SOLAS Pipefitting cheat sheet

Hazard controls follow the hierarchy: elimination, substitution, engineering controls, administrative controls, then PPE last.

Permit-required tasks include hot work, confined-space entry, line breaking, and work at height; each permit states its own isolation and gas-test requirements.

Confined-space entry requires testing for oxygen (19.5–23.5%), flammables, and toxics before entry and continuously during occupancy.

Hot work near piping requires a fire watch maintained at least 30 minutes after work stops, with combustible gas testing below the LEL.

Lockout/tagout requires zero-energy verification by attempt to start or by test meter before work begins; a tag alone is not an isolation.

PPE for pipefitting: safety glasses with side shields, face shield for grinding, gloves matched to chemical and cut hazard, and hearing protection above 85 dBA.

A cylinder of oxygen must never be used to blow out lines or to power pneumatic tools; oil and grease plus oxygen is an ignition hazard.

A dropped object rule: tools above head height are tethered or in a bag; hard hats are required where overhead work is in progress.

SOLAS Chapter II-1 Regulation 26 requires piping systems essential to the safety of the ship to be designed, constructed, and installed to the Administration's satisfaction.

Classification society rules (ABS, DNV, Lloyd's, BV) supplement SOLAS; where they conflict, the more stringent requirement is applied.

Piping carrying fuel oil, lube oil, and other flammable liquids is prohibited above or close to hot surfaces and electrical equipment per SOLAS II-2.

A piping system's design pressure is the maximum allowable working pressure (MAWP); the design temperature is the maximum expected service temperature.

Hydrostatic test pressure is typically 1.5 times design pressure; the test is held for at least 10 minutes at stabilized pressure.

Material certificates must be traceable to the heat number and to the specification; pressure-containing parts use the grade called out on the drawing.

Any alteration to a class-approved system requires re-approval; field changes cannot substitute for an approved drawing revision.

Nominal pipe size (NPS) is a dimensionless designation; actual outside diameter is fixed per NPS, and wall thickness is set by schedule.

Schedule number approximates 1000 × internal pressure / allowable stress; higher schedule means thicker wall for the same NPS.

Common marine grades: carbon steel ASTM A106 Gr B, A53 Gr B; stainless 316L (UNS S31603) for seawater-adjacent and chemical service.

Galvanized carbon steel is not used in seawater service; the zinc coating fails and the underlying steel corrodes rapidly.

Butt-weld fittings to ASME B16.9; socket-weld and threaded fittings to ASME B16.11; flanges to ASME B16.5 (NPS 1/2–24).

A gate valve is for isolation, a globe valve for throttling, a ball valve for quick shutoff, and a check valve for one-way flow only.

Valve pressure class (150, 300, 600) is the maximum allowable non-shock pressure at the rated temperature, not a burst rating.

Gasket selection: spiral-wound with graphite filler for high temperature and pressure; non-asbestos sheet for low-pressure water and air.

Take-off measurement: center-to-center distance minus fitting take-outs equals the cut length of straight pipe.

A 90° long-radius elbow take-out equals 1.5 × NPS; a 45° elbow take-out equals 0.625 × NPS (approximately).

For a 45° offset, the travel equals the offset divided by the sine of 45° (0.7071); the run equals the offset for a 45° set.

For a rolling offset, true offset = square root of (horizontal offset squared + vertical offset squared).

Cut pipe square: end squareness within 1 mm for butt weld prep; bevel angle 30° +5/−0° with a 1.6 mm root face for standard V-groove.

Clean the bevel and 25 mm of adjacent surface to bare metal before welding; remove all oil, paint, and scale.

Allow for thermal expansion: ΔL = L × α × ΔT, with α ≈ 0.012 mm/m·°C for carbon steel.

Cold spring is not a substitute for a properly designed expansion loop; it is used only where the design specifies it.

Butt-weld joints are full-penetration; the root pass must be complete and fused to the bevel before the fill passes.

Socket-weld joints leave a 1.6 mm gap at the bottom of the socket to allow expansion and prevent cracking at the root.

Threaded joints use tapered NPT threads; sealant is applied to the male thread, leaving the first two threads bare.

Flanged joints: bolts are tightened in a star or crisscross pattern in stages to the specified torque; gasket is centered on the flange face.

Brazing for copper: filler melts above 450°C but below the base metal melting point; soldering filler melts below 450°C.

Purging with argon is required for stainless steel root protection; oxygen content in the purge gas should be below 0.1% for critical welds.

Post-weld heat treatment is required for carbon steel above specified thickness (commonly 25 mm for P-No.1) and for certain alloy steels.

Support spacing for carbon steel water lines: NPS 1 ≈ 2.1 m, NPS 2 ≈ 3.0 m, NPS 4 ≈ 4.3 m, NPS 6 ≈ 5.2 m (typical values, verify against project spec).

A rigid support restrains all movement; a spring hanger allows vertical movement while carrying load; a guide allows axial movement only.

An anchor restrains translation and rotation at one point and directs expansion to the designed loops or offsets.

Expansion loops absorb thermal growth; loop leg length is sized so the developed stress stays within the allowable range.

A pipe shoe raises the pipe off the support and reduces friction; it is not a substitute for a guide where lateral restraint is needed.

A cold pull (cold spring) of 50% is common where specified, applied to the open end before final tie-in.

Vibration isolation uses resilient pads or spring isolators; hard supports transmit vibration into the structure.

Hydrostatic test: fill, vent all air, pressurize in steps to 1.5 × design pressure, hold 10 minutes minimum, inspect all joints.

Pneumatic testing carries stored-energy risk; where used, test pressure is typically 1.1 × design pressure and the area is barricaded.

Test water temperature should be above the ductile-to-brittle transition temperature of the material to avoid brittle fracture.

After hydrotest, drain and dry; stainless steel lines are rinsed with low-chloride water to prevent chloride attack.

Visual inspection of welds covers bead profile, undercut, spatter, and fit-up; it does not detect internal defects.

Non-destructive examination: radiography for volumetric internal defects, dye penetrant for surface-breaking defects on non-porous materials, magnetic particle for surface and near-surface in ferromagnetic material.

Acceptance criteria for weld defects are found in the applicable code (e.g., ASME B31.3 or the class rule), not in the fabricator's judgment.

Bilge system: branches from each compartment lead to a bilge main, with non-return valves preventing backflow into compartments.

Ballast system: separate from bilge; cross-connections require an approved arrangement and a non-return valve.

Fuel oil transfer and service systems require quick-closing valves operable from outside the space and remote shutoff at the tank.

Sea water cooling systems use non-ferrous or corrosion-resistant materials; velocity is limited (typically under 3 m/s) to control erosion-corrosion.

Steam lines require drain traps at low points and at the end of mains; water hammer results from inadequate drainage or fast valve closure.

Air and sounding pipes must remain clear and terminate above the freeboard deck with approved closures.

A relief valve protects against overpressure; its set pressure does not exceed the MAWP of the protected system.

An isometric shows three axes at 30° from horizontal; north arrow and line number identify the run.

Line number format typically: size, service code, sequence, material class, and insulation code (e.g., 4"-FO-102-A1A).

A bill of materials on the isometric lists every fitting, valve, and gasket with quantity and size; the pipe spool length is the cut length.

Welds are numbered on the drawing; the weld map ties each number to the welder, procedure, and NDE result.

The piping specification defines material class, pressure rating, gasket, and bolting for each service; the drawing must not contradict it.

Revision clouds and the revision block record changes; only the latest revision is used for fabrication.

Field-run dimensions are marked on the drawing at the point of tie-in; they are verified on site before cutting.

Pipe cutters: wheel cutter for small bore; abrasive saw or plasma for larger; cutting torch requires hot work permit and fire watch.

Pipe threading: hand die or power threader; thread length is set by the pipe size chart, and cutting oil is required.

Pipe bender: manual or hydraulic; bend radius must meet the minimum for the material and wall thickness to avoid ovality and thinning.

Torque wrench is calibrated and used within its range; a torque value is applied to the fastener, not to the wrench handle extension.

Grinder guards must be in place; the wheel is rated for the tool speed, and the operator stands clear of the wheel plane.

Lifting: slings are rated and inspected; never stand under a suspended load; tag lines control the load.

Housekeeping: combustible waste removed from hot work area, hoses routed clear of walkways, and gas cylinders secured upright.