Within the Off Shore industry a firm had a lot of problems producing fire rsistant doors. Due to gastightness regulations production people were 5 hours busy adjusting the framework of the door to the door. Due to gastightness demands the seal connected to the door has to make contact with the framework all around the door. Due to the way the framework was produced (4 pieces of framework were made by bending flat steel plates) it could happen that one of the pieces of framework is not laying in the same plane as the other three parts of the framework. This is visualised exaggerated here. The seal has to make contact with the framwork all around the door to meet gastightness requirements. Due to the fact that one bend is laying backwards the other three parts of the seal have to be compressed more so the last piece of seal contacts the framework also. As a cosequence the opening force of the door rises. Due to healt and safety regulations the opening force should not exceed 23 kilo. The problem lays in the way the framework was welded on a flat table. The problems will reduce very much when all framework is produced not at 90 degree bending angle but at 88 degree with a tolerance of +/- 2 degree. Due to this change in bending angle the places where the seal touches the framwork are more in one plane. The problem is explained more in this picture.
Due to the fact that the opening force of these doors were very high sometimes these automatic closing doors were blocked by using a piece of wood. This was not good for the safety of the people. That was also a reason for me to change the design of a new seal. The old seal always wanted to curl up when opening a door. This raised the opening force. The new seal shown in above pdf does not have this problem.
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