There are many and varied ways to measure the liquid level inside a tank. Today we talk about one of the most widespread: the level measurement by magnetic transmission, and specifically, of our LT series level gauges.
The level measurement has numerous technologies for this and, for that same reason, the most complicated thing for a user is usually the selection of the one that would fit best its application. Normally, the price and accuracy that we require are usually the determining factors to make a decision.
By-pass magnetic level gauges are usually very robust and resistant to extreme temperature and pressure conditions, as well as corrosive chemicals, depending on the manufacturing materials used.
Although they are not suitable for very dirty or highly viscous fluids, they are easy to install and can incorporate switches, which allow sending alarm signals to remote equipment, and also (level transmitters) resistive sensors with 4-20 mA transmitter proportional to the level.
For these, and for some other reasons that we indicate later in this article, it is one of the most widely used forms of level measurement in the industry.
Today we will talk about them, in particular, the level gauges that we manufacture in Tecfluid.
Working principle of by-pass magnetic level gauges
The working principle of operation of these indicators is based on the principle of communicating vessels. A float inside a chamber communicated with the tank, whose liquid level is to be measured, floats on liquid surface and moves together with it as the level of the tank increases or decreases.
The float, which contains a magnet inside, is designed for the specific working liquid density and shows the tank level by means of magnetic coupling with an external float or with a magnetic strips rail.
It can displays the local level indication in two ways:
Thanks to an external magnetic float housed in a borosilicate glass tube that rises or falls depending on the height of the level in the tank.
This type of magnetic coupling corresponds to our LT models.
LT models include graduated scale in cm and the maximum temperature of the application liquid can reach 400ºC for versions in AISI 316L.
or by means of bi-colour magnetic strips (red-white), which mounted externally to the chamber on an anodized aluminium rail and isolated of the level gauge chamber, change colour with the magnetic field.
This type of magnetic coupling corresponds to our LTL models.
LTL models can optionally have a scale graduated in cm. The maximum temperature of the application liquid for versions in AISI 316L can reach 200ºC.
Its installation is vertical with lateral fixation to the tank:
How is the level reading performed on a by-pass magnetic level gauge?
For level gauges with a glass tube (LT models), the value of the level is read on the scale at the height of the top of the external follower.
For level gauges with indication through magnetic strips (LTL models), the reading is taken where the strips change from red to white. Optionally LTL models can also be supplied with graduated scale.
In this other article of our blog, we explain to you more about how magnetic strips work.
Materials and connections
The LT series level gauges is manufactured in different materials:
- AISI 316L
- AISI 316 with internal PTFE coating
And with different types of connections to process:
- EN 1092-1 or ANSI flanges (other flange standards on request)
- BSP or NPT threaded connections
- Others on request
In addition, they can be supplied with individualized options adapted to the application /installation:
- In separate sections for indication heights of up to 15m
- with double heating-cooling chamber
- with/without drain, with drain+valve, with/without vent or with vent+valve…
- with switches
- with transmitter…
Level gauge LTL106 model with NPT angled drain and vent valves
Level gauge LTL106 model with double heating-cooling chamber and
LTL–AAR switch with thermal separator for high temperature
LTSP model with 3 overlapped LTL106 level indicators
in 3 sections Buffer tank
Float material will depend on the density of the liquid and the nominal pressure/temperature of the application.
In Tecfluid we can supply the floats of Titanium, EN 1.4404 stainless steel and different plastics such as PVC, PP, PVDF and PTFE.
What advantages does a by-pass magnetic level gauge have?
- It is a waterproof system without the risk of leaks.
- Possibility of installing switches along the indication range.
- It does not require calibration.
- Reliable local reading.
- No external power supply is needed.
And disadvantages? (as always, we consider them)
- It cannot be used to measure the level of very dirty or highly viscous liquids.
- The moving parts may wear out with the use, being necessary a regular maintenance.
Switches/transmitters that can be associated
The by-pass magnetic level gauges can incorporate different types of adjustable and bi-stable switches: reed, electric micro-switches, inductive, with plastic or aluminium housing, with thermal separator for high temperature, with control relay, for ATEX version…
and also 4-20 mA transmitters: resistive sensor, with TDR technology, compact or remote version, in plastic or aluminium box, with HART™, with Profibus PA, option for explosive atmospheres, …
… but this will be part of a new technical article that we are already developing and will publish in a few weeks. Meanwhile, subscribe to our newsletter and you will be up to date with our new technical articles and news J. You can also download our global product catalogue for free.
LT106 level gauges with
switches in explosion-proof enclosure
LTL17Y level gauge with TR3420 transmitter
Most common applications of by-pass magnetic level gauges
Applicable to all types of industries, they are one of the most used level measurement methods and especially suitable for:
- Chemical, petrochemical and process industries
- Thermal plants and cryogenic installations
- Ship industry and boilers
- Storage installations
- Energy plants
- Water treatment
- Pharmaceutical industry
- Food and beverage industry…
Do you need more technical data on this type of level gauges? Here you have them.
If you are still not sure if a by-pass magnetic level gauge could be useful for your application, call us or contact us here. We help you decide the best option.