Red Seal Boilermaker flashcards

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

Hoop stress formula

For a thin-walled cylinder, hoop (circumferential) stress equals pressure times diameter divided by twice the wall thickness. Longitudinal stress is half of that, so hoop governs shell design.

Joint efficiency E

A factor reducing allowable shell stress to account for weld quality. Full radiography gives 1.0, spot radiography about 0.85, and no radiography about 0.70 for double-welded butt joints.

Hydrostatic test pressure

A pressure test typically set at 1.3 times the maximum allowable working pressure for vessels, adjusted for test temperature, with water above the brittle fracture transition temperature.

Carbon equivalent

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Values above about 0.4 indicate a hardenable steel that usually needs preheat to avoid hydrogen-assisted cracking.

Low-hydrogen electrode storage

E7018 electrodes must be kept dry in a holding oven at roughly 120 to 150 degrees Celsius after opening, because absorbed moisture causes hydrogen cracking and porosity.

Fillet weld throat

The throat, the effective load-carrying depth of a fillet weld, equals 0.707 times the leg length for a 45-degree weld. Capacity uses throat times length times allowable stress.

Bend allowance formula

BA = (pi/180) times bend angle times (inside radius plus K times thickness). The K-factor locates the neutral axis and typically ranges from 0.33 to 0.5.

Parallel line development

A pattern method for prisms and cylinders: divide the girth into equal divisions, project heights from the elevation, and transfer those heights to the stretch-out line.

Triangulation development

A pattern method for transitions and offsets such as square-to-round pieces: divide the surface into triangles, find each side's true length, and build the pattern triangle by triangle.

True length by rotation

An inclined line appears foreshortened in a view. Rotating it parallel to a reference plane, or using the rise and run as a right triangle, gives its true length.

Oxy-fuel cut drag

Drag is the lag of the exiting cut stream behind the entering stream. Slight drag of zero to five degrees is acceptable; excessive lag means travel speed is too fast.

Springback in forming

Elastic recovery after bending. It increases with yield strength and radius-to-thickness ratio, so the part must be overbent by the measured springback angle.

Press brake tonnage

Required force rises with tensile strength, with thickness squared, and with length, and falls as the die opening widens. Narrow dies raise tonnage and tighten the inside radius.

Rolling cylinder flat spots

Flat spots at the ends of a rolled shell come from insufficient pre-bending. Pre-bend the ends with tighter roll settings and check the curvature with a template as you go.

Sling tension at angle

Each leg of a two-leg bridle carries load divided by two, divided again by the cosine of half the included angle. Wider angles raise leg tension sharply.

Sling angle capacity loss

Sling capacity drops as the angle from horizontal decreases. At 60 degrees it is about 87 percent of vertical rating; at 30 degrees it is only 50 percent.

Wire rope rejection criteria

Reject wire rope with ten broken wires in one lay, five broken wires in one strand in one lay, kinking, bird-caging, or more than ten percent diameter reduction.

Center of gravity pick

A suspended load hangs directly below the hook. If the hook is not above the center of gravity, the load tilts, so multi-point picks must account for that shift.

Confined space atmosphere limits

Entry requires oxygen between 19.5 and 23.5 percent, flammable gas below 10 percent of the lower explosive limit, and toxic gases such as hydrogen sulfide and carbon monoxide within exposure limits.

Hot work fire watch

A fire watch is required wherever sparks can reach combustibles and must remain in place for at least 30 minutes after the hot work ends to catch smoldering fires.

Cylinder separation rule

Oxygen and fuel gas cylinders in storage must be separated by at least 6 metres or by a fire-rated barrier with at least a 30-minute rating, and kept upright and secured.

Scaffold height-to-base ratio

Supported scaffolds generally need a height-to-base ratio no greater than 3 to 1, or 4 to 1 for mobile scaffolds, with guardrails, toe boards, and full planking.

GMAW transfer modes

Short-circuit for thin material at low current, globular as a transition, spray at high current with argon-rich gas for deep penetration, and pulsed spray for controlled heat at lower average current.

GTAW polarity selection

Direct current electrode negative suits steel; alternating current suits aluminum because the positive half-cycle breaks the oxide layer. Tungsten is non-consumable and filler is added separately.

Post-weld heat treatment

Soaking a completed weldment at roughly 595 to 690 degrees Celsius for carbon steel, about one hour per 25 millimetres of thickness, relieves residual stress and tempers the heat-affected zone.

Distortion control methods

Balance welds about the neutral axis, use back-step or skip sequences, clamp or fixture the parts, and pre-set the joint opposite to the expected shrinkage direction.

Bolt edge distance

Minimum edge distance is about 1.5 times the hole diameter at sheared edges and 1.25 times at rolled edges; shorter distances cause tear-out instead of bearing failure.

Galvanizing vent holes

Vent and drain holes, typically at least 12 millimetres, are needed at high and low points so molten zinc enters and air escapes; overlapping surfaces closer than about 2 millimetres must be avoided.

Pipe thermal expansion

Change in length equals original length times the coefficient of expansion times temperature change. Carbon steel expands about 12 micrometres per metre per degree Celsius.

Long-radius elbow

A long-radius elbow has a centreline radius of 1.5 times the nominal pipe size; a short-radius elbow is 1.0 times. Miter bends are restricted by pressure and code.

Flange bolt tightening pattern

Tighten bolts in a star or crisscross pattern in stages, commonly 30, 60, and 100 percent of final torque, so gasket seating stress and bolt preload stay even.

Ultrasonic versus radiographic testing

Ultrasonic testing finds planar defects such as cracks and lack of fusion and measures thickness. Radiographic testing finds volumetric defects such as porosity and slag, with sensitivity set by source size and image quality indicators.