NCCER Sheet Metal Worker flashcards
NCCER Sheet Metal Worker · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Fall protection trigger height
- In construction under OSHA 29 CFR 1926.501, employers must provide fall protection when workers are exposed to falls of 6 feet or more to a lower level.
- Ladder 4:1 rule
- An extension ladder is set so the base is 1 foot out for every 4 feet of working height, and it extends 3 feet above the landing point.
- Hot work fire watch
- A fire watch is posted during welding, cutting, or grinding and maintained for at least 30 minutes after the work ends to catch smoldering fires.
- SDS accessibility
- Under OSHA Hazard Communication, a Safety Data Sheet for every hazardous chemical on site must be readily accessible to workers during their shift.
- Aviation snip color code
- Left-cut snips are red and cut counterclockwise curves, right-cut snips are green and cut clockwise curves, and straight snips are yellow.
- Pittsburgh lock machine
- A lockformer machine rolls the Pittsburgh seam, a folded interlocking joint with a pocket that joins two duct sections longitudinally.
- Box and pan brake
- A brake with removable finger sections that lets the operator form boxes, pans, and return flanges that a plain bar folder cannot produce.
- Hand seamer capacity
- Hand seamers (hand brake pliers) fold flanges, and the jaw depth sets the maximum flange width, commonly 1 inch for standard models.
- Third-angle projection
- In North American third-angle projection, the top view is placed above the front view and the right side view is placed to the right of the front view.
- Architectural scale 1/4 inch
- At 1/4 inch = 1 foot, one quarter inch on the drawing equals 12 actual inches, so a measured 3 inches equals 12 feet actual.
- Parallel line development
- This layout method develops prisms and cylinders by dividing the surface into parallel lines; the stretch-out of round duct equals pi times the diameter.
- Radial line development
- This layout method develops cones and pyramids by radiating lines from an apex, and it is used for round and square-to-round transitions.
- Bend allowance formula
- Bend allowance equals (pi divided by 180) times the bend angle times (inside radius plus K times thickness), with K typically between 0.33 and 0.50.
- Bend deduction formula
- Bend deduction equals two times the setback minus the bend allowance, and subtracting it from the sum of outside dimensions gives the flat pattern length.
- Shear clearance rule
- Blade clearance on a squaring shear is set to roughly 5 to 10 percent of material thickness; wrong clearance causes edge cracking or heavy burrs.
- Metal fume fever
- Welding galvanized steel releases zinc oxide fume that causes flu-like metal fume fever, so ventilation and coating removal at the weld zone are required.
- CFM from velocity and area
- Airflow in cubic feet per minute equals velocity in feet per minute multiplied by duct cross-sectional area in square feet.
- Velocity pressure formula
- Velocity pressure in inches of water column equals velocity in feet per minute divided by 4005, then squared, for standard air at 0.075 lb per cubic foot.
- Sensible heat equation
- Sensible heat in BTUH equals 1.08 times CFM times the dry-bulb temperature difference for standard air at sea level.
- Duct aspect ratio limit
- Aspect ratio is the long side of a rectangular duct divided by the short side; keeping it at or below 4:1 limits friction and noise.
- Hanger spacing rule
- Horizontal rectangular duct is commonly supported at 8-foot maximum intervals, with closer spacing for wide duct; follow SMACNA and the project specification.
- SMACNA Seal Class A
- Seal Class A requires sealing of all transverse joints and all longitudinal seams, the most stringent of the three SMACNA seal classes.
- Fire damper requirement
- A fire damper is installed where a duct penetrates a fire-rated wall or floor assembly, and it must remain accessible for inspection and testing.
- Flexible duct sag limit
- Flexible duct should sag no more than 1/2 inch per foot of span and should not be compressed, because both raise pressure drop sharply.
- Roof pitch to angle
- A 4:12 pitch rises 4 inches per 12 inches of run, an angle of about 18.4 degrees; the slope factor is the rafter length divided by the run.
- Step flashing location
- Step flashing is installed in overlapping pieces where a roof plane meets a sidewall, working with the shingles or panels to shed water.
- Standing seam thermal movement
- Steel expands about 0.0000065 inch per inch per degree Fahrenheit, so standing seam clips must allow panels to move without buckling.
- EPDM washer fastener
- Metal roofing screws carry an EPDM washer that seals the hole; overdriving crushes the washer and creates a leak path.
- SMACNA duct standards
- SMACNA publishes the HVAC Duct Construction Standards for rectangular and round duct, plus the Architectural Sheet Metal Manual and the Duct Leakage Test Manual.
- UL 555 fire dampers
- UL 555 is the standard for fire dampers, while UL 555S covers smoke dampers and UL 181 covers factory-made air ducts and connectors.
- NFPA 90A duct clearance
- NFPA 90A governs commercial air handling systems and generally requires duct to be spaced from combustible material unless listed for reduced clearance.
- Submittal approval rule
- Shop drawings and product data must be reviewed and approved before fabrication begins; a submittal register tracks the status of each item.