Pressure gauge range selection - Solutions - Huaqiang Electronic Network

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1. To ensure the elastic element of the pressure gauge operates reliably within the safe range of elastic deformation, the selection of the pressure gauge range should not only consider the magnitude of the measured pressure but also the rate at which the pressure changes. There should be sufficient room for operation. When measuring stable pressure, the maximum working pressure should not exceed 2/3 of the gauge's range.

2. When measuring pulsating pressure, the maximum working pressure should not exceed 1/2 of the gauge’s range.

3. For high-pressure measurements, the maximum working pressure should not exceed 3/5 of the range. To maintain accuracy, the minimum working pressure should not be less than 1/3 of the range. Based on this principle, after calculating a value based on the maximum measured pressure, it is recommended to select a range slightly larger than the calculated value from the pressure gauge catalog.

4. The selection should also depend on the boiler’s working pressure. The upper limit of the measurement range should be 1.5 to 3.0 times the working pressure, ideally 2 times. In industrial boilers, the actual working pressure is usually lower than the rated pressure indicated on the nameplate. For example, a 4t/h steam boiler with a rated pressure of 1 MPa should be equipped with a 1.6 MPa range pressure gauge if the manufacturer specifies 1.5 times the rating. If the user requires the process to operate at 0.5 MPa, the pointer will be below one-third of the scale, making it difficult to read accurately. This indicates that the selected gauge has an excessively large range.

The same applies to hot water boilers. For example, a heating boiler with a rated pressure of 0.7 MPa should use a 1 MPa or 1.6 MPa gauge. If a 1 MPa gauge is used, there may be concerns about overload during hydraulic testing, so a 1.6 MPa gauge is often chosen. However, in normal operation, when only 0.2 MPa is needed, the pointer will sit at around 1/8 of the scale, which reduces both accuracy and sensitivity.

5. To solve these issues, two types of pressure gauges should be used: one for hydraulic testing, which is selected according to the boiler’s rated pressure, and another for daily operations, which should have a range twice the actual working pressure. For instance, if the working pressure is 0.2 MPa, a 0.4 MPa gauge is suitable. This ensures the pointer remains in the middle of the dial, providing better readability and reliability.

6. Additionally, the set pressure of the safety valve should be adjusted according to the working pressure. This allows the pressure gauge to have enough margin to indicate overpressure conditions effectively.