PEB Singapore PPE Mechanical cheat sheet

Bending stress σ = My/I = M/Z, with section modulus Z = I/c; maximum stress occurs at the extreme fibre.

Transverse shear stress in a beam section τ = VQ/(It); for a rectangular section the peak is 1.5 × the average shear stress V/A.

Torsion of a circular shaft: τ = Tr/J; for a hollow shaft J = π(do⁴ − di⁴)/32.

Thin-walled cylinder under internal pressure p: hoop stress σ = pr/t, longitudinal stress σ = pr/2t; a thin sphere has σ = pr/2t throughout.

Euler buckling load Pcr = π²EI/(KL)², with K = 0.5 fixed-fixed, 0.7 fixed-pinned, 1.0 pinned-pinned, 2.0 cantilever.

Modified Goodman line for fatigue: σa/Se + σm/Sut = 1; the Soderberg line replaces Sut with Sy and is more conservative.

Endurance limit Se = ka·kb·kc·kd·ke·Se′, with Se′ ≈ 0.5·Sut for steels up to about Sut = 1400 MPa.

Notch sensitivity q = (Kf − 1)/(Kt − 1), so the fatigue stress-concentration factor Kf = 1 + q(Kt − 1).

Fully restrained thermal stress σ = E·α·ΔT; a simply supported beam with a central point load deflects δ = PL³/(48EI).

Affinity laws at constant impeller diameter and air density: flow ∝ N, pressure/head ∝ N², shaft power ∝ N³.

Chiller COP = cooling output ÷ electrical input; since 1 refrigeration ton = 3.517 kW, kW/RT = 3.517/COP.

Sensible heat of an air stream Qs (W) ≈ 1.21 × volume flow (L/s) × ΔT (K), from ρ = 1.2 kg/m³ and cp = 1.005 kJ/kg·K.

Air changes per hour ACH = 3600 × volumetric flow (m³/s) ÷ room volume (m³).

Duct velocity pressure Pv = 0.6·v² (Pa with v in m/s); total pressure equals static plus velocity pressure.

Darcy–Weisbach friction loss Δp = f(L/D)(ρv²/2); equivalent circular diameter of a rectangular duct De = 1.30(ab)^0.625/(a + b)^0.25.

Moist-air enthalpy h = 1.006T + W(2501 + 1.86T) kJ/kg dry air, with T in °C and humidity ratio W in kg/kg.

Coil bypass factor = (h_off − h_ADP)/(h_in − h_ADP); a lower bypass factor indicates a deeper or more effective cooling coil.

Singapore practice: SS 553 governs ACMV design, SS 530 sets equipment efficiency standards, and design setpoints are typically 24–26 °C with RH ≤ 65%.

ASME VIII Div 1 circumferential-stress shell equation: t = PR/(SE − 0.6P), with E the joint efficiency and S the allowable stress.

Hydrostatic test pressure = 1.3 × MAWP × (allowable stress at test temperature / allowable stress at design temperature).

LMTD = (ΔT1 − ΔT2)/ln(ΔT1/ΔT2); apply a correction factor F < 1 for multipass and cross-flow exchangers.

Pump shaft power P(kW) = ρgQH/(1000·η), with Q in m³/s, H in m and ρ in kg/m³.

NPSHa = (Pa − Pv)/(ρg) + Hs − Hf; cavitation occurs when NPSHa falls below the pump's NPSHr.

Pressure relief valves are sized to API 520/521; set pressure must not exceed MAWP and the valve must pass the governing relieving case.

ASME B31.3 governs process piping; minimum design metal temperature and impact-testing requirements control low-temperature service.

Corrosion allowance is added to the calculated minimum thickness for the life of the equipment and is not counted as load-bearing strength.

Total float = LS − ES = LF − EF; activities with zero total float lie on the critical path.

PERT expected duration te = (O + 4M + P)/6 and activity standard deviation σ = (P − O)/6.

Earned value: CV = EV − AC, SV = EV − PV, CPI = EV/AC, SPI = EV/PV; forecast EAC = BAC/CPI when current performance persists.

A WBS decomposes work into deliverable-based work packages that can be costed, scheduled and assigned to a single responsible party.

Quality assurance is process-based and preventive; quality control is inspection and testing of the finished output.

Extension of time is due for employer-risk and neutral events, not contractor-default delay; concurrent delay generally preserves time but can bar prolongation cost.

Typical Singapore retention is 10% deducted from each payment, capped at 5% of the contract sum, with half released at practical completion.

Resource levelling shifts work within float and cannot shorten the project; crashing shortens duration by adding cost to critical-path activities.

The duty to public safety, health and welfare is paramount and overrides loyalty to a client or employer.

Sign and seal only drawings and reports you personally prepared or directly supervised; splitting scope to evade this is professional misconduct.

Declare any financial or personal interest in tenderers, suppliers or competitors and decline the appointment if the conflict cannot be managed.

Accept only work within your current competence; where a task exceeds it, engage a qualified specialist and remain accountable for coordination.

Undisclosed commissions, gifts or hospitality capable of influencing technical judgement are prohibited under the Prevention of Corruption Act.

Client confidentiality survives the end of the engagement, except where disclosure is required by law or necessary to protect safety.

Advertising and fee proposals must not be misleading; contingency fees on safety-critical certification are improper.

Report unsafe or non-compliant work to the employer first, then escalate to the Professional Engineers Board, BCA or MOM if unresolved.

The Professional Engineers Act requires registration with the PEB and a valid practising certificate to supply professional engineering services in Singapore.

The Building Control Act requires plans and structural or applied-system works to be signed by an appropriate qualified person and submitted to the Commissioner of Building Control.

The WSH Act imposes duties on every employer, self-employed person, principal and occupier to ensure safety so far as is reasonably practicable.

The Security of Payment Act creates a statutory right to progress payments and rapid adjudication; 'pay when paid' provisions are void.

Public sector projects use the PSSCOC; private sector projects commonly use the PAM or SIA forms of contract.

Liquidated damages must be a genuine pre-estimate of the employer's loss; a clause that is a penalty in disguise is unenforceable.

In design-and-build procurement the contractor carries design risk, so the employer's requirements must be stated as clear performance criteria.

Contractual time bars extinguish claims if notice is not served within the stated period; the exact period must be read from the contract conditions.

Hierarchy of controls, applied top-down: elimination, substitution, engineering controls, administrative controls, then PPE.

Risk = likelihood × severity; residual risk after controls must be reduced to ALARP before work proceeds.

The WSH (Risk Management) Regulations require every workplace to conduct, record and periodically review risk assessments.

Noise exposure limit is 85 dB(A) over 8 hours; hearing protection and a hearing conservation programme apply at or above that level.

Confined space entry needs a permit, gas testing for oxygen, flammables and H2S, continuous ventilation, a standby man and rescue arrangements.

A permit-to-work combined with lock-out/tag-out is required to isolate stored energy before maintenance on plant and machinery.

FMEA ranks risk by RPN = severity × occurrence × detection; HAZOP applies guide words to nodes of a P&ID to find deviations.

ISO 45001 addresses occupational health and safety management; ISO 14001 addresses environmental management systems.

NPV = Σ Ct/(1 + r)^t − C0; accept a project where NPV > 0 at the required discount rate.

IRR is the discount rate at which NPV = 0 and is compared against the organisation's hurdle rate.

Simple payback = capital cost ÷ annual net savings; it ignores the time value of money and all cash flows after payback.

Life-cycle cost covers capital, energy, maintenance, replacement and disposal, and energy typically dominates chiller economics over 15–20 years.

BCA Green Mark ratings run Certified, Gold, GoldPLUS, Platinum, Super Low Energy and Zero Energy, scoring energy, water and environmental performance.

Singapore's grid emission factor is about 0.42 kg CO2e per kWh, so each kWh saved avoids roughly 0.4 kg CO2e.

Chiller plant efficiency: about 0.65 kW/RT is good practice and 0.5 kW/RT or lower is best in class.

Variable-speed drives capture cube-law savings at part load; savings are quantified through measurement and verification such as IPMVP.

SS 530 sets minimum energy performance standards for air-conditioners and chillers regulated for sale in Singapore.