Despite the saturation of the market many varieties of high-tech polymer pipes, metal for the installation of heating systems, hot and cold water are used today enough wide. Metal pipes for these purposes mainly made of steel and copper, less of aluminum. Each type of such pipes, depending on the manufacturing material has a plurality of individual characteristics, providing ample opportunity for the customer when choosing maneuver.
One of the most common varieties of products are pipes made of steel with a zinc coating - material having many positive characteristics, but in a specific application. Consider what kind of material, and how to use galvanized pipes for heating.
Methods of production and the species of galvanized pipes
The main enemy of the steel pipe is corrosion. One way to protect against it is applying to the surface of a steel pipe a protective layer of zinc, whereupon the material ranked as a separate subgroup - galvanized pipe for water supply systems and heating.
The method is moderately expensive, so the cost of the steel pipe after galvanizing remains available - with an approximate ratio of the prices can be found on the data in the table:
| PRT-Pipe Size (Gazovodoprovodnoy) |
Price (rub. / M) | |
| black steel | galvanized | |
| 15h2,8 st1-3sp / ps | 33 | 50 |
| 20h2,8 st1-3sp / ps | 42 | 66 |
| 25h2,8 st1-3sp / ps | 59 | 95 |
| 32h2,8 st1-3sp / ps | 81 | 127 |
| 40h2,8 st1-3sp / ps | 90 | 155 |
| 50h2,8 st1-3sp / ps | 117 | 194 |
a zinc coating may be applied to a steel pipe manufactured by any technology --welded, with spiral seam, seamless, however galvanized pipes by a factor seam presence classified as well as ordinary.
Independent standard for galvanized products do not exist. Steel pipes with a zinc protection made in accordance with the regulations for electric products with straight seam (GOST 10704) and the material for pipelines (GOST 3262-75).
Methods for coating zinc
The zinc coating, depending on the operating conditions of the pipe, may be performed both on its outer surface and the inside.
There are 4 methods galvanizing pipes, each of which is applied depending on the dimensions and manufacturing requirements for strength and thickness of the zinc coating:
- hot - prepared part is immersed in molten zinc, which ensures high quality and durability of the coating, but the process of high energy consumption;
- cold - products one of the ways of painting a coloring agent containing zinc that is not provides a high strength of the zinc coating (applied for corrosion protection already mounted structures);
- electro-galvanic - electrolysis is carried out coating process, i.e. deposition on the workpiece (anode) zinc dissolved in the electrolyte (cathode), by passing an electrical current;
- gazotermicheskih - a device protective coating by flame spraying on the surface of the part of the zinc powder drawback - porosity and low strength layer;
- thermodiffusion - parts are covered with a zinc layer, located after heating to 2500 deg. in the vapor state is used for processing of small parts in large quantities - screws, bolts, nuts, washers, requiring high adhesion of the zinc to the metal.
Parameters steel tube coated with zinc
The main technical parameters of steel tubes coated with zinc are:
- an outer diameter (10.2 - 165 mm);
- w 1 m tube (0.4 - 22 kg);
- nominal width (6 - 150 mm);
- wall thickness (1.8 - 5.5 m);
- length (4 - 12 m).
As with conventional tubes, the walls of galvanized articles can be lungs, reinforced or standard, is assigned execution accuracy ordinary or elevated.
Important! The protective zinc coating must be applied to the entire surface of the article and have a thickness of 30 microns. Peeling off the protective layer, peeling and bulge on it are not permitted ( "steel tubes for water and" Technical conditions GOST 3262-75, rev. №4,6).
Advantages and disadvantages
Most characteristics AIV-galvanized pipes, both positive and negative, coincides with the parameters of black steel, but there are individual features.
dignity
- Strength (particularly tear).
- Fire resistance.
- Low coefficient of thermal elongations.
- Absolute tightness.
- Resistance to shock loads.
- Durability.
- Ability to use as a heat exchanger.
- Possibility of installation, including maintenance, with their own hands.
- Two assembly method (welding, threaded connection).
- Simple disposal.
In favor of the steel-pipe GWP by the fact that the outer lining of the pipeline by pipeline to consumers is allowed only from a steel material.
disadvantages
- A significant proportion.
- Electrical conductivity.
- High thermal conductivity (heat insulation pipe in need of heating and hot water systems).
- Exposure to zinc corrosion damage protection.
Methods of assembly and mounting
Galvanized pipes, forming a heating or hot water system, mounted in three different ways:
- welding;
- Flanged;
- threaded connection;
- soldering.
Each of these methods has its pluses and minuses. Consider these methods of installation and related nuances.
Welding galvanized pipes
Gas conducting tube coated with zinc, or may be coupled electro gas welding - both types of installation are convenient in that they take little time. But there is one negative factor, the effect of which should be minimized as to completely eliminate it will not work.
The fact that the weld temperature reaches 1200 degrees, and zinc boils at 906 degrees and the heating during the welding process starts to evaporate. In this case, the following occurs:
- detrimental effect on the zinc vapor welder, until the onset of suffocation, because they are toxic;
- evaporating zinc Bare steel and makes it vulnerable to corrosion;
- contribute to the formation of zinc vapors in the weld cracks and pores, reducing bond strength.
To maximize the localization of these processes before the start of welding, apart from the mandatory effective ventilation device space, proceed as follows.
- prepare the joint edge, i.e. they perform outer chamfer and remove zinc coating is 25-30 mm in both sides of the connection;
- produce a weld joint with subsequent stripping from weld slag and coating the bare portion zinc bearing pipe paint (content of zinc powder - 94% binder - 6%) - cold galvanizing.
To prevent boiling of the zinc layer may be treated with hydrochloric acid, the abutment 5 cm in both directions, but in this case the acid will be generated during vaporization welding.
Important! According n. SP 4.6 (Building Regulations) 73.13330.2012 device welds in steel galvanized pipes are not allowed, since the inner zinc pipe surface prior to welding is not removed, and zinc vapors, formation of which is not avoided, cause the formation of pores in the seam and shells. But this document - voluntary application and, if the project is not a reference to the mandatory use of the item, the installation of galvanized pipe welding is permissible.
In order to minimize the quality of electric zinc exposure installation should be carried out with the following recommendations:
- perform welding at a low speed, but avoid burning the tube, and with a higher value of current intensity;
- use with rutile electrodes (electrode composition comprises titanium oxide).
Electric welding pipe zinc coated welder requires specific skills. In addition the composition of the outer coating of the electrode, the quality of the weld affects the thickness of its shaft, causes the output arc - too thick electrode would pierce the wall, and thin would not provide the required strength of the weld connection. For welding galvanized pipes with a wall thickness of 1.5 - 5 mm, a diameter of 2-3 mm electrodes.
Flanged galvanized pipes
This method is based on interconnecting bolts fragments of pipes, the ends of which are welded flanges - steel ring with an inner diameter equal to the outer diameter of the tube, and holes for mounting around the perimeter bolts. Two different fragments flange are applied to each other with an intermediate seal and tightened bolt-nuts or bolts.
The same negative factor is present in this method of installation, and in that the weld joint - in welding the flanges to pipes occurs zinc boiling and destruction of the protective layer in the vicinity of the welding seam. Therefore, it is also necessary to take measures to localize the impact of temperature on the zinc layer, and after clean closure welding seam and cause it to the zinc anti-corrosion coating (cold galvanizing).
Flanged not compact, so it is used in most cases when laying pipeline in utility rooms or outside. On butting the flange has an annular area, called mirror. Between two mirrors abutting flanges before contraction set paronita gasket with a hole the diameter of which must coincide with the inner diameter of the pipe. The outer diameter of the gasket is performed equal to a distance between the opposed fastening bolts.
Threaded connection
This installation method eliminates the need to use thermal bonding methods and is performed using various kinds of fittings intended for connecting the individual pipe pieces after cutting them thread.
Build on the thread also has its drawbacks:
- thread cutting process is time consuming and requires a different time;
- threaded tool (die) at threading steel layer removes a certain thickness with a protective zinc coating.
- sealing a threaded connection is provided by winding the thread-FUM tape or tow sealing paste with application of paint, which will eventually lose their properties and require replacement.
Pike galvanized pipes
To mount a heating or hot water system of pipes with a galvanized zinc coating without damaging the layer of solder is applied, which is performed in the following sequence:
- the mating ends of the pipe end and, if the wall thickness is greater than 3 mm, operate on the outer edges of the chamfer;
- joints degreased by heating, and then warmed up also ductility flux (composition HLS-B) thick layer applied to the surface which abuts with the proposed compound;
- ends with a gap of 2-3 m;
- the flame is exposed to excess oxygen.
Burner size is selected depending on the diameter and wall thickness of the galvanized tubes:
For quality soldering galvanized pipes must adhere to the rules: the size of the burner must be one less than the welding of the pipe of the same size without a zinc coating. During soldering flame should be concentrated on the connected edges and the joint gap to avoid heating and vaporization of zinc from the flux layer.
Connecting joints quality of produced soldering galvanized pipes do not require additional corrosion protection, but applying to the zinc bearing ink as insuring operation will not be superfluous.
Specificity use galvanized tubes in heating and hot water systems
Tubes coated with zinc in heating systems and water supply systems are used, taking into account operating conditions.
If the coolant temperature does not exceed 65 degrees, the zinc coating is successfully carrying out its functions. In the northern regions where the parameter is much higher, the inner zinc layer under high temperature reacts with water:
Zn + H2O = ZnO + H2.
Both substances, resulting from this interaction are negative factors:
- ZnO - it flakes which precipitate and clog the lumen of small diameter pipelines;
- H2 - is hydrogen, which in admixture with air in certain proportions explosive or at least forms a tube in the system.
Therefore, in the hot water and heating systems with a boiler water temperature above 60 degrees allowed tubes having only an outer protective zinc coating which will protect the pipeline from corrosion during periods just me. However, if water is spilled on the hot surface of the tube shell zinc begins to flake off the ground, however, To avoid this, it is necessary coating of such pipelines over zinc, which will lead to an even greater increase in the cost system.
Output: use in hot water and heating systems with a boiler water temperature above 60 degrees pipes, galvanized on the outside, unduly expensive and galvanized inside - is harmful and dangerous.
conclusion
Water and gas Galvanized steel pipe - demanded to date material, but use and mount it should be taking into account the features a protective coating to a zinc advantages rationally used instead of becoming a factor only increases the cost works.
