Material Balance
Template (Excel)

A material balance (also called mass balance or stream summary) is the process engineering deliverable that tabulates every numbered stream on the Process Flow Diagram (PFD) and lists its composition, mass flow, molar flow, volumetric flow, temperature, pressure, density, and phase. The total mass in must equal total mass out at every node per the law of conservation of mass. The material balance is paired with the heat balance to form the Heat and Material Balance (HMB) document, which is the foundation of process design and is referenced by every downstream discipline: equipment sizing, line sizing, control valve sizing, relief device sizing, and utility load aggregation.

At minimum: stream number, stream description, PFD reference, phase, component-wise mole or mass fraction, total mass flow, total molar flow, total volumetric flow, operating temperature, operating pressure, density, molecular weight, viscosity, source equipment tag (From), and destination equipment tag (To). Add Cp, thermal conductivity, vapour fraction, and enthalpy when the balance feeds heat exchanger thermal design or simulation export. Most EPC templates include a Design Case column flagging Normal / Min / Max / Start-up / Upset cases. See the PFD standard reference for stream-numbering conventions.

Pathnovo, an engineering document intelligence platform, extracts stream numbers and stream tables directly from PFDs and cross-references the corresponding heat and material balance sheets, simulation export files, and process datasheets. The platform parses tabular stream data, validates total-in equals total-out at every node, and flags any closure violation greater than 0.5%. Typical project turnaround is 48 hours for the initial batch with closure-tested output. Output is configurable to your exact template structure (EIL, L&T, Worley, Technip Energies, Bechtel HMB formats pre-configured). See the P&ID and PFD extraction workflow for the full pipeline.

Downstream consumers: equipment sizing uses stream conditions to size vessels, exchangers, pumps, and compressors per ASME Section VIII and API 660. Line sizing uses mass flow, density, and viscosity to set line diameters per the project hydraulic philosophy. Control valve sizing uses Cp data and flow ranges. Relief device sizing uses worst-case mass flow per API 520. Utility load aggregation sums steam, cooling water, and instrument air loads across all streams. Simulation export feeds Aspen HYSYS or PRO/II rating runs. The material balance is the master process register that drives every downstream sizing decision.

The material balance tabulates stream composition and mass flow (what is flowing). The heat balance tabulates stream enthalpy and heat duty across each unit operation (how much energy is transferred). Together they form the Heat and Material Balance (HMB) document. The material balance is checked by ensuring total mass-in equals total mass-out at every node. The heat balance is checked by ensuring total enthalpy-in plus heat added equals total enthalpy-out plus heat removed at every node. Both must close to within project tolerance (typically 0.5% for mass, 1% for heat). See the heat balance template for the energy register.

Add a Design Case column flagging each stream row as 'Existing-Operating', 'Revamp-New', 'Revamp-Modified', or 'Revamp-Tie-In'. Existing-Operating rows preserve the as-built operating data from plant DCS history. Revamp-New rows are sized per the new feedstock or capacity case. Revamp-Modified rows recompute conditions after revamp scope. This pattern is critical for Indian PSU refinery revamps where IOCL, BPCL, and HPCL brownfield projects must reconcile existing operating data against post-revamp design data on the same PFD. The template includes the Design Case column.

The material balance itself is a process engineering deliverable, not a code-driven document. But the streams it tabulates feed equipment that is code-driven: ASME Section VIII Div 1 / Div 2 pressure vessels, API 650 atmospheric tanks, API 660 shell-and-tube exchangers, and API 520 / 521 relief device sizing. For Indian refinery scope, hydrocarbon stream classification per OISD-118 drives hazardous area classification downstream. See the ASME Section VIII reference for vessel design data inputs and the OISD-118 compliance reference for refinery hydrocarbon classification.