KST – KROMSCHRÖDER SYSTEM TECHNOLOGY
Gas min. low-pressure cut-off (SIL 2, PL d)
The Gas min. low-pressure cut-off described in EN 746-2:2010 subclause 188.8.131.52.2.1 is designed to monitor the static gas pressure during the burner start and the burner operation of the system. If the level falls below the set limit value, the system must perform a fault lock-out.
CO formation due to gas deficiency (cold flame) → 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 flame safeguard (SIL 3, PL e) shuts off the gas supply safely in the event of flame failure, the probability that a hazardous event occurs is rather low. → 2 points
Avoidance Av: the hazard can be avoided by regular maintenance and the use of a flame safeguard. → 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.
Calculating the SIL, PL
Select products in the adjacent “app”. Depending on the product click on whether the function should have one or two channels and enter the demand rate per hour or per year.