DN 69 what is the diameter of the outer and inner. What is the nominal diameter of the pipe

This article will focus on such an important characteristic of any pipes as a nominal diameter. We will tell you what the nominal diameter of the pipeline is, what they are, and also how pipes are classified depending on the size of the nominal diameter.

So, first of all, it is worth saying that the conditional diameter of the pipe is the average value of the internal section of the pipes, which determines their throughput. GOST 28338-89 defines the classification of pipes precisely by this value. In addition, by given parameter not only pipes are selected, but also fittings.

It is important to understand that the scope of its application and the possible configuration of the pipeline will depend on the throughput of the pipe.

Standard sizes of nominal pipe diameters

According to GOST 28338-89, all pipe products are divided into 40 standard and 9 special nominal sizes. In general, the nominal diameter of the pipe can vary between 2.5-4000 mm.

Special pipes include pipes with diameters of 16, 63 and 160 mm, which are used only in hydraulic or pneumatic systems. And types of products with a nominal section of 0.175; 2.6; 3.2; 3.6 and 3.8 meters belong to special-purpose pipe-rollers and are not used in everyday life.

How pipes are marked

To make it clear what a DN pipe is, you need to talk about the generally accepted marking of pipes according to GOST. That is, "DU" is the nominal diameter, and its value is indicated in numerical terms. For example, if the nominal diameter of the pipeline is 150 mm, then such products are marked DN 150.

However, we note that the real indicators of the internal section of pipes with such markings can be completely different. In particular, with such a marking, pipe products with an external and internal section of 156/144 or 156/149 mm can be produced.

This discrepancy is due to the fact that GOST provides only two standard sizes sections - 125 and 150 mm. Therefore, these passage values ​​are rounded up to a "conditional" indicator.

Since pipe products of domestic and imported origin must be similar in size, the same standards for conditional sizes have been adopted abroad, and pipes are marked with DN.

Classification of pipes according to the nominal section

Nominal diameter of a pipe is one of the parameters that largely depends on the type of steel production.

In general, four types of pipes are distinguished depending on the production technology:

• 20-500 mm - such products are produced by hot rolling according to GOST 8732-78;
• 5-250 mm - similar values ​​\u200b\u200bare determined by GOST 8734-75 for the cold rolling method;
• 10-1400 mm - this group of pipe products refers to welded products with longitudinal seams, and their parameters are specified in GOST 10704-91;
• 160-2400 mm - these are the size limits for welded steel pipes with spiral seams, given in GOST 8696-74.

In this case, steel pipe products are presented in 38 sizes, the nominal diameters of which range from DN 5 to DN 2400. These include four specialized groups that are provided for hydraulic and pneumatic systems.

Parameters of conditional passages of pipes made of polypropylene

For polymer products, in particular, polypropylene pipes, nominal bore parameters are provided by GOST 18599-2001. According to this document plastic pipes are divided into 32 sizes with limiting diameters of 10 and 1600 mm.

At the same time, this document distributes all products into 7 groups depending on the wall thickness - their dimensions range from 2-70 mm, and the working pressure varies from 0.16 to 2 MPa.

Thus, we can conclude that not only the maximum allowable pressure in the system, but also the throughput of the pipeline depends on the indicator of the nominal diameter of the pipe. This is important to take into account at the design stage of any highway.

Pipe diameter is a very important indicator when working with pipes..

It doesn’t matter if you are replacing the riser in your own apartment or developing a plan for laying a water supply system on a city-wide scale, in any case, you need to understand the peculiarities of pipe diameters from different materials.

General information about the diameters of water pipes

At the moment, the most popular material for plumbing is metal-plastic. Materials such as copper, plastic, polyethylene and polyvinyl chloride are also used everywhere, so it is necessary to take into account the difference in pipe sizes.

For this, a special classification of measurement measures was developed.

big pipe

Parameters for determining the dimensions of water pipes:

• inner diameter pipes. Based on this conditional characteristic, the size of the inner diameter is determined, both for connector assemblies and for water pipes;
• Dy, the nominal diameter of the pipe. The nominal value of the inner diameter, indicated in millimeters. This value is rounded up;
• Dn, nominal diameter value;
• outer diameter of pipes;
• wall thickness dimension.

Previously, it was not necessary to calculate the diameter of the pipes. But with the advent various materials, it became clear that it is necessary to take into account the diameters of plumbing products. The table of diameters of pipe metal takes into account that the “inch” diameter values ​​\u200b\u200bdo not correspond to real metric sizes.

For example, for the inner diameter of products with different threads, it will look like this:

• the inner diameter of the 0.5 inch pipe is 12.7 mm;
• the inner diameter of the pipe 3/4 corresponds to 19.0 mm;
• and for a 2-inch pipe ID size, this is 50.8 mm.

For diameters pipe thread it will look like this:

• 0.5 inch pipe - 20.4-20.7 mm;
• 3/4 inch pipe - 25.9-26.2 mm;
• and pipe 2-inch pipe - 57.9-58.3 mm.

Knowing the dimensions of the pipes for the water supply, you can quickly make right choice. If it is necessary to join pipes made of plastic and metal, then the diameters of the plastic and the diameters of the metal pipes must be taken into account.

The size table of products for plumbing from different materials takes into account not only the diameter of the pipes, but also their throughput.

Polyethylene pipes

You can go the other way and use a special calculation formula that takes into account the decrease in water pressure, which depends on the number of turns, joints and the length of the entire pipeline, but it is not practical to use such a formula for intra-apartment wiring.

Most often, pipe metal is chosen for the water supply system, the diameter of which is 10 and 15 mm, which corresponds to 3/8 inch and 1/2 inch. When installing the riser, the inner diameter of the pipes is chosen, as a rule, equal to 20 and 25 mm, which corresponds to 3/4 inch and 1 inch.

Water pipes

Steel water pipes are joined with plastic ones by means of special standard transition elements, taking into account the dimensions of pipe metal and the material from which they are made.

The situation is a little more complicated with copper and aluminum pipes, because. their release is regulated by the corresponding metric standard. In this case, the actual metric outer and inner diameter of steel pipes is taken into account. It is worth noting that all parameters are strictly regulated, including pipe diameters, according to GOST. The table of correspondence of the dimensions of the dimensions of the products is as follows:

Table of correspondence of pipe diameters

Nominal pipe diameter Dy, mm	Thread diameter G", inch	Pipe outer diameter Dn, mm
		VGP	ES, BS	Polymer
10	3/8″	17	16	16
10	3/8″	17	16	16
15	1/2″	21,3	20	20
20	3/4″	26,8	26	25
25	one"	33,5	32	32
32	1 1/4″	42,3	42	40
40	1 1/2″	48	45	50
50	2″	60	57	63
65	2 1/2″	75,5	76	75
80	3″	88,5	89	90
90	3 1/2″	101,3	102	110
100	4"	114	108	125
125	five"	140	133	140
150	6″	165	159	160
160	6 1/2″		180	180
200			219	225
225			245	250
250			273	280
300			325	315
400			426	400
500			530	500
600			630	630
800			820	800
1000			1020	1000
1200			1220	1200

Depending on the type of material used in the manufacture of pipes, various systems designations. In most cases steel and cast iron pipes designate by conditional passage or internal diameter. Copper pipes, some types of steel pipes, pipes made of polymer materials indicated by the outside diameter. Therefore, you should carefully consider the choice of the required pipe, as well as take into account the wall thickness.

The true inner diameter of the pipes usually does not match (but sometimes there are exceptions) the nominal diameter. For example, for pipes with an outer diameter of 159 mm and a wall thickness of 8 mm, the true inner diameter is 143 mm, and for a wall thickness of 5 mm - 149 mm, however, in both cases, the nominal diameter is assumed to be 150 mm.

GOST 28338-89 regulates a number of nominal (conditional) diameters of pipes and fittings. Such a table is necessary so that pipeline elements (pipes, valves) from different manufacturers can be assembled into a single pipeline, that is, they must be interchangeable.

The OD of a pipe for a single NPS diameter is kept constant, while the ID of the pipe will vary depending on the 'gauge' or wall thickness of the pipe. Changing the nominal pipe diameter (NPS) will change the gauge and actual wall thickness.

The outer diameter is a constant value, defined in GOST e. To increase the strength of the product, the wall thickness increases. This results in the actual inner dimensions circles are different from the conditional pass. For example, for a pipe with external value O273 and a wall of 9 mm, the actual internal is O255 mm, and the nominal bore is 250 mm, that is, the value of the standard scale is closer.

When changing a steel pipe to a different diameter, transition fittings are used in the form of fittings. Their device is simple - it expands an element with two holes of different sizes. The connection can be made both along the central axis and along the bottom line. Pipes located vertically are connected along the central axis, horizontally along the bottom line.

Longitudinal products comply with GOST-u 10706 ( technical requirements- O , tolerances, quality of longitudinal and transverse seams, theoretical weight). Small diameter (12 - 51) is used mainly in the production of hydraulic and compression systems, for the supply of process fluids, in climate equipment, in the manufacture of furniture, in the construction of electrical circuits.

A steel pipe is characterized by length, outer and inner diameter and wall thickness. The outer diameter is most often referred to as the distance between the outer edges. It depends on the method of manufacture, manufacturer, wall thickness and application. Everything standard diameters steel pipes are determined by the corresponding type of GOST - th.

The steel free flange on the weld ring consists of two parts - a flange and a ring. The flange and ring must be of the same nominal diameter and pressure. These flanges are easy to install, because only the ring is welded to the pipe, and the flange itself remains free, which ensures easy mating of the bolt holes of the free flange with the bolt holes of the valve or equipment flange without turning the pipe. They are often used in the installation of pipeline fittings and equipment in hard to reach place or when frequent repairs(testing) flange connections (eg in the chemical industry).

Flanged connections are used in the installation of pipelines and equipment in almost all industries. The materials from which the flanges are made are very diverse, which allows the use of these products in almost any conditions. environment and the medium passes through the pipeline.

Steel grades are selected taking into account the use of flanges for this operating temperature, conditional pressure and the medium is transported in the pipeline. Requirements for the steel grade of the flange, depending on the working pressure and medium temperature, are given in GOST 12816-80.

The most important parameter on the basis of which pipes are chosen for organizing all types of sewer systems, both external and internal, is the diameter of the pipe. The sizes of plastic sewer pipes are different and are included in the standard range. This allows you to choose those products that are suitable for each specific task:

Another parameter depends on the diameter - the weight of the pipe and, accordingly, the amount of material used for its manufacture. One running meter with a diameter of 110 mm it weighs about one kilogram, and with a diameter of 160 mm the weight will already be 2.129 kg.

When choosing a pipe for draining sewage, the determining parameter is the inner diameter. This size varies according to the role that the pipe will play and where it will be installed. These are the standard values:

So, in order to properly design and organize a sewerage system, it is necessary, in strict accordance with the design parameters, to purchase sewer pipes and fittings: the sizes of these products vary in a very wide range and they can be matched to almost any sewer system. The main thing is to take into account all the basic parameters, then the system will serve for a long time and without failures.

The most important characteristic of any design is the diameter. It can be conditional, nominal, external and internal. To accurately make a design calculation, taking into account all the necessary characteristics, you need to know a lot about the products used. For this, the existing classification by size and wall thickness is used. Designers greatly facilitate their work standards that regulate this value.

For steel products, constant values ​​are characteristic (according to the technological conditions of production). And since for structures intended for operation under high pressure conditions, the thickness of the walls is increased, this size will differ from the passage. An example of such a difference is the following calculation.

The abbreviation Du indicates the conditional diameter of the product. This indicator does not correspond to the nominal diameter Dn, but demonstrates its throughput. The Du indicator also characterizes the parameters of the connecting parts to pipes and valves.

Specifications for water and gas pipes are regulated by GOST 3262-75. This standard applies to non-galvanized and galvanized steel welded pipes with cut or knurled cylindrical threads and without threads.

The choice of pipe size and materials for manufacturing is carried out on the basis of technological and design requirements presented in each particular case. But in order to standardize the dimensions of the pipes, their classification and unification was carried out. The main criterion was the allowable pressure at which the pipe can be operated.

Let's take the tabular values ​​of the coefficients of local resistance of a normal valve for diameters of 40 and 80 mm. Let us assume that the graph of the values ​​of the coefficients on this interval is a straight line. We compose and solve a system of equations in order to find a graph of the function of the dependence of the coefficient of local resistance on the diameter of the pipe:

Calculation of the optimal pipeline diameter is a complex task that requires technical and economic calculations and taking into account many particular factors. This is due to the close relationship between the parameters of the pipeline being designed and the flow of the medium pumped through it. An increase in the speed of the pumped medium makes it possible to reduce the diameter of the pipeline necessary to maintain a given flow rate, reduces its material consumption, and facilitates and reduces the cost of installing the system. At the same time, an increase in speed inevitably entails pressure losses and requires additional energy costs for pumping the medium. Excessive speed reduction can also lead to undesirable consequences.

With laminar flow and the corresponding low values ​​of the Reynolds number (Re), characterized by uniformity and the absence of mixing of adjacent layers of liquid or gas, the effect of roughness is insignificant. This is due to the fact that the extreme viscous sublayer of the pumped medium often turns out to be thicker than the layer formed by irregularities and protrusions on the surface of the pipeline. Under such conditions, the pipeline is considered to be hydraulically smooth.

To check the mechanical properties of the metal, one sample is cut from each selected pipe and coupling blank. The specimens shall be cut along either end of the pipe and the coupling blank by a method without changing the structure and mechanical properties of the metal. Samples of all pipes with outboard ends should be cut out of the hanging out part.

2.14.10. After screwing the pipe and the coupling on the machine, the communication of the end of the pipe and the thrust shoulder of the coupling around the entire perimeter of the junction of the thrust surfaces (see Fig. 12) must be ensured. A gap between the thrust surfaces of the pipe and the coupling is NOT over 0.5 mm (for execution B).

At the request of the consumer, on pipes with a nominal bore of more than 15 mm, made by furnace welding and hot reduction, on inner surface pipes in the seam zone, a gentle thickening with a height of not more than 0.5 mm is allowed.

2.5. At the request of the consumer, on pipes with a nominal bore of 20 mm or more, on the inner surface of the pipe seam, the lattice must be cut off or flattened, while the height of the burr or its traces must not exceed 0.5 mm.

3.1. Pipes are accepted in batches. The batch must consist of pipes of the same size, the same steel grade and be accompanied by one quality document in accordance with GOST 10692 with an addition for pipes intended for the manufacture of parts for water and gas pipeline structures, from steel in accordance with GOST +1050; chemical composition and mechanical properties of steel - according to the document on the quality of the enterprise - the manufacturer of the workpiece.

This standard applies to non-galvanized and galvanized steel welded pipes with threaded or knurled cylindrical threads and without threads used for water and gas pipelines, heating systems, as well as for parts of water and gas pipeline structures.