A significant amount of construction of the main facilities in the oil refining, metallurgical, and food industries is allocated to the arrangement of technological pipelines. They play a critical role in the operation of strategically important systems. Technological pipelines are also used in agricultural complexes, heat supply systems and in many other industries.
Basic concepts
A pipeline is a device designed to transport a variety of substances. It consists of pipe sections, connecting and stop valves, automation and fasteners.
What is the meaning of the concept of "technological pipelines?" The definition designates them as systems for supporting industrial enterprises through which semi-finished products and finished products are transported, as well as substances that ensure the conduct of the entire process.
Piping arrangement
In the process of laying, you must follow these recommendations:
- process pipelines should have a minimum length;
- sagging and stagnation are unacceptable in the system;
- providing free access for technological control;
- the ability to locate the necessary trucks;
- providing insulation to prevent moisture from entering and retaining heat;
- protection of pipelines from possible damage;
- unhindered movement of fire extinguishing means and lifting mechanisms.
Slope angles
The operation of process pipelines provides for forced stops. To do this, slopes are laid in the project that will ensure arbitrary emptying of the pipes. The device of technological pipelines provides the following slope angle depending on the moving medium (values are given in degrees):
- gaseous medium: in the direction of movement - 0.002, against it - 0.003;
- liquid easily moving substances - 0.002;
- acid and alkaline environment - 0.005;
- substances of high viscosity or quick setting - up to 0.02.
The design may not provide for bias, then special measures should be provided for emptying the pipelines.
Preparatory work
The installation of process pipelines must first be accompanied by the following actions:
- All project details are checked and necessary changes are made.
- The degree of readiness of building structures and structures for installation is determined.
- The complete set of lines with necessary fittings, elements and parts was checked.
- Separate pipeline units and components have been adopted, according to regulatory documents.
- The readiness of temporary sites for installation works equipped with lighting, power sources for welding, devices for high-altitude work was checked.
- The necessary recommendations for the installation of process pipelines in accordance with safety regulations have been complied with.
Road marking
This operation consists in transferring the axes of fastening of valves and compensators directly to the place where the process pipelines will be laid. The marking location can be performed with the following tools:
- roulettes;
- plumb bob;
- level;
- hydraulic level;
- Templates
- angles.
If a large number of process pipelines are laid for a building structure, the time allocated for marking is significantly reduced through the use of special layouts. They give a visual representation of the location of the pipeline lines in relation to the building structure. After marking, all applied elements are checked with the project, after which they begin to fix the supporting structures.
Installation of supports and fixtures
During the arrangement of the foundation of the building, holes should be provided for bolting it, bolting support. They can be made mechanized equipment. During the installation of supports, the following recommendations should be taken into account:
- Technological pipelines, which have fixed supports described above, require the installation of fasteners in close proximity to devices and fittings. The installation of pipes on such supports should be tightly fixed, not allowing shear. The same requirements are met for clamps.
- The movable supports are mounted with the possibility of unhindered movement of the pipeline in order to freely extend it when necessary. The safety of thermal insulation should also be provided for in case of potential movement from expansion.
- The installer of technological pipelines must check all installed supports for horizontal and vertical correspondence. Possible deviations are provided that cannot exceed such limits:
- intra-workshop pipelines - ± 5 mm;
- external systems - ± 10 mm;
- slopes - 0.001 mm.
Insertion into existing systems
For this, special permissions are required, and the installer of technological pipelines that serves these lines must be present at the place of work. Carry out the insertion when the new mounted component is connected to the existing system. Usually, for such cases, the installation of locking equipment is provided, but if the current system does not have one, then they resort to an insert. There are several features here:
- The existing pipeline must be disconnected and emptied.
- Pipes through which flammable and explosive atmospheres were transported must be neutralized and washed.
- The weld-in fitting must pass preliminary tests. Also, according to the documentation, the steel grade is set.
- Welding work must be carried out by a highly qualified specialist with special access to critical structures.
- Before the installation of process pipelines begins, the connection unit must pass all the tests.
Purge and Flush
The assembled pipeline is subjected to cleaning, the method of which depends on the size of the pipe:
- diameter up to 150 mm - washed with water;
- over 150 mm - blown by air;
The area to be cleaned must be sealed with other plugs. Water flushing is carried out until water begins to flow out of the pipe without pollution. Purge within 10 minutes. These methods are used if the technology does not provide for other standards for cleaning. After the work, you can start the tests, which are performed in two ways: hydraulic and pneumatic.
Hydraulic test
Before verification, technological pipelines are divided into separate conventional sections and carry out the following measures:
- control by external inspection;
- verification of technological documentation;
- installation of air valves, temporary plugs (the use of permanent equipment is prohibited);
- shutdown of the test segment;
- connecting the test section to the hydraulic pump.
Thus, a check is carried out simultaneously for the strength and density of the pipeline. To establish the degree of strength, the special value of the test pressure is taken into account:
- Steel pipelines operated at operating pressures up to 5 kgf / m². The value of the test parameter is 1.5 of the working pressure, but not less than 2 kgf / m².
- Steel pipes operating at pressures exceeding 5 kgf / m². The value of the parameter for testing will be 1.25 working pressure;
- Cast iron, polyethylene and glass - 2 kgf / m².
- Pipelines from non-ferrous metals - 1 kgf / m².
- For pipes made of other materials - 1.25 working pressure.
The exposure time under the set pressure value will be 5 minutes, only for glass pipelines it increases four times.
Pneumatic test
For testing, compressed air or inert gas is used, which is taken from factory networks or from portable compressors. This option is preferred in cases when hydraulic tests are impossible for a number of reasons: lack of water, very low air temperature, and also when dangerous stresses can arise from the weight of water in the pipeline construction. The value of the ultimate test pressure depends on the size of the pipeline:
- with pipe diameters up to 200 mm - 20 kgf / m²;
- 200-500 mm - 12 kgf / m²;
- over 500 mm - 6 kgf / m².
If the pressure limit value is different, special instructions for testing should be developed for such conditions.
Pneumatic test requirements
Pneumatic testing is prohibited for ground cast iron and glass structures. For all other materials from which process pipelines can be made, there are special requirements for testing:
- the pressure in the pipeline rises gradually;
- inspection can be carried out when pressure reaches 0.6 of the operating value (it is unacceptable to increase it in the process of work);
- leak testing is carried out by smearing with soap and water, tapping with a hammer is prohibited.
The results of hydraulic and pneumatic tests are considered satisfactory, if during the process of conducting them there was no pressure drop along the pressure gauge.
Pipeline commissioning
At all stages of installation, relevant documents are drawn up, fixing the types of work, tolerances, tests, etc. They are transmitted at the stage of delivery of pipelines as supporting documentation, they include:
- acts of delivery of supporting structures;
- certificates for welding consumables;
- pipeline internal cleaning protocol;
- acts of quality control of welded joints;
- test report on valves;
- tests of strength and density;
- a list of welders who performed the joints and documents confirming their qualifications;
- schemes of pipeline lines.
Technological pipelines are commissioned along with industrial plants, buildings and structures. Separately, only inter-workshop systems can be rented.
Recommendations for the operation of process pipelines
Periodic monitoring should include the following operations:
- Checking the technical condition during the external inspection and non-destructive methods.
- Checking areas subject to vibration with special instruments that determine its frequency and amplitude.
- Troubleshoot problems that were reported during previous audits.
Equally important is the safe operation of process pipelines, which is ensured by compliance with all established rules.
A monthly system health check should cover the following:
- flange connections;
- welds;
- insulation and coating;
- drainage systems
- supporting fasteners.
If leaks are detected, for safety reasons, the working pressure must be reduced to atmospheric pressure, and the temperature of the heating lines should be reduced to 60 ° C to carry out the necessary measures for troubleshooting. The results of the audit should be recorded in special journals.
Audit
This control method is used to determine the condition and operational capabilities of pipelines. It is advisable to conduct an audit in areas where the operation of technological pipelines is carried out in particularly difficult conditions. The latter include vibration, increased corrosion.
The audit of pipelines includes the following operations:
- Checking the thickness of the structure by non-destructive methods.
- Measurement of areas subject to creep.
- Inspection of welded joints that are in doubt.
- Check threaded connections.
- The condition of the support fixtures.
The first audit control should be carried out after a quarter of the appointed time in the regulatory documents, but no later than 5 years after the launch of the facility. As a result of the timely conduct of all inspections, the safe operation of technological pipelines will be ensured.