Types of devices and converters for measurement of level
With the constant density use hydrostatic and buoy level meters and converters of level to measurement of the fluid level.
The principle of operation of hydrostatic level meters is based on measurement of pressure in liquid determined by the mass of the fluid column located between the point of measurement and поверхностью liquids in capacity.
If capacity also liquid which level is measured is discovered it is not aggressive, then as the measuring device use manometers (with the capacity height
it is not lower than 4 m) or the naporomer (with the height of capacity lower than 4 m) established close the bottoms of the rezervuayor.
Pressure shown by the device at the constant density of liquid will be in proportion to the fluid level.
For measurement of level of aggressive fluids which contact with the chuvyostvitelny element is inadmissible they are separated the flow of compressed air or gas which is supplied to the connecting line. In this case the sensing device of the manometer will not contact to liquid, the level of koyotory is measured.
Fig. 1 Key diagram of hydrostatic measurement of level: 1 - 2 - reducing мневмоклапан, the 3rd valve, 4 - the glass, 5 - the manometer
The hydrostatic converter of level, postyoroyenny by such principle, represents the tube of 1 (fig. 1) to which from the reducing pnevmoyoklapan 2 through the valve 3 and the glass 4 give compressed air. At the small consumption of air which is regulated the valve on number of puyozyrk of air in the glass 4 for the unit of time pressure, izmerenyony the manometer 5 will be equal to fluid column hydrostatic pressure between the end of the tube and the surface of liquid. At the constant density of liquid of the indication of the manometer will be proportional to the fluid level.
Level in the capacity which is under pressure ри is measured by the differential pressure gage. Pressure differential (to fig. 2 and) to p = (ri + the RG) i.e. is equal to liquid hydrostatic pressure.
Fig. 2 Difmanometrichesky level with the straight line(s) and the return scale: 1, 2 - selections, 3 - the leveling vessel
Selections 1 and 2 (fig. 2 and) the differential pressure gage establish at the top of and in the bottom of capacity, the leveling vessel 3 - at the level of selection 2 and fill in in it the measured liquid. The vessel is connected to selection 1. In that case when over the surface of liquid there are condensable steams or gases, the leveling vessel 3 (fig. 2) is installed at the level of selection 1 and connected to it. At steam condensation or gases in the vessel level in is mute remains to constants as excesses of condensate merge in the emyokost through the connecting line and selection 1. At the upper arrangement of the vessel to zero differential pressure there correspond the maximum value of the measured level and the scale of the differential pressure gage will be the return. For measurement of level of aggressive fluid in both tubes under identical davleyoniy (big ри) and with the identical expense compressed air is blown.
Fig. 3 Key diagram of the buoy converter of level: 1 - the camera, 2 - the branch pipe, 3,5 - levers, 4 - the membrane, 6 - loads, 7 - the support, 8 - the zero adjuster
The buoy measuring transducers of level apply to precise measurement of the fluid level in the vessels which are under the pressure up to 40 MPas. They are chamber and tubeless. In chamber converters of level the camera 1 (fig. 3) 2 is connected by branch pipes to the vessel where measure level. In the camera on the lever 3 the anchor buoy is suspended. Through the steel flexible membrane the 4th lever is brought out of the camera.
According to the Archimedes' principle at immersion in liquid the anchor buoy will be affected by the floating force equal to the weight of the liquid which is forced out by the submerged part of the anchor buoy. The best effort, deyyostvuyushchy from the anchor buoy on the lever 3, will be in the absence of liquid in the camera (zero level), minimum - at full immersion of the anchor buoy. The created moment of force is measured and on it judged value of the fluid level. Range the izmereyoniya of the converter is defined by length of the float and height of installation of the camera on tanks. As converters with different diapazoyona of measurement have different weight, for compensation of initial effort the lever 5 with the counterbalance 6 which can peremeyoshchatsya on this lever 3 is provided.
In tubeless converters of level the float is placed neposredyostvenno in the vessel in which measure level. If density of the measured liquid at in advance known moment and for the known term changes, scales of devices remake and indications adjust.
It is impossible to measure the fluid level which change of density has sluyochayny character by the considered devices.
For measurement of the fluid level with the variable density and also the level of bulks use capacity converters уровня. Operation of capacity converters of levels is based on change of capacity of electrode system at change of the measured level. Vertically submerge the isolated electrode in the vessel in which measure level (for example, the rope on insulators). The measuring device izmeyoryat the capacitor capacitance which facings are the izolirovanyony electrode and the body of the vessel (earth). At change of level the capacitor capacitance as dielectric permittivity of the environment between facings changes changes. If the electrode to arrange not vertically, and is horizontal, then change of capacity will sharply happen, jump as liquid or the loose environment will reach the electrode at the same time on all surface. Sharp change of capacity can be recorded by the signaling device.Top