Patent ID: 7360611

Claim:
A flow strainer system for use upstream of a drilling choke comprising: (a) a selectably operable first flow branch including a first flow strainer device, the first flow strainer device having (i) a first normal through flow passageway, (ii) a first reverse flow passageway, and (iii) a first valve plug containing a first entry port and a first perforated exit port, wherein the first valve plug is rotatable between a first normal and a first reverse position, wherein when the first valve plug is in the first normal position the first entry port is aligned with the first normal through flow passageway and when the first valve plug is in the first reverse position the first entry port is aligned with the first reverse flow passageway; (b) a selectably operable second flow branch including a second flow strainer device, the second flow strainer device having (i) a second normal through flow passageway, (ii) a second reverse flow passageway, and (iii) a second valve plug containing a second entry port and a second perforated exit port, wherein the second valve plug is rotatable between a second normal and a second reverse position, wherein when the second valve plug is in the second normal position the second entry port is aligned with the second normal through flow passageway and when the second valve plug is in the second reverse position the second entry port is aligned with the second reverse flow passageway; (c) a selectably operable bypass flow branch; (d) an inlet connected to the first flow branch, the second flow branch, and the bypass flow branch; and (e) an outlet connected to the first flow branch, the second flow branch, the bypass flow branch, a drilling choke, and a bifurcated backflow branch having a selectably operable fluid connection to the first reverse flow passageway and a selectably operable fluid connection to the second reverse flow passageway.