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1. Requirements for hydrostatic testing 1.1 The hydrostatic testing of boilers is generally divided into testing at the rated operating pressure and over-pressure testing. The over-pressure testing pressure for the boiler itself (including the superheater) is 1.25 times the rated operating pressure of the steam drum, while the over-pressure testing pressure for the reheater is 1.5 times the rated operating pressure at the reheater inlet. 1.2 A superpressure hydrostatic test is required in any of the following situations: a. For newly installed boilers before starting up for trial operation ； b. After major modifications or replacements of the pressure-bearing components of the boiler ； c. Boilers in operation shall be inspected once every six years (in conjunction with major overhauls). 1.3 A working pressure hydrostatic test is required in any of the following situations: a. After regular major or minor repairs, or emergency repairs, the boiler shall undergo a working pressure hydrostatic test following the repairs ； b. For units that have been out of service for more than 30 days, a hydrostatic test at working pressure must be conducted prior to restarting them ； c. Hydrostatic testing of the reheater system is generally not carried out; in special cases, it may be proposed by the technical department and implemented upon approval by the chief engineer. 1.4 The hydraulic test of the boiler shall be carried out in accordance with relevant regulations. 1.5 The boiler hydrostatic test must be accompanied by a test plan and measures, and approved by the chief engineer. 1.6 The test operations shall be uniformly directed by the shift supervisor, with two persons assigned to control the pressure and monitor the pressure gauge. 1.7 During maintenance, all constant-force hangers on the main steam and reheat steam pipes, as well as all spring hangers in the top suspension devices, should be temporarily fixed using pins or positioning plates (to be removed after the hydrostatic test is completed). To prevent these hangers from failing due to overload. 1.8 During the hydrostatic test, no less than two pressure gauges that have passed calibration should be installed on the boiler (the accuracy of these pressure gauges should be 0.5 grade or higher, with a range of 40 Mpa). The test pressure shall be determined based on the reading of the pressure gauge located in the upper drum; the pressure gauge in the control room as well as the pressure gauge at the superheater outlet must be calibrated by thermal engineers to ensure they match the readings of the pressure gauge in the upper drum. 1. When raising pressure to 1.9 liters, it is necessary to anticipate potential accidents and prevent overpressure. In emergency situations (such as loss of control of the feed water pump or control valves), the following measures can be taken in sequence: a. Open the superheater drum drain valve ； b. Open the drum emergency drain valve ； c. Open row or fixed-row doors ； d. Shut down the feed water pump urgently. 2. Scope of hydrostatic test 2.1 The primary circuit includes the feedwater pipes, economizer, steam drum, downcomer, water wall, superheater, main steam pipes, as well as the headers and connected pipes. 2.2 The secondary circuit includes the cold reheat pipeline, reheater, hot reheat pipeline, along with associated headers and connecting pipes. 2.3 The hydraulic testing of all exhaust pipes, drain pipes, instrument pipes, and chemical feed pipes shall be carried out up to the secondary valve. 2.4 The local water level gauge and safety valve of the steam drum are only involved in the working pressure hydrostatic test, not in the overpressure hydrostatic test. 3. Inspections and preparations before the hydrostatic test 3.1 Inspect the steam and water systems related to the boiler’s hydrostatic test to ensure that the maintenance work is complete, that the work order has been closed, and that there is no one working inside the furnace or in the rear flue ducts. 3.2 Upon receiving the notice of the hydrostatic test, contact the chemistry department to prepare for the boiler hydrostatic test. 3.3 Standard pressure gauges have been installed locally at the steam drum and reheater inlets. These gauges have been calibrated correctly; their accuracy is at least 0.5 grade. Additionally, more than two pressure gauges connected to different sampling points are in use and have been calibrated as well. Communication devices should be provided between the site and the control room. The pressure gauges for the drum, superheater, reheater, and feedwater, as well as the electric contact level gauge for the drum, are put into operation. 3.4 Take measures to prevent water from entering the turbine. 3.5 Connect power to the accident drain valve; ensure it operates smoothly and that the drain pipe is unobstructed. 3.6 The water used for hydrostatic testing shall be precisely treated deionized water, and its quality requirements shall comply with those specified in the hydrostatic testing plan. Set the superheater electromagnetic pressure relief valve control switch to the off position. 3.7 Check that all valves are in the correct position. 4. Hydrostatic test procedures 4.1 After completing the inspections and preparatory work prior to the test, report to the person in charge of the test and the shift supervisor; with the supervisor’s approval, water can be introduced. The process of introducing water must be carried out strictly in accordance with the regulations specified in the preparation phase. Stop feeding water when the water level visible in the drum reaches -100 mm. 4.2 Open the electric shut-off valve for the secondary desuperheating water in the superheater, and adjust the secondary desuperheating water control valve to feed water back into the boiler. 4.3 When water continuously overflows from the various air valves of the boiler, close each air valve in the order of the water flow direction and pause water supply. 4.4 After receiving the pressure increase command, operate the secondary cooling water control valve to increase the pressure gradually; the pressure increase rate shall not exceed 0.3 MPa/min. Once the pressure reaches 10 MPa, the pressure increase rate shall not exceed 0.2 MPa/min. 4.5 When the pressure is raised to about 10% of the lowest setting pressure of the safety valve (with a drum pressure of 2 MPa and a reheater pressure of 0.43 MPa), stop raising the pressure. Check the primary and secondary pressure gauges of the drum and conduct an initial inspection; only if no leaks are detected can the pressure be raised further. 4.6 When the pressure is raised to about 80% of the minimum setting pressure of the safety valve (with a drum pressure of 15.8 MPa and a reheater pressure of 3.5 MPa), stop raising the pressure and maintain stable pressure, then inform the maintenance team to install a clamping device on the safety valve. 4.7 When the pressure reaches the operating pressure of the boiler, close the water inlet valve for 5 minutes, record the pressure drop, and then slightly open the water inlet valve to maintain the operating pressure for a thorough inspection. 4.8 If a overpressure test is conducted, once it is confirmed that everything is functioning normally, the local water level gauge should be disconnected. The pressure should then be increased to the overpressure test level and maintained for 5 minutes. After that, the water inlet valve should be closed, and the drain valve located at the economizer inlet should be opened. The pressure should be reduced at a rate of 0.2–0.3 MPa per minute. Once the pressure reaches the operating level, the drain valve should be closed to stop the pressure reduction. The pressure drop over 5 minutes should be recorded. Then, the water inlet valve should be slightly opened to maintain the operating pressure, allowing for a thorough inspection. 4.9 After the hydrostatic test is completed, pressure is released using a steam trap or a drain control valve, at a rate of 0.2–0.3 MPa/min. Once the pressure in the drum drops to 15.8 MPa and the pressure in the reheater drops to 3.5 MPa, the safety valve’s holding device is released, after which pressure reduction continues. 4.10 When the pressure drops to 0.2 MPa, open the respective air valves to relieve pressure. 4.11 Once the pressure drops to 0 MPa, open all drain valves to release water and restore the operation of the local level gauge. If, after the hydrostatic test, the boiler is ready for operation and the water quality meets the requirements, it should be brought to the ignition level, and additional drainage should be ensured for the superheater, main steam pipeline, and reheater; otherwise, all water should be drained and new water added. 4.12 Acceptance criteria for hydrostatic testing: a. The pressure drop in the boiler itself shall not exceed 0.1 MPa/min, and the pressure drop in the reheater shall not exceed 0.05 MPa/min ； b. There are no signs of water droplets or mist leakage on the metal walls and welds of the compressed components ； c. The heated element shows no significant residual deformation. 5. Precautions for hydrostatic testing: 5.1 The hydrostatic testing shall be supervised by the person in charge of maintenance, with the participation of operation and maintenance staff. In case of any abnormal conditions or failures, the operation staff shall take appropriate actions in accordance with the relevant procedures and regulations ； 5.2 The hydrostatic testing is carried out in the order of low pressure first and then high pressure; first, the hydrostatic testing of the reheater system is performed, followed by that of the main boiler and superheater systems ； 5.3 Before and after water is supplied, the reading of the expansion indicator should be recorded, and it should be checked whether the expansion is normal. The amount of water introduced should be adjusted in a gradual and steady manner; the valves must not be opened or closed suddenly to avoid water shock ； 5.4 During the hydrostatic test, it is necessary to ensure that the temperature of all metal components in the boiler as well as the water temperature remain above 21°C; the water temperature for the hydrostatic test is generally between 30 and 50°C℃ ； 5.5 The water supply to the boiler should not be too rapid, and it must be even. During winter, the water inflow time should be no less than 4 hours; at other times, it should be no less than 2–3 hours. When the temperature of the incoming water is close to the temperature of the drum wall, the water inflow rate can be increased appropriately ； 5.6 During the overpressure test, no inspections shall be carried out; all personnel must stay away from the pressure-bearing components. Inspections of these components can only be performed once the pressure has dropped to the operating level ； 5.7 The hydrostatic test pressure shall be based on the accurate local pressure gauge at the boiler drum or reheater inlet ； 5.8 The water used for hydraulic testing is highly alkaline; take precautions when discharging it and ensure proper treatment of the discharged water ； 5.9 Record in detail the test conditions and any problems encountered.