Seamless boiler tube is a kind of boiler tube and belongs to the category of seamless steel tube. The manufacturing method is the same as that of the seamless tube, but there are strict requirements on the steel type used in the manufacture of the steel pipe.
High-pressure boiler seamless tubes are often under high temperature and high pressure conditions when used, and the pipes will be oxidized and corroded under the action of high-temperature flue gas and water vapor. Steel pipes are required to have high durable strength, high resistance to oxidation and corrosion, and good structural stability. High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, gas guide tubes, main steam tubes, etc. of high-pressure and ultra-high pressure boilers.
1. What is a seamless boiler tube hydrostatic test?
The seamless boiler tube hydrostatic test is divided into two types: working pressure test and overpressure test. The purpose of the hydrostatic test is to test the strength and tightness of the pressure-bearing parts. Generally, after the maintenance of the pressure-bearing parts, such as the replacement or maintenance of some valves, boiler tubes, headers, etc., and the medium and minor repairs of the boiler, the working pressure test must be carried out. For newly installed boilers, overhauled boilers and boilers with large-scale replacement of heating surface tubes, an overpressure test of 1.25 times the working pressure should be carried out.
2. How to prevent the seamless boiler tube from overpressure during the hydrostatic test?
Hydrostatic test is a major operation related to the safety of the boiler, it must be carried out carefully, and attention should be paid to:
(1) Check the input status of the pressure gauge carefully before carrying out the hydrostatic test.
(2) The power supply of the air exhaust and accident water discharge valves is connected, the switch is flexible, and the steam exhaust and water discharge pipes are unblocked.
(3) During the test, the chief engineer or a professional designated by him should be on site to direct, and the boosting speed should be controlled by a special person, and no replacement is allowed midway.
(4) After the boiler is pressurized, close the water inlet adjustment door and control the pressure increase speed to no more than 0.3MPa/min.
(5) When the pressure is increased to 70% of the working pressure of the boiler, the pressure increase speed should be appropriately slowed down, and safety measures to prevent overpressure should be taken.
3. What are the qualified conditions for the boiler hydrostatic test?
(1) When the upper water door is completely closed, the pressure drops within smin: the high-pressure boiler is qualified if it does not exceed 0.2-0.3MPa, and the medium-pressure boiler does not exceed 0.1-0.2MPa. The pressure drop of the ultra-high pressure boiler is not more than 98kPa per minute.
(2) There are no water drops or mist on pressure-bearing parts, metal walls and welds.
(3) There is no sign of residual deformation of pressure-bearing parts.