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Ignition position monitoring (SIL 2, PL d)

The ignition capacity of the burner during the start-up procedure until the operating signal of the automatic burner control unit is received must be limited.

Requirement as per EN 746-2


Pressure surge caused by exceeding the start fuel flow rate

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 safety time safely limits the pilot gas volume (SIL 3, PL e), the probability that a hazardous event occurs is rather low. → 2 points

Avoidance Av: as the pilot gas volume is limited by a fixed orifice, it is probable that the hazard is avoided. → 1 point

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 details


Enter the calculated values in the adjacent “app” to determine the required safety level.



Select products








The required SIL and PL can be achieved with these products. The calculation (see below) provides verification of this.

Sensor and logic: Gasfeuerungsautomat PFU (Bei dieser Art der Zündmengenbegrenzung ist ein separater Sensor nicht erforderlich.)

Actuator: solenoid valve 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.


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