This document specifies requirements for limiters which are incorporated into safety systems for shell boilers as specified in EN 12953-1:2012. The design requirements and examination of the limiters are covered in this document. NOTE See Annex E for determination of the characteristic data for use in protective circuits with a safety integrity level (SIL) rating. The requirements for limiters with regard to the safety integrity level (SIL), for example, in accordance with EN 61508 are not covered in this document.