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 220.127.116.11 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.
App: Determining the required SIL, PL
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.