SOLAS Pipefitting common mistakes
SOLAS Pipefitting · Understand the traps and how to avoid them.
Treating SOLAS as a general piping code and answering code questions from generic ASME B31.3 knowledge instead of the marine statutory framework, e.g. missing that SOLAS Chapter II-1 governs machinery and piping arrangements and that classification society rules (ABS, DNV, Lloyd's, BV, ClassNK) supply the detailed acceptance criteria SOLAS delegates to them.
Candidates with land-based industrial piping backgrounds study the pressure-piping code they already know and assume SOLAS is a synonym for 'marine piping standard'. The exam is delivered against the SOLAS/IMO regulatory structure, so generic code answers fail even when the engineering is sound.
What to do instead
Build a one-page map of SOLAS structure before studying details: Chapter II-1 (machinery, bilge, ballast, fuel oil arrangements), II-2 (fire protection, fire main, sprinkler and fixed systems, emergency fire pump), plus the FSS and FTP Codes. For each pipe system, note which SOLAS regulation sets the requirement and which class rule or ISO standard supplies the acceptance test. Answer code questions by naming the SOLAS chapter and regulation first, then the delegated standard.
Confusing the bilge, ballast, fuel oil, and fire main systems when identifying a line from its service description, and applying the wrong material, test pressure, or valve requirement to it. For example, fitting a cast iron valve in a bilge line where the exam expects the specified material, or sizing a fire main branch without accounting for the required pressure at the hydrant.
All four systems use similar pipe sizes, similar fittings, and often run adjacent to each other in the engine room. Candidates memorize pipe schedules without anchoring each system to its function, hazard, and regulatory requirement, so they pattern-match on appearance rather than service.
What to do instead
Create a system-by-system table with columns for function, medium, typical material, valve type, test requirement, and governing SOLAS regulation. Drill by reading a service description only (no drawing) and stating the system, then the material and test. Pay particular attention to the fire main, which has explicit pressure and flow requirements at hydrants, and to fuel oil lines, which have their own arrangement and protection rules.
Reading an isometric drawing as if it were an orthographic projection: assuming lines drawn at an angle are true lengths, ignoring the north arrow and the isometric axes, and missing the elevation callouts that establish which way a run rises or falls. Candidates then calculate a cut length from a scaled measurement on the isometric.
Isometrics are not drawn to scale, and candidates who are used to scaled plan drawings try to measure them. The 30-degree axes, the vertical axis, and the offset symbols are unfamiliar, and the drawing convention that pipe runs are shown as single lines with fittings represented symbolically is not intuitive.
What to do instead
Practice reading isometrics with the rule that the drawing gives topology and dimensions, never scale. Train the habit of locating the north arrow, identifying the three axes, and tracing one line from origin to terminus while writing down each dimension and each change of direction. Verify cut lengths against the dimension strings and the fitting take-out tables, never against a ruler on the sheet. Work several exercises where two different isometrics describe the same physical run so the convention becomes automatic.
Calculating a cut length without deducting fitting take-outs (fitting allowances) and thread engagement, or applying the take-out for the wrong fitting type or size. The candidate measures centre-to-centre, subtracts nothing, and cuts the pipe long, or subtracts a socket-weld allowance on a buttweld run.
Take-out values depend on fitting type (elbow, tee, reducer), angle, schedule, and joining method, and they are tabulated rather than derived. Candidates who have not internalized the take-out concept treat the centre-to-centre dimension as the pipe length.
What to do instead
Memorize the method rather than a single number: pipe length equals centre-to-centre dimension minus the sum of the take-outs of the fittings at each end, adjusted for thread engagement on threaded joints and for root gap on buttweld joints. Practice with a take-out table for 45 and 90 degree elbows across at least three nominal sizes and two schedules. Always state the joining method before selecting the allowance, and show the subtraction explicitly in worked answers.
Specifying or accepting a joint type that is not permitted for the service or location, for example a threaded joint in a fuel oil line in a location where the exam expects welded construction, or a flanged joint in a concealed space without access for maintenance. Similarly, mismatching flange facing, gasket, and bolt grade so the joint is dimensionally compatible but not pressure-rated as an assembly.
Candidates learn joining methods in isolation and never build the decision rule that links service, pressure, temperature, location, and maintenance access to an acceptable joint. Flange rating questions are answered by matching nominal size only, ignoring pressure class, facing, and gasket compatibility.
What to do instead
Learn the joint-selection hierarchy: for each service, state the permitted methods and the reason (leak risk, fire risk, vibration, accessibility). For flanges, always answer as a set: pressure class, facing type, gasket material, and bolt grade must all be compatible, and the assembly rating is the lowest-rated component. Review worked examples where a correctly sized flange fails because the gasket or bolt grade is wrong.
Ignoring thermal expansion and support requirements: running a hot line without expansion loops or offsets, placing a rigid anchor where a guide or slide is needed, or spacing hangers by a rule of thumb without regard to pipe size, schedule, contents, and temperature. Candidates also forget that supports must allow the pipe to move in the designed direction.
Expansion and support design is treated as a layout detail rather than a structural requirement, and the difference between anchors, guides, slides, and spring hangers is blurred. The exam tests whether the candidate can predict where movement occurs and which support type permits or restrains it.
What to do instead
For every hot or cold line, first identify the fixed points and the direction and magnitude of expected movement, then select support types that permit that movement. Learn the function of each support type in one sentence: anchor restrains all movement, guide permits axial movement only, slide permits axial and lateral movement, spring hanger carries load while allowing vertical movement. Practice reading a simple route and marking where an expansion loop or offset is required and where guides must be placed.
Choosing the wrong test medium or test pressure for a pressure test, or testing a system before it is ready. Examples: hydrotesting a line that the specification requires to be pneumatically tested, applying a test pressure that is not the specified multiple of design pressure, failing to isolate or remove components that cannot take the test pressure, and not venting high points before pressurizing.
Candidates memorize a single test pressure rule and apply it universally, ignoring that the specification, the class rule, and the service determine the medium and the multiplier. The procedural steps that must precede pressurization are studied separately from the pressure value and get dropped.
What to do instead
Study pressure testing as a sequence: verify the specification for medium and test pressure, confirm all joints are complete and accessible, isolate or remove incompatible components, fill and vent high points, pressurize in stages, hold, inspect, and record. Learn why pneumatic testing is restricted (stored energy hazard) and what extra precautions it demands. Practice calculating test pressure from design pressure and stating the multiplier and its source.
Answering inspection and quality control questions by naming a test rather than the acceptance criterion, e.g. stating 'radiograph the weld' without stating what indication is unacceptable, or confusing a hydrostatic leak test with a strength test. Candidates also fail to distinguish examination methods (visual, PT, MT, RT, UT) by what defect type and location each can detect.
NDT methods are learned as a list of acronyms without the defect-detection logic, so the candidate cannot match method to defect. Acceptance criteria live in the applicable code or specification, and candidates who skip that document default to a vague 'no defects' answer.
What to do instead
Build a matrix of NDT methods against defect types: surface-breaking versus internal, ferromagnetic versus non-ferromagnetic material, and the typical application for each. For every inspection question, answer in two parts: the method, and the acceptance criterion with its source. Practice identifying which method would find lack of fusion, porosity, a crack at a weld toe, and a lamination in plate.
Applying a safety rule generically instead of to the specific hazard: entering a confined space without testing and permitting, hot work without a gas-free certificate and fire watch, or working on a line without confirming isolation, depressurization, and drain. Candidates also misjudge lifting and rigging limits for pipe spools and valves.
Safe work practice questions look easy, so candidates answer from general awareness rather than the marine-specific permit regime. The exam expects the sequence of controls, not just the existence of a control, and the confined space and hot work regimes on board ship are stricter than shore practice.
What to do instead
Learn each high-risk activity as an ordered control sequence. For confined space: isolate, ventilate, test atmosphere, permit, attendant, rescue plan. For hot work: permit, gas-free certificate, remove or protect combustibles, fire watch, post-work monitoring. For line work: identify, isolate, depressurize, drain, vent, lock and tag, then verify. State the sequence in answers rather than a single measure.
Treating the specification and documentation as background reading and answering material or fabrication questions from memory. The candidate selects a pipe grade, wall thickness, or welding procedure without checking the project specification, the approved welding procedure specification, or the material certificate, and cannot state which document governs when two documents conflict.
Specifications are long and candidates skip to the drawings, then answer from general knowledge. The exam tests whether the candidate knows where the requirement lives and which document takes precedence, which is a documentation skill as much as a technical one.
What to do instead
Practice the document hierarchy: regulatory requirement, then project specification, then referenced standard, then drawing, with the more stringent requirement governing where they conflict. For any material or fabrication question, name the governing document and the property it controls (grade, schedule, impact requirement, procedure qualification). Learn what a mill certificate, a WPS, and a procedure qualification record each establish and which one authorizes the work.