Current situation and development trend of pressure gauge selection

Current situation and development trend of pressure gauge selection

1. First, select the type of pressure gauge according to different parts and requirements. Pressure gauges can be divided into many types according to different classification methods, such as pointer pressure gauge and digital pressure gauge according to their display mode; It can be divided into ordinary pressure gauge, ammonia pressure gauge, oxygen pressure gauge, electric contact pressure gauge, remote pressure gauge, vibration resistant pressure gauge, pressure gauge with inspection pointer, double needle double tube or double needle single tube pressure gauge, digital display pressure gauge, digital precision pressure gauge, etc.

2. When selecting the application range of the pressure gauge, it is appropriate to select 1 / 3 ~ 2 / 3 of the full range. The accuracy of this application range is high, and the application range is very high, which shall not exceed 3 / 4 of the full scale. 3. Select the accuracy level according to the allowable error required by the very small value of the measured pressure. Precision pressure gauges have Accuracy grades of 0.1, 0.16, 0.25, 0.4 and 0.5; General industrial pressure gauges are divided into four accuracy levels: Level 1, level 1.6, level 2.5 and level 4. The allowable errors (calculated according to the percentage of the upper limit of measurement) are ± 1%, ± 1.6%, ± 2.5% and ± 4% respectively.

4. The name of the manufacturer or its abbreviation shall be on the dial of each pressure gauge. Manufacturers can be selected by comprehensively considering the use requirements, quality, price, after-sales service and other factors. 2、 Several special pressure gauges 1 Oil prohibition pressure gauge jjg52-2013 specification for elastic element general pressure gauge, pressure vacuum gauge and vacuum gauge

There are corresponding provisions on the oil prohibition pressure gauge in:

(1) For pressure gauges measuring oxygen, hydrogen, acetylene and other combustible (combustion supporting) gases, the name of the measured medium and the color warning mark of the measured medium shall be marked on the index plate. The oxygen pressure gauge must also be marked with red "no oil" on the index plate or with standard no oil mark.

(2) There should be no grease in the inner cavity of the connector box of the oxygen pressure gauge.

(3) When the oxygen pressure gauge is required to be checked without oil, it shall be checked without oil, that is, it shall be judged by the principle of "water and oil insoluble". Generally, the oxygen meter can be used instead of the argon meter, because argon is an inert gas. For example, pure argon used in direct reading spectrometer mostly uses the oxygen meter. 2. Electric contact pressure gauge electric contact pressure gauge is widely used in petroleum, chemical industry, metallurgy, power station, machinery and other industrial departments or supporting electromechanical equipment to measure the pressure of various fluid media without explosion risk. Usually, the instrument can realize the purpose of automatic control and alarm for various gas and liquid media under controlled pressure through the instrument after being used together with corresponding electrical devices. The electric contact pressure gauge is an additional electric contact signal device on the ordinary pressure gauge. It is a circuit switch operated by the pressure gauge. The pressure part is the same as that of the ordinary pressure gauge. After the pressure part is qualified, the electric contact signal device needs to be tested.

3. Capsule pressure gauge, also known as micro pressure gauge, is suitable for measuring the low micro pressure of liquid, gas or steam without explosion risk, crystallization, solidification and corrosion to copper and copper alloy. Jjg52-2013 covers the contents of jjg573-2003 specification for bellows pressure gauge.

The main differences between capsule pressure gauge and pressure gauge are as follows:

(1) Pressure gauge is a general term of gauge, including capsule pressure gauge.

(2) Capsule pressure gauge can only be used to measure gas or micro pressure, while pressure gauge can measure many media or high pressure. (3) There are many Accuracy grades of pressure gauges, and grades 1.6 and 2.5 are very common. The accuracy grade of capsule pressure gauge is divided into grade 1.6 and grade 2.5, but most of them are grade 2.5. More than 90% of capsule pressure gauges encountered in ordinary experiments are grade 2.5. (4) Only capsule pressure gauges expressed in kPa are encountered in the laboratory.

(5) Generally, the pressure gauge takes the spring tube as the inner core, and the workmanship is relatively rough. Capsule pressure gauges generally use diaphragm material as the inner core, and the workmanship is relatively exquisite. 3、 Special problems in pressure gauge 1 Through years of experience in pressure gauges and communication with users, it is found that many users reflect that their pressure gauges are not broken, but broken before being disassembled or damaged during reassembly, that is, they are "broken after inspection". As a more precise instrument, the pressure gauge must take into account the precautions in all aspects, such as installation, disassembly, transportation, reinstallation, etc. After installation, it is more necessary to consider the tightness. Most users use raw tape to ensure the tightness.

Some installers may have a relatively large amount of winding due to their strong hand; In consideration of the installation position, observation direction and other factors, some masters will also have differences... Therefore, some pressure gauges are qualified, and it will be more troublesome to disassemble them after reinstallation, and some must use a wrench to screw them off; Some users will mistakenly think that the watch is broken because the air tightness cannot be reached after reinstallation, resulting in the immobility of the pointer; The screw thread of some pressure gauges has been seriously damaged after several disassembly and installation,