Brush seals work by absorbing radial deflections from the rotor during transient operations. The seal then follows the rotor back to the steady state operating position to maintain minimum leakage. Each metal seal’s brush pack is composed of thousands of finely packed wire bristles. The bristle material, a cobalt/nickel alloy, is chosen to provide an optimal combination of wear properties and oxidation resistance. The back plates and side plates are typically fabricated from stainless steel or nickel alloys and are chosen based on the case material to account for thermal expansion