Slip Blinds at Pressures Causing Permanent Deformation

Slip blinds are frequently used for hydrotesting piping. In addition, when maintaining equipment or piping, the equipment or piping must be isolated to assure a safe working environment. Separating flange pairs and inserting a blind flange against the process side prevents hazardous substances from entering the work area. Slip blinds are often used for this type of service. However, slip blinds are generally limited to low pressure service since at excessive pressures the blind will become dished and may leak or become impossible to remove. For this paper, slip blinds of various sizes and thicknesses were hydrostatically tested to determine their deformation as a function of pressure. Nonlinear finite element analysis was used to determine the theoretical deformation of slip blinds. The goal of the testing and FEA was to determine allowable pressures which would limit permanent deformation of the blinds to specified values.