In response to your question about the selection of boiler feedwater flow meters, and considering the given operating conditions (medium temperature of 177 ℃, DN40 size, American standard flange 600 pound connection, flow range of 0-7m ³/h), turbine flow meters are not suitable due to high medium temperature. It is recommended to use vortex flow meters or orifice flow meters. The following is a specific analysis:

 

1、 Reasons for unsuitability of turbine flowmeter

Although turbine flow meters have the advantages of high measurement accuracy, high pressure resistance, and strong anti-interference output signals, their applicable range for medium temperature is usually -20 ℃ to 80 ℃ (some models can be extended to -200 ℃ to 400 ℃, but special design is required). In the operating conditions you provided, the boiler feedwater temperature is 177 ℃, far exceeding the temperature tolerance limit of ordinary turbine flow meters, which may cause impeller deformation, accelerated bearing wear, or sensor failure, thereby affecting measurement accuracy and lifespan. Therefore, it is reasonable for technicians to suggest excluding turbine flow meters.

 

2、 Comparison and recommendation of vortex flowmeter and orifice flowmeter

1. Vortex flowmeter

Advantages:

Wide range ratio: The intelligent vortex flow metering range ratio can reach 1:9 to 1:10, covering a flow range of 0-7m ³/h (it needs to be confirmed whether the lower limit of 3m ³/h meets actual needs).

Small pressure loss: The pressure loss is only 1/4 to 1/2 of that of an orifice flowmeter, which helps to reduce system energy consumption.

High reliability: no moving parts, not easily worn, and requires minimal maintenance.

Wide applicability: capable of measuring gases, liquids, and vapors, insensitive to changes in fluid density, pressure, and temperature.

Disadvantages:

Lower limit flow velocity limit: When the flow velocity is below a certain value, the vortex becomes unstable, which may affect the measurement accuracy. In the operating conditions you provided, the lower limit of flow rate is 0m ³/h, but in actual operation, it is necessary to ensure that the flow rate is not lower than the minimum allowable value of the vortex flowmeter (such as 3m ³/h).

Weak seismic performance: sensitive to pipeline vibration, seismic mitigation measures need to be taken.

Applicability:

The parameters of the vortex flowmeter you provided (316 material, American standard 600 pound flange connection, flow range 3-7m ³/h) have a high degree of compatibility with the operating conditions, but it needs to be confirmed whether the lower limit of 3m ³/h meets the flow measurement requirements for low load operation of the boiler.

 

2. Orifice flowmeter

Advantages:

Strong vibration resistance: suitable for working conditions with high vibration.

Measurement range optional: can adapt to different flow ranges by changing the size of the orifice plate.

Suitable for high temperature and high pressure: It can measure fluids with temperatures above 500 ℃ and pressures greater than 40MPa.

Disadvantages:

High pressure loss: Belonging to throttling devices, long-term operation may increase system energy consumption.

Installation complexity: Three valve groups, differential pressure transmitters, condenser pipes, and other accessories need to be installed, resulting in high maintenance costs.

Narrow range ratio: When equipped with domestic differential pressure transmitters, the range ratio is generally 1:3, while imported transmitters can reach 1:6.

Applicability:

If the boiler operates stably and is not sensitive to pressure loss and installation complexity, an orifice flowmeter can be used as an alternative solution.

 

3、 Recommended plan

Priority should be given to vortex flow meters:

Confirm whether the lower limit of flow during actual operation is consistently below 3m ³/h. If not, vortex flowmeter is a better choice because of its low pressure loss and low maintenance.

If the lower limit of flow may be lower than 3m ³/h, it is necessary to consider reducing the diameter or choosing other flow meters.

Alternative orifice flowmeter:

If the operating conditions of the boiler are complex (such as frequent start-up and shutdown, large load fluctuations), or require extremely high measurement accuracy, the anti vibration and high-temperature and high-pressure applicability of orifice flow meters are more advantageous.