Whether you are completing a PUWER 98 inspection or CE Marking Machinery, in most cases you will require some knowledge of functional safety. EN 13849 is the most common standard used for this purpose since it can be used for pneumatic and hydraulic circuits as well as electrical. Other standards that may be used are EN 62061 or EN 61511 but this is depending on the technology used and the industry.
A safety function exists where the failure of a control system may result in an immediate increase in risk.
Where the increase in risk is linked to the potential for exposure to dangerous moving parts (see PUWER Regulation 11) then there is an absolute duty in UK law to ensure that the hazardous situation for this risk does not come to pass.
PUWER 98 identifies EN 13849 as a source of guidance for ensuring compliance in this area and demonstrating that your arrangements endeavour to ensure work equipment is in compliance with it be design and condition is evidence of good due diligence on the part of an employer of machine manufacturer.