Fire door hinges have a system of grading under BS EN 1935 – this indicates the maximum weight that the hinge can take. For instance a Grade 13 hinge will take up to 120kg in weight (more details about hinge loadings/adjusted door weights coming in another post soon).
However, in order to make sure that the hinge can perform to the spec it’s been tested to, it’s important that the hinge is fitted correctly.
Apart from the obvious things like morticing the hinge blade into both door and frame and using all of the fixings, it’s also important to install the hinge the right way round.
You may encounter 3 part knuckles and 5 part knuckles on different hinge types, however the rule is the same for both – the hinge blade that has the top and bottom part of the knuckle should be mounted on the frame.
The weight of the door is obviously being taken off the door frame – therefore it’s important that the inner pin that runs from top to bottom of the knuckle is held at both ends by the frame component of the hinge.
If you fit the hinge the wrong way around, it’s possible that the pin will become bent causing the hinge to not function efficiently.