Work out the net external collapse load at a depth and check it against the pipe rated collapse pressure.
Collapse happens when the pressure outside a pipe exceeds what the inside can resist, and the pipe crushes inward. The worst case is usually an evacuated or partially evacuated string with full external mud hydrostatic acting on it — for example after losses, during a DST, or when running empty casing. This tool works out the net external (collapse) pressure at a depth and compares it against the pipe’s rated collapse to give a safety factor.
Get the rated collapse for your exact size, weight and grade from the tubular data tables, then check it against the load here.
Mud weights in ppg, depth in ft (true vertical). 0.052 is the ppg-to-psi/ft gradient constant. Set internal fluid weight to 0 for a fully evacuated string (the worst case).
Simplified single-point check at one depth with static hydrostatic only. It ignores combined loading (collapse is reduced by tension), temperature, and pressure transients. Use full load-case analysis for design.
At 10,000 ft with 12.0 ppg mud outside and an empty string inside: external = 0.052 × 12 × 10,000 = 6,240 psi; internal = 0; net collapse load = 6,240 psi. Against a pipe rated 7,020 psi collapse, safety factor = 7,020 / 6,240 = 1.13.
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