Airless Spraying—From Pump to Pattern | Article 9 of 18

Matching the Tip to the Sprayer’s Capacity

A Tip Can Fit the Gun and Still Be Too Big for the Machine

What Does Sprayer Capacity Mean?

Sprayer capacity describes the equipment’s ability to move coating and maintain useful pressure while material is flowing through the tip.

Capacity may be represented by several manufacturer specifications:

• Maximum recommended tip size
• Maximum fluid-delivery rate
• Maximum working pressure
• Recommended weekly production
• Number of spray guns supported
• Coating or application recommendations

These specifications describe different aspects of performance. They should not be treated as interchangeable.

Maximum Pressure Is Not Maximum Output

Two airless sprayers may both have a maximum working pressure of 3,300 PSI while having very different fluid-delivery capacities and maximum tip ratings.

A smaller sprayer may create high pressure through a small tip but be unable to supply the material required by a much larger orifice. A larger pump may maintain comparable pressure while supporting a larger tip, longer hose, heavier coating, or multiple spray guns.

Pressure is the force available to move and atomize the coating. Flow is the quantity of material moving through the system over time.

An effective airless system needs both:

• Enough pressure to atomize the coating
• Enough flow capacity to supply the selected tip

The Maximum Tip Rating

Airless sprayer manufacturers commonly publish a maximum recommended tip size. A rating of 0.021 inch, for example, indicates that the manufacturer identifies 0.021 inch as the largest nominal tip orifice the sprayer is designed to support under the stated conditions.

This rating should be treated as an operating limit—not proof that a 0.021-inch tip is correct for every coating or job.

The coating may require a smaller orifice. The workpiece may need a narrower fan. The finish may require more control. A multiple-gun setup may reduce the available capacity per gun.

Published capacity also assumes that the equipment is properly configured, maintained, and operating within the manufacturer’s instructions.

Why the Tip Creates Flow Demand

The orifice in the spray tip is the final restriction in the fluid path. As the orifice becomes larger, it can allow more coating to pass at a given pressure under comparable conditions.

The pump must replace the material leaving the gun quickly enough to maintain the required pressure.

If material leaves through the tip faster than the pump can supply it:

• Pressure falls while the gun is triggered.
• The fan may narrow.
• Heavy edges or tails may appear.
• The pattern may pulse or surge.
• Atomization may become inconsistent.
• The pump may run continuously without catching up.

Turning the pressure control higher cannot add physical displacement to an undersized pump. The sprayer may try harder, but it does not become larger.

Static Pressure Can Be Misleading

A sprayer may build and hold pressure normally while the spray-gun trigger is closed. This is static or dead-head pressure.

The real capacity test begins when the trigger is pulled and coating starts moving.

If pressure drops sharply during spraying, possible causes include:

• The tip is too large for the sprayer.
• The tip is worn and its orifice has enlarged.
• The pump is worn or damaged.
• The inlet cannot supply material fast enough.
• A filter or fluid passage is restricted.
• The coating is too difficult to move through the setup.
• The hose arrangement creates excessive restriction.
• Multiple guns exceed available capacity.

The Coating Has the First Vote

The coating manufacturer may recommend an airless tip-orifice range. That range should be compared with the sprayer’s maximum tip rating.

If a coating requires a 0.025- to 0.031-inch tip and the sprayer supports only a 0.021-inch tip, the equipment and coating are not properly matched.

Possible choices include:

• Selecting a larger-capacity sprayer
• Using a different approved application method
• Consulting the coating manufacturer for a permitted alternative
• Selecting a different coating suited to the available equipment

The wrong response is to install an undersized tip outside the coating recommendation or thin the material without written authorization merely because the existing machine is convenient.

Do Not Confuse Gallons per Minute with Gallons per Week

A sprayer’s maximum delivery rating and its recommended production category describe different things.

A sprayer may be capable of moving a high instantaneous flow while not being intended for continuous heavy weekly production. Another may be designed for demanding daily use even when the application does not require its maximum output.

Select equipment for both immediate tip demand and expected workload.

Working at the Maximum Leaves Less Allowance

A sprayer operating at its maximum published tip size may perform properly when:

• The pump is in good condition.
• The coating is within the expected viscosity and temperature range.
• The filters and fluid passages are clean.
• The hose arrangement is suitable.
• The tip is new and correctly sized.
• Only the approved number of guns is operating.

Real jobs are not always that cooperative. Coatings get cold. Filters begin loading. Packings and valves wear. Hose runs grow. Tips wear larger.

Operating at the maximum may leave less reserve for changing field conditions. When production reliability is important, selecting a sprayer with capacity beyond the minimum requirement can provide useful operating margin.

That does not mean buying the largest sprayer available. It means avoiding a system that begins every job with no capacity left in reserve.

A Worn Tip Can Outgrow the Sprayer

As a tip wears, its orifice enlarges. A tip originally within the sprayer’s capacity may eventually demand more material than it did when new.

This can cause:

• Pressure loss while spraying
• Pattern tails
• A narrowing fan
• Excessive pump cycling
• Higher coating consumption
• Inconsistent film build

If a familiar setup begins demanding more pressure or losing pattern quality, compare the working tip with a known new tip before condemning the pump.

Multiple Guns Change the Calculation

Operating two or more spray guns from one pump can improve production, but every triggered gun adds material demand.

Two guns equipped with 0.017-inch tips do not create the same demand as one 0.017-inch tip. They create two simultaneous flow paths.

Do not add the orifice diameters together and assume that provides an equivalent single-tip size. Compare the combined published flow requirements of all tips with the manufacturer’s approved multiple-gun capacity.

When planning a multiple-gun system, consider:

• Combined tip flow at the intended pressure
• Maximum number of guns approved for the sprayer
• Hose lengths and diameters
• Manifold and fitting sizes
• Coating viscosity and solids
• Whether all guns may trigger simultaneously
• Pump condition and required production duty

If one pattern weakens when the second gun is triggered, the combined demand or system arrangement may exceed available capacity.

Hose and Filters Use Some of the Available Pressure

Even when the tip is technically within the sprayer’s maximum rating, restrictions between the pump and gun can affect performance.

Pressure loss can increase with:

• Longer hose runs
• Smaller hose diameters
• More viscous coatings
• Higher material flow
• Loaded or overly fine filters
• Restrictive fittings and passages
• Multiple guns and branch lines

The pump must supply the tip through the complete fluid path—not through the idealized system described by one specification.

Pump Condition Changes Practical Capacity

Published ratings assume equipment in proper working condition. Worn or contaminated components can reduce practical output.

Capacity may be affected by:

• Worn packings
• Worn or contaminated inlet and outlet valves
• Damaged valve seats
• Leaking prime or return valves
• Air entering the suction system
• Restricted inlet components
• Pressure-control problems
• Improper maintenance

A machine that supported a particular tip when new may struggle after wear develops. That does not necessarily mean the original rating was incorrect. It means the sprayer is no longer delivering its original performance.

A Practical Matching Process

1. Identify the coating.
   Use the current product data sheet to find the recommended airless tip range and application conditions.
2. Select the required orifice.
   Choose a size within the coating manufacturer’s recommendation.
3. Select the fan width.
   Match the pattern to the size and shape of the work.
4. Check the sprayer’s maximum tip rating.
   Confirm that the selected orifice does not exceed the manufacturer’s limit.
5. Account for every spray gun.
   Use combined published flow demand and the manufacturer’s multiple-gun guidance.
6. Consider hose and system restrictions.
   Long runs, heavy coatings, small passages, and multiple filters can affect pressure at the gun.
7. Consider equipment condition.
   A worn pump or tip may not perform according to its original rating.
8. Test under actual flow.
   Make sure the sprayer maintains an acceptable pattern while every required gun is operating.
9. Verify the applied film.
   Check coverage and wet-film thickness where appropriate.

What an Undersized Sprayer Looks Like

Before Pulling the Trigger

• Verify the coating manufacturer’s recommended tip range.
• Confirm the sprayer’s maximum recommended tip size.
• Check the manufacturer’s multiple-gun guidance where applicable.
• Use current published tip-flow information.
• Inspect the tip for wear.
• Confirm that filters, hoses, guns, and fittings are appropriate.
• Test performance while material is flowing.
• Verify the spray pattern and wet-film thickness.

The Bottom Line

The spray tip determines how much material the system is being asked to deliver. The pump must be capable of supplying that demand while maintaining enough pressure to produce an acceptable pattern.

Check the coating requirement. Check the tip flow. Check the sprayer rating. Account for hose, filters, wear, workload, and every gun that may trigger.

A tip can fit the guard and still be wrong for the machine. The threads and locking tabs only tell you that it can be installed. The spray pattern tells you whether the system can actually support it.

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