How The Magnetic Level Indicator Works
Each Series Magnetic Level consists of three basic parts.
- The Chamber: Usually manufactured out of Stainless Steel, but available in Hastelloy, Alloy 20, and other materials. The chamber allows for measurement as well as containment of the liquid to be measured.
- The Float: Contains a Magnet assembly. The float is engineered to ensure buoyancy based on the specific gravity, temperature, and pressure of the liquid to be measured. Each float is weighted so the liquid level will be equal to the position at which the magnet is mounted in the float.
- The Indicator: Mounted outside of the chamber, includes magnetized wafers or flags that react to the magnet included in the float.
The chamber is mounted parallel to the tank application. The liquid level in the chamber will match the movement of the liquid level of the tank. The float movement matches the liquid movement and causes the reaction of the visual indicator.
How to Install The Magnetic Level Indicator
Use care in lifting the instrument from the package or crate. Remove any flange covers or thread caps. If possible, always install isolation valves between the Level Gauge and the process tank. This will allow for gradual pressurization of the Level Gauge chamber as well as facilitate any future maintenance necessary. The gauge should be mounted level to ensure proper float travel without friction.
WARNING:
IF THIS CHAMBER OR SYSTEM REQUIRES A HYDROSTATIC TEST, THE FLOAT MUST NOT BE INSTALLED WITH TESTING!
The float is designed to withstand the maximum pressure specified for the level application. Damage can occur to the float if it is not removed during Hydrostatic Testing.
Once the hydrostatic test is complete, the float should be installed in the Magnetic Level Indicator chamber. Each float is etched with the serial number of the instrument, the specific gravity, and arrows “Up” showing the correct positioning of the float in the chamber. The end of the float with the “Up” arrows should be positioned upward as the float is deployed in the instrument. If the float is installed upside down, problems will arise with associated instruments and the accuracy of the level gauge.
IMPORTANT!
Once the Magnetic Level Indicator is attached to the application and the vent and drain connections are confirmed to be closed, utilize the following procedure for start up, ESPECIALLY FOR HIGH PRESSURE AND TEMPERATURE APPLICATIONS!
- Slowly open the top Valve first. This will allow for equalization of pressure in the chamber to the process.
- Slowly open the bottom Valve. Liquid can now fill the chamber gradually.
Failure to follow this procedure can lead to damage of the float!
The tank level should be raised to maximum height to check the upper connection for leaks. If applicable, verify that all switch operation is correct and that the transmitter indicates the correct level.
WARNING
Once the pressure in the Gauge Chamber has been equalized with the process pressure, DO NOT open the vent or drain connections. Damage to the float can occur!
See the section entitled “Maintenance” to learn the proper procedure for removing this instrument from service.
Functional Test
The best way to provide a functional test for this instrument is to raise and lower the level of the material in the tank, and, therefore, the gauge. Many times this is not possible. If this is the case, utilize one of the following options.
- Make sure the chamber is isolated from process conditions by closing the valves at the connection points. Drain off any remaining liquid in a manner compatible with plant requirements. As most floats will be buoyant upon water, slowly fill the level gauge through the vent connection. Observe the movement of the visual indicator as the gauge fills with water. If applicable, monitor the outputs of switches and transmitters accompanying this instrument.
- If it is not possible to fill the gauge with water or another liquid, either open the drain connection or remove the bottom flange. Carefully manipulate the float with a piece of instrument tubing or a device that affects the movement of the float in the chamber. Observe the movement of the visual indicator as the float moves. If applicable, monitor the outputs of switches and transmitters accompanying this instrument.
- Often times there will not be enough ground clearance to insert an object to manipulate the float. If this is the case, such a test can be completed prior to installation while the instrument is lying on a workshop bench.
Maintenance
Normally, Magnetic Level Indicators operate free from maintenance and wear when applied properly. Depending on the application, occasionally mud or other floating substances can gather in the lower portion of the instrument. Should this be the case, follow the below steps to remove the gauge from service.
- Isolate the chamber from service by closing the process valves starting with the lower valve and then the top valve.
- Allow pressure to equalize with atmosphere by slowly opening the vent connection.
- Drain off any remaining liquid in a manner compatible with plant requirements.
- Remove the flange on the bottom of the gauge.
Caution!
Take care to not allow the float to drop on the floor.
This can cause damage to the float and/or the magnet assembly.
- Clean out chamber with a brush and wash with water if compatible. Make sure there are no remaining solid particles. Look for items or debris that will inhibit the movement of the float. Further inspect the gauge chamber to ensure that it is free from unexpected corrosion or damage.
- Replace the float with the arrows in the “Up” position.
- Using a new gasket, replace the bottom flange and tighten all fasteners to the proper torque.
