Upon completion of the installation of the pipeline , it is further tested for strength and tightness. The hydraulic or pneumatic method can be used, sometimes they are used in combination. Such verification is necessary in accordance with the requirements of sanitary norms and rules.
Preparatory work before hydraulic testing of pipelines for strength
Before carrying out hydraulic tests, thorough preparatory work should be carried out. For this, the structure is divided into divisions, then its external examination is carried out. The next step is checking the technical documentation. Drain valves are fixed to the divisions, air valves and plugs are connected to them. From pressing and filling devices, a temporary pipeline line is installed. The test section is disconnected from the remaining pipe divisions; for this, plugs with shanks are used.
Equipment and apparatus must also be disconnected. It is unacceptable to use complex stop valves for the wire. Strength test involves connecting the pipeline to hydraulics, among such devices should be highlighted:
- air networks;
- pumping stations;
- compressors.
All this allows you to provide the necessary pressure to check. Tests should be conducted under the guidance of a master or manufacturer, while taking into account the requirements of technical documentation, design papers and instructions. It is important to comply with safety regulations and regulations of state technical supervision.
For reference
Strength testing involves the use of test fixtures and pressure gauges. They must first pass an expert examination, be surely sealed. Pressure gauges should belong to the accuracy class, the minimum level of which is kept within 1.5, which corresponds to state standards 2405-63. The diameter of the case should be 1.5 cm or more. The thermometers used must have a division value of up to 0.1 ° C.
Methodology
A hydraulic strength test is also carried out to determine the density. When testing experiments, the pressure value is set in accordance with the design documentation in kgf / cm 2 . As for steel structures, their operating threshold should not exceed 4 kgf / cm 2 , with a system operating temperature exceeding 400 ° C. The pressure in this case will be equal to the limit from 1.5 to 2.
If the working threshold of the steel structure exceeds 5 kgf / cm 2 , then the pressure will be 1.25. Sometimes this value is determined by the formula, which assumes the sum of the workload and the value of 3 kgf / cm 2 . If we are talking about products made of cast iron or polyethylene, then the pressure will be 2 or more. As for non-ferrous metal alloys, the figure is equal to one. The following types of presses are used to obtain the required loads:
- operational;
- gear gears;
- mobile plunger;
- manual (piston);
- hydraulic.
Testing
Tests for strength and tightness using the hydraulic method are carried out in several stages. On the first, a press or a hydraulic pump is connected. Then the manometers are mounted by the brigade, and the structure itself is filled with water. It is important to ensure the displacement of air from the system, for this the air vents are left open. If water gets into them, then this means that there is no air left.
As soon as the system is completely filled with liquid, its surface should be inspected for cracks, leaks and blemishes that may occur around the perimeter in the connecting elements. The test for strength and tightness in the next step involves the supply of pressure with prolonged exposure. The load can be gradually reduced until the indicative values have reached the standard level. This will allow you to examine the state of the system again. The pipeline at the next stage is freed from water, and the equipment can be disconnected and removed.
Secondary inspection and final work
If glass compounds are present in the system, then they must be subjected to loads for 20 minutes, but for other materials 5 minutes will be enough. During the secondary inspection, it is necessary to pay attention to adhesions and welds. They should be tapped with a hammer weighing 1.5 kg or less. It is important to provide access within 20 mm.
When testing elements of non-ferrous metals, you should use a wooden hammer, whose weight does not exceed 0.8 kg. The remaining materials are not subject to such tapping, as they may be damaged. Hydraulic strength tests are considered successful if the pressure gauge did not show a drop in pressure, the leaks were not fixed, and the welds and flange joints worked stably, withstanding the load.
The check should be repeated if the results were unsatisfactory, but work should only be carried out after all errors have been eliminated. For hydraulic tests (at low temperatures), substances that reduce the crystallization temperature of water can be added to the liquid. The liquid can be heated, and the pipes can be additionally insulated.
Pneumatic test
When considering strength testing methods, pneumatic testing should be highlighted. It is used to test strength and / or density. Freon and ammonia products are not hydraulically inspected, in this case only pneumatic inspection is used.
Sometimes it happens that hydraulic studies cannot be applied. This can happen when the air temperature drops below zero or there is no water in the area. If there is a prescription to use air or inert gases, then hydraulic tests cannot be used.
Pneumatic testing should also be used if high voltage is noted in the supporting structures and piping due to the impressive mass of water. Inert gas or air is used to carry out such tests. Use mobile compressors or a compressed air network.
Tests for strength and density require compliance with the pressure and length of the divisions. Thus, if the diameter is 2 cm, then the pressure should be equal to 20 kgf / cm 2 . If the diameter varies from 2 to 5, then the pressure should be 12 kgf / cm 2 . When the diameter exceeds 5 cm, the pressure should be equal to 6 kgf / cm 2 . If the project requires it, then you can use other values.
Helpful information
Elevated structures made of glass and cast iron do not pass pneumatic tests. If the steel system has cast iron fittings, then inert gas or air can be used for testing, as an exception, malleable cast iron parts are used .
Work procedure
Strength testing by the pneumatic method involves filling the pipeline with air or gas in the first stage. Further pressure rises. When the level rises to 0.6, you can proceed to the inspection of the inspected area. This is true for designs in which the working pressure indicator reaches 2 kgf / cm 2 .
During inspection, the load should be increased. However, hammering on surfaces that are under load is unacceptable. At the final stage, the system is inspected during workloads. Tests of the tensile strength of welded joints and seams, flanges and seals involves the application of a soap solution.
If the system conveys flammable, toxic toxic substances, the leak test is supplemented by a density test. For this, a pressure drop is simultaneously investigated. It is important to check all equipment that is connected to the system. If during the strength test the pressure on the manometer did not decrease, and sweating and leaks were not detected in the seals and connecting joints, then the result is considered satisfactory.
Test Report Information
When tests are carried out by a construction organization or commission, the following documentation is submitted:
- executive scheme;
- test site design;
- welding journal;
- isolation work journal;
- test of strength and tightness.
As an additional application, certificates for parts and pipes, as well as passports for equipment, are made. The test result of a single site is an act.
Based on the results of the leak investigation, the commission draws up an act, materials that must contain:
- name of company;
- composition of the commission;
- information about the test parameters;
- certificate for collapsed (defective) pipe;
- information about the design of the pipeline;
- extract from the welding journal;
- elevation mark of the gap;
- Act of production and acceptance of construction works.
The act of testing the pipeline for strength is prepared taking into account current regulations. It necessarily involves an indication of the composition of the commission, the timing of the work and the conclusion, signatures of those responsible. From these documents it will be possible to find out under what parameters a leak test was carried out. This should include not only pressure, but also the overall length of the system. The act of testing the pipelines for strength will contain the name of the used devices, other equipment, as well as the place of their installation and the length of the section from which water was removed after the test.
Conclusion
Pipeline testing and evaluation should be carried out exclusively by qualified personnel. They should receive job descriptions and have appropriate skills. It is important to remember that the test of the pipeline for strength and tightness must be carried out in a timely and thorough manner, because only in this way it will be possible to exclude accidents, losses and even accidents.