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Magnetic liquid-level indicator is intended for both direct visual control of liquid level in tanks and vessels of different dimensions as well as indirect remote control by converting the liquid level into a unified DC current of 4–20 mA.
Liquid level alarms are used for control of fixed liquid levels within the entire control range MLLI is intended for operation with a wide range of liquids including corrosive, hazardous and toxic ones: ethyl mercaptan, acid, alkali, perluxe, gasoline, oil etc.
MLLI consists of the following main units:
The indicator's housing is connected to a tank or vessel with the liquid based on U-tube principle, inside the housing there is a leak-proof float with magnetic system. VIFM, RIFM, and LLA are installed outside of the indicator's housing.
The visual indicator of how a float moves has two modifications. In the first one the indication of the float position is carried out by two-colour rollers installed longitudinally on the indicator's housing ~ with 10 mm pitch. Each roller is painted in two contrast colour sand has a permanent magnet. As magnetic fields of the float and rollers interact, the rollers are rolled over to the required side.
In the second modification the indication of the float position is carried out by a permanent magnet installed in a transparent tube/guide. The magnet is hold by the float's magnetic field and moves smoothly along the guide following after the float.
A resistor array is used as sensing element in RIFM, it is switched with the usage of magnetoperated contacts (magnetically operated sealed switches). A group of magnetically operated sealed switches is sealed by the float's magnetic system.
The magnetically operated sealed switch is used as a sensitive element, which closes and opens an electric load circuit of recording device under the influence of the float's magnetic field.
| Maximum range of liquid level control, mm | 3000 |
| Maximum liquid pressure, MPa | 7,5 |
| Maximum liquid temperature, °С | 300 |
| Housing material | Steel 12Х18Н10Т |
| Float material | Steel 12Х18Н10Т, titanium VT1-0 |
| Eternal diameter of housing's tube, mm | 40 |
|
Technological connection to a tank or vessel (side, axial, combining) |
By order |
|
Design of connection to a tank or vessel (flanged, welded) |
By order |
| Service life, years | > 12 |
| Version 1 | |
| Error of level control, mm, at least | ± 10,5 |
| Version 2 | |
| Error of level control, mm, at least | ± 5 |
| Error of level measurement control, mm, at least | ± 1,5 |
| Service life, years | > 12 |
| Level control range, mm | 300, 600, 900, 1200, 1500, 1800 |
| Error of conversion: | |
| absolute, cm | < 1,0 |
| auxilliary reduced, % | ≤ 0,1/10 0С |
| Supply voltage, V | от 9 до 30 |
| MT diagram connection | Two- or four wire if optical relay contacts are used |
| MT load resistance, kOhm | ≤ 0,75 |
| MT level protection according to GOST 14254-96 | IP 65 |
| Mean time to failure, H | >100 000 |
| Service life, years | >12 |
| Explosion-proofness marking (at availability only RIFM) | 1ExdsIIBT5 |
| Switching capacity of LLA: | |
| voltage, V | Up to 24 |
| current, mA | Up to 150 |
| Level protection of LLA according to GOST 14254-96 | IP 54 |
| Response tolerance of LLA, mm, at least | ± 6 |
| Explosion-proofness marking of LLA | ExibIIВT5 |
| Service life, years | >12 |
It operates at a number of electric power plants instead of LLIs with level glasses, at gas distributing stations for odorant level control, at gas transmission units for oil level control since 2004.
Explosion-proofness Certifcate MLLI No. С2-677/09 dated11.11.09, Certicate of Conformity No. C-RU.AB.00684.
MLLI is ordered based on a data sheet.
