Magnetic level gauges
Magnetic level gauge is a continues level measurement A Magnetic Level Indicator (MLI) is a vertical indicator made up of a chamber parallel to the process vessel and a column with visual indicators that show the level.
The MLI chamber contains magnetic floats that move up and down with the level and trigger or move the visual indicators in the column. The floats can also trigger any magneto strictive sensors, which are sensors that respond when they are exposed to a magnetic field.
The chamber is constructed from non-magnetic material which is compatible with the process fluid(s), temperature, and pressure. The chamber is parallel to the process vessel so the level of the fluid(s) in the chamber is at the same level as the fluid in the process but is less turbulent. The chamber is connected via instrument piping to the process vessel and may have several connections. It will contain the same fluids and fluid interfaces that are present in the process vessel, provided that the connections are located such that fluid flow allows good representation of vessel contents.
The magnetic float or floats contained in the chamber are designed to sit at the total level and/or the interface between two adjacent fluids based on their specific gravity. The indicators typically comprise a housing containing a column of flippers or rollers. The flippers or rollers are flipped as the lines of flux from the magnetized float or floats pass through the chamber walls and trigger them to move, typically so that they show an alternate color which is on the back side of the flipper or roller. This will indicate the position of the float or floats contained in the chamber. As the level of the fluid or fluid interface(s) within the chamber rises and falls, the float or floats rise and fall, and the level is communicated to and displayed by the MLI’s indicators. The magnetic lines of flux also stimulate any other magneto strictive sensors or switches, such as reed switches, attached to the column.
“These types of level Gauges are used for highly hazardous/toxic liquids where gauge glasses are susceptible to attack by the process medium.”
Their maximum working temperature and pressure range can be 400 Degree C and 220 bar respectively. Use of these devices is mainly recommended for combustible, risky and corrosive fluids. Besides, they are capable for inter-phase level detection. Liquids involving extreme temperature and pressure can also measured by these gauges. They can be installed in underground storage tanks also. These types of level sensors work upon two fundamental principles. One is the Archimedes Principle which states that any object submerged in a fluid tends to experience the same buoyant force as the weight of the liquid put out of place. The other principle is the phenomena of attraction and repulsion between opposite poles and similar poles of permanent magnets respectively.
Applications :- Mostly used corrosive and non-sticky fluid.
Design Temperature :- from − 196 to 400 ° C ( − 320 to 750 ° F).
Range :- 250 mm to 3 m.
Price :- up to $1500 (Depending upon size)
Magnetic level gauge advantages and disadvantages
Advantage of Magnetic level indicator:-
- Magnetic Level Indicators are typically used to provide operating personnel with a visual indication of the level of the process fluid contained within a given vessel.
- They have an advantage over a sight glass in that the visual indicator itself does not contain any process fluid so the risk of fluid release into the environment due to a broken sight glass or ineffective seals is avoided.
- Additionally the level of fluids can be observed from some distance, colorless fluids can be observed.
Disadvantage / Limitations of of Magnetic level indicator
- Magnetic Level Indicators rely on floats which occasionally foul and stick. If iron filings are present in the media, they can get caught on the magnet and hang the float up.
- Floats are additionally vulnerable to collapse during hydro testing, steam cleaning, process start-up, and process shut down.
- The MLI indicators sometimes use a bobber that is magnetically linked to the float and moves as the float moves.
- Float design is dependent on the pressure in the vessel and the specific gravity of the process liquid over the entire temperature range.
- Applications with high temperature, high pressure, and low specific gravity are the most difficult.
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Magnetic level gauge technical specification :
|1||TAG. NO./ VESSEL NO||:||LG-101|
|3||INDICATOR TYPE||:||MAGNETIC FOLLOWER|
|4||INDICATING SCALE||:||SS WITH SS|
|6||U BOLTS & NUTS MATL.||:||ASTM A 193 B7/|
|7||:||ASTM A 194 2H|
|10||DRAIN CONN. SIZE||:||1/2″ NPT(F)|
|11||VENT CONN. SIZE||:||1/2″ NPT(F) WITH PLUG|
|13||Design and operating Pressure||:||30/18 Kg/cm2|
|14||Design and operating temperature||:||60/36 Deg C|
|15||C-C Distance/Visuality||:||2300 mm/ Full Range|
|16||Process Connection and Rating||:||1 1/2″ 300#|
|17||MOC/ Chamber material||:||SS316|
|19||Drain Valve||:||1 1/2″ NPT (F) Connection|
|20||Vent Valve||:||1 1/2″ NPT (F) Connection|
Magnetic level gauge or indicator installation procedure
Magnetic level gauge or indicator Manufacturer
- Kubler Steur