During the construction of industrial, chemical, gas, oil or energy pipelines, pipes of different sizes have to be connected. To do this, use special elements - transitions. What they are, how they are made - more on that later.
Transitional Details
Transitions are pipe fittings. These are pipe segments, the ends of which have different diameters. Due to this, it is possible to smoothly reduce or increase the diameter of the pipeline and, accordingly, optimally distribute the load on each specific section of the structure.
Industrial enterprises produce two types of transitions: concentric and eccentric.
In the former, the inlet and outlet are located symmetrically to the axis, due to which the details resemble a truncated cone. Use this type of product when arranging vertical pipelines. The eccentric transitions shown in the photo also resemble a truncated cone, but with one in which the bases are offset relative to the axis. Use this type of product where the transported substance should not stagnate in horizontally located pipes.
Product Features
Eccentric transitions are used to install pipes in which a non-aggressive working medium is pumped under high pressure. So that the products can withstand a pressure of about 16.0 MPa and a temperature difference from -70 ° C to + 450 ° C, low-alloy or carbon steel is used for their manufacture.
Each material is intended for the manufacture of elements for a working environment with certain characteristics and for specific operating conditions. So, if the medium in the pipeline is medium or slightly aggressive (oil, gas, various types of oil products), carbon steel is used to make eccentric transitions. If the products are designed for highly aggressive environments, then they are made of alloyed or high alloy steel.
Parts of this type are designed to test huge loads, high pressures and temperature extremes, so the most stringent requirements are observed during their production, which ensures the reliability of products and the strength of materials. In addition, before allowing products to be used, they must be tested in various ways.
Technical requirements
According to the requirements of GOST, eccentric transitions on the outer surface should not have the following defects:
- Scum.
- A flaw.
- Sunsets, bundles.
- Metal clamps (wrinkles).
- Cracks.
The presence of rowan, prodir, prints, sinks from scale, the depth of which does not exceed 0.8 mm, scratches from 0.2 (on walls with a thickness of about 1.9 cm) to 0.4 mm (for walls thicker than 1.9 cm) by defects not considered.
Main characteristics
They make products in several ways, which allows you to purchase different types of products:
- Stamped elements.
- Molded products.
- Welded eccentric transitions.
- Turned.
- Stamped.
Stamped and turned parts have no seams. These methods are used when it is required to manufacture small or non-standard products.
Regardless of the manufacturing method, the following parameters are taken into account when selecting an eccentric steel transition for a particular pipeline:
- The diameter of the larger outer end.
- The diameter of the smaller outer end.
- Conditional pass.
- Conditional pressure.
- The wall thickness at the larger end.
- The wall thickness at the smaller end.
In addition, material of manufacture, maximum pressure in the pipeline, climatic performance, strength class and other parameters are taken into account.
Operating conditions and safety measures
According to the technical requirements and the requirements of the supervisory authorities, it is necessary to conduct tests, monitor installation work and issue a technical survey before launch in accordance with the rules approved and submitted by them. Their violation is unacceptable - this entails various problems, including leaks, accidents, premature failure of products.
So that eccentric transitions can serve from 20 years or more, it is necessary to monitor the following features:
- The working temperature of the transported substance must not exceed +400 ° C.
- The products used must not have defects - their presence provides the appearance of corrosion and erosion of the metal both from the inside and from the outside.
- When operating the products, only static internal pressure must be ensured.
Features of transportation and installation
For transportation, products are packaged so that they are conveniently and safely unloaded / loaded. Products with a diameter of up to 8 cm are tied into bundles at the production site and only after that they are placed in boxes or containers. Store in rooms protected from moisture.
An eccentric transition is connected to the pipeline with a weld, which runs end-to-end along the ends of the product. Moreover, the welding joint should be equally strong along the entire length and at the same time not affect the mechanical characteristics of the material from which the parts are made. If it is stipulated in the design, project or regulatory documentation that welding is unacceptable, it is possible to connect parts in other ways.
They use parts both for carrying out new pipelines and for repairing existing ones in metallurgy, mechanical engineering, energy and other industrial fields. Eccentric crossings are in demand by companies that conduct heating systems, water and sewer pipes.