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2K and 3K Coating Systems for OEM Product Finishers

Article 17 of 24

System Startup, Priming, Production, and Shutdown

Moving a stationary plural-component system safely and consistently from an idle condition into production—and back again

Startup Is a Controlled Process

A plural-component system should never be placed into production by simply turning on the pumps and pulling the spray-gun trigger. The operator must confirm that the equipment is ready, the correct materials are available, each component path is properly primed, the approved recipe is selected, the mixed-material path is filled, and the delivered coating is acceptable.

Shutdown requires the same discipline. Activated coating must not be left in the equipment beyond its approved working time, and the system must be left in a known condition for the next shift or production campaign.

Learning Objectives

After completing this article, the learner should be able to:

• Distinguish initial commissioning, cold startup, daily restart, and recipe change.
• Conduct a structured pre-start inspection.
• Explain why each unmixed component path must be primed separately.
• Describe how the mixed-fluid path is filled and verified.
• Identify the operating information that should be monitored during production.
• Select an appropriate response for planned stops and abnormal shutdowns.
• Explain what must be verified before production restarts after a fault.

Know the Starting Condition

The correct procedure depends on the condition in which the system was left. Before startup, determine which of the following applies:

• Initial commissioning: The equipment is new, rebuilt, relocated, or has never processed the current material.
• Cold startup: The system has been emptied, cleaned, preserved, or left out of service.
• Daily restart: Approved unmixed components remain in their separate paths, but the mixed path was properly flushed.
• Short-stop restart: Mixed material remains in the system and is still within the validated working window.
• Recipe-change startup: The system has completed an approved color or component change and must load the new recipe.

If the system's condition cannot be confirmed, do not assume that the fluid path is clean or that the material is usable. Treat the condition as unknown and follow the approved inspection and recovery procedure.

Use the Exact Equipment Procedure

The sequence in this article provides a professional operating framework. It does not replace the operating manual for the installed proportioner, material-supply system, spray applicator, robot, electrostatic equipment, booth, or production line.

Valve order, controller modes, pressure settings, filling volumes, purge steps, and interlock behavior differ among systems. The facility's written procedure must be based on the current manufacturer instructions and the commissioned installation.

Pre-Startup Inspection

Before energizing or pressurizing the system, verify:

• The work area is clean, ventilated, and ready for operation.
• Required guards, covers, grounding conductors, and safety devices are installed.
• Hoses, tubes, fittings, filters, pumps, meters, valves, regulators, and manifolds show no visible damage or leakage.
• Every component is rated for the required fluid pressure and material.
• The correct resin, hardener, catalyst, reducer, additive, and flushing materials are connected.
• Material containers are properly identified and within their approved shelf life.
• Material temperature and conditioning are within the approved range.
• Agitation and circulation have been completed where required.
• Waste containers and discharge paths are available and correctly grounded where required.
• The static mixer, tip, nozzle, air cap, bell cup, filters, and applicator configuration match the recipe.
• Compressed air, electrical power, communication, and ventilation systems are available.
• No unresolved maintenance tag, alarm, bypass, or lockout condition remains.

Confirm the Production Recipe

The operator should compare the scheduled work order with the controller recipe and the connected materials. This verification should include more than a color name.

Confirm:

• Coating manufacturer and product designation
• Component A, B, and C identities
• Material batch or lot information where required
• Mixing ratio and whether it is by volume or weight
• Ratio tolerance and alarm limits
• Pot life and mixed-path renewal volume
• Approved flushing material and purge program
• Target flow, pressure, temperature, and application settings
• Recipe revision and authorization status

Prime the Unmixed Component Paths

Components A, B, and C should be introduced through their separate supply paths before they are allowed to combine. Priming removes storage fluid, flushing material, air, or previous material from each unmixed path.

A controlled priming process generally:

1. Confirms the correct supply valve and return or dump path.
2. Starts the component supply at the approved low operating pressure.
3. Moves material through the assigned pump, filter, regulator, meter, valve, and hose.
4. Discharges transition material to the approved collection point.
5. Continues until the correct material is present without visible air, cleaner, or contamination.
6. Closes or returns the path to its correct operating condition.
7. Repeats the approved procedure for every remaining component.

Remove Air Before Ratio-Controlled Production

Air in a component stream can compress, interrupt pump filling, disturb valve response, create meter signals that do not represent the expected liquid delivery, and produce unstable dosing.

Do not depend on the static mixer to correct an air-filled component path. Each supply circuit must be properly primed and stabilized before the controller is expected to maintain the coating ratio.

Stabilize Component Delivery

After priming, establish the approved supply pressures, circulation conditions, material temperatures, regulator settings, and controller status. Observe the system for leakage, cavitation, abnormal pulsation, unstable pressure, or unexpected material movement.

If filters, regulators, or circulation valves were serviced, verify their orientation and operating condition before enabling the mix manifold. A component path can appear filled while remaining restricted or improperly regulated.

Filling the Mixed-Material Path

When the system enters its approved mix or fill mode, the selected components begin dosing in the programmed relationship. The first material discharged may contain cleaner, air, unmixed component, old coating, or a transition mixture.

The fill procedure should:

1. Direct discharge to the approved waste or collection point.
2. Enable the approved recipe and confirm the selected components.
3. Begin controlled proportioning at an approved flow condition.
4. Displace at least the validated mixed-path fill volume.
5. Observe material appearance and consistency where safe and practical.
6. Confirm stable flow, pressure, ratio, and alarm status.
7. Prevent transition material from reaching production parts.

Fill volume must be based on the actual internal volume of the mix manifold, mixer, regulators, hoses, splitters, and applicators—not on guesswork or the first visible color change.

Verify Before Releasing Production

Before coating saleable parts, confirm:

• The controller is in the correct operating mode.
• The selected recipe matches the work order.
• The mixed path has been completely filled.
• Ratio, flow, and pressure conditions are stable.
• No active warning, alarm, bypass, or interlock remains unresolved.
• The applicator produces the approved spray pattern.
• The test panel or first-off part meets wet-film, appearance, and coverage requirements.
• Production release has been documented where required.

Production Operation

Once production begins, the operator's role shifts from setup to controlled observation. Automatic controls provide valuable protection, but they do not remove the need to watch the process.

Monitor:

• Selected recipe and production mode
• Component supply levels and material identity
• Individual component pressures
• Mixed-material pressure and flow
• Ratio status and dosing corrections
• Material temperature and viscosity-related behavior
• Pot-life timer and production interruptions
• Spray pattern, atomization, film build, and appearance
• Leaks, pulsation, unusual sounds, and increasing restrictions
• Warnings, alarms, bypasses, and communication status

Material Replenishment During Production

Running a component supply empty can introduce air, interrupt dosing, damage pumps, cause a ratio alarm, and contaminate the mixed path. Replenishment should occur before the material reaches the minimum approved operating level.

Before adding material, verify:

• The product and component designation
• Batch compatibility and expiration status
• Container condition and identification
• Required agitation, conditioning, and filtration
• Whether production must stop during replenishment
• The required lot-change and traceability record

Match the Response to the Type of Stop

Short Production Interruptions

During a validated short stop, the system may remain in standby with activated coating in the mixed path. The stop time must remain inside the approved working window, including the time required to verify and restart the process.

Before restarting, confirm that the pot-life limit has not been reached, pressures remain normal, no material has leaked or cured, and the required fresh-material displacement has occurred.

If the material's age or condition is uncertain, it should not be sprayed onto production parts.

Normal Production Shutdown

A normal end-of-run shutdown generally includes:

1. Complete the last production part and record the stopping point.
2. Move the applicator to the approved purge or service position.
3. Disable spraying and electrostatic charging where applicable.
4. Close or isolate the production-material valves in the approved sequence.
5. Direct discharge to the approved waste or collection path.
6. Remove activated coating from the entire common mixed-material path.
7. Run the validated flushing sequence.
8. Verify purge completion rather than relying only on elapsed time.
9. Relieve pressure according to the equipment manufacturer's procedure.
10. Place unmixed component paths in the approved standby or storage condition.
11. Clean and inspect the applicator and required process components.
12. Record material use, waste, alarms, maintenance needs, and final system condition.

Flushing the Mixed-Material Path

The purge must clean every shared passage containing activated coating. This can include the mix manifold, injection valves, static mixer, regulator, filter, hose, splitter, gun valve, nozzle, dump line, and sampling passages.

The validated procedure may use solvent, water, another approved cleaner, alternating air-and-liquid pulses, multiple purge stages, or separate cleaners for incompatible coating families. The exact sequence must be approved for the coating and equipment.

The absence of visible color does not always prove that reactive residue has been removed. Purge acceptance should be based on the commissioned time, volume, sequence, and inspection requirements.

Do Not Leave Activated Material in the System

Material left beyond its working time may gel in mixers, hoses, valves, regulators, filters, and applicators. Increasing pressure will not safely restore the system and may damage components or create a high-pressure release.

When shutdown time may exceed the validated pot life, complete the approved purge before the remaining response window expires.

Short-Term and Long-Term Shutdowns

Short-Term Shutdown

The mixed path is flushed, but approved unmixed materials may remain in their separate supply circuits. Material agitation, circulation, heating, pressure, and sealing conditions must follow the coating and equipment manufacturers' instructions.

Long-Term Shutdown

The system may require removal of production materials, complete cleaning, drying or approved preservation, pressure relief, isolation of power and air, protection from corrosion or freezing, and documentation of the condition in which each circuit was left. Restart after long-term storage should be treated as a controlled cold startup.

Emergency Shutdown Is Not Normal Shutdown

An emergency stop is used to address an immediate hazard. Depending on the equipment, it may stop pumps, close valves, remove control power, disable motion, or place equipment in another designed safe state.

It may not automatically relieve every trapped pressure, clean the mixed-material path, preserve pot-life information, or complete the normal purge program.

After the immediate hazard is controlled, authorized personnel must evaluate stored energy, material age, equipment condition, affected production, and the safe recovery procedure before resetting or restarting the system.

Common Startup and Shutdown Problems

Restarting After an Alarm or Repair

Before returning the system to production:

1. Identify and document the initiating fault.
2. Complete the required pressure relief and energy-control procedures.
3. Repair or correct the cause rather than merely clearing the alarm.
4. Inspect the mixed path for aged, cured, or contaminated material.
5. Prime, flush, or refill the affected circuits as required.
6. Verify calibration or mixing ratio when the fault could affect delivery accuracy.
7. Confirm that all alarms, interlocks, guards, and communications function correctly.
8. Produce and inspect a representative test panel or first-off part.
9. Determine the disposition of parts coated during the questionable period.
10. Obtain the required production or quality release.

Shift Handoff

The outgoing operator should leave the system in a defined condition and communicate that condition to the incoming operator.

The handoff should identify:

• Active recipe and material batches
• Current production order and last completed part
• System mode and mixed-material status
• Elapsed pot-life or interruption information
• Material levels and replenishment needs
• Alarms, bypasses, maintenance, or unusual observations
• Required action before production resumes

Key Takeaways

• The correct startup procedure depends on the condition in which the system was left.
• Every unmixed component circuit must be separately primed and stabilized.
• Air must be removed before the controller can be expected to maintain an accurate ratio.
• Transition material must be discharged before production parts are coated.
• Production requires continuous observation of materials, ratio, pressure, flow, pot life, alarms, and finish quality.
• The shutdown response must match the expected stop duration.
• Activated coating must be removed before its usable life expires.
• A system should not restart after a fault until the cause, material condition, equipment condition, and affected production are resolved.

Knowledge Check

1. Why must the operator identify the system's starting condition?
2. Why should Components A, B, and C be primed separately?
3. Why is the first mixed material directed to an approved collection point?
4. What should happen when a production stop may exceed the coating's working time?
5. Why is an emergency stop not a complete shutdown procedure?
6. What must be confirmed before restarting after a ratio alarm or repair?

Technical References and Further Study

• WAGNER 2K Smart Operating Manual
• WAGNER TwinControl Operating Manual
• Graco Manual 312779 — ProMix 2KS Automatic Systems Operation
• Graco Manual 312776 — ProMix 2KS Manual Systems Operation
• Graco ProMix 2KS Operation and Support Resources
• Sames Cyclomix Evo Electronic Mixing and Dosing System

Professional responsibility: Startup, priming, production, flushing, pressure-relief, and shutdown procedures must be written for the specific installed system. Follow the current coating manufacturer's technical data and safety information and the equipment manufacturer's operating manuals. When requirements conflict or remain unclear, obtain written technical direction before placing the system into production.

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