All about the production of ventilation ducts. Air duct manufacturing technologies. Production of galvanized air ducts

Manufacturing on our own even small batches of air ducts required for equipping ventilation systems at various facilities, as a rule, is beneficial not only from an economic point of view. And if the company provides services for the provision of equipment for ventilation systems and performs their installation, the presence of its own production sites makes it possible to reduce prices and gain an advantage in the market.

Today, the production of air ducts can be carried out according to several technologies and be organized in different geographically. As for the organization of production, it can be:

Organized on a stationary production base;
Be mobile and deploy directly at the facility where the ventilation system is being installed;
Use combined approaches to organizing production.

Both the one and the other method of organizing production has its advantages, which ultimately allows you to reduce the cost finished products and transportation costs. For example, when working on large objects, it is often much more profitable to deliver machines and equipment to the site than to incur significant transportation costs for the transportation of air ducts manufactured in the main production.

Technologies for the production of rectangular air ducts

Rectangular and square air ducts are often used for arranging ventilation systems and can be manufactured using welding or soldering, or using a mechanical lock. The technology itself for the production of rectangular air ducts is quite simple and consists of several stages:

First, a sheet of metal is cut according to the scan of the finished product;
Then the finished workpiece is bent on a sheet bending machine until it is given the required shape;
Sealing of joints is carried out either using the seam lock technology, welding or soldering.

It is worth noting that a mechanical lock is faster to manufacture and the manufacturing technology of such a joint is less laborious, its use leads to a slightly higher metal consumption. In addition, the joints of the duct turn out to be leaking and can worsen the performance of the ventilation system with a significant length. However, with a small thickness of a metal sheet, and therefore a low cost of an air duct, such a lock can be considered optimal for the manufacture of air ducts for ventilation hoses of small and medium length.

With a small thickness of the sheet from which the air duct is made, soldering can be used to achieve complete tightness of the structure. If the metal thickness is from 1.5 mm or more, a welded joint of the seam can be used.

Round air ducts can be manufactured in two ways:

By bending on a rolling machine with subsequent seam welding or using a folded lock;
According to the technology of winding on a winding machine from a metal tape.

The rolling technology has almost the same features as the manufacture of rectangular air ducts. As for winding air ducts, the manufacturing process is simpler and does not require subsequent sealing. In addition, winding air ducts can be made of non-standard length, which allows you to optimize costs in the manufacture of non-standard ventilation systems.

Good day!

No residential, office, retail, industrial or warehouse space today . And galvanized steel air ducts deservedly occupy a leading position among various ventilation ducts. We will tell you about the reasons for this popularity and how not to get lost in the variety of the presented assortment in the next article.

Galvanized air ducts are the most common type of ventilation pipes. Which is easily explained.

Advantages of galvanizing:

Low weight, due to which the structures to be installed create minor loads on the buildings. In addition, the lightness of the material facilitates the process of delivery to the installation site and engineering work.
The flexibility of the material makes it possible to give any shape to the air duct elements, which not only expands their model range, but also improves the aerodynamic characteristics of the line.
Durability and resistance to open fire and corrosive environments. This significantly expands the scope of use and increases the service life of ventilation pipes made of thin sheet galvanized steel from 10 years or more.
Low cost.

Galvanized ventilation ducts are easy to maintain. They do not require preliminary priming, since the metal is not subject to an active corrosive process. Aesthetic appeal allows them not to be painted.

The disadvantages of galvanized steel include:

Increased noise level typical of any metal structure. However, this problem can be solved either by a well-thought-out wiring diagram that minimizes the number of bends and transitions, or sound insulation.
The tendency to form and accumulate condensation. As a solution - pipeline insulation.
Susceptibility to deformation as a result of powerful mechanical stress caused by strong impact, displacement or fall of the structure. Under normal operating conditions, such difficulties do not arise.

The combination of quality, material cost and a variety of technologies to minimize disadvantages makes galvanized pipelines the most popular types of air ducts used in the arrangement of ventilation ducts.

Types of galvanized air ducts

The variety of galvanized air ducts is due to a number of technical characteristics that are endowed with products during the production process. So the following types of products are distinguished:

By the shape of the cross-section: rectangular or round.
By type of seam: welded and folded.
In the direction of the seam: spiral-wound and longitudinal seam.

Rectangular and round

	Round steel duct	Steel rectangular duct
Aerodynamics	Even air distribution and, as a result, improved aerodynamics.	High aerodynamic resistance
Air mass movement speed	High.	Low. For large circuits, forced air circulation is required.
Noise figure	Good sound absorption properties due to the absence of turbulence.	High quality soundproofing is required.
Care requirements	The high air velocity prevents dirt and dust particles from settling in the piping.	Requires periodic cleaning of the pipeline.
Estimated data	The cross-sectional shape makes it difficult to calculate the data on the area of the structure.	Rectangular shape makes calculations easy.
Mounting	The products are lighter and do not require reinforced fasteners. Time saving and low labor costs.	The severity of the structure requires the arrangement of reliable clamps.
Price	Cheaper by an average of 30%. Minimum costs for transportation, storage, installation and thermal insulation.	In view of the high aesthetics, the costs of masking and decorating the highway disappear.

The advantage of rectangular air ducts lies in the configuration and variety of the model range, which allows the ventilation circuit to be adapted to the characteristics of any room without compromising the calculated cross-sectional area, playing with the width and height of the pipe.

Straight seam and spiral wound

Straight seam are made by bending a sheet of galvanized steel into a round or rectangular pipe... This technology reduces the cost of production, but it also limits its length, which increases the number of pipeline connecting elements.

Spiral-wound (spiral-lock or spiral-welded) air ducts are twisted from a thin metal tape. In this case, the seam goes in a spiral and plays the role of a stiffener, which increases the strength of the pipe, and when using the welding method, ensures its tightness.

Spiral wound air ducts are characterized by:

less weight;
increased tightness;
a small number of butt elements;
the increased speed of movement of the air mass, because the spiral shape creates additional rotation in a closed loop;
reduced noise level.

However, the ribbing of the surface provokes the accumulation of dust inside the pipeline.

Tightness and tightness

Tightness and pressure are indicators that ultimately determine the efficiency and cost of the ventilation circuit. A leaky pipeline reduces the quality of air exchange and entails an unreasonable overestimation of the capacity of pumping equipment, an increase in energy costs, and also leads to the accumulation of condensate inside the pipes.

There are 3 classes of air duct tightness:

A (low). Air permeability from 1.35 to 0.45 l / s / m².
B (middle). Air permeability from 0.45 to 0.15 l / sec / m².
C (high). Air permeability less than 0.15 l / s / m².

According to the coefficient of internal pressure (density), there are:

H-models (normal pressure). Designed for ventilation and smoke evacuation systems of objects belonging to the category of fire hazard class "B" and "G". They do not require strong sealing, because allow a certain percentage of leakage. Rubber seals are commonly used as a sealant.
P-models (dense). Installed at facilities equipped with powerful pumping equipment and classified as fire and explosion hazard. They are characterized by 100% tightness of seam joints and the presence of a sealed lock at the junction of the elements with each other.

What is better and where is it used?

The protective layer of zinc resists the destructive effects of open air, moisture and ultraviolet radiation. Therefore, galvanized ventilation ducts are actively used both indoors and outdoors for arranging systems:

natural and forced ventilation,
air conditioning;
aspiration (removal of small particles contained in the air);
smoke removal (removal of combustion products);
exhaust gas removal;
transportation of gas mixtures, air purifiers and humidifiers.

Even the organization of a conventional hood in the kitchen is most often carried out by means of steel air ducts.

When deciding on the use of one or another type of air duct, one should be guided by the features of the operation of the future structure:

Rectangular ducts are used to save space in small, predominantly residential or office space(private houses, apartments or offices).
For the aspiration and transport of hazardous gases, circular pipes with a welded seam are suitable, providing maximum speed air movement and complete body tightness.
In industry, preference is given to round shapes, which are characterized by both the highest efficiency and the lowest cost.

Elements of the ventilation system

The ventilation duct is always a complex structure, consisting of numerous elements that allow:

change the direction of the contour depending on the configuration of the premises;
bypass the ledges;
connect several circuits into a single network.

Elbows and ducts

The main elements of the duct that set its direction are ducts and bends. The former pave the way in a straight line, the latter change the geometry of the contour at an angle of 15⁰, 30⁰, 45⁰, 60⁰ or 90⁰.

Other fittings

Ventilation is a complex and ramified network of canals, which is problematic to mount without appropriate elements. Such components are usually called fittings.

These include:

Adapters connecting the contours of different diameters - confusers and diffusers. The first narrows the highway, the second widens.
Tees and collar inserts that ensure the abutment of two lines.
Crosspieces used to cross two perpendicular air streams.
S-shaped adapters (wefts) connecting two contours that do not coincide in axis and / or section.
Round nipples and couplings connecting two round boxes. The former are inserted inside, the latter are put on over the pipes.
Plugs installed at the ends of the circuit.
A roof umbrella that prevents atmospheric precipitation from entering the ventilation shaft.
Supply and exhaust grilles and other fittings.

Dimensions (edit)

GOST

GOST 14918-80 - air ducts made of steel sheet with a thickness of 0.5 to 1 mm by rolling and designed to transport air with a humidity of not more than 60% and a temperature of less than 80⁰C.
GOST 5632-72 - air ducts characterized by a high degree of tightness, resistance to corrosion and high temperatures (about 500⁰C) and designed to move hot air and chemical gases.

Weights and diameters table

Production of galvanized air ducts

Galvanized air ducts are manufactured on special metalworking equipment from thin sheet cold-rolled steel in accordance with the standards established by the state (SNIP 41-01-2003 and TU 4863-001-75263987-2006). Metal cutting takes place in automatic mode according to the parameters set by the program.

Parts of circular cross-section are processed by rollers, which set the required diameter for the workpiece, followed by rolling the longitudinal edge on a folding machine.
Spiral-wound are made using a different technology: steel 137 mm wide is twisted in a spiral with a seam inward.

The use of high-quality galvanizing does not allow peeling of the galvanized coating from the metal in the places where the product is folded.

Technological standards prescribe for each type of section to use metal of a certain sheet thickness:

Average cost and where to buy

The cost of galvanized steel air ducts depends on the size of its cross-section and the thickness of the metal. The price is calculated for 1 m². On average, the cost of 1 m² of a product on the market is about 320 rubles. Installation work will cost an average of 700 rubles. for the same square meter.

Despite the wide representation of air ducts in online stores, it is still worth buying them directly from the manufacturer, who is able to accompany each product with a quality certificate.

How to choose?

The operation of the air exhaust system (SVO) depends on how correctly its cross-sectional area is calculated.

S - Sectional area.

P - Productivity of CBO.

v - The speed of movement of the air mass (for residential premises, an indicator of 3-4 m / s is used).

Determination of ventilation capacity involves determining the amount of air required for comfortable stay in room. It is calculated in 2 ways:

By volume of required air:

P - Productivity of CBO.

A - The number of people in the room for an hour.

n - Air consumption rate according to SNIP 41-01-2003 and MGSCh 3.01.01.

By the frequency of ventilation (ventilation):

P - Productivity of CBO.

V - The volume of the room (with equal data, the whole room)

k - The ventilation rate established by the SNIP 41-01-2003 standards.

Shape and diameter

The quality of air exchange, energy efficiency and design of the room depend on the selected configuration and size of the duct section. Therefore, the choice of air ducts should be approached in detail:

The smaller the diameter of the air duct, the higher the speed of movement of the air mass. It is important to be guided by the "golden mean" principle, since the higher the speed, the higher the noise level.
Round air ducts provide faster air movement, are easier to install and are cheaper.
Rectangular are stronger and harmoniously fit into the design of any room.

Construction and rigidity

Depending on the specifics of the application of the structure, there are:

rigid, semi-rigid, or flexible;
standard or thermally insulated;
fire retardant.

The tighter the seams, the stronger the connection and the longer the service life.

Material

Galvanized ventilation ducts are manufactured standard view and insulated.

The construction of insulated models provides a special insulating layer made of mineral fiber, polyurethane, foam elastomer, felt or other materials. They maintain the optimum air temperature inside the circuit, preventing the formation and freezing of condensation on the walls. In addition, they reduce the noise level.
Zinc coating can be single-sided or double-sided. Due to the formation of condensate inside the circuit, double-sided galvanizing is more practical, because protects the circuit from internal corrosion process.

Not so long ago, aluminum-zinc-coated air ducts appeared on the market, the coating of which is 95% zinc and 5% aluminum. They are characterized by greater plasticity and improved anti-corrosion properties.

Fastening

How to fix the air ducts depends on the configuration:

with a circular cross-section, coupling, bandage and nipple connection of elements are used;
rectangular air ducts are fastened with latches and mounting angles.

Welding is sometimes used.

Rules for installing galvanized ventilation

The laying of ventilation ducts made of thin-sheet galvanized steel is carried out in stages.

For the manufacture of air ducts, metal, non-metal and metal-plastic materials are used, as well as building structures. Materials for the manufacture of air ducts are selected depending on the characteristics of the medium transported through the air ducts.

Duct materials
Characteristics of the transported medium	Products and materials

Air with a temperature of no more than 80 ° С with a relative importance of no more than 60%	Concrete, reinforced concrete and gypsum ventilation blocks; gypsum plasterboard, gypsum concrete and wood concrete boxes; sheet, galvanized, roofing, sheet, coil, cold-rolled steel; fiberglass; paper and cardboard; other materials that meet the requirements of the specified environment






The same, with a relative humidity of more than 60%	Concrete and reinforced concrete blocks; galvanized sheet steel, sheet steel, sheet aluminum; plastic pipes and plates; fiberglass; paper and cardboard with appropriate impregnation; other materials that meet the requirements of the specified environment





Air mixture with reactive gases, vapors and dust	Ceramic and pipes; plastic pipes and boxes; blocks of acid-resistant concrete and plastic concrete; metalloplast; Sheet steel; fiberglass; paper and cardboard with protective coatings and impregnation corresponding to the transported medium; other materials that meet the requirements of the specified environment

Note: Air ducts made of cold-rolled and hot-rolled steel sheets must have a coating that is resistant to the transported medium.

Carbon steel of ordinary quality by the rolling method is hot-rolled, if the billet is preheated, and cold-rolled, i.e. without heating the workpiece. In terms of thickness, such steel is subdivided into thick-sheet steel - with a thickness of 4 mm or more and thin-sheet steel - up to 3.9 mm thick. Thin sheet steel with a thickness of 0.35 to 0.8 mm is called roofing.

Hot rolled sheet steel are made in sheets with a thickness of 0.4 ... 16 mm, a width of 500 ... 3800 mm, a length of 1200 ... ... 9000 mm and in rolls with a thickness of 1.2 ... 12 mm, a width of 500 ... 2200 mm. They are used for the manufacture of general ventilation and aspiration ducts.

Cold rolled steel sheet made in sheets with a thickness of 0.35 ... 0.65 mm and in rolls with a thickness of 0.35 ... 3 mm. They are used for the production of spiral-seam air ducts.

Galvanized sheet steel produced with a double-sided galvanized coating that protects steel from corrosion, in sheets with a thickness of 0.5 ... 3.0 mm, a width of 710 ... 1500 mm. They are used for the manufacture of folded air ducts only.

Cold Rolled Carbon Steel Coil used with a width of 100 ... 1250 mm, a thickness of 0.6 ... 2 mm.

Cold Rolled Low Carbon Steel Strip 0.05 ... 4 mm thick, up to 450 mm wide are used for the manufacture of spiral-lock air ducts.

In the manufacture of air ducts and parts of ventilation systems, construction materials are widely used - section and shaped steel, as well as rolled aluminum.

Strip steel produced in width from 12 to 200 mm, thickness from 4 to 16 mm. These products are delivered in skeins or strips, depending on the size. Flanges and fasteners are made of strip steel.

Corner equal steel make profiles No. 2 ... No. 16, which corresponds to the width of the shelf in centimeters; the thickness of such steel is from 3 to 20 mm. Frames, air duct flanges are made of steel.

Non-ferrous metals

Aluminum- silvery white, light (ρ = 2700 kg / m3) and ductile metal. Interacting with oxygen in the air, aluminum is covered with a thin and durable film of aluminum oxide, which protects the metal well from corrosion. Seamed and welded air ducts are made of aluminum.

Sheets of aluminum and aluminum alloys, produced with a thickness of 0.4 to 10 mm, a width of 400, 500, 600, 800 and 1000 mm, a length of 2000 mm, are used for the manufacture of air ducts and individual parts of ventilation systems.

Extruded corners of aluminum and aluminum alloys are produced with shelf widths from 10 to 250 mm. With the same flange width, the profiles can have different thicknesses. Separate elements of network equipment are made from the corners.

Aluminum foil produced in thickness from 0.05 to 0.4 mm and supplied in rolls. Use foil for flexible corrugated air ducts. The height of the corrugation is 4 mm, the distance between the corrugations is 10 mm. Such air ducts bend easily and serve for connection to local suction units.

Titanium- a silvery-white refractory metal with high corrosion resistance (especially to acids), sufficiently ductile, with a density ρ = 4500 kg / m3. The high strength of titanium alloys remains at temperatures from -253 to +500 ° C.

Technically pure titanium grade VT1-00 or VT1-0, as well as low-alloyed alloys of increased plasticity grade CT4-0 or CT4-1 in the form of sheets with a thickness of 0.4 to 4 mm are used for the manufacture of air ducts. Titanium air ducts are generally welded.

Copper- ductile reddish metal, heat and electrical conductive, sufficiently ductile, which allows it to be processed by rolling, stamping, and drawing. As a rule, pure copper is not used in ventilation systems; usually use copper alloys with other metals. An alloy of copper and zinc is called brass. Compared to copper, brass is stronger, more ductile and harder, more resistant to corrosion, and has good mold filling during casting.

Copper-zinc alloys (brass) are produced in seven grades: L96, L90, L85, L80, L70, L68, L62 (the numbers indicate the average percentage of copper in the alloy). Spark-proof ventilation equipment is made of brass.

Metal-reinforced plastics

Metalloplast- structural material, which is a low-carbon cold-rolled sheet steel covered with a film. The industry produces metal-plastic of two types: with one- and two-sided coating.

Metalloplast with one-sided coating produced in the form of a steel tape 0.5 ... 1 mm thick, protected on one side with a polyvinyl chloride film with a thickness of (0.3 ± 0.03) mm. Metalloplast is supplied in rolls with a strip width of (1000 ± 5) mm, weighing up to 5.5 tons. The outer diameter of the roll is not more than 1500 mm, the inner diameter is (500 ± 50) mm.

Metalloplast with double-sided coating is a steel tape 0.5 ... 0.8 mm thick, both sides of which are protected by a modified polyethylene film with a thickness of 0.45 mm.

Metalloplast has properties inherent in metal and plastics; it is plastic, can be processed on mechanisms that manufacture folded air ducts.

Nonmetals

Sheets made of plasticized polyvinyl chloride (vinyl plastic sheet) are made from an unplasticized polyvinyl chloride composition with the addition of auxiliary substances (stabilizers, lubricants and others) by pressing films or extrusion.

Sheets of unplasticized polyvinyl chloride are produced with a length of at least 1300 mm, a width of at least 500 mm. The thickness of the sheets depends on their brand and is for sheet vinyl plastic: VI - from 1 to 20 mm; VNE and VP - from 1 to 5 mm; VD - from 1.5 to 3 mm.

Vinyl plastic sheet has high mechanical strength, lends itself well to both manual and mechanical processing on conventional metal-woodworking machines. When heated, it acquires plasticity and is easily molded. After cooling the heated vinyl plastic, all its mechanical properties are restored. Viniplast is an electrical insulating material.

I use sheet vinyl plastic in the manufacture of air ducts as an anticorrosive material operating at temperatures from -20 to + 00 ° C.

Polyethylene- synthetic polymer, dense, characterized by high chemical resistance. Applied at temperatures up to 60 ° C. A film for ventilation ducts is made of high-density polyethylene, which comes to the construction site in the form of a roll wound on a sleeve. A roll is wound 300 ... 400 m of film up to 4000 mm wide, from 30 to 200 microns thick.

Fiberglass- a material formed by interlacing mutually perpendicular strands of glass fiber. Flexible reinforced air ducts are made of SPL fiberglass, impregnated with latex, using glue and spring wire from carbon steel with a diameter of 2 ... 2.5 mm.

Textile materials

Types of air ducts

1. Round 2. Rectangular

Rice. 1. Details of air duct networks:

1 - straight sections of round air ducts (a) and rectangular (b) sections;

II - knots of branches of round ducts (v) and rectangular (d) sections;

III - bends and half-bends of round (d) and rectangular air ducts (e) sections;

IV - transitions;

1 - tee;

2 - transition;

3 - crosses;

4 - plug

Rice. 2. Standardized parts for circular air ducts: a- longitudinal seam straight part; b - spiral lock straight part; fittings: v - bend 90 degrees; G- bend 30, 45, 60 degrees; d - symmetrical transition to B == 400 mm; e-transition asymmetrical over V= 400 mm; f-internal nipple, designed to connect straight parts of air ducts to each other; s - external nipple, designed to connect the fittings of the air ducts to each other; and- end cap

Rice. 3. Unified details of rectangular air ducts: a - straight part: fittings; b - bend 90 degrees; v- outlet 45 degrees; G - stub; d - duck; e- transition from a rectangular section to a round one; f - transition from rectangular section to rectangular

3. Semi-oval

A - minor axis;

V- major axis

Rice. 5. Shaped parts of semi-oval air ducts:

a - bend 90 degrees:

a1 - vertical;

a2- horizontal;

b - asymmetrical transition;

v - the transition is symmetrical;

G - internal nipple;

d - stub;

e - tee;

f- inset in a circle;

s - transition from an oval section to a round one;

and - transition from oval to rectangular

4. Spiral-lock

Rice. 6. Spiral-lock air duct

Rice. 7. Installation diagram (a) for the production of spiral-lock air ducts:

1 - decoiler,

2 - a mechanism for cutting and welding the ends of the strip,

3 - belt degreasing mechanism,

4 - ribbon,

5 - roll forming mill,

6 - forming head,

7 - spiral-lock pipe

5. Spiral welded

Rice. 8. Spiral-welded air duct

6. Semi-rigid and textile

Rice. 9. Semi-rigid air ducts:

a- schematic diagram of a semi-rigid air duct;

b- semi-rigid air duct

Rice. 10. Textile duct

7. Reinforced plastic

Rice. 11. Air duct made of metal-plastic:

a -general form,

b - seam design,

c, d- double-sided and one-sided metal-plastic,

1- polyvinyl chloride film,

2 - glue,

3 - steel tape

Folded joints

Rice. 12 Types of folded joints;

a - recumbent fold,

6-fold double cut-off fold,

в - corner fold,

g - corner seam connection with grooved latches,

d - standing seam,

e-zig connection,

w-lath connection

Rice. 13. Seam connection of round elements on a zig

Rice. 14. Reclining fold

Rice. 15. Standing fold

Rice. 16. Corner fold

Figure 17 Pitsburgh (Moscow) fold

In the manufacture of air ducts, the sheets are interconnected:

welded (butt-weld or overlap)
on the folds

Welded connections

Rice. 1.2.1 Welded connections:

a - butt, 6 - overlap

Fig. 19. Diagrams of welding round air ducts:

a - overlap,

6 - along the bent edges on one side,

c - along the bent edges on both sides

Rice. 18. Classification of seams:

a - depending on the position of the parts to be welded,

6 - in the direction of efforts,

c - in length,

d - according to the degree of amplification

Rice. 20. Types of welded joints used in welding metal air ducts:

a - longitudinal seam for round and rectangular air ducts, paintings,

6 - circular seam for round bends,

c - welding of round flanges and fittings of rectangular air ducts,

d - welding of rectangular flanges and fittings,

e - welding of flanges of rectangular and round sections,

g - tacking of rectangular flanges,

h - welding of spiral-welded air ducts,

and - welding of ventilation ducts

Rice. 21. Welding scheme of a rectangular duct section:

a - welding of nodes,

6 - tacking a branch to a straight section

Rice. 22. Snap fold

Methods for connecting air ducts to each other

Flange connections

Angle flanges

Rice. 23. Angle steel flange

Flanges made of profiled galvanized tape

Rice. 24. Z-bar flange:

1 - Z-rail;

2 - C-rail;

3 - seal 8 x 15;

4 - inner corner;

5 - decorative corner

Rice. 25. Flange made of profile "tire"

Flat steel flange

Rice. 26. Flange made of strip steel for flanged air ducts with a diameter of 100 ... 375 mm

Sheet steel flange

Rice. 27. Sheet steel flange with collars

Rice. 28. Position of the closing transverse end

seam on round air ducts

Flangeless connections

Fig. 29. Wafer connection of rectangular air ducts:

a, b- the sequence of preparation of air ducts;

v- connection cross-section;

G- connection assembly;

1 - lock profile;

2 - rubber compressor;

3 - nylon corner;

4 - decorative corner;

5 - connecting rail;

6 - corner of stiffness

Socket (nipple) connection

Rice. 30.Nipple connection for circular ducts

Bandage connection

Rice. 31. Bandage connections of round duct links:

a - with rubber seals;

b - with butteprol sealant;

c - riveted;

d - with inserts during installation:

1 - bandage;

2 - sealant;

3 - steel corners;

5 - branch pipe;

6 - an apron;

7 - air duct;

8 - bandage with buteprol sealant;

9 - bottom loop;

10 - buteprol

Telescopic connection

Rice. 32. Telescopic duct connection:

a - on self-tapping screws;

b - using combined rivets;

1 - self-tapping screw;

2 - blind rivet

Rice. 33. Joining parts with one-sided riveting:

1,2 - details;

3 - rivet body;

4 - rod head;

5 - weakened cross-section of the rod;

6 - riveter or gun;

7 - rivet collet;

8 - rod.

Bar connection

Fig. 34. Steel bar connection

air ducts:

a - general view;

b - types of planks;

c - T-shaped slats

Production of round air ducts

Rice. 2.1. Typical technological layout of the production area for the manufacture of rebated air ducts:

a - straight sections;

6 - fittings;

1- container for metal;

2 - marking table;

3 - guillotine scissors;

4 - bending mechanism;

5- rolling mechanisms;

6- roller tables;

7 - containers for flanges;

8 - spot welding machine;

9 - folded rolling mechanisms;

10- mechanisms for flanging;

11- workbenches;

12 - painting conveyor;

13 - mechanism for

flanging of rectangular air ducts;

14 - welding transformer;

15 - folding mechanism;

16 - die-cutting mechanism;

17 - a mechanism for bending curved edges;

18 -zig machine;

19 - mechanism for upsetting corner folds;

20 - selenium rectifier

Manufacturing sequence

Work cycle	Operation	Equipment and tools	Operation sketch
Marking and cutting of blanks	Cut both sides of a standard sheet at a 90 ° angle (if necessary)	Guillotine shears
	Mark the elements of the ventilation blank	Marking table, templates, scribe, ruler, compasses
	Cut out corners of elements	Manual pneumatic scissors
	Straight cutting of elements according to the marking	Guillotine shears
	Curvilinear cutting of elements by marking	Die cutting mechanism
Procurement of semi-finished products	Roll seam (straight)	Folded rolling mechanisms
	Roll curved seam and edge	Curved edge forming mechanism
	Roll (bend) workpiece elements	Rolling mechanisms
		Bending mechanisms
	Cut elements from the drawer side to form a ridge and corrugation	Mechanisms for the manufacture of bends, ring templates, rollers
Assembling the elements	Assemble the ventilation blank, close and close the fold	Fold upsetting mechanism
	Assemble the ventilation blank, close and close the fold	Locksmith's workbench; hammer
	Assemble the ventilation blank on the zig	Mechanism for making bends
	Collect the elements of the parts on the rail and besiege	Locksmith workbench, mallet, hammer
Flanging
	Install the flanges on the ends of the assembled products and flange onto the flange mirror or weld	Semi-automatic welding in the environment with 2
Coloration	Air duct painting and drying	Paint conveyor
Picking and marking
Stacking in a warehouse or in a container

INTRODUCTION

Welding, along with casting and forming, is the oldest technological operation mastered by man in the Bronze Age during the acquisition of experience in working with metals. Its appearance is associated with the need to combine various parts in the manufacture of tools, military weapons, jewelry and other products.

The first welding method was forging, which provided a sufficiently high quality of the joint for those times, especially when working with ductile metals such as copper. With the advent of bronze (harder and worse forging), casting welding arose. In casting welding, the edges of the parts to be joined were molded with a special earthen mixture and filled with heated liquid metal. This filler metal fused with the parts and solidified to form a seam. Such compounds were found on bronze vessels that have survived from the times of Ancient Greece and Ancient Rome.

With the advent of iron, the range of metal products used by man has increased, therefore the scope and scope of welding has expanded. New types of weapons are being created, the means of protecting a warrior in battle are being improved, chain mail, helmets, and armor appear. For example, in the manufacture of chain mail, more than 10 thousand metal rings had to be joined by forge welding. New casting technologies are developing, knowledge is gradually being acquired related to heat treatment of steel and giving it different hardness and strength. Often this knowledge was obtained by chance and could not explain the essence of the processes taking place.

For example, a manuscript found in the Temple of Balgon in Asia describes the process known to us as steel hardening: “Heat the dagger until it shines like the morning sun in the desert, then cool it down to the color of royal purple by sticking the blade into the body a muscular slave. The strength of a slave, turning into a dagger, gives him firmness. " Nevertheless, despite the rather primitive knowledge, even before our era, swords and sabers were made that had unique properties and were called Damascus. In order to give the weapon high strength and hardness and at the same time provide plasticity, which did not allow the sword to be fragile and break from impacts, it was made layered. Alternately, in a certain sequence, hard layers of medium or high carbon steel and soft strips of low carbon steel or pure iron were connected by welding. The result was a weapon with new properties that cannot be obtained without the use of welding. Subsequently, in the Middle Ages, this technology was used for the manufacture of highly efficient, self-sharpening plows and other tools.

Forge and foundry welding for a long time remained the main method of joining metals. These methods fit well into the production technology of that time. The profession of a blacksmith-welder was very honorable and prestigious. However, with the development in the XVIII century. machine production, the need for the creation of metal structures, steam engines, various mechanisms has increased dramatically. The known welding methods in many cases ceased to meet the requirements, since the absence of powerful heat sources did not allow uniformly heating large structures to the temperatures required for welding. Riveting became the main method of obtaining permanent joints at this time.

The situation began to change at the beginning of the 20th century. after the creation of the Italian physicist A. Volta sources of electrical energy. In 1802, the Russian scientist V.V. Petrov discovered the phenomenon of an electric arc and proved the possibility of its use for melting metal. In 1881. Russian inventor N.N. Benardos proposed using an electric arc burning between a carbon electrode and a metal part to melt its edges and connect to another part. He named this method of joining metals "electrohephaestus" in honor of the ancient Greek god-blacksmith. It became possible to connect metal structures of all sizes and various configurations with a strong welded seam. This is how electric arc welding appeared - an outstanding invention of the 19th century. She immediately found application in the most complex industry at that time - steam locomotive construction. The discovery of N.N. Bernardos in 1888 was improved by his contemporary N.G. Slavyanov, replacing the non-consumable carbon electrode with a consumable metal one. The inventor proposed to use slag, which protected the weld from air, making it more dense and durable.

At the same time, gas welding developed, in which the flame formed during the combustion of a combustible gas (for example, acetylene) mixed with oxygen was used to melt the metal. At the end of the XIX century. this method of welding was considered even more promising than arc welding, since it did not require powerful sources of energy, and the flame, simultaneously with the melting of the metal, protected it from the surrounding air. This made it possible to receive enough good quality welded joints. Around the same time, thermite welding began to be used to join the joints of rail tracks. When termites (a mixture of aluminum or magnesium with iron oxide) are burned, pure iron is formed and a large amount of heat is released. A portion of termite was burned in a refractory crucible and the melt was poured into the gap between the joints being welded.

An important stage in the development of arc welding was the work of the Swedish scientist O. Kelberg, who in 1907 proposed to apply a coating on a metal electrode, which, decomposing during arc burning, provided good protection of the molten metal from air and its alloying with elements necessary for high-quality welding. After this invention, welding began to find more and more applications in various industries. Of particular importance at this time were the works of the Russian scientist V.P. Vologdin, who created the first welding department at the Polytechnic Institute in Vladivostok. In 1921 at Far East the first welding shop for ship repair was opened, in 1924 the largest bridge across the Amur River was repaired using welding. At the same time, tanks were created for storing oil with a capacity of 2000 tons, a generator for Dneproges was made by welding, which was two times lighter than a riveted one. In 1926, the first All-Union Welding Conference was held. In 1928, there were 1200 units for arc welding in the USSR.

In 1929, a welding laboratory was opened in Kiev at the Academy of Sciences of the Ukrainian SSR, which in 1934 was transformed into the Institute of Electric Welding. The institute was headed by a famous scientist in the field of bridge construction, Professor E.O. Paton, after whom the institute was later named. One of the first major works Institute was developing in 1939 automatic submerged arc welding. It made it possible to increase the productivity of the welding process by 6-8 times, to improve the quality of the joint, to significantly simplify the work of the welder, turning him into an operator to control the welding installation. This work of the institute was awarded the State Prize in 1941. Automatic submerged-arc welding played a huge role during the Great Patriotic War, for the first time in the world it became the main method of joining armor plates up to 45 mm thick in the manufacture of the T34 tank and up to 120 mm in the manufacture of the IS-2 tank. In the conditions of a shortage of qualified welders during the war, the increase in welding productivity due to automation made it possible to short term significantly increase the production of tanks for the front.

A significant achievement of welding science and technology was the development in 1949 of a fundamentally new method of fusion welding, called electroslag welding. Electroslag welding plays a huge role in the development of heavy machine building, as it allows welding very thick metal (more than 1 m). An example of the use of electroslag welding is the manufacture of a press at the Novokramotorsk Machine-Building Plant by order of France, which can create an effort of 65,000 tons. The press has a height equal to the height of a 12-storey building, and its weight is twice the weight of the Eiffel Tower.

In the 50s. of the last century, the industry has mastered the method of arc welding in an environment of carbon dioxide, which has recently become the most common welding method and is used in almost all machine-building enterprises.

Welding is actively developing in the following years. From 1965 to 1985, the volume of production of welded structures in the USSR increased 7.5 times, the fleet of welding equipment - 3.5 times, the output of welding engineers - five times. Welding began to be used for the manufacture of almost all metal structures, machines and structures, completely replacing riveting. For example, the usual a car has more than 5 thousand welded joints. The pipeline through which gas is supplied from Siberia to Europe is also a welded structure with more than 5 thousand kilometers of welded seams. No high-rise building, TV tower or nuclear reactor can be manufactured without welding.

In the 70-80s. new methods of welding and thermal cutting are being developed: electron-beam, plasma, laser. These methods make a huge contribution to the development of various industries. For example, laser welding allows you to qualitatively connect the smallest parts in microelectronics with a diameter and thickness of 0.01-0.1 mm. The quality is ensured by the sharp focusing of the monochromatic laser beam and the most precise dosage of the welding time, which can last 10-6 seconds. Mastering] laser welding made it possible to create a whole series of new element base, which in turn made it possible to manufacture new generations of color televisions, computers, control and navigation systems. Electron beam welding has become an indispensable technological process in the manufacture of supersonic aircraft and aerospace vehicles. The electron beam allows you to weld metals up to 200 mm thick with minimal structural deformations and a small heat-affected zone Welding is the main technological process in manufacturing sea vessels, platforms for oil production, submarines. The modern nuclear submarine, about 200 m high and a 12-storey building, is a fully welded structure made of high-strength steels and titanium alloys.

Without welding, the current achievements in space would not have been possible. For example, the final assembly of the missile system is carried out in a welded assembly shop weighing about 60 thousand and a height of 160 meters. The missile holding system consists of welded towers and masts with a total weight of about 5 thousand tons. All critical structures at the launch site are also welded. Some of them have to work in very difficult conditions. The impact of a powerful flame at the start of the rocket is absorbed by a welded flame divider weighing 650 tons, 12 m high. Complex welded structures are tanks for storing fuel, a system for supplying it to the tanks and the fuel tanks themselves. They have to withstand enormous hypothermia. For example, a liquid oxygen tank has a capacity of over 300,000 liters. It is manufactured with a double wall - stainless steel and mild steel. The diameter of the outer sphere is 22 m. The tanks for liquid hydrogen are designed in a similar way. The liquid hydrogen supply line is welded from a nickel alloy, it is located inside another aluminum alloy... The kerosene and superactive fuel lines are welded from stainless steel, while the oxygen supply lines are from aluminum.

With the help of welding, multi-ton BelAZ and MAZ trucks, tractors, trolleybuses, elevators, cranes, scrapers, refrigerators, televisions and other industrial and consumer goods are manufactured.

1. TECHNOLOGICAL SECTION

1 Description of the welded structure and its purpose

The fan casing works in particularly harsh conditions. It is directly exposed to dynamic and vibration loads.

The fan casing consists of

Pos 1 Body 1 piece

V = π * D * S * H = 3.14 * 60.5 * 0.8 = 151.98 cc.

Q = ρ * V = 7.85 * 151.98 = 1193.01 gr. = 1.19 kg

Pos 2 Flange 2 pcs.

fan welding deformation arc

V = π * (D bed 2. - D inside 2) * s = 3.14 * (64.5 2 -60.5 2) * 1 = 1570 cubic meters. cm

Q = ρ * V = 7.85 * 1570 = 12324.5 gr. = 12.33 kg.

Pos 3 Ear 2 pcs

V = h + l + s = 10 * 10 * 0.5 = 50 cubic meters. cm

Q = ρ * V = 7.85 * 50 = 392.5 g = 0.39 kg

Cross-sectional area of the weld

t. sh. = 0.5K² + 1.05K = 0.5 * 6² +1.05 * 6 = 24.3 sq mm

2 Justification of the material of the welded structure

Chemical composition of steel

Equivalent carbon content

Se = Cx + Cp

Cx - chemical equivalent of carbon

Cx = C + Mn / 9 + Cr / 9 + Mo / 12 = 0.16 + 1.6 / 9 + 0.4 / 9 = 0.38

Cp - correction to carbon equivalent

Cp = 0.005 * S * Cx = 0.005 * 8 * 0.38 = 0.125

Preheat temperature

T p = 350 * = 350 * 0.25 = 126.2 degrees.

1.3 Specifications for the manufacture of a welded structure

The fan casing works in particularly harsh conditions. It is directly exposed to dynamic and vibration loads.

4 Determination of the type of production

The total weight of the spar is 32.07 kg. With a production program of 800 pcs, we select the serial production type

In serial production, the type of production is characterized by the use of specialized assembly and welding devices, welding of units is carried out on stationary workers

5 Selection and justification of assembly and welding methods

This structure is made of steel 16G2AF, which belongs to the group of well-welded steels. When welding, preheating to 162 degrees and subsequent heat treatment is required.

Steel is welded by all types of welding. The thickness of the parts to be welded is 10 mm, which allows welding in carbon dioxide with wire Sv 08 G2S

1.6 Definition of welding modes

sv = h * 100 / Kp

where: h - penetration depth

Кп - proportionality coefficient

c in = 0.6 * 10 * 100 / 1.55 = 387 A

Arc voltage

20 + 50 * Iw * 10⁻³ / d⁰² В

20 + 50 * 387 * 10 ⁻³ / 1.6⁰² = 20 + 15.35 = 35.35 V

Welding speed

V sv = K n * I sv / (ρ * F * 100) m / hour =

1 * 387 / 7.85 * 24.3 * 100 = 34.6 m / hour

where K n is the coefficient of surfacing, g / A * hour

ρ is the density of the metal, taken for carbon and low-alloy steels, equal to 7.85 g / cm3;

F is the cross-sectional area of the deposited metal. mm 2

7 Selection of welding consumables

Steel 16G2AF is welded by any type of welding using various types of welding consumables. Therefore, for welding we use wire SV 08 G 2 C. Wire SV 08 G2S has good weldability, low emission of welding aerosols, low price.

7.1 Consumption of welding consumables

The consumption of an electrode wire when welding in a CO2 environment is determined by the formula

G e. pr. = 1.1 * M kg

M is the mass of the deposited metal,

M = F * ρ * L * 10 -3 kg

M t. Sh. = 0.243 * 7.85 * 611.94 * 10 -3 = 1.16 kg

Consumption of electrode wire

G e. pr. = 1.1 * M = 1.1 * 1.16 = 1.28 kg

Carbon dioxide consumption

G co2 = 1.5 * G e. pr. = 1.5 * 1.28 = 1.92 kg

Power consumption

W = a * G e. pr. = 8 * 1.28 = 10.24 kW / h

a = 5 ... 8 kW * h / kg - specific power consumption per 1 kg of deposited metal

8 Selection of welding equipment, technological equipment, tools

MAGSTER WELDING SYSTEM

· Professional welding system with a 4-roller feed mechanism of the famous Lincoln Electric quality at the price of the best Russian analogues.

· Gas-shielded welding with solid and flux-cored wires.

· It is successfully used for welding structural low-carbon and stainless steels, as well as for welding aluminum and its alloys.

· Step-by-step adjustment of welding voltage.

· Infinitely adjustable wire feed.

· Gas pre-purge.

· Thermal overload protection.

· Digital voltage indicator.

· High reliability and ease of management.

· Synergistic system of the welding process - after loading the type of wire and diameter, the correspondence of the feed speed and voltage is set automatically by means of a microprocessor (for model 400,500).

· Multi-functional liquid crystal display - showing the parameters of the welding process (for models 400, 500).

· Water cooling system (for models with index W).

· All models are equipped with a socket for connecting a gas heater (the heater is supplied separately).

· Designed in accordance with IEC 974-1. Protection class IP23 (outdoor work).

· Supplied in ready-to-use sets and include: power source, feeder with transport trolley, 5 m connecting cables, 5 m power cable, "MAGNUM" welding torch 4.5 m long, clamp for the workpiece.

AGSTER 400 plus MAGSTER 500 w plus MAGSTER 501 w Maximum power consumption, 380 V. 14.7 kW. 17 kW. 16 kW. 24 kW. 24 kW. Welding current at 35% duty cycle. 315 A. 400 A. 400 A. 500 A. 500 A. Welding current at 60% duty cycle. 250 A. 350 A. 350 A. 450 A. 450 A. Welding current at 100% duty cycle. 215 A. 270 A. 270 A. 350 A. 450 A. Output voltage. 19-47 V. 18-40 V. 18-40 V. 19-47 V. 19-47 V. Weight without cables. 88 kg 140 kg 140 kg 140 kg 140 kg

TECHNICAL PARAMETERS OF THE WIRE FEEDING MECHANISM

· Wire feed speed. 1-17 m / min 1-24 m / min 1-24 m / min 1-24 m / min 1-24 m / min Wire diameters. 0.6-1.2 mm 0.8-1.6 mm 0.8-1.6 mm 0.8-1.6 mm 0.8-1.6 mm Weight without torch. 20 kg. 20 kg. 20 kg.

9 Determination of technical standards of time for assembly and welding

Calculation of technical standards for assembly and welding of the unit.

	Parameter	Time rate min	Time min	A source
Remove oil, rust and other contaminants from welding areas.		0.3 per 1 m. Seam
Install det pos 2 into the tool.	Weight children. 12.33 kg
Install det pos. 1 for children pos 2
Grab children poses 1 to children poses 3 for 3 potholders		0.09 1 ad
Install det pos. 2 for children, position 1	Weight children. 12.33
Grab children poses 2 to children poses 1 for 3 potholders		0.09 1 ad
Install 2 pieces of pos. 3 for children pos 1	Weight children. 0.39
Grab 2 children poses 3 to children poses 1 to 4 tacks		0.09 1 ad
Remove the assembly unit and put it on the welder's table	Weight sat. units 32.07 kg
	L seam = 1.9 m	1.72 min / m seam
Weld the edges of det pos 1 to each other	L seam = 0.32 m	1.72 min / m seam
Weld det pos 2 to det pos 1	L seam = 1.9 m	1.72 min / m seam
Remove splashes from the weld seam.	Lzach = 4.12 m	0.4 min / m seam
Control by a worker, a foreman
Remove assembly unit

Table 1

table 2

Time for the installation of parts (assembly units) when assembling metal structures for welding

Assembly type	Part weight, assembly unit


fixator

Table 3

Tack time

Thickness of metal or legs, mm	Tack length, mm	Time for one tack, min

Time to remove assembly units from the fixture and place them at the storage site

Main time for welding 1 m. Seam

F - cross-sectional area of the weld

ρ - specific density of the deposited metal, g / cu. cm.

a - deposition coefficient

a = 17.1 g / a * hour

That. tsh = = 1.72 min / 1 m seam

10 Calculation of the amount of equipment and its load

Estimated amount of equipment

C p = = = 0.09

T gi is the annual labor intensity of the operation, n-hour;

T gi = = = 308.4 n-hour

F d o - the annual valid fund of equipment operation

F d o = (8 * D p + 7 * D s) * n * K p = (8 * 246 + 7 * 7) * 2 * 0.96 = 3872.6 hours

D p, D s - the number of working days per year, respectively, with the full duration and reduced;

n is the number of work shifts per day;

K p - coefficient taking into account the time spent by the equipment in repair (K p = 0.92-0.96).

Load factor

K z = = = 0.09

Ср - the estimated amount of equipment;

Spr - accepted amount of equipment Spr = 1

11 Calculation of the number of employees

The number of main workers employed directly in the execution of technological operations is determined by the formula

Ch o.r. = = = 0.19

T g i - annual labor intensity, n-hour;

Ф д р - annual real fund of working time of one worker, in hours;

K in - the coefficient of fulfillment of production standards (K in = 1.1-1.15)

Annual active fund of working time of one worker

F d p = (8 * D p + 7 * D s) * K nev = (8 * 246 + 7 * 7) * 0.88 = 1774.96 hours

where D p, D s - the number of working days per year, respectively, with the full duration and reduced;

K nev - coefficient of absenteeism for good reasons (K nev = 0.88)

12 Methods for dealing with welding deformations

The whole range of measures to combat deformations and stresses can be divided into three groups:

Activities that are carried out before welding;

Activities in the welding process;

Post-weld activities.

Pre-welding deformation control measures are implemented at the design stage of the welded structure and include the following activities.

Welding of the structure should have a minimum volume of weld metal. The legs should not exceed the design values, butt seams, if possible, should be performed without cutting edges, the number and length of seams should be as low as possible.

It is necessary to use welding methods and modes that provide minimal heat input and a narrow heat-affected zone. In this respect, welding in CO 2 is preferable manual welding, and electron beam and laser welding are preferable to arc welding.

Weld seams should be as symmetrical as possible on the welded structure, it is not recommended to locate seams close to each other, to have a large number of intersecting seams, without the need to use asymmetric grooving. In structures with thin-walled elements, it is advisable to place the seams on or near rigid elements.

In all cases, when there are fears that unwanted deformations will occur, the design is carried out in such a way as to ensure the possibility of subsequent editing.

Measures used in the welding process

A rational sequence of overlapping welds, on the structure and along the length.

When welding alloy steels and steels with a high carbon content, this can lead to the formation of cracks, therefore, the stiffness of the fasteners should be assigned taking into account the metal to be welded.

Preliminary deformation of the parts to be welded.

Swaging or rolling of the weld seam, which is carried out immediately after welding. In this case, the shortening plastic deformation zone undergoes plastic upsetting in thickness.

1.13 Choice of quality control methods

The system of operational control in welding production includes four operations: control of preparation, assembly, welding process and obtained welded joints.

.) Control of preparation of parts for welding

It provides for the control of the processing of the front and back surfaces, as well as the end edges of the parts to be welded.

The surfaces of the edges to be welded must be cleaned from dirt, preservative grease, rust and scale, to a width of 20 - 40 mm from the joint.

.) Assembly - installation of the parts to be welded in the appropriate position relative to each other when welding T-joints, control the perpendicularity of the parts to be welded. When checking the quality of the tacks, pay attention to the surface condition and the height of the tacks.

.) Control of the welding process includes visual observation of the process of metal melting and formation of a seam, control of the stability of the mode parameters and the equipment operability.

.) Inspection of welded joints. After welding, welded joints are usually inspected visually. The welded seam and the heat affected zone are inspected. Usually the control is carried out with the naked eye. When detecting surface defects less than 0.1 mm in size, optical devices are used, for example, a magnifier of 4-7 times magnification.

The main structural elements of welded seams are:

· Seam width;

· Amplification and penetration height;

Smooth transition from amplification to the base metal, etc.

1.14 Safety, fire prevention and environmental protection

The harmful effects of welding and thermal cutting on humans and industrial injuries during execution welding works are caused by various reasons and can lead to temporary disability, and in an unfavorable combination of circumstances - and to more serious consequences.

Electric current is dangerous to humans, and alternating current more dangerous than permanent. The degree of danger of electric shock depends mainly on the conditions for including a person in the circuit and the voltage in it, since the strength of the current flowing through the body is inversely proportional to the resistance (according to Ohm's law). For the minimum design resistance of the human body, 1000 ohms are taken. There are two types of electric shock: electrical shock and injury. With an electric shock, the nervous system, muscles of the chest and ventricles of the heart are affected; paralysis of the respiratory centers and loss of consciousness are possible. Electrical injuries include burns to the skin, muscle tissue, and blood vessels.

Light radiation from the arc, acting on the unprotected organs of vision for 10-30 s within a radius of up to 1 m from the arc, can cause severe pain, lacrimation and photophobia. Long-term exposure to arc light under such conditions can lead to more serious diseases - (electrophthalmia, cataract). The harmful effect of the rays of the welding arc on the organs of vision affects the distance up to 10 m from the welding place.

Harmful substances (gases, vapors, aerosols) during welding are emitted as a result of physicochemical processes arising from melting and evaporation of the metal being welded, components of electrode coatings and welding fluxes, as well as due to the recombination of gases under the action of high temperatures of welding heat sources. The air in the welding zone is contaminated with welding aerosol, consisting mainly of oxides of the metals being welded (iron, manganese, chromium, zinc, lead, etc.), gaseous fluoride compounds, as well as carbon monoxide, nitrogen oxides and ozone. Prolonged exposure to welding aerosol can lead to the appearance of occupational intoxication, the severity of which depends on the composition and concentration of harmful substances.

Explosion hazard is caused by the use of oxygen, shielding gases, flammable gases and liquids in welding and cutting, the use of gas generators, cylinders with compressed gases, etc. Explosive chemical compounds of acetylene with copper, silver and mercury. The danger is in the form of kickbacks in the gas network when working with burners and low pressure torches. When repairing used tanks and other containers for storing flammable liquids, special measures are required to prevent explosions.

Heat burns, bruises and injuries are caused by the high temperature of the welding heat sources and significant heating of the metal during welding and cutting, as well as the limited visibility of the surrounding area due to the work using shields, masks and goggles with light protective glasses.

Unfavorable meteorological conditions affect welders (cutters) - builders and installers for more than half of the year, since they have to work mainly in the open air.

The increased fire hazard during welding and cutting is due to the fact that the melting point of metal and slags significantly exceeds 1000 ° C, and liquid combustible substances, wood, paper, fabrics and other flammable materials ignite at 250-400 ° C.

2. ELECTRICAL SAFETY MEASURES

The chassis must be reliably grounded. welding machine or installations, clamps of the secondary circuit of welding transformers, used to connect the return wire, as well as welded products and structures.

2.It is forbidden to use ground loops, pipes of sanitary devices, metal structures of buildings and technological equipment... (During construction or repair, metal structures and pipelines (without hot water or an explosive atmosphere) can be used as a return wire for the welding circuit and only in cases where they are welded.)

4. Protect the welding leads from damage. When laying welding wires and each time they are moved, do not damage the insulation; contact of wires with water, oil, steel ropes, hoses (hoses) and pipelines with combustible gases and oxygen, with hot pipelines.

With their considerable length, flexible electric wires for controlling the circuit of the welding installation must be placed in rubber sleeves or in special flexible multi-link structures.

6. Only electrotechnical personnel have the right to repair welding equipment. Do not repair live welding equipment.

When welding in especially dangerous conditions (inside metal tanks, boilers, vessels, pipelines, in tunnels, in closed or basements with high humidity, etc.):

welding equipment should be located outside these containers, vessels, etc.

electric welding installations must be equipped with a device for automatically shutting off the open-circuit voltage or limiting it to a voltage of 12V within no more than 0.5 s after the termination of welding;

allocate an insuring worker, who must be outside the tank, to monitor the safety of the welder. The welder is supplied with an assembly belt with a rope, the end of which must be at least 2 m long in the hands of the belayer. There must be an apparatus (switch, contactor) near the belayer to disconnect the mains voltage from the welding arc power source.

Welders in wet gloves, shoes and overalls must not be allowed to arc welding or cutting.

9. Cabinets, consoles and frames of contact welding machines, inside which there is equipment with open live parts that are energized, must have an interlock that relieves the voltage when they are opened. Pedal start buttons of contact machines must be grounded and the reliability of the upper guard, which prevents unintentional switching on, must be monitored.

10. In case of electric shock, you must:

urgently turn off the current with the nearest switch or separate the victim from the live parts, using dry materials at hand (pole, board, etc.) and then put it on a mat;

immediately call for medical assistance, given that a delay of more than 5-6 minutes can lead to irreparable consequences;

in case of unconsciousness and lack of breathing in the victim, release him from the restraining clothes, open his mouth, take measures against the sinking of the tongue and immediately begin to perform artificial respiration, continuing it until the doctor arrives or the restoration of normal breathing.

3. PROTECTION AGAINST LIGHT RADIATION

To protect the welder's eyes and face from the light radiation of the electric arc, masks or shields are used, into the viewing holes of which protective glass-light filters are inserted that absorb ultraviolet rays and a significant part of light and infrared rays. The outside of the filter is protected from splashes, drops of molten metal and other contaminants with ordinary transparent glass installed in the viewing hole in front of the filter.

Light filters for arc welding methods are selected depending on the type of welding and welding current strength, using the data in Table. 3. When welding in an inert gas shielding environment (especially when welding aluminum in argon), a darker filter must be used than when welding with an open arc at the same current strength.

Table 3. Light filters to protect eyes from arc radiation (OST 21-6-87)

2. To protect the surrounding workers from the light radiation of the welding arc, portable shields or screens made of non-combustible materials are used (with a non-permanent workplace of the welder and large products). In stationary conditions and with relatively small sizes of the welded products, welding is performed in special cabins.

3. To weaken the contrast between the brightness of the arc light, the surface of the walls of the workshop (or cabins) and equipment, it is recommended to paint them in light colors with diffused light reflection, as well as to provide good illumination of the surrounding objects.

If the eyes are damaged by the arc light radiation, you should immediately consult a doctor. If it is impossible to obtain quick medical care, eye lotions with a weak solution of baking soda or tea leaves are applied.

Protection against harmful gases and aerosols

To protect the body of welders and cutters from harmful gases and aerosols released during the welding process, it is necessary to use local and general ventilation, the supply of clean air to the breathing zone, as well as low-toxic materials and processes (for example, use rutile-type coated electrodes, replace welding with coated electrodes for mechanized welding in carbon dioxide, etc.).

2. When welding and cutting small and medium-sized products at permanent places in workshops or workshops (in cabins), it is necessary to use local ventilation with fixed side and bottom suction (welder's table). When welding and cutting products at fixed places in workshops or workshops, it is necessary to use local ventilation with an intake funnel attached to a flexible hose.

Ventilation should be carried out supply and exhaust with fresh air supply to the welding areas and its heating in cold weather.

When working in enclosed and semi-enclosed spaces (tanks, tanks, pipes, compartments of sheet structures, etc.), it is necessary to use a local suction on a flexible hose to extract harmful substances directly from the welding (cutting) place or provide general ventilation. If it is impossible to carry out local or general ventilation, clean air is forcibly supplied to the breathing zone of the worker in an amount of (1.7-2.2) 10-3m3 per 1s, using a mask or helmet of a special design for this purpose.

LITERATURE

1. Kurkin SA, Nikolaev GA Welded constructions. - M .: Higher school, 1991 .-- 398p.

Belokon V.M. Production of welded structures. - Mogilev, 1998 .-- 139p.

Blinov A.N., Lyalin K.V. Welded structures - M .: - "Stroyizdat", 1990. - 352s

Maslov B.G. Vybornov A.P. production of welded structures -M ,: Publishing Center "Academy", 2010. - 288 p.

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Air duct production

Boxes for ventilation and air conditioning systems are used in the construction of any duct systems. The material for their manufacture is selected depending on the actual operating conditions, the parameters of the working environment, as well as on the purpose. For the manufacture of air ducts uses low-carbon steel, "galvanized" or "stainless steel", as well as different kinds plastic.

Air ducts for ventilation made of "galvanized" are used in air exchange systems with a working environment with a temperature of up to + 80C (possibly a short increase up to + 200C) and humidity up to 60%. Galvanized steel air ducts can be used in areas with any climate in accordance with GOST 15150, provided that they are not aggressive working environments (air and gas-air). Galvanized air ducts do without additional protective coating, since the upper zinc layer protects the metal from corrosion even in places of damage (due to galvanic steel-zinc pair, which forms an oxide film under the influence of atmospheric oxygen).

Air ducts made of stainless steel are designed to work with overheated air and aggressive gas-air mixtures. Working environment temperature - up to + 500C (short-term increase up to + 70C is allowed). Steel according to GOST 5632-72 (heat and corrosion resistant) is used as a blank material for the production of stainless steel air ducts.

"Black" air ducts are made of low-carbon steel. Workpiece thickness - from 1.2 to 15 mm. "Black" ventilation ducts tolerate high temperatures and exposure to open flames well (they are weakly susceptible to deformation - the ventilation system ducts will not depressurize, and the fire will not spread to neighboring rooms).

For aspiration systems and smoke extraction "black" ventilation ducts are the right choice. Ventilation systems made of plain carbon steel are mainly in demand in production areas where excessive gas, dust, etc.

Air ducts can be round or rectangular in cross section... The production of rectangular air ducts is a classic of ventilation systems, but thanks to progressive technologies, the market is increasingly giving way to round air ducts, since they are more technologically advanced in manufacturing, have better aerodynamic characteristics and are convenient to install. Today the production of round air ducts is gaining momentum, becoming more and more popular.

For the installation of air ducts in a single line, various shaped components are used, which are conventionally subdivided into typical (corners, turns, splitters, "ducks", transitions, etc.) and atypical (adapters for ventilation grilles or reducers for air exchange systems).

In some cases, air ducts made of polymers (plastic) can become an excellent alternative to metal counterparts. Among the advantages of plastic air ducts, it is necessary to highlight a small specific gravity, ease of installation (no need for special tools and fixtures), reasonable price. But plastic air ducts are not suitable for moving chemically aggressive gas-air mixtures.

Distinguish between rigid, semi-rigid and flexible plastic air ducts. Rigid air ducts can be round or rectangular, while flexible and semi-rigid air ducts have only a circular cross-section.

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