Egypt Engineering Consultant Mechanical cheat sheet

Cooling load = sensible + latent; sensible heat ratio SHR = Qs/(Qs+Ql); room design typically 24-26 °C DB and 50-60 % RH in Egyptian comfort applications.

Sensible heat Qs (W) = 1.23 × L/s × ΔT (°C) for air at ~20 °C, or Qs = 1.08 × cfm × ΔT (°F); latent Ql (W) = 3.0 × L/s × Δw (g/kg).

Psychrometric coil process: apparatus dew point ADP and bypass factor BF = (h_out − h_ADP)/(h_in − h_ADP); lower BF means deeper coil and lower chilled-water temperature.

Chilled water ΔT design 5-7 K (commonly 6.7 K, 12/6.7 °C); flow L/s = Q(kW)/(4.19 × ΔT); pipe velocity 0.9-2.4 m/s to limit erosion and noise.

Duct sizing: equal-friction 0.8-1.2 Pa/m for main runs; velocity limits 4-6 m/s main, 2-3 m/s branch to control regenerated noise; Darcy-Weisbach Δp = f(L/D)(ρv²/2).

Refrigeration cycle COP_R = evaporating effect / compressor work; Carnot COP = T_evap/(T_cond − T_evap) in kelvin; each 1 K lower evaporating temperature raises compressor power roughly 2-4 %.

VRF/VRV diversity factor 0.7-0.9 applied to connected indoor capacity; refrigerant R-410A GWP 2088 and R-32 GWP 675 drive Egyptian refrigerant-selection and leak-record obligations.

Fresh-air rate per ASHRAE 62.1: Vbz = Rp·Pz + Ra·Az; Egyptian practice often adds 10-15 % margin and requires filtration to EN 779/ISO 16890 class for outdoor dust load.

Fixture units (FU) convert to design flow via Hunter curves; a water closet = 2.5 FU cold, 3 FU combined; flush valve systems need higher residual pressure (min ~100 kPa) than flush tanks (~50 kPa).

Domestic cold-water velocity limit 1.5-2.0 m/s in pipes to control noise and erosion; hot water 1.0-1.5 m/s; minimum pressure at most remote fixture 50-100 kPa depending on fixture type.

Gravity drainage slope: 1-2 % for 100 mm and smaller, 1 % for 150 mm and larger; drain pipe self-cleansing velocity ≥0.6 m/s at design flow; vent stack sized to limit trap-seal pressure variation to ±250 Pa.

Soil stack and vent: each trap needs a water seal of 50-75 mm; wet venting is limited to same-storey fixtures; air admittance valves are accepted only where the code permits and never as the sole vent for a building.

Fire hose reel minimum residual pressure 2-3.5 bar at the most remote outlet; sprinkler design density from hazard class (light 2.25, ordinary 5.0, extra 7.5-12.5 mm/min over the design area).

Sprinkler design area: light hazard 84 m², ordinary hazard 144-216 m², extra hazard 232-465 m²; add 30 % area for dry-pipe or sloped-ceiling allowances per NFPA 13.

Fire pump rated flow must not be less than the system demand; churn pressure typically ≤140 % of rated; jockey pump set to start at ~10 psi above pump start and stop below it.

Egyptian fire requirements: Civil Protection Law 308/1955 and its executive regulations, plus NFPA 13/14/20 and EN 12845 as design references; occupancy classification and travel distance drive egress design.

First Law for steady flow: Q − W = ṁ[(h2 − h1) + (V2² − V1²)/2 + g(z2 − z1)]; for a compressor, W_in ≈ ṁ(h2 − h1) when kinetic and potential terms are negligible.

Conduction: Fourier law q = −kA dT/dx; plane wall R = L/(kA); cylindrical pipe R = ln(r2/r1)/(2πkL); add convection films 1/(hA) in series for the overall U.

Convection: Nu = hL/k; Dittus-Boelter Nu = 0.023 Re^0.8 Pr^n (n = 0.4 heating, 0.3 cooling) valid for Re > 10,000 and 0.7 < Pr < 160.

Radiation: q = εσA(Ts⁴ − Tsurr⁴), σ = 5.67 × 10⁻⁸ W/(m²·K⁴); surface emissivity of galvanised steel ~0.25, black paint ~0.95.

Reynolds number Re = ρVD/μ; laminar < 2300, transitional 2300-4000, turbulent > 4000; friction factor f = 64/Re for laminar; Colebrook or Swamee-Jain for turbulent.

Bernoulli with losses: p1/ρg + V1²/2g + z1 = p2/ρg + V2²/2g + z2 + h_f + h_m; minor loss h_m = K V²/2g; pump head H = Δp/ρg + Δz + losses.

Pump affinity laws: Q ∝ N, H ∝ N², P ∝ N³; system curve H = H_static + kQ². Operating point is the intersection of pump and system curves; avoid operation far left of BEP.

Second Law: entropy generation Ṡ_gen ≥ 0; isentropic efficiency η_s = (h2s − h1)/(h2 − h1); exergy destruction = T0·Ṡ_gen.

Diesel generator sizing: prime rating for continuous duty, standby rating for emergency; apply 0.8 power factor and derate for altitude and ambient temperature above 40 °C (about 1 % per 5 °C).

Generator load step limits: single-step load acceptance typically 25-50 % of standby rating for diesel; motor starting kVA drives the transient dip (max 15-20 % voltage dip).

Chiller efficiency metrics: COP = kW cooling/kW input; EER = BTU/h per W; IPLV/NPLV weights part-load points; a kW/TR of 0.55 equals COP 6.4.

Boiler efficiency: direct method η = Q_out/Q_in; indirect (BS 845) accounts for dry flue gas, moisture, unburned carbon and radiation losses; each 20 °C reduction in flue gas temperature saves roughly 1 % fuel.

Steam: h_fg falls with pressure; superheat added at constant pressure; steam trap selection depends on condensate load and differential pressure; flash steam fraction = (h_f1 − h_f2)/h_fg2.

Gas turbine Brayton cycle η = 1 − 1/rp^((γ−1)/γ); regeneration raises efficiency at low pressure ratio; combined cycle reaches 55-62 % using HRSG steam bottoming.

Fan and pump power P (kW) = Q(m³/s) × Δp(Pa)/(1000 × η); belt, gear and motor efficiency multiply to the overall drive efficiency.

Energy auditing: energy use index kWh/m²·yr; measure, benchmark, then apply no-cost, low-cost, and capital measures; verify savings with IPMVP Option A/B/C/D.

Motor full-load current from nameplate; cable sizing considers continuous load × 1.25, voltage drop ≤3 % branch and ≤5 % total, and derating for ambient temperature and grouping.

Three-phase power P = √3 V I cos φ; a 0.85 power factor and 400 V supply give P ≈ 0.589 kVA per amp; capacitor kVAr = P(tan φ1 − tan φ2) for correction.

Protection coordination: discrimination between upstream and downstream devices; MCCB settings (Ir, Isd, Ii) must sit below cable withstand and above motor starting current.

Motor starting: DOL gives ~6× FLC; star-delta reduces to ~1/3 torque and current; soft starter and VFD limit inrush; VFD harmonics require THD assessment per IEEE 519.

BACnet object model: Analog Input/Output, Binary Input/Output, and scheduling; MS/TP up to 76.8 kbps, BACnet/IP over Ethernet; device instance must be unique on the internetwork.

Sensors and actuators: 4-20 mA into 250 Ω gives 1-5 V; 0-10 V control; RTD PT1000 changes ~3.85 Ω/°C; accuracy and range determine control loop stability.

Control loops: PID output = Kp·e + Ki∫e dt + Kd·de/dt; tune by Ziegler-Nichols or trial; deadband and anti-hunting prevent valve and damper oscillation.

Interface points between mechanical and electrical: status, command, alarm, and analog feedback; each point needs a defined signal type, range, and fail-safe position.

Egyptian Fire Code: Law 308/1955 and its executive regulations govern fire protection; the Egyptian Code for Design and Implementation of Fire Protection (ECP) supplements it with occupancy and egress rules.

Egyptian Electrical Code: the Egyptian Code for Electrical Installations aligns with IEC 60364 principles; the Egyptian Organization for Standardization (EOS) issues national standards.

Egyptian Code for Plumbing and Sanitary Works sets fixture unit values, pipe slopes, and venting; it references international practice where local clauses are silent.

Egyptian Code for Air Conditioning (ECP) covers load calculation, ventilation, and duct design; ASHRAE 15 and EN 378 apply to refrigerant safety and machinery rooms.

Structural and MEP coordination: the Egyptian Code for Loads and Forces (ECP 201) and the Concrete Code (ECP 203) define imposed loads and penetrations that MEP must respect.

Contract documents hierarchy: agreement, conditions, specifications, drawings, bill of quantities; the order of precedence clause resolves conflicts, usually drawings before BoQ.

FIDIC Red Book 2017: Engineer's determination, 28-day claim notice, and 84-day payment cycle; Egyptian contracts often adopt FIDIC with local amendments.

Egyptian Syndicate of Engineers regulates registration and practice; the Consultant's stamp and registration are required for permit submissions.

Earned value: CV = EV − AC, SV = EV − PV, CPI = EV/AC, SPI = EV/PV; EAC = BAC/CPI when the current cost performance is expected to continue.

Critical path method: float = LS − ES = LF − EF; total float on the critical path is zero; crashing costs the least per unit of time saved on the critical path.

Cost estimate classes (AACE): Class 5 −30 %/+50 % at 0-2 % definition, Class 3 −20 %/+30 %, Class 1 −10 %/+15 % at full definition.

Contingency vs allowance: contingency covers identified risks and is drawn down; management reserve covers unknown-unknowns and sits outside the project budget.

Quantity take-off: measure from drawings, apply wastage (pipes 5-10 %, duct sheet 10-15 %), and price with labour, material, plant, overhead and profit.

Payment terms: advance payment guarantee, interim payment certificates, retention typically 5-10 % released at taking-over and after the defects liability period.

Delay analysis: time impact analysis, as-planned vs as-built, and windows analysis; concurrent delay generally shares responsibility and limits extension of time.

Risk register: probability × impact scoring, mitigation owner and date; update at each progress meeting and link to the contingency drawdown.

Hierarchy of controls: eliminate, substitute, engineering controls, administrative controls, PPE; PPE is the last line and never the primary control.

Confined space: test for oxygen (19.5-23.5 %), flammable gas (<10 % LEL), and toxics before entry; continuous monitoring, attendant, and rescue plan are mandatory.

Work at height: guardrails at 2 m and above; fall-arrest harness with anchor point rated 15 kN; permit-to-work and rescue plan required.

Hot work: permit, fire watch, 10 m clearance of combustibles, and fire extinguisher at the point of work; re-check the area for 30-60 minutes after completion.

Refrigerant safety: ASHRAE 15/EN 378 set refrigerant concentration limits (RCL); machinery rooms need detection, ventilation, and alarms for A2L/A3 refrigerants.

Electrical safety: lock-out/tag-out, test before touch, arc-flash boundary and PPE category from incident energy study per NFPA 70E.

Environmental: Egyptian Law 4/1994 amended by Law 9/2009 governs environment; environmental impact assessment (EIA) is required for major projects before permitting.

Waste and emissions: refrigerant recovery and no venting; noise limits at boundary; dust and asbestos control during demolition; spill response for fuel and chemicals.

Engineer's duty: competence, honesty, and public safety paramount; sign and seal only work you prepared or directly supervised.

Conflict of interest: disclose any financial or personal interest in a supplier, contractor, or product; decline the assignment if the conflict cannot be managed.

Confidentiality: client information, drawings, and cost data are confidential and not reused for other clients without permission.

Liability: negligence requires duty, breach, causation, and damage; professional indemnity insurance covers errors and omissions, not deliberate acts.

Standard of care: the degree of skill of a reasonably competent engineer in similar circumstances; not a guarantee of perfection.

Bribery and gifts: refuse or disclose gifts that could influence judgment; comply with anti-corruption law and the client's code of conduct.

Records: keep design calculations, correspondence, and site instructions; the limitation period and contractual liability period define exposure.

Whistleblowing: report unsafe or illegal practice to the client and, where required, to the authority; document the report and the response.

Cooling load = sensible + latent; sensible heat ratio SHR = Qs/(Qs+Ql); room design typically 24-26 °C DB and 50-60 % RH in Egyptian comfort applications.

Sensible heat Qs (W) = 1.23 × L/s × ΔT (°C) for air at ~20 °C, or Qs = 1.08 × cfm × ΔT (°F); latent Ql (W) = 3.0 × L/s × Δw (g/kg).

Psychrometric coil process: apparatus dew point ADP and bypass factor BF = (h_out − h_ADP)/(h_in − h_ADP); lower BF means deeper coil and lower chilled-water temperature.

Chilled water ΔT design 5-7 K (commonly 6.7 K, 12/6.7 °C); flow L/s = Q(kW)/(4.19 × ΔT); pipe velocity 0.9-2.4 m/s to limit erosion and noise.

Duct sizing: equal-friction 0.8-1.2 Pa/m for main runs; velocity limits 4-6 m/s main, 2-3 m/s branch to control regenerated noise; Darcy-Weisbach Δp = f(L/D)(ρv²/2).

Refrigeration cycle COP_R = evaporating effect / compressor work; Carnot COP = T_evap/(T_cond − T_evap) in kelvin; each 1 K lower evaporating temperature raises compressor power roughly 2-4 %.

VRF/VRV diversity factor 0.7-0.9 applied to connected indoor capacity; refrigerant R-410A GWP 2088 and R-32 GWP 675 drive Egyptian refrigerant-selection and leak-record obligations.

Fresh-air rate per ASHRAE 62.1: Vbz = Rp·Pz + Ra·Az; Egyptian practice often adds 10-15 % margin and requires filtration to EN 779/ISO 16890 class for outdoor dust load.

Fixture units (FU) convert to design flow via Hunter curves; a water closet = 2.5 FU cold, 3 FU combined; flush valve systems need higher residual pressure (min ~100 kPa) than flush tanks (~50 kPa).

Domestic cold-water velocity limit 1.5-2.0 m/s in pipes to control noise and erosion; hot water 1.0-1.5 m/s; minimum pressure at most remote fixture 50-100 kPa depending on fixture type.

Gravity drainage slope: 1-2 % for 100 mm and smaller, 1 % for 150 mm and larger; drain pipe self-cleansing velocity ≥0.6 m/s at design flow; vent stack sized to limit trap-seal pressure variation to ±250 Pa.

Soil stack and vent: each trap needs a water seal of 50-75 mm; wet venting is limited to same-storey fixtures; air admittance valves are accepted only where the code permits and never as the sole vent for a building.

Fire hose reel minimum residual pressure 2-3.5 bar at the most remote outlet; sprinkler design density from hazard class (light 2.25, ordinary 5.0, extra 7.5-12.5 mm/min over the design area).

Sprinkler design area: light hazard 84 m², ordinary hazard 144-216 m², extra hazard 232-465 m²; add 30 % area for dry-pipe or sloped-ceiling allowances per NFPA 13.

Fire pump rated flow must not be less than the system demand; churn pressure typically ≤140 % of rated; jockey pump set to start at ~10 psi above pump start and stop below it.

Egyptian fire requirements: Civil Protection Law 308/1955 and its executive regulations, plus NFPA 13/14/20 and EN 12845 as design references; occupancy classification and travel distance drive egress design.

First Law for steady flow: Q − W = ṁ[(h2 − h1) + (V2² − V1²)/2 + g(z2 − z1)]; for a compressor, W_in ≈ ṁ(h2 − h1) when kinetic and potential terms are negligible.

Conduction: Fourier law q = −kA dT/dx; plane wall R = L/(kA); cylindrical pipe R = ln(r2/r1)/(2πkL); add convection films 1/(hA) in series for the overall U.

Convection: Nu = hL/k; Dittus-Boelter Nu = 0.023 Re^0.8 Pr^n (n = 0.4 heating, 0.3 cooling) valid for Re > 10,000 and 0.7 < Pr < 160.

Radiation: q = εσA(Ts⁴ − Tsurr⁴), σ = 5.67 × 10⁻⁸ W/(m²·K⁴); surface emissivity of galvanised steel ~0.25, black paint ~0.95.

Reynolds number Re = ρVD/μ; laminar < 2300, transitional 2300-4000, turbulent > 4000; friction factor f = 64/Re for laminar; Colebrook or Swamee-Jain for turbulent.

Bernoulli with losses: p1/ρg + V1²/2g + z1 = p2/ρg + V2²/2g + z2 + h_f + h_m; minor loss h_m = K V²/2g; pump head H = Δp/ρg + Δz + losses.

Pump affinity laws: Q ∝ N, H ∝ N², P ∝ N³; system curve H = H_static + kQ². Operating point is the intersection of pump and system curves; avoid operation far left of BEP.

Second Law: entropy generation Ṡ_gen ≥ 0; isentropic efficiency η_s = (h2s − h1)/(h2 − h1); exergy destruction = T0·Ṡ_gen.

Diesel generator sizing: prime rating for continuous duty, standby rating for emergency; apply 0.8 power factor and derate for altitude and ambient temperature above 40 °C (about 1 % per 5 °C).

Generator load step limits: single-step load acceptance typically 25-50 % of standby rating for diesel; motor starting kVA drives the transient dip (max 15-20 % voltage dip).

Chiller efficiency metrics: COP = kW cooling/kW input; EER = BTU/h per W; IPLV/NPLV weights part-load points; a kW/TR of 0.55 equals COP 6.4.

Boiler efficiency: direct method η = Q_out/Q_in; indirect (BS 845) accounts for dry flue gas, moisture, unburned carbon and radiation losses; each 20 °C reduction in flue gas temperature saves roughly 1 % fuel.

Steam: h_fg falls with pressure; superheat added at constant pressure; steam trap selection depends on condensate load and differential pressure; flash steam fraction = (h_f1 − h_f2)/h_fg2.

Gas turbine Brayton cycle η = 1 − 1/rp^((γ−1)/γ); regeneration raises efficiency at low pressure ratio; combined cycle reaches 55-62 % using HRSG steam bottoming.

Fan and pump power P (kW) = Q(m³/s) × Δp(Pa)/(1000 × η); belt, gear and motor efficiency multiply to the overall drive efficiency.

Energy auditing: energy use index kWh/m²·yr; measure, benchmark, then apply no-cost, low-cost, and capital measures; verify savings with IPMVP Option A/B/C/D.

Motor full-load current from nameplate; cable sizing considers continuous load × 1.25, voltage drop ≤3 % branch and ≤5 % total, and derating for ambient temperature and grouping.

Three-phase power P = √3 V I cos φ; a 0.85 power factor and 400 V supply give P ≈ 0.589 kVA per amp; capacitor kVAr = P(tan φ1 − tan φ2) for correction.

Protection coordination: discrimination between upstream and downstream devices; MCCB settings (Ir, Isd, Ii) must sit below cable withstand and above motor starting current.

Motor starting: DOL gives ~6× FLC; star-delta reduces to ~1/3 torque and current; soft starter and VFD limit inrush; VFD harmonics require THD assessment per IEEE 519.

BACnet object model: Analog Input/Output, Binary Input/Output, and scheduling; MS/TP up to 76.8 kbps, BACnet/IP over Ethernet; device instance must be unique on the internetwork.

Sensors and actuators: 4-20 mA into 250 Ω gives 1-5 V; 0-10 V control; RTD PT1000 changes ~3.85 Ω/°C; accuracy and range determine control loop stability.

Control loops: PID output = Kp·e + Ki∫e dt + Kd·de/dt; tune by Ziegler-Nichols or trial; deadband and anti-hunting prevent valve and damper oscillation.

Interface points between mechanical and electrical: status, command, alarm, and analog feedback; each point needs a defined signal type, range, and fail-safe position.

Egyptian Fire Code: Law 308/1955 and its executive regulations govern fire protection; the Egyptian Code for Design and Implementation of Fire Protection (ECP) supplements it with occupancy and egress rules.

Egyptian Electrical Code: the Egyptian Code for Electrical Installations aligns with IEC 60364 principles; the Egyptian Organization for Standardization (EOS) issues national standards.

Egyptian Code for Plumbing and Sanitary Works sets fixture unit values, pipe slopes, and venting; it references international practice where local clauses are silent.

Egyptian Code for Air Conditioning (ECP) covers load calculation, ventilation, and duct design; ASHRAE 15 and EN 378 apply to refrigerant safety and machinery rooms.

Structural and MEP coordination: the Egyptian Code for Loads and Forces (ECP 201) and the Concrete Code (ECP 203) define imposed loads and penetrations that MEP must respect.

Contract documents hierarchy: agreement, conditions, specifications, drawings, bill of quantities; the order of precedence clause resolves conflicts, usually drawings before BoQ.

FIDIC Red Book 2017: Engineer's determination, 28-day claim notice, and 84-day payment cycle; Egyptian contracts often adopt FIDIC with local amendments.

Egyptian Syndicate of Engineers regulates registration and practice; the Consultant's stamp and registration are required for permit submissions.

Earned value: CV = EV − AC, SV = EV − PV, CPI = EV/AC, SPI = EV/PV; EAC = BAC/CPI when the current cost performance is expected to continue.

Critical path method: float = LS − ES = LF − EF; total float on the critical path is zero; crashing costs the least per unit of time saved on the critical path.

Cost estimate classes (AACE): Class 5 −30 %/+50 % at 0-2 % definition, Class 3 −20 %/+30 %, Class 1 −10 %/+15 % at full definition.

Contingency vs allowance: contingency covers identified risks and is drawn down; management reserve covers unknown-unknowns and sits outside the project budget.

Quantity take-off: measure from drawings, apply wastage (pipes 5-10 %, duct sheet 10-15 %), and price with labour, material, plant, overhead and profit.

Payment terms: advance payment guarantee, interim payment certificates, retention typically 5-10 % released at taking-over and after the defects liability period.

Delay analysis: time impact analysis, as-planned vs as-built, and windows analysis; concurrent delay generally shares responsibility and limits extension of time.

Risk register: probability × impact scoring, mitigation owner and date; update at each progress meeting and link to the contingency drawdown.

Hierarchy of controls: eliminate, substitute, engineering controls, administrative controls, PPE; PPE is the last line and never the primary control.

Confined space: test for oxygen (19.5-23.5 %), flammable gas (<10 % LEL), and toxics before entry; continuous monitoring, attendant, and rescue plan are mandatory.

Work at height: guardrails at 2 m and above; fall-arrest harness with anchor point rated 15 kN; permit-to-work and rescue plan required.

Hot work: permit, fire watch, 10 m clearance of combustibles, and fire extinguisher at the point of work; re-check the area for 30-60 minutes after completion.

Refrigerant safety: ASHRAE 15/EN 378 set refrigerant concentration limits (RCL); machinery rooms need detection, ventilation, and alarms for A2L/A3 refrigerants.

Electrical safety: lock-out/tag-out, test before touch, arc-flash boundary and PPE category from incident energy study per NFPA 70E.

Environmental: Egyptian Law 4/1994 amended by Law 9/2009 governs environment; environmental impact assessment (EIA) is required for major projects before permitting.

Waste and emissions: refrigerant recovery and no venting; noise limits at boundary; dust and asbestos control during demolition; spill response for fuel and chemicals.

Engineer's duty: competence, honesty, and public safety paramount; sign and seal only work you prepared or directly supervised.

Conflict of interest: disclose any financial or personal interest in a supplier, contractor, or product; decline the assignment if the conflict cannot be managed.

Confidentiality: client information, drawings, and cost data are confidential and not reused for other clients without permission.

Liability: negligence requires duty, breach, causation, and damage; professional indemnity insurance covers errors and omissions, not deliberate acts.

Standard of care: the degree of skill of a reasonably competent engineer in similar circumstances; not a guarantee of perfection.

Bribery and gifts: refuse or disclose gifts that could influence judgment; comply with anti-corruption law and the client's code of conduct.

Records: keep design calculations, correspondence, and site instructions; the limitation period and contractual liability period define exposure.

Whistleblowing: report unsafe or illegal practice to the client and, where required, to the authority; document the report and the response.