Abstract: An apparatus is provided for blocking off process lines between various pieces of processing equipment, for example, storage tanks, wherein a block housing is provided having pipes on opposite faces thereof connected to the processing vessels. Means are provided for blocking the flow using an axial expansion means for insertion into seats provided on opposite faces of the block housing. During periods of time of normal operation, i.e., when blocking of the process lines is not desired, a flow-thru pipe assembly having male and female ends thereto and locking means provided thereto is provided for insertion into the block housing and for mating and joining the opposite pipes on the opposite faces of the block housing.