NCCER Pipefitter flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Nominal Pipe Size (NPS)

A dimensionless size designation where outside diameter is fixed for each NPS while wall thickness varies by schedule; inside diameter changes with schedule.

Schedule number

A wall-thickness designation for pipe; higher schedule numbers mean thicker walls, lower inside diameter, and higher pressure rating for a given nominal size.

Take-out (fitting allowance)

The distance a fitting consumes along the pipe centerline, subtracted from center-to-center length to obtain cut length; based on face-to-center or face-to-face dimensions.

45° offset formulas

For a 45° offset, set equals 1.414 times run and travel equals 1.414 times set; the multiplier comes from the sine and cosine of 45 degrees.

Rolling offset

An offset that moves both vertically and horizontally; true offset equals the square root of vertical squared plus horizontal squared.

Travel, run, and set

Travel is the hypotenuse of the offset triangle, run is the horizontal leg, and set is the vertical leg; travel equals run divided by cosine of the angle.

Pipe slope conversion

One-quarter inch per foot equals about 2.08 percent grade; one-eighth inch per foot equals about 1.04 percent grade, used for drainage lines.

Thermal expansion formula

Change in length equals original length times coefficient of expansion times temperature change; carbon steel uses about 6.5 microinches per inch per degree Fahrenheit.

Hydrostatic test

A pressure test using water at typically 1.5 times design pressure, held at least two hours, with calibrated gauges at the system low point.

Weld bevel angle

A 37.5 degree bevel on each pipe end produces a 75 degree included angle; root gap and land are set by the welding procedure specification.

Hi-lo gauge

A tool that measures internal misalignment between two pipe ends before tack welding, ensuring the bore is smooth enough to meet code.

Isometric drawing

A three-dimensional single-line drawing showing pipe runs, fittings, and elevations with a north arrow; used for layout and material takeoff.

Line number

An identifier on piping drawings encoding nominal size, service, sequence number, and insulation or tracing class, linking drawings to specifications.

Pipe support spacing

Maximum hanger and support spacing depends on pipe size, schedule, contents, and temperature; spacing tables in the code govern design.

Flange rating class

A pressure-temperature rating designation such as 150, 300, or 600; allowable pressure decreases as temperature increases for the same class.

Gasket selection

Gasket material is chosen for fluid, temperature, and pressure; spiral-wound and ring-joint gaskets suit high pressure, while sheet gaskets suit low pressure.

Butt-weld joint

A joint where two beveled pipe ends are welded together for full penetration; strongest joint type and standard for high-pressure and process piping.

Socket-weld joint

A joint where pipe inserts into a recessed fitting and is fillet welded; used for small-bore piping, with a gap left for expansion during welding.

Threaded joint

A joint using tapered NPT threads sealed with pipe dope or tape; limited to smaller sizes and lower pressures than welded joints.

Flanged joint

A bolted connection between two flanges with a gasket; allows disassembly and is common at equipment connections and valves.

Pipe cutting methods

Cutting is done by abrasive saw, band saw, or torch; cuts must be square to the centerline within tolerance before beveling and fit-up.

Pipe bending radius

The centerline radius of a bend; minimum radius depends on pipe size, wall thickness, and method, with hot bends allowing tighter radii than cold bends.

Anchor and guide

Anchors restrain pipe movement at a point; guides allow axial movement while preventing lateral displacement, working with expansion loops.

Expansion loop

A U-shaped or offset configuration that absorbs thermal growth by flexing; loop size depends on expansion amount and allowable stress.

Cold spring

Deliberate pre-stressing of piping during installation to offset thermal movement; a percentage of the calculated expansion is built in at ambient temperature.

Pipe marking and color code

Labels identify contents and flow direction; color codes follow facility or industry standards and must be visible along the run.

Valve types

Gate valves isolate flow, globe valves throttle, check valves prevent backflow, and ball or butterfly valves provide quick quarter-turn shutoff.

Pipe insulation class

Insulation thickness and material are specified by service temperature and purpose, such as personnel protection, freeze protection, or heat conservation.

Hydrostatic vs pneumatic test

Hydrostatic testing uses water and is preferred for safety and energy storage reasons; pneumatic testing is limited to cases where water is impractical.

Weld symbol reading

A weld symbol on a drawing shows joint type, size, length, and whether the weld is on the arrow side or other side of the reference line.

Pipe weight calculation

Weight per foot equals the cross-sectional area of the metal times density; area uses outside diameter and wall thickness in consistent units.

Pressure rating derating

Allowable pressure for a flange or pipe decreases with increasing temperature; the rating table for the material and class must be consulted.