NCCER Pipeline Mech cheat sheet

Pipe size is stated as nominal pipe size (NPS) with wall thickness by schedule number; for a given NPS, higher schedule numbers mean thicker walls and smaller inside diameter.

Line pipe dimensions follow API 5L; grade designations such as X42, X52, X65, and X70 give minimum yield strength in ksi (X65 = 65,000 psi minimum yield).

Barlow's formula: internal pressure P = 2St/D, where S is allowable stress, t is nominal wall thickness, and D is outside diameter; design codes apply a design factor F to S.

Hydrostatic test pressure is typically 1.25 to 1.5 times the maximum allowable operating pressure, held long enough to inspect for leaks and pressure loss.

Buttweld fit-up: root gap, bevel angle (commonly 30 degrees per land), and line-up clamp alignment must meet the welding procedure specification before the root pass.

Flange bolt tightening uses a star or crisscross pattern in stages (typically 30, 60, 100 percent of target torque) to seat the gasket evenly and avoid uneven loading.

Cold field bends on line pipe are limited by code to a minimum radius (commonly 18 to 24 times pipe diameter) and must be checked for ovality and wall thinning.

Coating holiday detection uses a high-voltage holiday detector set to the coating thickness; excessive voltage can damage sound coating and give false indications.

Pipe lowering-in requires enough sideboom spread so that combined stresses from span and curvature stay within allowable limits; long unsupported spans cause overstress and buckling.

Trench safety: spoil piles and equipment are kept back from the excavation edge, and protective systems (sloping, shoring, shielding) are required in unstable or deep excavations.

Pipeline pigging: a gauging pig verifies bore roundness, a cleaning pig removes debris, and a smart or instrumented pig records metal loss and geometry for integrity assessment.

Cathodic protection criterion commonly used is a pipe-to-soil potential of -0.85 V (copper/copper sulfate reference) or more negative for coated steel pipe.

Hot work near a live pipeline requires gas testing for flammables and oxygen, plus isolation or purging of the section before welding or cutting.

Torque values for bolted connections come from the project specification or manufacturer data; lubricant condition changes the achieved clamp load for the same torque.

A pipeline pressure test must be held with the section isolated, gauges calibrated, and air and water vented so trapped gas does not cause a violent release on failure.