Common faults of pressure gauges
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Common faults of pressure gauges include: (1) The pointer does not move. When the pressure increases, the pressure gauge pointer does not move. The reason may be: The cock is not open ； The cock, pressure gauge connecting pipe or water trap is clogged ； The pointer and the central axis are loose or the pointer is stuck. (2) The pointer shakes. The causes of pointer jitter include: Hairspring damaged ； The cock or trap channel is partially blocked ； Both ends of the central shaft are bent, and the rotation of the two ends of the shaft is not concentric. (3) The pointer cannot return to zero when there is no pressure. The reason for this phenomenon is that: The spring bend causes permanent deformation and loses elasticity ； The pointer and the central axis are loose, or the pointer is stuck ； The passage of the cock, pressure gauge connecting pipe or water trap is blocked. (4) The indication is incorrect and exceeds the allowable error. This is mainly due to excessive deformation of the spring tube due to high temperature or overload. ； Gears worn and loose ； hairspring disorder ； Caused by cock leakage and other reasons.
The installation of pressure gauges should comply with the following requirements: (1) Each boiler must be equipped with a pressure gauge directly connected to the steam space of the drum. Pressure gauges should be installed in front of the water supply regulating valve, between the outlet of the separable economizer, the outlet of the superheater and the main steam valve. (2) For boilers or pressure vessels where the working medium is high-temperature steam, a water trap should be installed on the nozzle of the pressure gauge to allow the steam to condense in this section of the elbow to prevent high-temperature steam from directly entering the spring tube of the pressure gauge, causing the components in the gauge to overheat and deform, affecting the accuracy of the pressure gauge. When steel pipes are used for water traps, their inner diameter should not be less than 10mm. A three-way cock should be installed between the pressure gauge and the water trap to facilitate pipe purging, removal and replacement, and calibration of the pressure gauge. (3) Draw a warning red line on the dial of the pressure gauge based on the maximum allowable pressure of the boiler or pressure vessel. However, the warning red line should not be drawn on the glass of the pressure gauge to avoid the illusion caused by the rotation of the glass and cause an accident. (4) For pressure vessels containing high-temperature, highly corrosive or high-viscosity media, a liquid-filled isolation device should be installed on the connecting pipeline between the pressure gauge and the vessel, or a corrosion-resistant corrugated flat membrane pressure gauge should be used. (5) The location where the pressure gauge is installed should have sufficient lighting to facilitate observation and inspection by the operator. Protect the pressure gauge from radiant heat, low temperature and vibration. (6) In order to facilitate the replacement and calibration of the pressure gauge, a three-way cock should be installed between the pressure gauge and the pressure-bearing equipment. The cock should be installed on the vertical pipe section and have an opening mark and a locking device.
The pressure gauge should be stopped from use when any of the following conditions occur:: (1) For a pressure gauge with a limited stop nail, when there is no pressure, the pointer cannot return to the stop nail after rotation. ； For a pressure gauge with an infinite stopper, when there is no pressure, the value of the pointer from the zero position exceeds the allowable error specified by the pressure gauge. ； (2) The dial cover glass is broken or the dial scale is blurred ； (3) The seal is damaged or the verification validity period has expired ； (4) The spring tube in the gauge is leaking or the pressure gauge pointer is loose. ； (5) Other defects that affect the accurate indication of the pressure gauge.
study* Got it! Is there anything about vacuum gauges? Do you use a vacuum gauge to measure vacuum?
Vacuum degree measurement of vacuum furnace Vacuum measurement is an important part of vacuum technology. The instrument used to measure vacuum is called a vacuum gauge. Vacuum gauges commonly used in vacuum heat treatment furnaces and vacuum melting furnaces include: Thermocouple vacuum gauge, ionization vacuum gauge, etc. Here's how they work: Heat treatment, metal heat treatment, heat processing, metallographic analysis, heat treatment equipment, heat treatment furnace, quenching medium, heat treatment work. Posts come from: Heat Treatment Forum http://www.rclbb s.com Heat treatment, metal heat treatment, heat processing, metallographic analysis, heat treatment equipment, heat treatment furnace, quenching medium, heat treatment work The authoritative technical exchange platform for the national heat treatment industry! http://ww w.r cl bbs.c om (1) Thermocouple vacuum gauge www.rclbbs.com The post comes from: Heat Treatment Forum http://www.rclbb s.com The thermocouple vacuum gauge consists of a sensitive element, a thermocouple gauge and a measuring instrument. The thermocouple gauge tube is connected to the vacuum system under test. The outer shell is a glass tube, and there are heating wires and thermocouple wires inside the tube. When the temperatures of the cold end and the hot end of the thermocouple wire are different, a thermoelectric potential is generated in the loop due to the temperature difference effect. If the heating wire voltage remains constant, the electric potential of the thermocouple wire depends on the temperature of the heating wire, and the temperature of the heating wire is related to the pressure of the gas being measured. The pressure is low, the thermal conductivity of the gas is small, and less heat is taken away by the gas. The temperature of the heating wire increases, and the thermoelectric potential of the thermocouple wire increases. ； On the contrary, the thermoelectric potential decreases. The thermoelectric potential in the loop is measured with a millivolt meter, and the number of millivolts in the meter reflects the degree of vacuum. In order to ensure the voltage stability of the heating wire, a regulated power supply is connected. Therefore, the measuring instrument consists of two parts: a millivolt meter for measuring thermoelectric potential and a regulated heating wire regulated power supply. Heat treatment forum permanent domain name R cl bbs http://www.rclbbs.com Welcome to the Heat Treatment Forum! The Heat Treatment Forum is a professional community that specializes in discussing heat treatment processes, metallographic analysis, electric furnace equipment, quenching media and heat treatment talent exchanges. Posts come from: Heat Treatment Forum http://www.rclbb s.com (2) Ionization Vacuum Gauge Welcome to the Heat Treatment Forum! The Heat Treatment Forum is a professional community for discussing heat treatment processes, metallographic analysis, electric furnace equipment, quenching media and heat treatment talent exchanges. www.rclbbs.com The permanent domain name of the Heat Treatment Forum, please look for the R clbbs domain name. This vacuum gauge is mainly used to measure high vacuum. In low-pressure strong gases, the number of positive ions generated by ionization of gas molecules is proportional to the gas pressure. Depending on the method of ion generation, a vacuum gauge that uses a hot cathode to emit electrons to ionize the gas is called a hot cathode ionization vacuum gauge. ； Among them, the hot cathode ionization vacuum gauge consists of a hot cathode gauge tube and a measuring instrument. The measuring instrument consists of regulated working power supply, emission current voltage regulator, ion current measurement amplifier and other parts. The hot cathode ionization gauge is connected to the vacuum system under test. The hot cathode ionization regulator is a triode tube with a cathode, grid and collector. Collector potential relative to cathode electronegative potential ； The gate is at a positive potential relative to the cathode. When the ionization regulator is energized and heated, the cathode emits electrons. When the electrons reach the gate, they collide with gas molecules to produce the ionization phenomenon of positive ions and electrons. When the emission current is constant, the number of positive ions is proportional to the pressure of the gas being measured. After the positive ions are collected by the collector, they are amplified by the measurement circuit and can be determined by the electrothermal treatment forum permanent domain name R cl bbs http://www.rclbbs.com The meter reads the vacuum degree to be measured. Heat treatment technology forum, professional heat treatment technology discussion and work exchange community, the authoritative technology exchange platform for the national heat treatment industry! http://ww w.r cl bbs.c om Welcome to the Heat Treatment Forum! The Heat Treatment Forum is a professional community for discussing heat treatment processes, metallographic analysis, electric furnace equipment, quenching media and heat treatment talent exchange http://www. rclbbs.com Heat Treatment Forum (3) Composite Vacuum Gauge Welcome to the Heat Treatment Forum! The Heat Treatment Forum is a professional community that specializes in discussing heat treatment processes, metallographic analysis, electric furnace equipment, quenching media and heat treatment talent exchanges. Heat Treatment Forum permanent domain name R cl bbs http://www.rclbbs.com Usually, the measurement of low vacuum and high vacuum cannot be completed with one vacuum gauge, but a composite vacuum gauge should be used. The most commonly used is the ionization and thermocouple type composite vacuum gauge. Its measurement range is 13.33--666.6×10-8Pa. Thermocouple vacuum gauge measures (10-1--10-3)×133.32Pa low vacuum ； The ionization vacuum gauge measures a high vacuum of 133.32×10-3--666.6×10-8Pa. The compound vacuum gauge is equipped with a thermocouple gauge tube and an ionization gauge tube, which are respectively connected to the vacuum system. The two gauge tubes can be heated separately through the knob and selected for use.
For vacuum degree measurement, please refer to the standard GB/T18443.2-2001 Test method for low-temperature insulated pressure vessels._Vacuum measurement
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