The WENLEN OE256 Pneumatic SIS / Final Element Subsystem has been independently certified by Risknowlogy in accordance with IEC 61508:2010 and IEC 61511:2016 (certificate 2250.649.14-0, issued 13 October 2026). The certification confirms that its safety functions meet the applicable hardware integrity requirements of both standards.

The OE256 serves a dual purpose. It provides autonomous pneumatic safety instrumented functions, and it acts as the final element for functions executed by an external logic solver. It can perform up to four low demand safety functions: closing the valve to tight shutoff on low-low or high-high line pressure, or when a 24 VDC signal from an external logic solver is lost, and preventing it from opening while the pressure difference across the closed valve is too high.

Risknowlogy assessed the safety requirements specification, hardware requirements, hardware architecture and hardware reliability. The assessment combined a qualitative and quantitative analysis of failure behaviour, using failure data from WENLEN and independent recognised sources. The subsystem is Type A and has no programmable application logic.

Based on this assessment, each of the four safety functions is suitable for use in SIL 2 safety functions at hardware fault tolerance 0, subject to the proof test intervals in the report: up to five months for the two pressure-trip functions, seven months for the differential-pressure function and twelve months for the voltage-loss function. Where the OE256 acts as a final element, the SIL achieved also depends on the other subsystems in the function.

The certification covers hardware only. Management of functional safety, basic safety, user documentation, validation testing and the external pneumatic feed are outside its scope. The end user remains responsible for correct design, installation, validation, operation, proof testing and maintenance, and for securing power and pneumatic supply for the energise-to-trip functions. Modifications require re-assessment and re-certification.

The detailed certification basis, safety functions, conditions of use and limitations are defined in the issued certificate and Risknowlogy certification report 2250.649.13.