Process Flow Diagram and P and ID

This Peters & Timmerhaus topic covers the drawings that communicate a design. You learn what belongs on each document — the coarse block flow diagram, the balance-carrying PFD with its stream table, and the fully instrumented P&ID — and how they progress from concept to a construction-ready reference used in HAZOP studies.

Relation 1 —

Write this relation with symbols exactly as in Peters Timmerhaus Plant Design — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 2 —

Write this relation with symbols exactly as in Peters Timmerhaus Plant Design — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 3 —

Write this relation with symbols exactly as in Peters Timmerhaus Plant Design — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Engineering communication is layered. The block flow diagram sketches the process as boxes and arrows to show the overall route. The PFD adds the real equipment, numbered streams and a stream table of flows, temperatures, pressures and compositions, so it is essentially the material and energy balance in drawing form. The P&ID then adds every valve, instrument, control loop and relief device with unique tag numbers; it says nothing new about the chemistry but everything about how the plant is measured, controlled and protected, which is why it is the legal basis for construction and safety review.

State assumptions explicitly before using any relation for process flow diagram and p and id — steady state, uniform properties, linear elastic material, ideal gas, incompressible flow, etc., as applicable.

Wrong assumptions invalidate the entire solution even when the formula is correct. In Plant Design & Economics viva and GATE descriptive questions, listing valid assumptions often earns separate marks.

1. Read the question and list given data with SI units (common in Plant Design & Economics papers).
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to process flow diagram and p and id.
4. Use equation 1: .
5. Use equation 2: .
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.

Process Flow Diagram and P and ID appears in project feasibility studies. In Indian chemical curricula this topic is tested because it connects theory to PFD, costing, and profitability.

GATE and semester exams often combine process flow diagram and p and id with earlier units — revise prerequisites before attempting mixed problems.

Industry interview panels sometimes ask: "Where did you use process flow diagram and p and id?" — answer with a lab, mini-project, or plant visit example if possible.

Students put instrumentation on a PFD or omit the stream table, and confuse the scope of the three drawings. Forgetting that the P&ID — not the PFD — is the document used for HAZOP is a common conceptual error.

Before attempting process flow diagram and p and id problems, confirm you can:

1. A block flow diagram precedes the detailed PFD
2. Heat and material integration is shown on the PFD before equipment sizing
3. The P&ID is the legal document for construction and HAZOP

Revise the solved examples in Peters Timmerhaus Plant Design — Standard reference and one previous-year GATE or university paper for this unit.