Level Measurement & Control


Magnetrol tank overfill protection level switches

September 2012 Level Measurement & Control

Magnetrol has supplied over 170 type A15 displacer level switches to southern African tank farms and depots over the past three years. While the A15 is not a new technology, current legislation has called for all tanks in the petrochemical industry to be equipped with a dedicated secondary ‘high level overfill protection alarm’, in addition to the continuous level transmitter.

One of the most common challenges tank farm and depot operators face is the functional testing of the overfill protection device. To date overfill protection instruments have needed to be either top mounted, on the roof of the tank for fixed roof tanks, or on a bracket at the rim of the tank for floating blanket type tanks. In response, Magnetrol developed the ‘Proofer’ system which allows personnel to operate the switch via a lever on the outside, thus solving the functional test issue without having to fill the tank, or rely on self test electronic functions to prove the working of an instrument that is a safety device and will not be called into operation in normal day to day operations.

Magnetrol makes use of historically proven displacer technology for the process interface. This allows the end user to adjust the switch set point on site and is not restricted in range. The switch logic is flexible, with most customers opting for DPDT type switching, or dual switches for redundancy. While the A15 has been used extensively for overfill protection, the same technology has a wide range of applications, including multiple switch points as well as pump control.

As all tank farms and depots are rated as hazardous areas, the A15 is certified by all leading authorities including ATEX for use in these areas; additionally they are suitable for use in SIL 2 loops. Being a mechanical device, without the need to be powered, provides a cost effective solution for end users with existing tanks that need to retrofit overfill protection.



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