Equipment Safety, Risk and Reliability Management
Domain 8 - Equipment Safety, Risk and Reliability Management
This domain tests whether you can identify hazards, rank them with a defensible method, and choose controls in the right order, plus the reliability arithmetic behind maintenance and spares decisions.
Core rules
- Risk assessment. LEC method: D = L × E × C (likelihood, exposure, consequence), with bands mapping D to risk levels. Risk matrices use likelihood × severity. Ranking without a stated method is unverifiable.
- Control hierarchy. Eliminate → substitute → engineering controls (guards, interlocks, relief devices) → administrative controls (procedures, training, permits) → PPE, which is the last line and never the first.
- Special equipment. Eight categories: boilers, pressure vessels, pressure piping, elevators, hoisting machinery, passenger ropeways, large amusement rides, in-plant motor vehicles. Manufacture and installation require licensing and 监督检验; use requires registration; periodic inspection depends on safety grade - grade 1 and 2 pressure vessels typically at least every 6 years, grade 3 every 3–6 years. Safety valves are normally calibrated at least annually.
- Reliability. R(t) = e^(−λt) at constant failure rate; MTBF = 1/λ; the bathtub curve has early-failure, random and wear-out regions. FMEA ranks by RPN = severity × occurrence × detection, but high severity alone can mandate action regardless of RPN.
- Safety devices. Relief valve and rupture disc are not interchangeable: a disc responds instantly but does not reseat; a valve reseats but may be obstructed by polymerising media. Interlocks and emergency shutdown need periodic proof testing.
Worked example
Three compressor failure modes: (a) seal leak, S 7, O 4, D 5, RPN 140; (b) lube-oil pump failure, S 9, O 3, D 6, RPN 162; (c) coupling guard missing, S 8, O 7, D 2, RPN 112. Ranking by RPN puts (b) first, but (c) is a cheaply removable hazard with high occurrence - fix it immediately regardless of score. For (b), detection is the weak factor: adding a lube-oil pressure trip and low-pressure alarm lowers D before it lowers O. Act on severity and control feasibility, not on rank alone.
Traps that cost marks
- Quoting RPN ranking without noting that severity-dominated risks override it.
- Treating PPE as an engineering control, or expecting training to fix a design hazard.
- Confusing inspection intervals, or applying boiler rules to pressure vessels.
- Assuming a safety valve covers every overpressure scenario, including rapid reaction or thermal expansion.
Project Case Analysis and Supervision Practice
Domain 9 - Project Case Analysis and Supervision Practice
This domain introduces no new theory; it tests whether you can apply the other eight domains to a messy narrative under time pressure, with the right responsible party and the right written instrument.
Core rules
- Answer structure. For each question: identify the issue → cite the governing rule or contract clause → state the conclusion → give the corrective action and who performs it. Marks sit in the reasoning chain, not only the verdict.
- Responsibility mapping. Owner: scope, funding, external conditions, timely decisions. Manufacturer/contractor: conformity of product and process, self-inspection, rectification. Supervisor: independent verification, timely written instruction, reporting. An answer that blames "the project" scores nothing.
- Escalation ladder. Nonconformity → 监理通知单 with a deadline → re-inspection and closure → if the contractor refuses or the risk is serious → written report to the client → 停工令 on the affected work → report to the competent authority for safety or special-equipment violations. Every step is written and dated.
- Evidence. Inspection records, W/H point sign-offs, NDT reports, calibration certificates, meeting minutes, correspondence log, photographs with time and location.
- Common case types. Arrival-inspection rejection, weld repair and re-testing, delay and claim entitlement, design-change impact, safety incident, acceptance dispute.
Worked example
At arrival inspection, a heat exchanger shows shell wall thickness 2 mm below drawing, while the mill certificate shows conforming thickness. Steps: (1) establish measurement validity - calibrated gauge, defined ultrasonic grid; (2) compare against the drawing and code minimum, not the certificate; (3) classify as a nonconformity of manufacture, not transport damage; (4) segregate and mark, do not install; (5) instruct the manufacturer in writing to propose disposition - recalculate the design with measured thickness and, if pressure-retaining margins hold, submit a concession for designer and client approval, otherwise replace the shell; (6) re-inspect 100 % of the affected area and update the dossier. Acceptance here is a design-margin question, not a courtesy question.
Traps that cost marks
- Giving a conclusion without the rule, or citing a rule without applying it to the facts.
- Writing "supervisor should strengthen management" - no measurable action, no mark.
- Forgetting the written record, the only evidence that the supervisor acted.
- Accepting the contractor's own test result as the closing evidence for a nonconformity.