These systems are most often used for commercial overhead doors, but they are paired with many residential ones too. Each system has two extension springs. They are typically mounted above the horizontal tracks. On one end, each spring is held in place by a bolt. On the other, it has a pulley. Each lift cable goes over this pulley and over another one. It is attached to the bottom of the door as well. When the door is closed, the springs are stretched to counterbalance its weight. When it opens, they pass the energy which they hold to the cables in order to facilitate the process and contract. A safety cable runs through each spring to hold it in place if it gets broken.
Due to the huge amount of work which they do, these components wear more quickly than the rest of the door hardware. No matter whether a door is equipped with extension or torsion springs, they will break eventually. When this happens, immediate replacement is paramount. The door must not be used in any way until the new part has been installed. If a spring has serious damage like stretched coils, the best fix is to change it. There is no point in waiting until it breaks. Unlike their extension counterparts, torsion springs can be adjusted to counterbalance the door perfectly and to achieve super smooth opening and closing. Usually, adjustment is part of maintenance. It can also be done when the door is seriously out of balance.