Patent ID: 8151891

Claim:
A formation saver sub, comprising: a tubular body including an upper section, a middle section, a lower section, an outer surface, and an inner surface; a mandrel including an upper section, a middle section, a lower section, an outer surface and an inner surface defining a mandrel bore, said mandrel being positioned interior of said body; a piston including an upper section, a middle section, a lower section, an outer surface, and an inner surface, said piston positioned between said inner surface of said body and said outer surface of said mandrel; a seat including an upper section, a middle section, a lower section, an outer surface, and an inner surface defining a seat bore, said seat releasably positioned in said mandrel bore, said upper section of said seat adapted to receive a plug; wherein said piston is actuated in a first direction in response to an increase in a fluid pressure, said actuation in said first direction maintains said positioning of said seat in said mandrel bore; and wherein said piston is actuated in a second direction in response to a bleed off of said fluid pressure, said actuation in said second direction releases said seat from said mandrel bore.