Red Seal Steamfitter/Pipefitter flashcards

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

Pipe wall thickness formula

For internal pressure, t = PD / (2(SE + PY)), where P is design pressure, D outside diameter, S allowable stress, E joint efficiency, and Y a temperature coefficient.

Thermal expansion formula

ΔL = L × α × ΔT. Carbon steel α is about 6.5 × 10⁻⁶ per °F, so a 100 ft line heated 300°F grows roughly 2.3 inches.

Hydrostatic test pressure

Per ASME B31.3, test pressure equals 1.5 times design pressure times the ratio of allowable stress at test temperature to allowable stress at design temperature.

Weld joint efficiency values

In B31.3 Table A-1B, seamless pipe has E = 1.00, electric resistance welded pipe 0.85, and furnace butt welded pipe 0.60. Higher E means less thickness required.

Pipe schedule meaning

Schedule numbers are nominal wall-thickness indicators only. Actual wall varies with nominal pipe size, so use tabulated outside diameter and wall values for calculations.

Steam quality definition

Quality x is the mass fraction of vapor in a wet steam mixture, calculated as (h actual − h saturated liquid) divided by latent heat of vaporization hfg.

Flash steam fraction

The fraction of condensate that flashes when pressure drops equals the difference in saturated liquid enthalpy divided by the latent heat at the lower pressure.

Steam main velocity guideline

Distribution mains are typically sized for 4,000 to 6,000 feet per minute; process lines run higher and condensate return lines stay under about 1,500 feet per minute.

Drip leg sizing rule

A steam main drip leg uses full line size, with length at least the pipe diameter plus 4 inches. The trap takeoff comes from the bottom of the leg.

Steam trap type selection

Thermostatic traps suit end-of-main drip points, inverted bucket or float-and-thermostatic traps suit process heat exchangers, and thermodynamic traps suit high-pressure drip and tracing.

Butt-weld bevel and root gap

Standard fit-up uses a 37.5 degree bevel per side for a 75 degree included angle, a 1/16 to 1/8 inch land, and a root gap set by the qualified welding procedure.

Preheat for carbon steel

B31.3 Table 330.1.1 requires 50°F minimum preheat below 0.30% carbon, 175°F for 0.30 to 0.40% carbon, and 250°F above 0.40% carbon.

Post-weld heat treatment threshold

For P-No. 1 carbon steel, PWHT is required above 3/4 inch nominal thickness per B31.3. Hold time is one hour per inch, minimum one hour.

Branch reinforcement zone

Reinforcement for a branch opening must lie within a zone extending 2.5 times the run pipe wall thickness from the outside surface of the run pipe.

Pipe bend radius minimums

Common practice sets minimum bend radius at 5 times outside diameter for hot bends and 3 times outside diameter for cold bends, with ovality under 8 percent.

Rolling offset true length

For an equal-spread offset, true offset equals the square root of offset squared plus advance squared. Subtract fitting takeoffs before cutting the connecting pipe.

45 degree fitting constants

For a 45 degree elbow, travel equals offset times 1.414, and fitting takeoff equals 0.625 times nominal pipe size for long-radius elbows.

Miter cut angle

Each miter cut equals half the included angle between the two pipe runs. A 90 degree turn made of two miters uses a 22.5 degree cut on each piece.

Pipe circumference development

Circumference equals pi times outside diameter. Divide it into equal parts and lay out ordinates from the sine of the cut angle to mark a wrap-around template.

Slope percentage conversion

To convert slope percentage to inches per foot, multiply by 12 and divide by 100. A quarter inch per foot equals about 2.08 percent.

Sling leg load formula

Load per leg equals vertical load divided by the number of legs times the cosine of the angle from vertical. Shallower angles sharply increase leg tension.

Pipe weight per foot

Weight in pounds per foot equals 10.68 times wall thickness times (outside diameter minus wall thickness), with both dimensions in inches.

Flange alignment tolerance

For a raised-face joint, offset and gap are held within 1/16 inch, and flange faces are parallel within 0.06 inch measured across the diameter.

Pressure test procedure

Pressurize in increments to half test pressure, inspect, then step to full pressure. Never exceed the lowest-rated component and use a calibrated gauge in its upper quarter.

Isometric drawing purpose

An isometric shows physical geometry, cut lengths, and spool breaks, while a P&ID shows process function and instrument loops. Both must agree before fabrication.

Line designation meaning

A designation such as 6"-P-1201-A1A gives nominal size, service, line number, and piping class. The piping class sets material and pressure rating.

Instrument tag letters

The first letter of an instrument tag names the measured variable: F for flow, T for temperature, P for pressure, and L for level, followed by function letters.

Weld map function

A weld map assigns a unique number to each weld, traced to the welder, procedure, and nondestructive examination record, forming the quality record for a spool.

Confined space atmospheric limits

Entry requires oxygen between 19.5 and 23.5 percent, flammable gas below 10 percent of the lower explosive limit, and hydrogen sulfide below 10 parts per million.

Hot work fire watch

Combustibles are cleared within 35 feet, fire blankets protect what cannot move, and the fire watch remains at least 30 minutes after hot work ends per NFPA 51B.

Ladder setup rule

Use the 4 to 1 rule: the base sits one unit out for every four units of height, the ladder extends 3 feet above the landing, and it is tied off.

Grinder wheel safety

The guard stays installed, the wheel speed rating must meet or exceed the tool speed, and bench grinder tool rests sit within 1/8 inch of the wheel.