KST – KROMSCHRÖDER SYSTEM TECHNOLOGY
Pre-purge (SIL 2, PL d)
The combustion chamber, the connected spaces and the flue gas system must generally be purged as described in EN 746-2:2010 subclause 22.214.171.124 to ensure that no flammable gas mixture remains in these areas.
Ignitable mixture in the combustion chamber → explosion
Determining the required SIL pursuant to IEC 62061
Frequency & exposure duration Fr: < 1 per h to ≥ 1 per day; > 10 min → 5 points
Probability Pr: as the two shut-off valves (SIL 3, PL e) shut off the gas supply safely, the probability that a hazardous event occurs is rather low. → 2 points (Above 1200 kW, EN 746-2 also prescribes a tightness control.)
Avoidance Av: the hazard can be avoided by regular maintenance and the use of a tightness control. → 3 points
Effects: death, loss of an eye or arm
Determining the required PL pursuant to ISO 13849-1
Severity of injury S: severe (usually irreversible injury including death) → S2
Frequency and/or duration of hazard exposure F: frequent to continuous and/or long exposure to hazard → F2
Possibility of avoiding hazard or limiting harm P: possible under certain conditions → P1
Enter the calculated values in the adjacent “app” to determine the required safety level.
The required SIL and PL can be achieved with these products. The calculation (see below) provides verification of this.
Sensor: pressure switch for gas DG
Logic: protective system control FCU
Actuator: solenoid valves for gas VAS
The flowchart shows how the products are integrated into the application to achieve the required safely level.