The water level gauge is also called a "liquid level gauge" or "liquid surface gauge". Because the water in the boiler vaporizes at high temperature for heating, the loss of water and steam is large. Water must be continuously added to keep the water level in the boiler at a certain height. If the water level is too low, the boiler is in danger of exploding. In order to keep track of the water level in the boiler at any time, a water level gauge is installed on the boiler. The water level gauge and the boiler form a connecting vessel. Commonly used ones include glass level gauges, pressure level gauges, float level gauges, capacitance level gauges, and resistance level gauges. Under high temperature and high pressure, isotope level gauges can also be used.
Product Introduction
An instrument that automatically measures and records the water level of rivers, lakes, irrigation canals and other water bodies. According to the sensor principle, it can be divided into float type, tracking type, pressure type and reflection type. The main water level recording methods are: recording paper description, data display or typing record, punched paper tape, magnetic tape and solid circuit storage. The accuracy of the water level meter is generally within 1 to 3 cm. The recording period of the water level meter made in China is 1 day, 30 days and 90 days. The travel time error is 2 minutes/day for mechanical clocks and less than 5 minutes/month for quartz crystal clocks.
Product Categories
Float-type water level gauge
The principle is that the float senses the rise and fall of the water level. There are ordinary water level gauges that use mechanical methods to directly use the float to drive the recording structure, there are telex and digital water level gauges that convert the rotation angle provided by the float into incremental electrical pulses or binary coded pulses for long-distance transmission, and there are digital sensing water level gauges composed of miniature floats and many reed switches. The most widely used is the mechanical water level gauge. The use of float-type water level gauges requires logging equipment, which is only suitable for low-sand river sections with stable bank slopes and small riverbed erosion and siltation.
Fiber optic water level gauge
The fiber optic water level gauge includes a water level gauge sensor part and a control circuit terminal part. Among them, the water level gauge sensor part uses an optical path coupling adjustment device to connect with the optical cable to transmit the optical signal carrying the water level information. The control circuit terminal part uses laser modulation technology to send modulated laser signals with different functions. Through modulation, comparison and detection, accurate information on the water level is obtained. This principle realizes full-range optical measurement, and no charged devices are used outdoors, which can eliminate static electricity hazards and prevent lightning damage.
Tracking water level gauge
Also known as contact water level gauge, it uses the electric probe on the heavy hammer to contact the water surface to send out an electric signal, so that the motor rotates forward or reversely, and tracks the position of the water surface point at any time to determine the water level. Generally, an iron pipe is set up on a steeper bank slope, and the hanging hammer and the suspension cable rise and fall in the pipeline to drive the recording or signal device. The water inlet of the iron pipe needs to have sand settling and static water facilities.
Pressure water level gauge
Its working principle is to measure water pressure and calculate water level. Its characteristics are that it does not need to build a static water logging well, the sensor can be fixed on the bottom of the river, and the atmospheric pressure can be eliminated by the pressure pipe, so as to directly measure the water level. There are two types of pressure water level gauges. One type is the bubble type, which continuously supplies air in the pressure pipe, and uses an automatically adjusted pressure balance to convert the water pressure into a mechanical rotation angle, thereby driving the recording mechanism. The other type is the electrical measurement type, which uses a solid-state piezoresistive device as a sensor, which can directly convert the water pressure into a voltage modulus or frequency output, and transmit it to the shore with a wire for processing and recording.
Acoustic water level meter
It is a kind of reflection water level meter, which uses the principle of sound wave reflection on different interfaces to measure water level. It is divided into air medium type and water medium type. The air medium type uses air as the propagation medium of sound waves. The transducer is placed above the water surface, and the sound waves are reflected by the water surface. The water level can be calculated and displayed according to the echo time. The instrument does not contact the water body, and is completely free from the influence of adverse factors such as mud, flow velocity impact and aquatic plants in the water. The water medium type is to install the transducer at the bottom of the river and emit sound waves to the water surface. The propagation speed of sound waves in the water medium is high, the distance is large, and there is no need to build a logging well. Both water level meters can be transmitted to the indoor display or storage record by cable.
Product Difference
There are many kinds of water level gauge products, among which glass tube level gauges and glass plate level gauges are the most used. Glass tube level gauges are divided into ordinary glass tube level gauges and quartz glass tube level gauges due to different materials. There are differences between the two.
Two-color quartz glass tube level gauge
1) Measuring range: 300~2200mm
2) Working temperature: -20~450℃
3) Working pressure: PN0~6.4MPa
4) Quartz tube test pressure: ≤13MPa
5) Meter body material: high-quality carbon steel or 1Cr18Ni9Ti
6) Green when there is liquid, red when there is no liquid
Ordinary glass tube level gauge
It is suitable for use in various environments under normal temperature and pressure. Its biggest features are low price and direct reading display.
Electric level meters are widely used in projects such as rivers, ambers, reservoirs, channels, and hydropower stations.
Features
There are four commonly used water level gauges: glass tube type, flat plate type, two-color water level gauge and low-level water level gauge.
Glass tube water level gauge
The nominal pressure of the glass tube water level gauge is generally not more than 1.6MPa. The nominal diameter is DN15 and DN20. The inner diameter of the glass tube should not be less than 8mm and the thickness should not be less than 3mm.
The glass tube water level gauge is mainly composed of steam cock, water cock, glass tube, drain cock and connecting flange.
The height and change of the water level in the boiler are displayed through the glass tube. The center line of the glass tube should be concentric with the center line of the steam and water cocks of the water level gauge to prevent the glass tube from breaking due to torsional stress. In order to prevent the glass tube from exploding and injuring people, a marble is installed in the cock in the water level gauge with a steel ball. The impact of the steam and water explosion causes the marble to automatically close the steam and water cocks. At the same time, a protective cover should also be installed. The protective cover is generally made of thicker heat-resistant tempered glass plate. If the protective cover is made of iron sheet, a 12~15mm wide gap should be opened on the front and rear walls of the cover in the direction of observing the water level. The length should be larger than the length of the glass tube. The gap at the back is to allow light to enter for easy observation. Do not use ordinary glass as a protective cover to prevent the glass tube from breaking, which will increase the danger.
Double-sided glass plate water level gauge
The double-sided glass plate water level gauge is mainly composed of steam valve, water valve, pressure plate, glass plate, drain valve, drain pipe and flange. Its characteristic is that the glass tube is replaced by a flat glass plate.
The inner surface of the glass plate usually has a triangular groove. The refraction of light in the groove makes the steam-water boundary very obvious. Due to the different refractive indices of steam and water, steam and water will show different colors. Steam is bright white, while water appears gray. The boundary between the two is very obvious and easy to observe.
When the working pressure of the boiler is high, mica sheets can be embedded behind the glass plate to improve operating safety and extend the service life.
Two-color water level gauge
Two-color water level gauges mainly include transmission type, reflection type and reverse transmission type.
1. Transmission type two-color water level gauge This water level gauge is composed of reflectors, light sources, red and green filters, cylindrical condensers, plane mirrors, screens, frames, and soda cocks.
The working principle of the transmission type two-color water level gauge is basically the same as other forms of water level gauges. The difference is that the light of the light source is reflected by the reflector and passes through the optical system, so that the part of the light that passes through the water appears green on the screen mirror, and the part of the light that passes through the steam appears red on the screen mirror, thus showing the change of the water level in the drum representing water green and steam red on the screen mirror.
2. Reflection type two-color water level gauge The reflection type two-color water level gauge uses the different refractive indices of light in water and steam. Through the reflection of the prism, the steam part of the water level gauge appears red and the water part appears green.
3. Reverse transmission type two-color water level gauge Its structure is between the transmission type and the reflection type. Its water level display uses both the transmission of light and the reflection principle of light. The green light source is installed on the tongue surface of the meter. The red light source is installed on the left side of the meter, and a color plate is also used. After transmission and reflection, the water part of the water level meter appears green and the steam part appears red.
Low-level water level gauge
According to regulations, when the water level gauge is higher than 6m from the operating surface, a low-level water level gauge should be installed.
There are two types of low-level water level gauges: liquid column differential pressure low-level water level gauge and mechanical low-level water level gauge.
The liquid column differential pressure low-level water level gauge is made by measuring the static pressure difference of two liquid columns using the principle of fluid static pressure. According to the different specific gravity of the liquid in the low-level water level gauge indicator, there are heavy liquid low-level water level gauges with a specific gravity greater than 1 and light liquid low-level water level gauges with a specific gravity less than 1. There are also differential pressure low-level water level gauges, etc.
The requirements for the working fluid used in the low-level water level gauge are as follows:
1. Insoluble in water.
2. Can be dyed into bright colors and can form a clear dividing line with water.
3. High boiling point and no corrosion.
4. The viscosity should be as small as possible.
The heavy liquid that can meet the above requirements is carbon tetrachloride (ρ=1623kg/m3). A mixture of chloroform (ρ=1489kg/m3, bromoform (ρ=2890 kg/m3), etc. or other solutions. The commonly used density of heavy liquid is 1600~2000 kg/m3. In order to facilitate the observation of water level, soluble dyes can be added: such as adding 0.01% croton red, the heavy liquid can be bright red. Light liquid is generally made of engine oil, kerosene and gasoline mixed in different proportions. And adding an appropriate amount of phenolphthalein can make the light liquid red. The commonly used density of light liquid is 700~800 kg/m3.
