Radar level gauge selection considerations
From radar level gauge measurement in engineering design, the main technological conditions of liquid level gauge probe, selection of transducer and a few options to consider.
1, instrument type choice: microwave level due to the different characteristics, different types of applications is different also, to consider based on the characteristics of instrument, model selection of the design to meet the requirements of the process parameters and installation.
(1) antenna type radar liquid level gauge
Due to wrong contact measurement, installation is more convenient, so is the first selection, in the petrochemical industry, there are three main areas of application:
❶ trade settlement and inventory management: this field is mainly used for fuel oil and chemical liquid storage and transport, measuring object is a large storage tank. For this kind of situation is level measurement radar liquid level gauge. According to international practice for trade settlement of high level gauge accuracy requirement; Low accuracy requirement for inventory management. Generally should be output by the digital communication, so that with other devices (average thermometer, pressure transmitter, tank next to the display, etc.) and the terminal management software interface is established. This kind of market steady increase, accounts for about 10% radar level gauge market
❷ tank level measurement: petrochemical, chemical, pharmaceutical and other industries have liquid products or semi-finished products need intermediate storage, storage tank general line for the cylindrical, vertical or horizontal, constellation size, liquid level range from a few meters to 20 meters. Acceptable accuracy of measurement is plus or minus 0.1%. The storage tank liquid surface calm, little disturbance, low pressure and room temperature. Such applications is growing rapidly, the original use float type, pressure type, and other products, radar level meter in the non-contact measurement way, higher accuracy, less maintenance quantity gradually replace other products. Currently accounts for 55% of radar level gauge applications. Acid-base tank a Shared insulating rod antenna, the other with conical horn antenna. Because of its small installation size, small beam Angle is small, the amount of measurable low dielectric constant, and gradually become the mainstream in the selection.
❸ process level measurement applications: mainly in petrochemical, chemical and other industries for different medium mixed reaction, high temperature and pressure. Tank structure is complex, with stirring, foam, hanging, steam and liquid level fluctuation. Range is generally small, about several meters. This kind of mixed hf radar level gauge is generally choose, beam Angle is small, requires a perfect echo processing function, also pay attention to the temperature, pressure, medium compatibility, etc. Such applications account for about 35% of radar level gauge applications.
(2) the guided wave radar level gauge
In the following occasions, radar level gauge cannot very good application of non-contact, good application: (A) and guided wave type tested material with low dielectric constant; (B) in a relatively narrow space measurement, or tank structure is complex, lead to echo is complex, difficult to confirm; (C) a very ACTS rest Angle or very low dielectric constant of bulk solid material level measurement; (D) high temperature and high pressure conditions; (E) liquid interface. Especially in high temperature and high pressure conditions, as probe institutions is a metal rod, high temperature, high pressure, and have no moving parts, and the measurement process and measured physical parameters, such as medium density has nothing to do.
2, process parameters considered
(1) of the measured medium dielectric constant
Application of radar level gauge, this is an important parameter. The launch of microwave energy for decision. Different types of radar level gauge can be used, MIN relative dielectric constant, the measurement would not be stable, to model selection of the left margin. Measuring the liquid interface, the upper and lower sides of the liquid permittivity must know, the upper liquid must be low dielectric constant, and the lower the liquid permittivity must be five times as the upper liquid dielectric constant, or the lower liquid is conductive.
(2) the operating pressure
Radar level gauge has the different stress levels, must be chosen to meet the requirements of industrial pressure products, antenna type usually pressure up to 4 mpa. Higher pressure to choose guided wave radar level gauge.
(3) the operating temperature
Radar level gauge is usually and process tank connected by flange, so the process of radar level gauge and heat-resistant refers to the temperature of the flange. Radar level gauge must also ensure the electronic components at the same time shell environment temperature is not more than 80 ℃.
(4) operating density
Operating density of different radar level gauge measurement process would not be affected.
(5) the operating viscosity
When choosing guided wave radar level gauge type, want to consider viscosity influence, causes on the coaxial probe and double pole type probe hanging in the medium is not applicable to this type of probe.
3, probe installation consideration
Mainly is the process of considering radar level meter in tank connection, and meet the requirements of process and measurement.
❶ measurement range
The optional level meter range must meet industrial measuring range, for guided wave radar level gauge type, must cover the probe inserted length measurement range.
❷ process connection forms and specifications and grades
Usually are connected by a threaded connection, flange connection, and health. According to the specification selection response connection forms and specifications and grades.
❸ antenna material
Antenna material main consideration and chemical compatibility with measured medium, especially the wave guide rod and the contact of the measured medium, can choose a compatible material and coating layer.
4, the transmitter
Radar level gauge is usually a body structure. Transducer is installed in the top of the liquid level gauge shell, selection considering mainly the electrical connection in the transmitter and the external, usually have: the power supply voltage, output signal, precision, explosion-proof registration, shell material, protection grade, the size of the cable entry, such as the selection according to the specification requirement.
Radar level gauge as in recent years the fastest growing liquid level measuring instrument, the applicable scope is wide, high measuring progress, convenient in operation and maintenance. With the rapid development of China's economy in recent years, more and more applications in the field of all kinds of process industry. Based on the technical features of radar level gauge and fully understand the technical parameters, the reasonable application of this new type of liquid level meter, can make its play more important role in the field of level measurement.