1. In order to ensure that the elastic components of the pressure gauge can work reliably within the safe range of elastic deformation, the selection of the pressure gauge range should not only be based on the magnitude of the measured pressure, but also consider the speed of the measured pressure change, and the range should have sufficient margin. When using a pressure gauge to measure stable pressure, the working pressure should not exceed 2/3 of the range; Use a pressure gauge to measure pulsating pressure, and the working pressure should not exceed 1/2 of the range.
2. When measuring high pressure with a pressure gauge, the working pressure should not exceed 3/5 of the range. To ensure measurement accuracy, the minimum working pressure should not be less than one-third of the range. According to this principle, after calculating a value based on the measured pressure, select a measurement range slightly larger than this value from the pressure gauge product catalog.
3. The selection should be based on the working pressure of the boiler, and the limit value of the range scale should be 1.5 to 3.0 times the working pressure, which is 2 times. In industrial boilers, the actual working pressure during operation is always lower than the rated pressure on the nameplate, which is the case for industrial steam boilers and hot water heating boilers. For example, for a 4t/h steam boiler with a rated pressure of 1MPa, if the manufacturer is equipped with a pressure gauge at 1.5 times, a 1.6MPa range pressure gauge should be provided. If the user can meet the process requirements by operating at a pressure of 0.5MPa due to production process requirements, the pointer of the pressure gauge will point to less than one-third of the range, and the angle of rotation of the pointer is very small, indicating that the selected pressure gauge has a too large range. The same goes for hot water boilers. For example, if the rated pressure of a heating boiler is 0.7 MPa, the pressure gauge equipped should be 1 MPa or 1.6 MPa. If a 1 MPa pressure gauge is equipped, there is a risk of overloading the pressure gauge during water pressure testing, so a pressure gauge with a range of 1.6 MPa is equipped. In actual operation, only 0.2MPa can meet the heating requirements, and the pointer of the pressure gauge points at one eighth of the range, making it difficult to believe in the accuracy and sensitivity of the pressure gauge.
4. To solve the above problems, two types of pressure gauges should be used, namely the pressure gauge equipped by the boiler factory according to the rated pressure during the hydrostatic test;
5. Equip a pressure gauge with twice the actual working pressure during daily operation. If the working pressure is 0.2MPa, a pressure gauge with a range of 0.4MPa should be used. This way, the pointer is in the middle position of the dial, vertically upward. The starting pressure of the safety valve is also adjusted according to the working pressure, and the pressure gauge still has sufficient margin to cope with overpressure indication.