In many instances subs and stabilizers are bored to be used with a float valve in a box connection facing up-hole rather than down-hole. Sometimes the requirements for float bore depth, which are derived for a "box-down" float bore, are not sufficient to ensure the proper sealing of the float valve within the float bore in this "box-up" configuration. Additionally, regardless of float bore orientation, there is a chance that the float bore depth requirement can be long enough that the float bore runs into the pin connection of the sub on which it is machined. This can result in high stress in the float bore which could lead to fatigue cracks and a reduced load capacity of the tool due to a decrease in cross sectional area. This paper details the design methodology used to ensure the proper sealing of float valves used in boxup float bores. Finite element analysis (FEA) was conducted to determine the distance from the back of the float bore to the shoulder of the pin connection necessary to substantially reduce the stress experienced as a result of connection make-up forces.
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