Patent ID: 8176933

Claim:
A packing unit for a blowout preventer, comprising: an elastomeric, annular body configured to be disposed about a longitudinal axis of the blowout preventer and configured to be displaced inwardly toward the longitudinal axis upon actuation of the blowout preventer; wherein the elastomeric, annular body comprises a first section having a first set of material properties and a second section having a second set of material properties and wherein spatial distributions of the first and second sections within the elastomeric, annular body are determined based on a strain analysis of the elastomeric, annular body when the blowout preventer is in a closed position such that the first section corresponds to a low strain and the second section corresponds to a high strain and the low strain is lower than the high strain, wherein the second section is configured to provide a first seal for a fluid flowing through the packing unit and the first section is configured to provide a second seal for such fluid that leaks past the first seal, and wherein the first section is provided at a first end of the elastomeric, annular body, along the longitudinal axis, and the second section is provided at a second end of the elastomeric, annular body, along the longitudinal axis; and a plurality of rigid inserts distributed at equal radial distances from each other within the elastomeric annular body and along the longitudinal axis of the blowout preventer, the rigid inserts extending along the first and second sections and configured to press the first and second sections towards the longitudinal axis of the blowout preventer.