KST – KROMSCHRÖDER SYSTEM TECHNOLOGY
The combustion chamber, the connected spaces and the flue gas system must generally be purged as described in EN 746-2:2010 subclause 18.104.22.168 to ensure that no flammable gas mixture remains in these areas. The system’s pre-purge must take place immediately before the burners are started.
During the pre-purge it must be ensured that there is an adequate air flow. For this purpose, the air volume is recorded by a differential pressure switch using a measuring orifice. As long as the flow rate is inadequate, the pre-purge time will not start to elapse. The minimum pre-purge time is guaranteed by switching devices specifically for this purpose. The differential pressure switch must be checked prior to system start-up to establish its “no flow” state. In the event of an error during the “no flow” state check, system start-up must be prevented.
If it is not possible to complete the pre-purge for process reasons, another suitable safety measure must be used. This measure must be determined by a safety assessment.
In general, five complete air changes of the combustion chamber/connected spaces and flue duct will suffice.
The function must comply with the requirements of the protective system to EN 746-2:2010 subclauses 5.7.2 and 5.7.3.
If failures or disturbances in the protective system can cause a hazardous situation or damage to the machine or product, suitable measures shall be taken to reduce the probability of occurrence of such failures or disturbances. The necessary measures and the extent to which they are implemented – either individually or in combination – depend on the level of risk associated with the application in question.