Metal seals are generally not considered reusable due to their design and the nature of their materials. Most metal seals undergo plastic deformation during installation, which means they conform to the surfaces they seal against. This deformation can create permanent impressions, making it difficult for the seal to function effectively if reused.

1. Design and Deformation: Metal seals, such as those CSE with soft iron layer, are designed with a soft outer layer, or with plating that permanently conforms to the mating surfaces. When removed, the seal may not retain its original shape, leading to potential leaks if reused.
   
   
2. Types of Metal Seals: Some types, like E-rings, may exhibit some elastic recovery and could be more suitable for reuse than others, such as O-rings and C-rings, which typically undergo significant plastic deformation. However, even E-rings are not commonly recommended for reuse due to the risk of leaks.
   
   
3. Surface Conditions: The condition of the mating surfaces also affects the potential for reuse. If the surfaces are rough or uneven, the chances of a proper seal upon reinstallation decrease, leading to possible leak paths.

In summary, while certain metal seals might have some capacity for reuse under specific conditions, the consensus is that they are generally intended for single use to ensure reliable sealing performance.