BS EN 12952-11:2007

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Requirements for limiters
  4.1 General
  4.2 Materials and design
  4.3 Electrical equipment
  4.4 Fault assessment
  4.5 Marking
5 Special requirements for water level limiters
  5.1 Components
  5.2 Design
  5.3 Floating devices
  5.4 Level electrode devices
  5.5 Examination of functional capability
  5.6 Fault detection
6 Special requirements for pressure limiters
  6.1 Components
  6.2 Additional fault assessment requirements
  6.3 Design
  6.4 Electrical equipment
  6.5 Examination of functional capability
  6.6 Fault detection
7 Special requirements for temperature limiters
  7.1 Components
  7.2 Design
  7.3 Electrical equipment
  7.4 Examination of functional capability
8 Special requirements for flow limiters
  8.1 Components
  8.2 Design
  8.3 Electrical equipment
  8.4 Examination of functional capability
Annex A (informative) Limiting device
Annex B (informative) Example of an examination plan
Annex C (informative) Marking of limiters
Annex D (normative) Immunity against electrical and
        electromagnetic influences - Requirements and testing
Annex ZA (informative) Relationship between this European
         Standard and the Essential Requirements of EU
         Directive 97/23/EC
Bibliography

Describes requirements for limiters (or limiting devices) which are incorporated into safety systems for water-tube boilers as defined in EN 12952-1.

This European Standard specifies requirements for limiters (or limiting devices) which are incorporated into safety systems for water-tube boilers as defined in EN 12952-1.

A limiter (or limiting device) can be either:

• a safety accessory as defined in the Pressure Equipment Directive, Article 1, clause 2.1.3, and needs to include the safety logic and final actuator, or

• one element of a safety system, for example, a self-monitoring water level sensor used as part of a safety accessory as defined in the Pressure Equipment Directive, Article 1, clause 2.1.3. The overall boiler protection function shall be provided in association with additional safety logic (where appropriate) and a final actuator.

The design requirements and examination of functional capability for the limiters are covered in this European Standard.

For an explanation of the extent of the limiter (or limiting device) see Figure A.1.