PRE-Galvanized Pipe
Pre-Galvanized Pipe
Pre-Galvanized Pipe shall be made from pre-galvanized steel strip in accordance with ASTM A446. The coated steel must be cold shaped and welded into the tube using a high-frequency induction welding process capable of producing a weld bead that is stronger than the parent metal. The exterior coating that has been damaged during welding must be restored by metalizing (spraying molten zinc wire). The interior weld area that has been damaged during welding must be left unprotected.
 PRODUCT FEATURES
The Application of Pre-Galvanized Pipe
Pre-galvanized steel pipes are widely utilized in a variety of applications, including steel structures, building structures, guard rails, fences, metal furniture, solar structures, and so on.
Dimensions and Sizes of Pre-Galvanized Pipe
DN | O. D. | W. T. | |||||||||||||||
Inch | mm | SCH5S | SCH10S | SCH10 | SCH20 | SCH30 | SCH40 | SCH60 | SCH80 | SCH100 | SCH120 | SCH140 | SCH160 | STD | XS | XXS | |
50 | 2″ | 60.3 | 1.65 | 2.77 | – | – | – | 3.91 | – | 5.54 | – | – | – | 8.74 | 3.91 | 5.54 | 11.07 |
65 | 2 1/2″ | 73 | 2.11 | 3.05 | – | – | – | 5.16 | – | 7.01 | – | – | – | 9.53 | 5.16 | 7.01 | 14.02 |
80 | 3″ | 88.9 | 2.11 | 3.05 | – | – | – | 5.49 | – | 7.62 | – | – | – | 11.13 | 5.49 | 7.52 | 15.24 |
90 | 3 1/2″ | 101.6 | 2.11 | 3.05 | – | – | – | 5.74 | – | 8.08 | – | – | – | – | 5.74 | 8.08 | – |
100 | 4″ | 114.3 | 2.11 | 3.05 | – | – | – | 6.02 | – | 8.58 | – | 11.13 | – | 13.49 | 6.02 | 8.56 | 17.12 |
125 | 5″ | 141.3 | 2.77 | 3.4 | – | – | – | 6.55 | – | 9.53 | – | 12.7 | – | 15.88 | 6.55 | 9.53 | 18.05 |
150 | 6″ | 168.3 | 2.77 | 3.4 | – | – | – | 7.11 | – | 10.97 | – | 14.27 | – | 18.26 | 7.11 | 10.97 | 21.95 |
200 | 8″ | 219.1 | 2.77 | 3.76 | – | 6.35 | 7.04 | 8.18 | 10.31 | 12.7 | 15.09 | 18.26 | 20.62 | 23.01 | 8.18 | 12.7 | 22.23 |
250 | 10″ | 273.1 | 3.4 | 4.19 | – | 6.35 | 7.8 | 9.27 | 12.7 | 15.09 | 18.26 | 21.44 | 25.4 | 28.58 | 9.27 | 12.7 | 25.4 |
300 | 12″ | 323.9 | 3.96 | 4.57 | – | 6.35 | 8.38 | 10.31 | 14.27 | 17.48 | 21.44 | 25.4 | 28.58 | 33.32 | 9.53 | 12.7 | 25.4 |
350 | 14″ | 355.5 | 3.96 | 4.78 | 6.35 | 7.92 | 9.53 | 11.13 | 15.09 | 19.05 | 23.83 | 27.79 | 31.75 | 35.71 | 9.53 | 12.7 | – |
400 | 16″ | 406.4 | 4.19 | 4.78 | 6.35 | 7.92 | 9.53 | 12.7 | 16.66 | 21.44 | 26.19 | 30.96 | 36.53 | 40.49 | 9.53 | 12.7 | – |
450 | 18″ | 457.2 | 4.19 | 4.78 | 6.35 | 7.92 | 11.13 | 14.27 | 19.05 | 23.83 | 39.36 | 34.93 | 39.67 | 45.24 | – | – | – |
500 | 20″ | 508 | 4.78 | 5.54 | 6.35 | 9.53 | 12.7 | 15.09 | 20.62 | 26.19 | 32.54 | 38.1 | 44.45 | 50.01 | – | – | – |
550 | 22″ | 558.8 | 4.78 | 5.54 | 6.35 | 9.53 | 12.7 | – | 22.23 | 28.58 | 34.93 | 41.28 | 47.63 | 53.98 | – | – | – |
600 | 24″ | 609.6 | 5.54 | 6.35 | 6.35 | 9.53 | 14.27 | 17.48 | 24.61 | 30.96 | 38.89 | 46.02 | 52.37 | 59.54 | – | – | – |
The Process of Producing Pre-Galvanized Pipe
The manufacturing process of pre-galvanized pipe is very similar to that of normal welded pipe. The only differences are the raw material and zinc spray. The raw material of the pre-galvanized pipe is pre-galvanized strips, and the strips are galvanized already before pipe production. However, the welding seam will be the only part without zinc coating, so the zinc spray process shall be applied after the welding process.
What is Pre-Galvanizing？
When steel components are used in the manufacturing of a more sophisticated completed product, they may be galvanized before assembly. This is referred to as pre-galvanization, or “pre-gal.” It is also known as “in-line,” “continuous,” or “mill” galvanizing. Steel components, such as sheets or wire, are galvanized using an automated process before being reduced to size.
Depending on the type of component being galvanized, this automated procedure will vary. In general, the steel components are immersed for a short time in a “galvanizing bath” of molten zinc. Excess zinc is removed from the steel after it has been taken from the bath using a mechanical wiper, air knife, or steam. This results in somewhat thin zinc galvanized coating.
The Performance of Pre-Galvanized Pipe
The pre-galvanized pipe can also be galvanized to EN 10240 utilizing an automated technique. Immersion times are quite brief, and steam may be pushed through the bore of the tube after extraction to provide an acceptable surface finish. Although the coating thickness can reach 45-55 m, the majority of the product produced has a much thinner coating of 20-30 m.
Because pre-galvanized pipe materials are normally only immersed in the galvanizing bath for a short period of time, the coating is rather thin. Hot-dip galvanization produces a thicker zinc coating than pre-galvanization, which provides better rust and corrosion protection, especially for pipes that are frequently used outside and exposed to snow, ice, rain, and salt.
The zinc coating on the steel sheet must be in accordance with ASTM A525 Grade G90 and G120. The combined zinc weight of the external and interior surfaces must range from 0.90 oz/sq ft (or 0.45 oz/sq ft each side) to 1.20 oz/sq ft (or 0.60 oz/sq ft each side). These coating weights do not apply to the welded area on the inside.
The Difference Between Hot Dip Galvanizing and Pre-Galvanizing
Feature | Hot Dip Galvanization | Pre-Galvanizing |
Coating Thickness | Thick coating with minimum average requirements of 45-85μm within BS EN ISO 1461 | The coating thickness may vary, but it is typically circa 20μm for sheets and 20-30μm for tubes |
Coating Continually | Continuous coating over the whole object | The uncoated area at cut edges |
Coating Bond | Strong metallurgical bond with the base steel | Strong metallurgical bond with the base steel |
Coating Formability | Forming after hot dipped galvanizing is not advised as it may damage the coating | A thin coating may be normally formed without any damage |
Coating Appearance | Normally bright, but can be variable | Normally bright |
Abrasion Resistance | A thicker layer of hard zinc-iron alloy gives a high resistance to abrasion | Thin alloy layer with reduced resistance to abrasion |
Sacrificial Protection | Offer the highest level of sacrificial protection | Reduced sacrificial protection due to thin layer coating and at some uncoated areas (cut edges) |
