Airless Spraying—From Pump to Pattern | Article 13 of 18

How to Shut Down, Flush, and Store an Airless Sprayer

The Job Is Not Finished Until the Coating Is Out of the Machine

Shutdown Begins Before the Coating Runs Out

A good shutdown is planned before the final container is emptied.

Consider:

• How much coating remains in the pump and hose
• Whether uncontaminated material can be recovered
• Which flushing material is required
• Whether an intermediate flushing step is necessary
• Where waste material will be collected
• How waste will be labeled and managed
• Whether the shutdown is brief, overnight, or long term
• Whether the coating has a limited pot life
• Whether water, solvent, or storage preservative can remain in the equipment

Waiting until the pump begins sucking air can fill the system with air, interrupt material recovery, and make flushing less controlled.

A Brief Pause Is Not the Same as Storage

Different interruptions require different responses. Do not assume that a method suitable for lunch is also suitable for a weekend.

When the coating or equipment instructions do not specifically permit material to remain in the system, the safer operating assumption is that proper flushing is required.

There Is No Universal Flushing Liquid

The correct flushing material depends on the coating, equipment, hose, seals, wetted components, next material, and storage conditions.

Possible flushing materials may include:

• Clean water
• Water with a manufacturer-approved cleaning product
• Mineral spirits
• A coating-specific solvent blend
• A manufacturer-approved flushing liquid
• An approved intermediate or transition fluid
• A specified storage or pump-preservation material

One fluid may not be compatible with both the existing coating and the next material. An intermediate flush may be required to prevent contamination, gelling, precipitation, or reaction.

Always review:

• The coating product data sheet
• The coating safety data sheet
• The flushing-material safety data sheet
• The sprayer and gun manuals
• Hose and seal chemical-compatibility information

Step 1: Prepare the Cleanup Area

Before moving material:

• Provide the required ventilation.
• Remove or control ignition sources.
• Prepare approved, properly labeled containers.
• Establish required bonding and grounding.
• Put on the required personal protective equipment.
• Protect the surrounding area from spills and discharge.
• Keep incompatible wastes separated.
• Route hoses so they cannot create a trip or traffic hazard.

Flushing can create vapors, static-electric charge, splashing, and pressurized discharge. Cleanup is not the point at which safety requirements become optional.

Step 2: Perform the Complete Pressure-Relief Procedure

Before removing the tip, loosening a fitting, opening a filter, or handling any pressurized component, follow the sprayer manufacturer’s complete pressure-relief procedure.

The exact sequence varies by model. It commonly addresses:

• Engaging the trigger lock
• Switching off or disconnecting the power source
• Reducing the pressure-control setting
• Grounding the gun against an approved container where required
• Triggering the gun in a controlled manner
• Returning the prime, bypass, or circulation control to the specified position
• Confirming that pressure has been released

Turning off the motor, engine, or air supply does not necessarily relieve pressure trapped in the hose and gun.

Step 3: Remove and Protect the Tip

After pressure has been properly relieved, remove the spray tip and tip guard as directed by the manufacturer.

Many airless systems are flushed with the spray tip removed. This reduces restriction and helps prevent high-pressure atomized discharge during cleaning.

Clean the tip, guard, and seal using:

• The approved cleaning material
• A soft-bristle brush or manufacturer-approved tool
• The cleaning procedure supplied with the tip

Do not use drill bits, needles, hard wire, files, or sharp metal objects in the precision tip opening.

Step 4: Recover Usable Coating Where Permitted

The pump and hose may contain a meaningful quantity of usable coating. Recovering appropriate material can reduce waste, particularly with long or large-diameter hose.

Recovery must be controlled so the coating is not contaminated with:

• Water
• Solvent
• Storage fluid
• Airborne dirt
• Dried coating
• Another color or material
• Material beyond its pot life

Do not return questionable transition material to the original coating container. Collect it separately according to the coating manufacturer’s instructions and workplace procedures.

Step 5: Flush the Pump and Return Circuit

Place the intake into the approved flushing material and secure the return hose in the proper container.

Using the model-specific control arrangement:

1. Begin at the lowest approved pressure or operating setting.
2. Establish circulation through the return or bypass path.
3. Use only enough pressure to maintain controlled fluid movement.
4. Continue until the coating is displaced by flushing material.
5. Move from recovery to waste collection at the proper transition point.
6. Continue until the return fluid reaches the cleanliness required by the manufacturer.

Keep the return hose secured. Do not allow it to whip or leave the container.

Step 6: Flush the High-Pressure Hose and Gun

The hose can hold substantially more coating than the pump. Cleaning the return circuit does not prove that the hose and gun are clean.

Follow the equipment manufacturer’s procedure for moving flushing material through the high-pressure hose and gun.

The procedure may include:

• Keeping the spray tip removed
• Using the lowest pressure necessary
• Directing the gun into an approved waste container
• Holding the metal part of the gun against a grounded metal container where required
• Triggering the gun under controlled conditions
• Continuing until coating and residue are removed

Do not spray atomized solvent or flushing fluid into the air merely to empty the hose.

Step 7: Clean Filters and Strainers

After completing the pressure-relief procedure, inspect and clean the filtration components specified by the equipment manufacturer.

These may include:

• Inlet strainer
• Pump or manifold filter
• Gun filter
• Other coating-specific strainers

Look for:

• Dried coating
• Skins and debris
• Damaged mesh
• Collapsed filter elements
• Improper filter size
• Damaged seals or housings

Replace damaged or questionable components. A filter that appears clean but has torn mesh is not protecting the tip.

Step 8: Complete the Final Flush

A first flush may remove most of the coating without leaving the system ready for storage or the next material.

The manufacturer may require:

• Fresh flushing liquid after the initial waste is removed
• Separate circulation through the pump and gun
• An intermediate fluid before changing coating types
• A final storage or preservation fluid
• Special handling for moisture-sensitive or reactive materials

Continue until the required cleanliness and fluid transition are achieved. “Mostly clean” can become “completely blocked” after the residue has time to cure.

Step 9: Protect the Pump for Storage

Water may promote corrosion or freeze in cold conditions. Some solvents may not be suitable for long-term contact with seals, hoses, or other components.

The equipment manufacturer may specify a pump-preservation or storage fluid designed to:

• Protect internal metal surfaces
• Keep packings conditioned
• Reduce sticking of valve components
• Displace water
• Prepare the unit for its next startup

Introduce and leave the approved storage material in the system only as instructed.

Some equipment also requires the piston or fluid section to be left in a particular position. Follow the model-specific manual rather than assuming every pump is stored the same way.

Step 10: Inspect and Store the Equipment

After the final pressure-relief and storage procedure:

• Engage the spray-gun trigger lock.
• Clean exterior coating from the equipment without forcing liquid into electrical or mechanical components.
• Inspect the hose for cuts, abrasion, kinks, bulges, and fitting damage.
• Coil the hose loosely without sharp bends.
• Protect the gun, tip, guard, filters, and fittings from dirt and damage.
• Store the sprayer upright in a clean, dry, secure location.
• Protect water-containing components from freezing.
• Keep equipment and residual chemicals away from heat and ignition sources.
• Label the fluid left in the pump where appropriate.
• Record maintenance or repair needs before the next job.

Do not leave the next operator to discover a damaged hose, missing filter, worn tip, or unidentified fluid during startup.

Special Concern: Short-Pot-Life Materials

Plural-component, catalyzed, moisture-cure, and other reactive materials can harden inside the pump, hose, gun, filters, and fittings.

Flushing must be completed before the material exceeds its usable pot life or safe circulation time.

Do not rely only on how the coating looks in the container. Material inside the hose may experience different temperatures and conditions.

Follow the coating and equipment manufacturers’ exact procedures. Cured material inside a high-pressure system may require major component replacement.

Special Concern: Freezing Conditions

Water left inside a pump, hose, filter, or gun can freeze, expand, and damage components.

If the equipment may be exposed to freezing temperatures:

• Follow the manufacturer’s winterization procedure.
• Remove or displace water as directed.
• Use only the approved storage material.
• Do not substitute automotive antifreeze unless specifically authorized.
• Store the equipment in the specified environment.

Special Concern: Changing Coating Types or Colors

A color change may require more than flushing until the discharge looks approximately right. Pigment can remain in filters, dead spaces, hose walls, fittings, and gun passages.

Changing between chemically different coatings may require:

• Separate compatible flushing stages
• Fresh filters
• Additional hose cleaning
• Dedicated equipment or fluid passages
• Verification that no incompatible residue remains

A small amount of incompatible residue can affect color, cure, adhesion, appearance, or equipment condition.

Airless Shutdown Checklist

• Plan cleanup before coating supply or pot life runs out.
• Prepare ventilation, grounding, approved containers, and personal protection.
• Follow the complete pressure-relief procedure.
• Remove and clean the tip and guard as directed.
• Recover suitable uncontaminated coating where permitted.
• Flush the pump and return circuit at controlled low pressure.
• Flush the high-pressure hose and gun.
• Clean and inspect filters and strainers.
• Complete any required intermediate and final flushes.
• Introduce approved storage fluid where required.
• Complete the final pressure-relief procedure.
• Inspect, label, document, and store the system safely.

The Bottom Line

A professional shutdown removes coating before it cures, controls compatible flushing fluids, cleans the complete fluid path, protects internal components, and leaves the equipment ready for its next assignment.

Relieve the pressure. Remove the tip. Recover suitable coating. Flush the pump, return circuit, hose, gun, and filters. Introduce the approved storage material. Inspect and store the equipment safely.

The last coat may be on the wall, but the job is not finished until the coating is out of the machine.

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