The selection of differential pressure mass flow meters in steam, gas, and liquid measurement requires comprehensive consideration of fluid characteristics, measurement requirements, installation conditions, and economy. The following are specific selection guidelines:
1、 Steam measurement selection
Steam type
Saturated steam: Temperature and pressure are strongly correlated, and temperature and pressure compensation functions (such as differential pressure+temperature and pressure sensors or intelligent flow integrators) need to be configured to ensure accurate density compensation.
Overheated steam: Under high temperature and high pressure conditions, vortex flowmeter (with a wide range and high temperature resistance) or differential pressure flowmeter (such as V-cone and orifice flowmeter) should be preferred, and a high temperature resistant differential pressure transmitter should be provided.
key parameters
Temperature/pressure range: Choose models that are resistant to high temperatures (≤ 350 ℃) and high pressures (≤ 4MPa), and higher specifications are required for superheated steam.
Straight pipe section requirements: Vortex flowmeters require a 5D straight pipe section after D, and differential pressure flowmeters require a 5D front and 3D back (which can be shortened if a flow regulator is installed).
Condensation protection: Differential pressure type requires the installation of a condensation tank to avoid liquid hammer damage to the sensor.
Recommended Model
Cost effectiveness priority: Vortex flowmeter (range ratio 10:1, with temperature and pressure compensation).
High precision requirements: differential pressure type (such as V-cone flowmeter, low pressure loss, high temperature and high pressure resistance).
2、 Gas measurement selection
Gas characteristics
Clean gas: Optional differential pressure (orifice plate, nozzle) or vortex flowmeter, considering gas density and compressibility.
Dirty gas: Choose non-standard throttling devices (such as circular orifice plates) or differential pressure flow meters with self-cleaning function.
key parameters
Pressure loss: Venturi tubes or low-pressure loss nozzles are preferred for low-pressure gas systems.
Range ratio: The vortex flow measurement range ratio reaches 15:1, suitable for situations with large flow fluctuations.
Anti vibration: Vortex flowmeters are sensitive to vibration and require the selection of anti vibration or differential pressure models.
Recommended Model
Large caliber gas: differential pressure type (orifice flowmeter, low cost, easy to maintain).
Small caliber high-precision: Vortex flowmeter (with temperature and pressure compensation).
3、 Liquid measurement selection
Liquid characteristics
Clean liquid: Optional differential pressure (orifice plate, Venturi tube) or electromagnetic flowmeter (no pressure loss, corrosion-resistant).
High viscosity liquids: When selecting target flow meters or elliptical gear flow meters, the influence of viscosity on Reynolds number should be considered.
key parameters
Requirements for straight pipe section: Differential pressure type requires a front 5D and back 3D straight pipe section, while electromagnetic flow meters do not have strict requirements.
Pressure loss: The Venturi tube has low pressure loss and is suitable for low-pressure systems; The pressure loss of the orifice plate is high, and the system pressure needs to be evaluated.
Corrosivity: Choose differential pressure flow meters made of stainless steel or Hastelloy alloy, or electromagnetic flow meters (with corrosion-resistant lining).
Recommended Model
General liquid: differential pressure type (orifice flowmeter, standard mature, low cost).
Corrosive liquid: Electromagnetic flowmeter (unobstructed flow component, corrosion-resistant).
High viscosity liquid: Target flowmeter (range ratio 3:1, suitable for viscosity ≤ 200mPa · s).
4、 General selection principles
Accuracy and repeatability: Select 0.5 level (high precision) or 1.5 level (general industrial) according to process requirements.
Output signal: 4-20mA, pulse or Modbus, compatible with PLC/DCS system.
Certification requirements: ATEX (Explosion proof), SIL (Safety Integrity) or FDA certification is required for the chemical/food industry.
Economy: Comprehensive evaluation of procurement costs, installation costs (such as differential pressure requiring matching transmitters), and operation and maintenance costs.