Exercise set

Chemical Process Commissioning, Startup, and Performance Test Exercises

Solved chemical commissioning exercises for flush volume, critical path, punch-list readiness, material balance, tracer recovery, utility startup and run-at-rate gates.

Branch: Chemical Engineering
Content: Exercise set
Updated: Jul 03, 2026
Revision: v1.1.0 · reviewed

These exercises focus on chemical process commissioning, startup and performance tests: flushing, critical path, punch-list readiness, material-balance acceptance, guarded capacity, heat-up time, tracer recovery, utility startup, hold capacity, turndown, availability, good product and run-at-rate release. Process design and scale-up sizing are handled in a separate specialist exercise set.

Use the calculations as commissioning gates. Real startup requires approved procedures, PSSR, line walks, instrument calibration, interlock proof tests, operator training, waste handling, sampling plans and management of change control.

How to use these exercises

Treat each exercise as a release gate inside a commissioning sequence. Start by naming the commissioning state: mechanical completion, pre-startup safety review, dry commissioning, wet commissioning, utility introduction, first feed, stabilization, performance test, run-at-rate or handover to operations. A calculation that is enough for dry commissioning may be insufficient for feed introduction.

For each problem, identify:

the system boundary, including temporary hoses, blinds, bypasses, dead legs, drains and off-spec routing;
the evidence boundary, such as a line walk, flush record, instrument calibration, sample plan, proof test, historian trend or lab result;
the authority boundary, including procedure approval, PSSR signoff, bypass approval, operator readiness and environmental permit constraints;
the decision boundary: start, hold, derate, retest, sequence utilities, clear punch items, rerun samples or continue commissioning under restriction.

The worked numbers are deliberately simple. Their value is in showing when a nominal pass is not enough because uncertainty, readiness, utilities, product quality or interlock status removes the release margin.

Release Evidence Notes

Commissioning evidence should state system boundary, flush path, temporary lineups, safety status, test procedure, acceptance criterion, instrument calibration, sample plan, punch-list class, operator readiness, utility alignment and authority to introduce feed. It should also state whether the evidence supports introducing water, solvent, utilities, inert gas, catalyst, reactants, heat, pressure or final product service.

Release records should preserve negative evidence as well as passing results: failed tracer recovery, unclosed bypasses, missing training, uncalibrated flowmeters, utility deficits, off-spec product, waste-treatment limits and unresolved class A or class B punch items. These are not administrative details; they define whether the calculation can support a startup decision.

Engineering Boundary Notes

The exercises simplify startup sequencing and test acceptance. They do not replace PSSR, functional safety testing, batch records, regulatory permits, quality release or vendor performance guarantees.

Flush-volume and tracer calculations assume that the path, dead legs, drain points and temporary lineups are known. A calculated turnover count can be meaningless if a valve is mispositioned, a bypass is open, a low point is unflushed or a sample point is not representative.

Performance-test calculations assume stable feed, representative samples, calibrated instruments, known inventory change and a valid guarantee basis. A run-at-rate claim should state whether downtime was planned or unplanned, whether product was in specification, and whether utilities, waste handling and operators were operating in the final intended mode.

Common Release Mistakes

Common mistakes include flushing nominal volume without dead-leg confirmation, closing punch lists by count instead of risk class, accepting performance from uncalibrated instruments, and declaring run-at-rate while product is off specification.

Other commissioning mistakes include:

accepting feed introduction while temporary bypasses or untested interlocks remain in service;
treating a guarded capacity failure as acceptable because the nominal average exceeds the guarantee;
ignoring waste, off-spec hold capacity or neutralization limits during first-product runs;
using a critical-path schedule without checking predecessor readiness and field access;
mixing mechanical completion, PSSR, startup and performance-test gates in one checklist;
closing a performance test without inventory reconciliation, sampling delay and lab turnaround evidence.

Scenario Map

Scenario	Exercises	Primary check	Engineering decision
Mechanical completion and readiness	1, 2, 3, 4, 14, 15	Flush volume, critical path, punch list, training and interlocks	Start, hold or finish prerequisites.
Performance testing	5, 6, 7, 8, 9, 10, 11	Balance closure, guarded capacity, tracer, heat-up, utility and hold capacity	Accept test, repeat or derate.
Startup release	12, 13, 16, 17, 18	Turndown, availability, good product, waste and final gate	Release, restrict or continue commissioning.

Exercise 4: Punch-List Readiness

There are 42 punch items: 0 class A, 7 class B and 35 class C. Startup allows no class A and at most 5 class B. Decide.

Solution

A=0,\qquad B=7>5

Startup readiness fails.

Engineering Comment

Risk class matters more than total punch-list count.

Plausibility Check

The class B limit is exceeded by two items.

Exercise 5: Material-Balance Closure

A performance test feeds 10,000 kg and measures 9350 kg product plus 520 kg waste. Find closure error.

Solution

E=\dfrac{10000-9350-520}{10000}\times100=1.30\%

Engineering Comment

Balance closure should include inventory change and meter uncertainty.

Plausibility Check

Unaccounted mass is 130 kg out of 10,000 kg.

Exercise 6: Capacity Test Claim

Guaranteed rate is 1200 kg/h. Test average is 1235 kg/h with uncertainty 45 kg/h. Use guarded rate. Decide.

Solution

R_g=1235-45=1190\ \text{kg/h}<1200\ \text{kg/h}

The guarded capacity claim fails.

Engineering Comment

Nominal pass should not be accepted when uncertainty removes the margin.

Plausibility Check

The nominal result is only 35 kg/h above guarantee, less than uncertainty.

Exercise 7: Heat-Up Time

Heat-up energy is 693,000 kJ and available steam duty is 240 kW. Estimate heat-up time.

Solution

t=\dfrac{693000}{240}=2888\ \text{s}=0.80\ \text{h}

Engineering Comment

Startup heat-up should account for losses, control limits and ramp-rate restrictions.

Plausibility Check

Hundreds of megajoules at hundreds of kW takes less than a few hours.

Exercise 8: Tracer Recovery

A tracer test injects 5.0 kg tracer. Recovered tracer is 4.72 kg. Acceptance range is 95 to 105 percent. Decide.

Solution

R=\dfrac{4.72}{5.0}\times100=94.4\%

The tracer test fails.

Engineering Comment

Low recovery can indicate holdup, sampling loss, bypass or analytical error.

Plausibility Check

Recovered mass is slightly below 95 percent of injected mass.

Exercise 9: Utility Header Startup Demand

Startup requires 1.3 kg/s cooling water. Existing users need 1.1 kg/s and header capacity is 2.2 kg/s. Find margin.

Solution

A startup package has 24 required interlock proof tests. Twenty-three pass and one is bypassed temporarily. Decide.

Solution

\text{bypassed interlocks}=1>0

Startup release fails unless the bypass is formally controlled and acceptable.

Engineering Comment

Temporary bypasses should be treated as operating risk, not paperwork exceptions.

Plausibility Check

One unclosed mandatory interlock item blocks normal release.

Exercise 17: Good Product per Available Hour

Good product is 24,100 kg over 21.5 producing hours. Find good-product rate.

Solution

R_g=\dfrac{24100}{21.5}=1121\ \text{kg/h}

Engineering Comment

This rate can be compared with guaranteed rate only if test conditions match the guarantee.

Plausibility Check

About 24 tonnes over about 24 hours gives near one tonne per hour.

Exercise 18: Commissioning Release Gate

Release requires no class A punch items, guarded capacity pass, utility margin nonnegative, training at least 95 percent and interlocks complete. Results are pass, fail, -0.2 kg/s, 83.3 percent and fail. Decide.

Solution

\text{capacity}=\text{fail},\qquad M<0,\qquad 83.3\%<95\%,\qquad \text{interlocks}=\text{fail}

The commissioning release fails.

Engineering Comment

The plant is not ready for feed introduction when capacity evidence, utility margin, training and interlocks all fail.

Plausibility Check

Multiple mandatory gates fail, so the hold decision is unavoidable.

Validation Package Checklist

PSSR, line walk, punch-list class and temporary bypasses are visible;
flush, drying and waste-handling boundaries are documented;
performance tests include uncertainty and calibrated instruments;
material balance, tracer and good-product evidence are reconciled;
training, interlocks and utilities are complete before feed introduction;
off-spec hold capacity, recycle route, waste neutralization and environmental limits are verified for the test duration;
sample timing, lab method, analyzer calibration and inventory change are reconciled before accepting material-balance or quality claims;
downtime is classified as planned, unplanned, utility-limited, quality-limited, safety-limited or operator-limited before availability is reported;
temporary changes, bypasses, blinds, jumpers and abnormal lineups have approved owners and removal criteria;
release decision states start, derate, retest, sequence utilities, finish punch items, clear bypasses, repeat training or hold.

The final commissioning record should state the controlling failed gate when release is denied. A plant can have a clean flush and still fail feed introduction because training is incomplete, utility margin is negative or an interlock remains bypassed.

REF