe installation, the need to suppress the test, in the process of testing, remember that no one should be close to, such as leakage and pressure instability, need to timely inspection and maintenance.

Pipe fittings are the general term of components that play the role of connection, control, direction change, shunt, sealing, support and so on in the pipeline system. A pipe fitting is a part that connects a pipe into a pipeline.
It mainly includes the following categories:

1. The pipe fittings used for pipe connection are flange, live joint, pipe hoop, clamp, jacket, throat hoop and so on.
2. Pipe fittings that change the direction of the pipe: elbows, bends.
3. Pipe fittings that change the diameter of the pipe: variable diameter (different diameter pipe), different diameter elbow, branch pipe table, reinforcement pipe.
4. Increase the pipe fittings of the pipeline branch: three links, four links.
5. Pipe fittings for pipeline sealing: gasket, raw material belt, wire hemp, flange blind plate, pipe plug, blind plate, seal head, welding plug.
6. Pipe fittings for pipeline fixation: clasp, drag hook, hanging ring, bracket, bracket, pipe card, etc.

Joint fittings are also called pipe fittings, connectors, joint parts and so on. In all kinds of pipeline systems, the pipe is connected by different joint pipe fittings to form pipe steel.

1. Malleable cast iron (Ma Steel) pipe fittings are made of malleable cast iron and are connected with pipes by thread (wire buckle). The pressure at work is within 0.1Mpa. Its appearance is characterized by a thick edge at the end. Four-way, used for pipe pass vertical cross connection; different diameter four-way, when connecting two smaller pipe diameters vertically on the pipe; also known as inner and outer filaments, internal and external diameters, small inner filaments, large outer filaments, outer wires connected with other pipe fittings, inner wires connected directly to pipes, used in the variable diameter connection of pipes; outer screw short joints, used to connect two close pipe fittings The pipe short joint made of lathe is commonly used to replace it, and the very short joint is called opposite wire; wire plug, also called plug head, is external thread, which is used to plug the hole of pipe fittings. The live joint is composed of two pipe joints which can buckle each other, the mother mouth and the sleeve mother connecting the common mouth and the mother mouth. The buckle part is lined with rubber pad or asbestos paper pad to avoid leakage, and the live joint is used in the pipeline where the same diameter pipe needs to be connected alive, that is, the pipe can be disassembled without rotating the pipe. In order to facilitate the removal and repair of the equipment in the pipe, in addition, the live joint is also essential in the pipeline installation. Root embellishment, also known as hoop, locking nut, with one end for short silk buckle, the other end for filament buckle (root non-tip degree) short segment and a root mother, plus an inner wall for through wire pipe hoop to form filament, its function with live joint, used as detachable live connection, when used in radiator repair center, wire pipe hoop can also be saved; flange, left and right two pieces to pay, acting as the same live joint. The specification is above the caliber d50mm, because the two ends of the large specification valve are mostly flange interfaces, so the flange is also often used for the connection between the pipe and the valve.
2. When steel and malleable cast iron pipe fittings are connected by thread, if the working pressure is high (but within 1.6Mpa), steel pipe fittings can be used. Steel pipe fittings are made of carbon steel, commonly known as cooked iron pipe fittings. It has good weldability and can be used in places where welding is needed, such as steel pipe hoops are often connected to steel equipment such as boilers or water tanks.
3. The feed iron pipe fittings are made of gray cast iron. There are two kinds of water supply cast iron pipe fittings, which are socket type and flange type. Their use is similar to that of malleable cast pipe. There are the following types: cross pipe, T tube (including three bearing cross pipe, three plate cross pipe, four bearing cross pipe, four plate cross pipe, double bearing tube, double disk tube, three bearing pipe, three plate tube, double bearing single disk tube, single bearing double disk tube). 90 °bend, 45 °bend; fork pipe; B pipe; hydrant pipe; casing and so on.
4. The main drainage cast iron pipe fittings are socket bending pipe, 90 °elbow, 45 °Y-shaped three-way, 90 °T-shaped three-way, 90 °TY three-way, oblique four-way, positive four-way, TY-shaped special-diameter three-way, different diameter four-way, pipe hoop, T-shaped bottle mouth three-way, 45 °elbow, Y-shaped special diameter three-way, socket cleaning port, S-shaped water storage bending, P-shaped storage bending, floor leakage and so on. Note: a variety of different joint pipe fittings can be made of different materials. At present, plastic joint pipe fittings have been widely used, because only with different materials, it will not be repeated here.

Galvanized steel pipe is divided into cold galvanized pipe, hot galvanized pipe. Cold galvanized pipe has been banned, hot galvanized pipe is also the country to promote temporary use. Galvanized steel pipe surface with hot dip plating or galvanizing layer of welded steel pipe. Galvanized steel pipe can increase corrosion resistance and prolong service life. Sixties and seventies, the international developed countries began to develop new pipe, and have banned galvanized pipe. China’s Ministry of Construction and other four ministries also issued a clear document from 2000 onwards banned galvanized pipe as a water supply pipe, the current new district cold water pipe has rarely used galvanized pipe, some district hot water pipe is galvanized pipe.
Often said galvanized pipe is now mainly used for gas transmission, heating. Galvanized pipe as a water pipe, use a few years later, a large number of rust inside the pipe, the yellow water flowing out not only pollute sanitary ware, but also mixed with the non-smooth inner wall of bacteria; The high content of heavy metals in water caused by rust is harmful to human health.
As the name implies, cold galvanized pipe is through the method of galvanizing, the outer wall of the steel pipe is coated with a layer of zinc. This treatment method is completely different from the principle of hot galvanization, so we call it cold galvanizing pipe. It is precisely because this method does not change the chemical composition of the steel pipe surface so the stability of the zinc coating is not high.
Difference between galvanized pipe and hot-dip galvanized pipe:
1, the process is different, a chemical treatment, a physical treatment; Hot-dip galvanizing coating is firm and not easy to fall off
2, hot galvanizing coating thick, so strong corrosion resistance. And galvanized (electroplating) coating uniform, surface quality is better, the coating thickness is generally between a few microns to ten microns.
3, hot-dip galvanizing is a chemical treatment, belongs to the electrochemical reaction. Galvanization is a physical treatment, just brush a layer of zinc on the surface, there is no galvanization, so the zinc layer is easy to fall off. Hot-dip galvanizing is used in construction.
4, hot-dip galvanized pipe is to make molten metal and iron matrix reaction to produce alloy layer, so that the substrate and the coating combined.
What should be noticed in the welding of galvanized pipe?

1. Galvanized steel pipe with diameter greater than 100mm should be connected by flange or special pipe fittings.
   2, galvanized steel pipe and flange welding, in order to ensure the welding quality, should be the welding mouth galvanized treatment, the application of hand grinding wheel or sand paper to clean the galvanized layer, or gas welding flame to clear the zinc layer.
   3, galvanized steel pipe and flange welding should be galvanized twice.
   Measures to ensure welding quality include:
   1, the human factor is the focus of gas galvanized pipe welding control. Due to lack of necessary post-weld control hand
   Section, easy to jerry-building, affecting quality; At the same time, the welding particularity of galvanized pipe makes it difficult to ensure the welding quality. Therefore, skilled welders who hold the appropriate boiler pressure vessel or equivalent welder’s certificate should be selected prior to the commencement of work. Carry out the necessary technical training and disclosure, refer to the boiler pressure vessel welder examination rules for on-site examination and approval, give the permission to enter the site welding. And shall not be replaced at will, to ensure the welding of the pipeline welders relatively stable.
   2, welding material control: to ensure that the procurement of welding materials is the normal channel, there is a warranty, certificate, meet the process requirements; Welding material acceptance, lead material formalities to formal and complete, electrode head recovery control strict, to ensure the flow direction, dosage; Welding materials should be strictly baked according to the process, and not more than half a day of supply.
   3, welding machine; Welding machine is welding machine, must ensure reliable performance, meet the process needs; Welding machine must have qualified current, voltage meter, to ensure the correct implementation of welding technology. Welding cable can not be too long, long to adjust the welding parameters.
   4, welding process method: ensure the strict implementation of special operation methods of galvanized pipe, according to the welding process before welding groove inspection, welding technology parameters, operation method control, after welding appearance quality inspection, when necessary, add after welding non-destructive testing. Control welding level, welding material consumption of each crossing.
   5, welding environment control: to ensure the welding temperature, humidity, wind speed in line with the process requirements. Welding shall not be performed unconditionally.

We’ve acquired dark moldable strung pipe fittings, including elbows, couplings, tees, associations, and bushings in various sizes. On the off chance that you’re joining your dark iron channeling to a line produced using a novel sort of steel, avoid consumption and line disappointment with one of our dielectric fittings. Strung dark metal fittings interface with dark steel and dark iron line for moving gas and water, safeguarding electrical wiring, or conveying high-pressure steam and air. Uncoated dark steel and iron fittings, likewise called dark flexible iron fittings, are made from consumption safe ungalvanized metal with a textured, dull hued iron oxide covering. These fittings are used in funneling strategies to change direction or associate with hardware or gadgets.

Wholesaler of treated steel, copper and cast iron line fittings. Administrations embrace valve robotization, seller oversaw stock, direct request passage and EDI. Maker of produced iron line fittings including elbows, tee, minimizers, finish covers, crosses, bushings, plugs, locknuts, ribs and exhaust associations. Virtual planning, improvement, designing, region, backing and fix administrations are likewise advertised. Serves the mechanical, plumbing framework, power, power, oil, gas, food, drink, wastewater and mining ventures. Producer of line fittings including fashioned iron strung fittings.

What is Mallebale iron line fitting Malleable iron fittings are lighter fittings in 150# and 300# pressure class. They are made for light modern and plumbing utilize something like 300 psi. Click here, you might find additional dark line fittings in an assortment of shapes, including crosses, spines, elbows, couplings, associations and bunches of extra. Dark metal line areolas ofpipe areola providers are in extreme interest all through the line fittings market in light of areas of strength for the, finish. Dark metal line fittings are exceptionally productive and erosion safe.

“Client administrations and relationship” is another significant space which we see great correspondence and associations with our clients is presumably the main energy to run it as a drawn out big business. The dark line cross fitting is probable absolutely perhaps the most normally utilized fitting. We can see them in many structures, Usually, they need a thicker divider and heavyweight to hinder the damage for four bearings pipe stringing.

These fittings are accuracy machined and strung for release free associations between fittings, instrumentation, and line. The qualities of the piece sort pipe nippleThe chomp type areola in pipe fittings has the advantages of simple development, light-weight, little estimation, advantageous use, no electric welding, pack… The materials utilized rely upon the kind of liquids it will convey. One of the more regularly utilized assortments is PVC fittings. Highlights of the PVC pipe fittings that make a proper is the stipend for a smoother divider floor which diminishes protection from the circle. Dark band BSPT CROSS, the surface is dark and not electrifies, furthermore known as dark product.

The firm has a yearly result of 50,000 tons, with full-process creation capacities like molds, projecting, warmth treatment, hot-plunge arousing, handling, and gathering. Give items, suppliers and answers for water supply and waste frameworks, chimney insurance frameworks, unadulterated fuel strategies, air con and warming procedures, mechanical stuff and different methods. Our moldable iron fittings are accessible an assortment of sizes. You can utilize the channel menu on the page to assist with finding Malleable iron fittings in your favored size, especially in the event that you’re taking a look at a particular becoming kind.

Dark line is not the same as electrifies pipe since it isn’t covered. The line is made with out joints, making it a more grounded and more secure fuel pipe. Dark metal line is likewise utilized in fire sprinkler techniques because of it’s more heat proof than stirred pipe. Our organization in the US is currently watching out for a specialist maker to buy cast iron soil line and fittings, ASTM A74 for EXTRA HEAVY and ASTM A888 for NO HUB pipes. If it’s not too much trouble, get in touch with me desperately assuming you have such stock out of your assembling unit.

Because of their strength and solidness, dark iron line and fittings are commonly utilized for oil and fuel purposes. They might be weighty commitment, however they can be introduced by pretty much anyone. Remember, you could require a few specific instruments to complete the entire interaction, however a set up just requires components and a couple of kind of string tape/pipe joint compound. To join dark iron fittings and line, envelop the male strings by a line string sealant tape, keeping up with bearing in considerations. In the event that you could do without working with tape, you can utilize pipe joint compound, black iron pipe fittings wholesale which is applied with a brush or cloth to male and female strings prior to interfacing.

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Whether you’re searching for elbows, plugs, covers, areolas, naming however various, BES could have the pliant iron fittings you really want. Dark iron line is used in private purposes to move unadulterated gas and propane gas. Dark metal line is produced to be consistent, which makes it a superior sort for normal fuel transportation and hearth sprinklers. Since it gives preferable security from hearth over aroused pipe, it is the best kind for fuel transportation and chimney sprinkler methods. Outrageous strain strung fittings get together with exorbitant tension (3001+ psi) pipe. It is extremely normal today to place in bendable iron lines in polyethylene sleeves.

This dimensionless amount assigns the strain temperature positioning. If it’s not too much trouble, note that we’re not stockist and the clarification we’re not stockist is because of it isn’t savvy. We are without a moment to spare supplier of Ductile Iron Pipe Fittings/Ductile Iron Fitting/DI Fittings. Least request sum is one holder so we will create it at Truform India and give it to your final location in UK or Europe. Bendable Iron Pipes and Fittings circulation is an extravagant errand with our capacity to import from Truform India and convey to your doorsteps in what we do as a discount supplier.

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Wholesaler of steel outlining techniques, wellbeing grinding stock and link plate stock. Fittings incorporate course and link, pipe, railing, and cylinder. Materials incorporate steel, chrome steel, aluminum, fiberglass, powder gets done, coatings, epoxy gets done, zinc plate gets done and electrifies wraps up. Applications embrace road pointers, roof walkways, mezzanines, catwalks, subfloors and different capacities.

Maker of acrylonitrile butadiene styrene , aluminum, cast iron, erosion safe, malleable iron, metal, nickel and nickel compound and hardened steel pipe fittings along with elbows. Elbows pass on through redirection, not by material effect, killing elbow wear, stopping, flooding and item debasement. Configurable for explicit modern capacities, possible in 45 and 90 certificate elbows in tube dia.

The last expense might be very surprising depending on the conveyance handle. Dark line is sturdy, ideal for dry, indoor capacities. Rough Enough To Last A Lifetime Our Kanaif Stainless steel is almost indestructible, with innate long-life properties that don’t decrease over the long run or rehashed use. For requests about our product or pricelist, kindly withdraw your email to us and we will be in contact in 24 hours or less. We give a wide range of Malleable Iron Pipe Fittings.

Dark iron line might be welded utilizing any welding method utilized for metal. This incorporates MIG, transition cored, TIG and anode bend welding. Nonetheless, dark line fittings are produced from pliable dark iron. Dark iron fittings are hard to weld with out really hurting the fittings. We give the best scope of hot aroused pliant iron line fittings which have been demonstrated to be to the best on the lookout. These are created with high grade of metallic uncooked materials.

1. Hot-dip galvanized pipe:
   Hot-dip galvanizing tube is to make the iron base and molten metal react to form alloy layer, so that the base and the coating bond. Hot-dip galvanizing requires pickling to remove iron oxide from the surface of the steel pipe. After pickling, it is washed in aqueous zinc chloride solution or ammonium chloride or mixed aqueous solution of ammonium chloride and zinc chloride, and then fed into a hot dip plating bath. Hot-dip galvanizing has the advantages of strong adhesion, uniform coating and long service life.
2. Cold galvanized pipe:
   Cold galvanizing is what we call zinc plating. The amount of galvanization is very small, and the corrosion resistance of the cold galvanized pipe is very different from the hot galvanized pipe, so many construction projects do not use the cold coated pipe. At present, the Ministry of Construction has officially declared that the backward technology of cold galvanizing pipe needs to be eliminated, and the cold galvanized pipe is not allowed to be used as a water gas pipeline in the future.
   Applications of galvanized steel pipe:
   Hot-dip galvanized steel pipe is widely used in construction, machinery, coal mine, chemical, electric power, railway vehicles, automobile industry, highways, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, survey machinery and other manufacturing. Welded steel pipe with hot-dip or electroplated zinc coating on the surface of galvanized steel pipe. Zinc plating can improve corrosion resistance of steel pipe and prolong its service life.
   Galvanized pipes are widely used, not only as pipelines for transporting water, gas, oil and other general low-pressure fluids, but also as oil well pipes and oil pipelines in the petroleum industry, Especially in the submarine oil field, the oil heater, the condensation cooler, the chemical coking equipment in the coal distillate wash oil exchange pipeline, the trestle pipe pile and the mine laneway support frame pipeline and so on.
   Therefore, in the choice of galvanized steel pipe, we should focus on quality, choose high quality, high price galvanizing steel pipe. The choice of pipeline has a great impact on the quality and safety of construction projects.
   Hot-dip galvanized steel pipe: hot-dip galvanizing steel pipe is first steel parts for pickling, in order to remove iron oxide on the surface of steel parts, After pickling, it is cleaned in a bath of ammonium chloride or zinc chloride aqueous solution or mixed aqueous solution of ammonium and zinc chloride, and then fed into a hot dipping bath. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life.
   Cold galvanizing steel pipe: Although now cold galvanized steel pipe has rarely been used on a large scale but since we tell the difference nature will also introduce under, Cold galvanizing is also called electroplating zinc, is the use of electrolysis equipment will be the pipe after oil, pickling into the composition of zinc salt solution, The anode of the electrolytic equipment is connected, and a zinc plate is placed on the opposite side of the tube. The positive electrode connected to the electrolytic device is connected with the power supply. The directional movement of current from the positive to the negative electrode can deposit a layer of zinc on the tube. The cold plating tube is processed first and galvanized later.
   To talk about the differences, we have to talk in several ways.
3. Different from the construction process: hot-dip galvanized steel pipe is to make molten metal and iron matrix reaction to produce alloy layer, so that the base and coating combined with the two and cold galvanized steel pipes are cold galvanized coating mainly through the electrochemical principle to anti-corrosion.
4. Different equipments required: pickling equipment, bottom withdrawal annealing furnace or hood annealing furnace. Cold galvanized steel pipe: electrolysis equipment.
5. Different performance: durable corrosion resistance, standard quality of hot dip galvanizing thickness makes it has excellent durability; The toughness of the coating is strong, hot dip galvanizing layer forms a unique smelting metal structure, this metal structure can withstand the transport and use of mechanical damage. Cold galvanizing: excellent environmental performance. Most solvents and diluents for cold galvanizing do not contain toxic organic solvents. Moreover, the evaporation of organic solvents is reduced, energy consumption is reduced and the process is beneficial to environmental protection.
6. Zinc coating thickness is different thickness: hot-dip galvanized steel tube zinc layer itself is relatively thick, there is more than 10 um thickness, although the surface is bright, but rough, there will be zinc flowers. And galvanized (cold galvanized steel pipe) zinc layer is very thin, as long as the thickness of 3-5um, although the surface is smooth, but there will be dark, dirty performance, good processing performance, lack of corrosion resistance.
7. Different applications: hot-dip galvanized steel pipe due to good corrosion resistance, Hot-dip galvanized steel pipe is widely used in power tower, communication tower, railway, highway protection, lamppost, marine components, building steel structural components, auxiliary facilities of substation, light industry and so on. Cold galvanized steel pipe is the main development direction of environmental protection of heavy corrosion protection coatings.

Galvanized steel pipe, is generally called cold plating pipe, choose electroplating, only in the steel surface galvanized, steel pipe cavity without galvanized.
Hot-dip galvanized steel pipe, the general selection is hot-dip galvanizing process, steel pipe inside, the surface is a zinc layer.
The difference between galvanized pipe and hot galvanized pipe:
1, processing technology is different, one is organic chemistry solution, a is physics solution; Hot-dip galvanised coating is firm and not easy to fall off.
2, hot-dip galvanizing coating is thick, so it has strong anti-corrosion ability. And galvanizing (electroplating process) coating symmetry, process performance is good, coating thin thickness is generally in the middle of 1 μm to more than 10 μm.
3, hot-dip galvanizing is an organic chemical solution, belonging to electrochemical corrosion. Galvanizing is a physical solution, just brush a layer of zinc on the surface, there is no galvanizing inside, so the zinc layer is easy to fall off. Hot dip galvanizing is used in construction engineering.
4, hot-dip galvanizing steel pipe is to make the molten metal material and the iron base material reflect and cause the aluminum alloy layer, and then make the base material and coating both closely together.
Electroplating zinc, commonly known as cold galvanizing, is the use of electrochemical methods, zinc ingots as the anode, After the zinc atom loses the electron to become the ion state to dissolve in the electrolyte, but the steel strip serves as the cathode, the zinc ion gets the electron reduction on the steel belt to the zinc atoms deposition to the steel surface, forms the coating.
There is a big difference between the galvanizing quantity of the hot dip galvanized sheet and the electrolytic galvanized sheet. The galvanizing amount of hot-dip galvanizing can not be too small, generally the minimum is 50 ~ 60g / m2 on both sides and the maximum can reach 600g / m 2. The galvanizing layer of electrolytic galvanized sheet can be very thin, and the minimum is 15g / m2. However, if the coating is thick, the production line speed is very slow and does not meet the characteristics of the modern process, the general maximum is about 100g / m2. Just because of this, the production of electrolytic galvanized sheet is very limited.
Hot dip galvanized sheet and electrolytic galvanized sheet are fundamentally different in the microstructure of the coating. There is a brittle compound layer between the pure zinc coating and the steel strip substrate on hot-dip galvanizing plate. Zinc flowers are formed when the pure Zn coating crystallizes and the coating is uniform and void. The zinc atoms in the zinc layer only precipitates on the surface of the steel strip, and is attached to the surface by physical action, there are many holes to dry, easy to cause pitting corrosion due to corrosive media, so hot dip galvanized sheet than electrolytic galvanized sheet more corrosion resistance.
Hot dip galvanizing and electrolytic galvanized sheet heat treatment process is also completely different, hot dip galvanized sheet generally hard plate as the raw material. Continuous annealing and hot dip galvanizing on the galvanizing line, the steel strip is heated and cooled in a short time, so the strength and plasticity are affected to some extent, and its stamping performance is worse than the cold rolled plate after degreasing annealing in the same professional production line. Electrolytic galvanized sheet, which is made of cold-rolled steel, has the same processability as the cold-rolled sheet. However, the complicated process flow of the electrolytic galvanizing sheet increases the cost of production. In short, the production cost of hot-dip galvanizing plate is lower, the application range is wider, and it has become the main variety of galvanized plate market.
Zinc plating is through the electrode reaction, for galvanizing, and hot-dip galvanizing is dipping raw materials into the zinc pot for galvanization, it is metal reaction and physical reaction.
When hot-dip galvanizing, the raw material surface is a layer of intermetallic compound, then zinc, while the surface of zinc plating is zinc, there is no intermediate layer.
Electroplated zinc zinc layer is thinner, and hot-dip zinc coating is thicker
Zinc plating can not be mass produced, low yield, and hot-dip galvanizing can be mass production, high yield.
The surface state and corrosion resistance of electroplating is better than hot-dipped zinc
Zinc plating is better than hot-dip galvanizing, so it is expensive
Zinc plating costs high, so the price is high. Hot galvanizing zinc aluminum alloy with high prices when more than 4W / ton……
Zinc plating and hot-dip galvanizing corrosion protection principle is the same. It’s just that the processes are different.
After electroplating zinc – the surface is clean. Bright appearance. But because the zinc layer is attached, it will fall off over time.
Hot dip galvanizing – some not as beautiful as electroplating. But zinc layer has penetration, use time is longer than electroplating.
1, hot-dip galvanizing plate general zinc layer is thicker, about 10 um above, corrosion resistance is stronger. So is a usually used galvanizing process. And electroplating zinc is very thin, About 3-5 um, hot plating surface rough, bright, serious cases with zinc flowers, plating is smooth, gray (hair pollution).
Galvanized steel sheet made by electroplating has good processability. But the coating is thinner and less resistant to corrosion than hot-dipped galvanized sheet. Cold galvanized sheet is electroplated zinc, The amount of galvanizing is very small, only on the outer wall of the galvanized (hot-dip galvanizing – both inside and outside), only 10-50g / m2, its own corrosion resistance than hot-dip galvanized sheet tube is much different.
2, chemical industry generally more zinc plating, suitable for small parts; Hot-dip galvanized sheet is generally used for power equipment and components, suitable for large components and equipment.
Zinc plating is commonly known as cold galvanizing plate, is the use of electrochemical way, the zinc ingot as an anode, After the zinc atom loses the electron to become the ion state to dissolve in the electrolyte, but the steel strip serves as the cathode, the zinc ion gets the electron reduction on the steel belt to the zinc atoms deposition to the steel surface, forms the coating.
In order to remove the iron oxide on the surface of the steel pipe, the hot-dip galvanized steel sheet is washed by ammonium chloride or zinc chloride solution or ammonium chloride and zinc chloride mixed aqueous solution tank after pickling, and then sent to the hot dip plating tank.
3, hot dip galvanized sheet and electrolytic galvanized sheet have a big difference in galvanizing quantity. The galvanizing amount of hot galvanizing plate can not be too small, generally the minimum is 50 ~ 60g / m2 on both sides, the maximum can be up to 600g / m2. The galvanizing layer of an electrolytic galvanized sheet can be very thin, with a minimum of 15g / m2, but the production line speed is very slow if the requirements of thick coating are not suitable for the characteristics of the modern process, the general maximum is about 1O0g / m2. Just because of this, the production of electrolytic galvanized sheet is very limited.
4, hot dip galvanized sheet and electrolytic galvanized sheet are fundamentally different in the microstructure of the coating. There is a slightly brittle compound layer between the pure zinc coating on the plate and the base of the steel strip. The pure Zn coating usually forms zinc sparkle when it crystallizes, and the coating is uniform without porosity. The zinc atoms in the zinc layer only precipitates on the surface of the steel strip, and is attached to the surface by physical action, there are many holes to dry, easy to cause pitting corrosion due to corrosive media, so hot galvanized sheet than electrolytic galvanized sheet more corrosion resistance.
5, hot dip galvanized sheet and electrolytic galvanized sheet heat treatment process is also completely different, the hot dip galvanizing sheet with cold hard plate as the raw material, in the galvanizing line continuously annealing and hot galvanized sheet, The steel strip is heated in a short time and then cooled, so the strength and plasticity are affected to a certain extent. Its stamping performance is worse than the same cold plate after degreasing annealing by professional production line. Electrolytic galvanized sheet, which is made of cold-rolled steel, has the same processability as the cold-rolled sheet. However, the complicated process flow of the electrolytic galvanizing sheet increases the cost of production. In short, the production cost of hot-dip galvanizing plate is lower, the application scope is wider, and it has become the main variety of galvanized plate market.
6, hot-dip galvanizing sheet pipe is to make the molten metal and iron matrix reaction and produce alloy layer, so that the matrix and coating two combination. Hot-dip galvanized sheet has the advantages of uniform coating, strong adhesion and long service life. Formal galvanized pipe manufacturers, in order to ensure quality, most do not use electroplating zinc (cold plating). Only those small, equipment old small enterprises use zinc plating, of course, their prices are relatively cheap. The Ministry of Construction has formally below, the elimination of backward technology cold galvanized pipe, is not allowed to use cold galvanized steel pipe for water, gas pipe.
The galvanizing plate that is commonly used now is hot-dip galvanization plate, and the electric line that uses the groove and so on uses is cold galvanize plate, color has certain difference.
Hot-dip galvanizing and cold galvanizing how to distinguish difference and discrimination?
First, the difference between processes is:
Hot-dip galvanizing is to remove oil, pickling, dipping, drying after immersion in molten zinc for a certain time, can be lifted out.
Cold galvanizing is also called galvanizing, it is to use electrolysis equipment to put the workpiece into the solution of zinc salt after deoiling, pickling, and connect the anode of electrolysis equipment. A zinc plate is placed on the opposite side of the workpiece and connected to the cathode of the electrolysis equipment. The power supply is switched on, and a layer of zinc is deposited on the workpiece by the directional movement of current from the cathode to the anode.
Difference in appearance: electroplated zinc appearance is relatively smooth, bright, using color passivation process electroplated layer is also yellow-green color, was colorful. The electroplating layer of white passivation process is bluish white or white is green light, and the coating of white passive process is slightly colorful under a certain angle with sunlight. In the corner of complex workpiece is easy to produce “electric burning” and become gray, this part zinc layer is thicker. Low current gray area is easily formed in the negative corner, which has thin zinc layer. The workpiece as a whole no zinc tumor, caking and other phenomena. The appearance of hot-dip galvanizing is slightly rougher than zinc plating, and is silver-white. It is easy to produce process water lines and a little drip, especially on the end of the workpiece. But the zinc layer of hot-dip galvanizing is dozens of times thicker than zinc plating, and the corrosion resistance is tens of times.
The difference between galvanized finished products:

1. Hot-dip galvanized steel pipe is galvanized inside and outside, but cold-galvanized steel only outside.
2. The cold coating is uniform and thin. The thermal coating is thick and the thickness is not uniform.
3. Cold plating appearance is bright, hot plating color is dark.
4. Because of the thin layer, the corrosion resistance is poor. The hot coating is several times thicker than cold galvanizing, and it forms an infiltration layer with the base metal, and has good corrosion resistance.
5. Cold galvanized steel pipe looks bright surface, smooth and flat; Hot-dip galvanizing surface is not cold galvanizing fine and bright, hot-dip galvanized steel tube surface seems to have some uneven bumps, and the surface does not shine, not too reflective.

Galvanized steel is widely used in various industries, due to its use in the process of application of air composition to form a dense oxide coating, A good protective film is formed on the metal zinc to protect the steel structure in the work, ensuring the reasonable and effective application of the engineering quality. In the case of welding, scratch, due to the presence of the primary battery, the corresponding active galvanizing management control, By sacrificing the performance of the anode, the rust of steel can be delayed, and the dead corner of the structure can meet the needs of the design, so as to ensure the complete and effective control measures and modes of application. In the end market of the West to East Gas Transmission Project, the use of a large number of galvanized pipes put forward higher requirements for the welding and quality of galvanized pipe. The traditional galvanized pipe thread connection is easy to leak, resulting in a large amount of maintenance work, and the installation of open pipe is used in the installation, which seriously restricts and affects the appearance of the architectural engineering form and aesthetic requirements. Under the influence of this trend and background, seeking new welding methods and welding modes is the main application measures and methods of galvanized pipe construction. Because of the existence of zinc plating layer, it is easy to produce cracks, blowhole and slag in welding, which makes it difficult to guarantee its quality in the welding process, and become the main defects and constraints affecting welding technology.
Welding characteristics of galvanized steel
Galvanized pipe is a new type of mixed material and action mode composed of a layer of zinc outside of low carbon steel, the thickness of the galvanized layer is generally about 20um, Because zinc has a high strength melting point of 419 °C and boiling point of 908 °C, so in the flux process is easy to form a variety of influence and constraints, become the basic premise of affecting the quality of galvanized pipe. In welding, zinc melts and floats as a liquid on the surface of the pool or at the root of the weld. And zinc in the welding time easy to produce a larger solid solubility, easy to penetrate into the weld metal, Thus forming a liquid metal state, this state of metal is a kind of easy to catalyze the metal and way, so it is easy to be affected by various factors and the impact of cracks and fracture phenomenon. These brittle phases reduce the plasticity of the weld metal, and are prone to produce defects such as fillet welds in installation and use, which cause serious influence and restriction factors on the construction quality.
When galvanized steel is welded, the zinc layer on the groove surface and edge is treated under the heat action of an electric arc, It can produce oxidation, melting and even evaporation, so that the treatment mode and treatment mode in the use of the process of easy to cause porosity in the weld.
If the selection of welding specifications are not appropriate, improper operation, it is easy to use suitable welding gaps and edges exist in the various zinc melting points for strict processing, To ensure that a variety of possible damage to the zinc coating, so that the various ways of welding and management control factors for comprehensive analysis and management, to ensure the operation of its arc welding under the welding. At the same time, due to the evaporation of zinc, a large number of white smoke, It can stimulate and hurt the human body, but also produce less dust in the welding process, so it must be considered in welding process and management control method.

Requirements for Welding Galvanized Pipe in City Gas Application
With the constant acceleration of the current social development, in the life of urban residents, the amount of gas is increasing. How to ensure that the urban residents in the life of the reasonable control of gas has become the focus of the current municipal gas supply engineering to explore and explore the form is the main basis of municipal engineering construction. As the main pipeline form of natural gas supply and transportation, the welding quality of galvanized pipe is the main method and measure to affect the application of natural gases. In galvanized steel welding method more, generally is to use common gas welding and arc welding as the main welding process, With the development of science and technology, carbon dioxide gas shielded welding, automatic submerged arc welding and other new welding methods have been applied in pipeline welding, and become the main means and methods of welding.
Gas welding used to be used in the welding of galvanized pipe, due to the welding in the process of welding is becoming more and more perfect, its mechanical properties in welding seam is too poor, its shortcomings and the management analysis of the application.
The welding performance of CO _ 2 gas shielded welding is good for galvanized steel. When suitable welding specification and matching shielding gas and welding material are adopted, high quality welding joint can be obtained. This method is seldom used in engineering practice.
Tungsten Argon Arc Welding (TIG) is a kind of welding method that is worthy to be used because of its concentrated arc energy, less damage to zinc coating and easier formation of good one-side welding and double-side forming joints.
Manual arc welding is the most popular welding method in pipeline installation. In the case of correct power and power electrode, such as titanium oxide and calcium titanium-type electrodes J421, J422 and J423, Because of the large amount of rutile and ilmenite in the coating, the melting rate of the electrode is large and the melting speed is relatively increased. If the zinc coating such as the front of the molten pool can be damaged under the condition of no swing, the melting zone will not be enlarged and the penetration of liquid zinc to the weld metal will be reduced. The welding quality with good mechanical properties and no defects can be obtained by using correct operation method and welding material.
According to the reality of the current construction team, because the manual arc welding is cheaper and faster than TIG welding, the manual electric arc welding process is adopted in the case of skilled welders.
Welding process control
The preparation before welding of galvanized steel is the same as that of ordinary mild steel. It is important to take care of the groove size and the galvanizing coating nearby. For penetration, groove size should be appropriate, generally 60 ~ 65 °, to leave a certain gap, generally 1.5 ~ 2.5 mm; In order to reduce the penetration of zinc on the weld, before welding, the groove can be removed after the zinc coating welding. In the actual supervision work, the centralized beveling technology is adopted, and the two-layer welding technology is used for centralized control, which reduces the possibility of incomplete penetration.
Welding rod should be selected according to the base material of galvanized pipe. Generally, J422 is more common in low carbon steel because of easy operation.
Welding technique: when welding the first layer of multi-layer welding, try to make the zinc layer melt and vaporize, evaporate and escape the weld, which can greatly reduce the liquid zinc in the weld. When welding fillet welds, the zinc layer is melted and vaporized and evaporated in the first layer as much as possible to escape the weld, The method is to move the end of the electrode forward about 5 ~ 7 mm, and then return to the original position to continue welding when the zinc layer is melted. When horizontal welding and vertical welding, if the use of short slag electrode such as J427, the tendency to undercut will be small; If the back and forth transportation strip technology is adopted, the welding quality without defects can be obtained.

Spiral welded pipe main uses: widely used in housing, bridges, roads and other civil engineering construction. Main origin: Spiral pipe manufacturers in China are mainly located in north and northeast China, North China such as Shougang, Tangshan Iron and Steel, Xuanhua Steel and Chengde Steel Co., Ltd., and Northeast China like Xilin, Beitai and Fugang. These two regions account for more than 50% of the total output of rebar. Spiral welded pipe is widely used in natural gas, petroleum, chemical industry, electric power, heat, water supply and drainage, steam heating, penstock for hydropower stations, thermal power generation, water sources and other long-distance transmission pipelines and piling, dredging, bridges, steel structures and other engineering fields. The horizontal ribs of spiral welded pipe are thin and low in quality. The reason is that in order to achieve a large negative tolerance, the pressure of the finished products is large, the iron type is small, and the hole is full.
The difference between spiral welded pipe and longitudinal welded pipe

1. Metallurgical properties of materials
   The LSAW pipe is made of steel plate, while the spiral welded pipe is manufactured by hot-rolled coil. For example, a water cooling system is installed on the output table to accelerate cooling, which allows the use of low alloy compositions to achieve special strength grades and low temperature toughness. This improves the weldability of the steel, but this system is not available in the steel plate production plant. The alloy content (carbon equivalent) of the coiled sheet tends to be lower than that of similar grade steel, which also improves the weldability of the spiral welded pipe.
   What is more, because the rolling direction of the spiral welded pipe is not perpendicular to the pipe axis (the clamping solution depends on the spiral angle of the pipe), The rolling direction of the steel plate of the straight seam pipe is perpendicular to the steel pipe axis, so the cracking resistance of the spiral welded pipe material is better than the straight slit pipe.
2. Welding process
   In terms of welding technology, the welding method of spiral welded pipe is the same as that of straight welded pipe, but it is inevitable that there will be a lot of T-weld. Therefore, the probability of existence of welding defects is also greatly increased, and the residual stress in the T-weld is large, the weld metal is often in a three-dimensional stress state, increasing the possibility of cracks.
   Moreover, according to the technical regulation of submerged arc welding, each weld should have arc starting and extinguishing, but each straight seam pipe in welding ring seam, can not reach this condition, so there may be more welding defects in the extinguishing.
3. Strength characteristics
   The spiral angle of spiral welded pipe is generally 50-75 degrees, so the combined stress of spiral weld is 60-85% of the main stress of straight welded pipe. At the same working pressure, the wall thickness of spiral welded pipe with the same diameter is smaller than that of longitudinal welded pipe.
   According to the above characteristics, we can see that:
   3.1 spiral welded pipe blasting, due to the weld by the normal stress and the synthesis stress is relatively small, the blasting hole generally does not originate in the spiral weld, its safety is higher than the straight seam welded pipe.
   3.2 When there is a parallel defect near the spiral weld, the spiral welds have less force, so the danger of its expansion is not as big as the straight weld.
   3.3 Because radial stress is the maximum stress existing in the steel pipe, so the weld in the direction of vertical stress bear the maximum load. That is to say, the load of straight seam is the biggest, that of circumferential weld is the smallest, and that of spiral weld is between them.
4. Static burst strength
   The yield pressure of spiral welded pipe and longitudinal welded pipe is in good agreement with the measured value and theoretical value of burst pressure. However, the yield pressure or burst pressure of spiral welded pipe is lower than that of longitudinal welded pipe. The blasting test also showed that the hoop deformation rate of spiral welded pipe was obviously higher than that of longitudinal welded pipe. It is proved that the plastic deformation ability of spiral welded pipe is better than that of longitudinal welded pipe. The burst hole is usually confined within one pitch, which is caused by the strong constraint of spiral weld on the expansion of crack.
5. Toughness and fatigue strength
   The development trend of pipeline is large caliber and high strength. As the diameter of the steel pipe increases and the grade of steel used increases, the tendency of the ductile fracture tip stable extension becomes greater. Spiral welded pipe and longitudinal welded pipe are of the same grade, but spiral welded pipes have higher impact toughness.
   Because of the change of transportation capacity, the pipe is subjected to random alternating load in actual operation. It is important to know the low cycle fatigue strength of steel pipes for judging the service life of pipelines.
   According to the results, the fatigue strength of spiral welded pipe is the same as that of seamless pipe and resistance welded pipe. The test data are distributed in the same zone as seamless and resistance pipe, but higher than that of general submerged arc longitudinal welded pipe.
6. Field weldability
   The weldability in the field is mainly determined by the material of the pipe and the size tolerance of the end fit.
   Taking into account the requirements of steel pipe installation construction, the continuity of the steel pipe processing and the consistency of the geometric dimensions is particularly important.
   The production of spiral welded pipe is a continuous process which is basically stable under the same working condition. The manufacturing process of longitudinal welded pipe consists of several stages, including the whole plate / indenter / precoiling / spot welding / welding / finishing / group etc. This is the spiral welded pipe production is different from the production of longitudinal welded pipe an important feature.
   The stable production condition is very convenient for the control of welding quality and the guarantee of geometrical size. Compared with the longitudinal welded pipe, the spiral pipe has very good ellipticity of the nozzle and verticality of the end face, which ensures the assembly precision of the welding in the field.
7. Influence on flow characteristics of conveying medium
   The pressure drop in the pipeline is directly proportional to the length of the pipe, the coefficient of fluid viscosity, fluid velocity, and fluid resistance. The resistance coefficient of the fluid depends on both the Reynolds number and the roughness of the inner surface of the pipe. The roughness of the inner surface of the pipe has a ten times greater effect than the area of the local bulge, such as spiral or longitudinal welds, or even inner girth welds.
8. Production and Management
   The production of spiral welded pipe can embody the advantage of high quality and high efficiency. The output of a spiral welded tube unit is equivalent to 5 – 8 units of longitudinal welded pipe equipment. It is a heavy work to make the production lines of multiple coiled pipe equipment reach the same production standard, that is, to meet the welding quality requirements and pipe manufacturing grade according to the unified production process specification and quality assurance system.
   The multi-head production ratio increases the amount of engineering management and quality supervision. There are many difficulties in production management, planning schedule, inspection and acceptance, delivery coordination and other aspects due to the differences of operation skills, quality awareness, distribution points and control procedures of the operators. Easy to cause management and coordination of the confusion and the quality of the manufacturers and construction units buck-passing.
9. Price analysis
   Because of the material technical performance and production technology of hot-rolled coil is higher, so on the one hand, domestic manufacturers in line with the standard than the plate manufacturers to less, on the other hand, its production process and quality level determine its market price is higher than hot-rolled steel plate. This is the main reason why the price of spiral welded pipe is higher than that of longitudinal welded pipe.

The China Zun Building will become the tallest building in Beijing after its completion. The low-carbon and environmental protection design runs through all the details of the “China Zun”. The pipe fittings stood out among many manufacturers participating in the bidding, and was designated as the only pipe fitting supplier by “China Zun”. Jianzhi Group will also provide the best quality pipe fittings and services for the “China Zun” project.
China Zun is a super high-rise building located in the core area of ​​CBD in Chaoyang District, Beijing. When completed, it will be the tallest landmark building in Beijing. The west side of the project faces the third phase of China World Trade Center, the current tallest building in Beijing, with a total height of 528 meters. It will be planned as the headquarters building of CITIC Group in the future. Construction started on September 12, 2011 and completed by the end of 2016, with an estimated total investment of 24 billion yuan. In April 2014, China’s Top Ten Contemporary Architecture Review Committee selected 20 buildings from more than 1,000 landmark buildings in China, synthesizing four indicators of age, scale, artistry and influence. The result is the ten largest contemporary buildings. China Zun is one of the shortlisted buildings in the preliminary evaluation. The concept of “China Zun” originated from the image of “Zun”, the most important treasure of traditional Chinese ritual vessels; the appearance of the building is a diamond-shaped mechanism, derived from bamboo ware, one of the traditional Chinese utensils; the space design at the top of the building is taken from the shape image of “Kongming Lantern”.