Hydraulic test and airtightness test

I believe that the water test is used to check for any leaks in the welds, while the airtightness test is used to examine the flanges. The pressure used in the water test is higher than that used in the airtightness test; it is 1.5 times the design pressure, whereas the pressure in the airtightness test is 1.1 times the design pressure.

The purposes of hydrostatic testing and airtightness testing are definitely different. Hydrostatic testing is used to determine whether pipeline equipment is leaking, and it takes into account factors such as the material used, manufacturing processes, and design. The pressure applied during hydrostatic testing is usually 1.5 times the design pressure. Airtightness testing, on the other hand, focuses on whether there are any defects or errors in the installation

Hydraulic testing is generally carried out on equipment to check for any issues and to determine its pressure resistance； The airtightness test is related to the production process, and it primarily checks whether the sealing of flange connections, manholes, etc. is proper

It should be a strength test and a airtightness test, as they serve different purposes.

Hydraulic and airtightness tests must be carried out properly; we encountered issues with the pipe material during the pressure testing here.

The hydrostatic test pressure should be such that it can assess the strength of the pressure-bearing components and reveal any defects, without causing damage to them. It is generally specified that the membrane stress on pressure-bearing components under hydrostatic test pressure shall not exceed 90% of the material’s yield limit at the test temperature. The specific pressure requirements for hydrostatic testing are as follows: (1) For pressure vessels, individual boiler drums, and welded boilers delivered complete, the test pressure can be selected. (2) Manifolds and other similar components should be subjected to a hydrostatic test at 1.5 times the working pressure. (3) The heated surface tubes and other pressure-bearing fittings subjected to butt welding shall be subjected to a hydrostatic test one by one, with the test pressure being twice the operating pressure of the components. The welded joints of the heat-exchange surface tubes and pipes assembled at the construction site can undergo a hydrostatic test simultaneously with the main body. The hydrostatic test shall be carried out after non-destructive testing has been successful and heat treatment is complete. The test procedure is as follows: (1) Before the test, all the fastening bolts of the connected components must be properly installed, and two pressure gauges with the same range and calibrated should be mounted on the test setup in easily accessible locations. (2) The test site should be equipped with reliable safety protection devices. Stop work unrelated to the experiment and evacuate personnel not involved in it. (3) After filling the boiler and pressure vessel with water, use the vent valve at the top to remove all the air from inside. Check whether the outer surface is dry. (4) Slowly increase the pressure to the maximum operating pressure; after confirming there are no leaks, continue to raise the pressure to the specified test pressure. The welded boiler shall be held at the test pressure for 5 minutes ； Pressure vessels are held under pressure for 10 to 30 minutes depending on their volume. Then it is reduced to the maximum operating pressure for inspection. The pressure should remain constant during the inspection. The acceptance criteria for the hydrostatic test are as follows: (1) After the hydrostatic test of the pressure vessel, there should be no leaks, no visible abnormal deformations, and no unusual noises during the test; in such cases, the hydrostatic test is considered successful. (2) During the boiler hydrostatic test, there are no water droplets or mist on the metal walls and welds of the pressure-bearing components ； At the flared area, no water droplets appear after the pressure is reduced to the operating level ； No residual deformation occurred after the hydrostatic test. If the above conditions are met, the hydrostatic test is considered successful. The airtightness test is primarily used to check whether there are any leaks at the various connection points of the container. Pressure vessels with a medium toxicity level that is extremely hazardous or highly hazardous, or those for which minor leaks are not permitted by design, must undergo a leak-tightness test. Pressure vessels shall undergo a leak test in accordance with the following requirements: (1) The leak test shall be carried out after the hydraulic test is successful. For pressure vessels whose design requirements call for a pressure test, the airtightness test can be carried out simultaneously with the pressure test, and the test pressure should be the same as that of the pressure test. (2) For pressure vessels made of carbon steel and low-alloy steel, the temperature of the gas used for testing shall be not lower than 5°C; for pressure vessels made of other materials, it shall be as specified in the design drawings. (3) The gas used for the airtightness test should be dry, clean air, nitrogen, or other inert gases. (4) When conducting a airtightness test, all safety accessories must be installed. (5) During the test, the pressure should be increased gradually; once the specified test pressure is reached, it should be maintained for 10 minutes before being reduced to the design pressure. Soap water should be applied to all welds and joints for inspection, and no leaks are considered acceptable. In the event of a leak, carry out hydraulic and airtightness tests again after repair. A gas-tightness test is different from a pressure test. Firstly, their purposes are different; the airtightness test is used to check the tightness of pressure vessels, while the pressure test is used to assess the pressure resistance of such vessels. Secondly, the test pressures are different: the airtightness test pressure is the design pressure of the container, while the pneumatic test pressure is 1.15 times the design pressure.

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1. Pressure pipelines must undergo pressure tests and gas leakage tests. 2. Pressure tests include partial pressure tests and air pressure tests. The test pressure for hydraulic tests is 1.5 times the design pressure at the same temperature, while the test pressure for pneumatic tests is 1.15 times the design pressure at the same temperature. Pressure tests should generally be conducted using liquids; pneumatic testing can be used as an alternative only with the approval of the technical supervisor of the construction party, and under the following conditions: 1) Pipeline systems with a nominal diameter of 300 DN or less and a test pressure of 1.6 MPa or less ； 2) Pipeline systems with a nominal diameter greater than DN300 and an experimental pressure of less than or equal to 0.6 MPa. 3. The gas leakage test, also known as a airtightness test, is conducted at the design pressure. The experimental medium is an inert gas.

The purpose of a hydrostatic test is to verify the pressure-bearing capacity of the equipment, while a pneumatic test is used to check whether there are leaks in the flanges connecting the equipment.

Airtightness testing and pressure testing are different. Firstly, their purposes are different; a hydrostatic test is used to verify the pressure resistance of pressure vessels, while a airtightness test is used to check the sealing quality of such vessels. Since gas molecules are smaller than liquid molecules, this means that the absence of leaks in liquids does not necessarily imply the absence of leaks in gases. I think, under the same pressure, conducting a leak test is a bit more difficult. There are two reasons: first, it is more difficult to seal, and it is not easy to maintain pressure. Secondly, air can be compressed much more difficult than water, so the pressure building up is slower.