Milestone map
Milestone map
3 milestones
Define System Boundary and Draw Process Flow
1–2 weeks (3–4 hrs/week)
Select a real or simulated chemical process — distillation column, heat exchanger network, reaction system, or separation train. Define system boundaries clearly: which streams cross the boundary, which unit operations are inside it. Draw a process flow diagram (PFD) with all streams labelled. Proper system definition prevents the most common mass balance error: accounting for streams that should be outside the boundary.
Proof required
Submit your system definition document: the process you selected (real or simulated), a drawn PFD with all stream labels, and a list of all streams crossing the system boundary with their known and unknown compositions/flow rates.
What gets checked
- PFD is drawn (not copied from a textbook) with every stream numbered and every unit operation named
- System boundary is marked on the PFD as a dashed line with all crossing streams explicitly listed
- Degree-of-freedom table is completed and shows zero degrees of freedom (system is fully determined)
Common mistakes
- Starting calculations without a completed PFD — you cannot correctly identify system boundaries without drawing the process first
- Degree-of-freedom analysis showing more unknowns than equations — the system is under-determined; add data or narrow the system boundary before proceeding to M2
Resources
Foundationstart here
Depthgo deeper
What a verifier looks for
- Confirm the PFD is hand-drawn or drawn in a tool — not copied from a textbook without modification.
- Confirm all streams are labelled with numbers and all unit operations are named.
- Confirm the degree-of-freedom table is completed and shows zero degrees of freedom (system is fully determined).
Perform the Mass and Energy Balances
3–4 weeks (4–5 hrs/week)
Calculate complete mass and energy balances for the system defined in M1. Mass balance: apply conservation of mass for each component across each unit operation; show all algebraic steps. Energy balance: calculate enthalpy of each stream (using heat capacity data or steam tables), heat duties for each unit operation, and total utility requirements. Showing every step is what distinguishes a competent calculation from a black-box result.
Proof required
Submit your calculation workbook (spreadsheet or written calculation set): complete mass balance tables (stream compositions and flow rates), energy balance tables (stream enthalpies, unit heat duties, utility requirements), and a summary table of results.
What gets checked
- Mass balances show component-level conservation — not just total mass flow
- Enthalpy data sources are cited (NIST WebBook, steam tables, or equivalent) — not unattributed values
- All calculation steps are shown — not just final results in a summary table
Common mistakes
- Omitting component mass balances and only reporting total mass flow — component balances are required for reactive systems or mixtures
- Using inconsistent units throughout the calculation (kg/h mixed with mol/s) — choose one unit system and convert everything before calculating
Resources
Foundationstart here
Depthgo deeper
What a verifier looks for
- Confirm mass balances close — in = out for each component within a stated tolerance (typically ±1% for textbook problems).
- Confirm enthalpy data sources are cited — NIST WebBook, steam tables, or equivalent; not unattributed values.
- Confirm all calculation steps are shown — not just final results.
Verify Results and Write the Balance Report
2–3 weeks (2–3 hrs/week)
Cross-check mass and energy balance results using an independent verification method — degree-of-freedom recount, spot-check of a single unit, or comparison against simulation output. Write a complete balance report documenting the process, the PFD, all balance tables, data sources, assumptions, and a discussion of key sensitivities. The report is what makes the calculation an engineering artefact, not just a spreadsheet.
Proof required
Submit your completed balance report (≥1,500 words including all tables): PFD, mass balance table, energy balance table, data source list, assumption log, verification method used and results, and discussion of sensitivities (which input has the largest effect on utility requirements).
What gets checked
- Independent verification method is named and results are reported (simulation comparison or independent re-derivation — not rechecking the same work)
- Assumption log lists every simplifying assumption with a justification for why it is acceptable
- Sensitivity analysis identifies the dominant uncertain input and states quantitatively how much utility requirements change
Common mistakes
- Reporting results without stating what assumptions were made — assumptions drive balances, and a reviewer cannot evaluate results without knowing them
- Skipping independent verification — transcription errors are common in large balance tables; verification is not optional
Resources
Foundationstart here
Depthgo deeper
What a verifier looks for
- Engineering Design Triad check: M1–M3 together produce a design artifact (PFD with system boundary), an analysis artifact (mass and energy balance tables with all calculation steps), and a documentation artifact (complete balance report with assumptions and verification) — confirm all three types are present.
- Confirm independent verification was performed — simulation comparison or independent re-derivation, not just rechecking the same calculation.
- Confirm assumptions are listed and justified — 'ideal gas assumed' without justification is insufficient.
- Confirm sensitivity analysis identifies the input with the largest effect on utility requirements.
- The Proof Accessibility Rule applies — DWSIM (free), ChemSep (free), NIST WebBook (free), IChemE free resources, and draw.io (free) are all accessible without plant access.