Lee-Dickens have four trip amplifiers that comply with the NAMUR NE43 recommendations. These non-processor based trip amplifiers have been assessed to IEC61508 and achieve SIL2 rating with a proof test interval of one year.
The NAMUR NE43 recommendation document sets out to define the “Out of Range” figures that are to be used with the industry standard 4 to 20mA signal. The four trip amplifiers have the standard process trips as well as an independent “out of range” trip. The “out of range” trip is activated when the input signal either falls below 3.8mA or exceeds 20.5mA.
The SIL rated instruments are the BD9431/BD9432, which are AC powered Single/Dual Level Trip Amplifiers respectively, and the BM9431/BM9432, which are DC powered Single/Dual Level Trip Amplifiers, respectively.