There are a variety of flange spreaders on the market. First, all flange spreaders operate at a different capacity, so make sure the model you selected has enough power for your application. The most commonly used spreaders require about 1/8″ or 1/4″ gap in order for the teeth of the spreader to be able to fit. When there is no gap in between flanges, one would then look to use a “no-gap” flange spreader. This uses a system of collets and grabs the bolt hole of the flange to pull the flanges apart.