Spray Nozzles, Part I:
Agents of Efficiency and Wash Quality
By Jerry Hagers

A good spray tip magnified.

A worn spray tip magnified.

Your business absolutely depends on spray nozzles.

Whether you own a conveyor-type car wash, an in-bay automatic system, or a self-serve operation, everything comes down to one critical point: the actual performance of the nozzles that clean and rinse your customers’ vehicles.
Depending on how well you maintain those nozzles, they can be a source of major savings — or needless expense. That’s why they deserve careful attention.

Without proper evaluation and maintenance, your spray system can drain a shocking amount of money from your operations. The cost of wasted water alone can amount to tens of thousands of dollars annually — even in a system with relatively minor performance problems.

But don’t forget to factor in all the additional expenses related to an inefficient spray system:

• The cost of excess soaps and chemicals from higher flow rates
• The cost of lost customers as a result of spray quality problems
• The cost of additional power used by pump equipment to keep up with higher flow rates or pressure losses
• The cost of unnecessary labor from unscheduled downtime and increase in maintenance In extreme cases, the true added cost can reach forty, sixty, or even a hundred thousand dollars per year.

That’s serious money — and to understand the true value of a spray-nozzle-maintenance program, you first need to get a handle on the reality of your own situation. Fortunately, a fast and convenient scenario calculator is now available online at www.spray.com/carwash to help you estimate the actual costs of sub-par spray-nozzle performance in your own operation. Plug in your own numbers to quickly determine how much money you could be saving — or wasting — every year.

Once you appreciate the magnitude of the issue, you’re ready to begin the process of optimizing your spray system. A good way to start is by understanding the typical causes of spray problems.

IDENTIFYING WORN SPRAY NOZZLES

A good spray tip.

A worn spray tip.

The human eye is a remarkable instrument, but it simply can’t provide an accurate picture when it comes to spray nozzle wear.

The graphic, above and right, illustrates this problem dramatically. The spray tip on the top is new. The spray tip on the bottom is badly worn, and sprays 30 percent over capacity. Yet the difference is totally undetectable with the naked eye.

Only under magnification is the difference revealed — unmistakably (see graphics on the right).

However, there are other tip-offs that something is amiss. Watch for these clues:

• Flow-rate change. The flow rate of a spray nozzle will increase as the surface of the orifice begins to deteriorate. In applications using positive displacement pumps, the spraying pressure and spray impact will decrease as the spray nozzle orifice enlarges. Even small changes in flow rate can have a negative impact on quality, so routine monitoring is important to reveal potential problems. Remember that in some instances the spray pattern will “look” fine to the untrained eye — so it will be necessary to check the spray-fluid output by actually collecting and measuring it in order to reveal the wear.
• Deterioration of spray pattern quality. When orifice wear occurs, the uniformity of the spray pattern is destroyed. In flat fan sprays, streaks, and heavier flows will be visible in the center of the pattern and the effective spray angle coverage will decrease. In hollow cone nozzles, streaks develop and the pattern becomes heavy or light in the circular ring of fluid. In full cone spray nozzles, more liquid typically flows into the center of the pattern.
• Lowered spray impact. Worn spray nozzles often operate at lower pressure, generally resulting in lower spray impact. However, in applications with centrifugal-type pumps, impact may actually increase because of the increased flow through the nozzle
• Quality control issues. Worn, clogged, and damaged spray nozzles will not perform per specification. Customers will experience poor rinsing, cleaning, and drying.
• Increased maintenance time. Unscheduled downtime, or an increase in nozzle cleaning frequency, is a strong indicator that a spray nozzle needs to be replaced.

CAUSES OF SPRAY NOZZLE TROUBLES

They may look simple enough, but in reality spray nozzles are highly-engineered precision components that can wear over time, and may suffer damage during normal operations or even cleaning. These are the most common problems that hamper spray performance:

• Erosion/wear. This is the single biggest cause of nozzle problems in a car wash operation. Gradual abrasion of material from the spray nozzle orifice and internal flow passages causes them to enlarge and/or become distorted. As a result, flow usually increases, pressure may decrease, the spray pattern becomes irregular, and liquid drops become larger.
• Corrosion. Spray nozzle material can also break down due to the chemical qualities of the sprayed material or the environment. The effect is similar to that caused by erosion and wear, with possible additional damage to the outside surfaces of the spray nozzle.
• High temperature. Certain liquids must be sprayed at elevated temperatures or in high-temperature environments. The spray nozzle may soften and break down unless special temperature-resistant materials are used.
• Caking/bearding. Build-up of material on the inside, on the outer edges, or near the orifice is caused by liquid evaporation. A layer of dried solids remains and obstructs the orifice or internal flow passages.
• Clogging. Unwanted solid particles can block the inside of the orifice. Flow is restricted and spray pattern uniformity is disturbed. This is often an issue in cases where you are using re-circulated water without sufficient filtration.
• Improper assembly. Some spray nozzles require careful re-assembly after cleaning so that internal components — such as gaskets, O-rings, and vanes — are properly aligned. Improper positioning can cause leaking and inefficient spray performance.
• Accidental damage. Damage can occur if a spray nozzle is dropped or scratched during installation, operation, or cleaning. This is a common occurrence in self-service car washes, since many customers do not treat spray wands with proper care and often let them fall onto, or scrape against, the concrete floor of the bay.

MONITORING AND MAINTENANCE

A comprehensive maintenance program will help ensure optimal spray nozzle performance in your car wash. The checklist that follows should become the foundation of your maintenance program. Consult with your nozzle manufacturer or supplier for additional suggestions.

• Flow Rate
  For centrifugal pumps: monitor flow meter readings to detect increases, or collect and measure the spray from the spray nozzle for a given period of time at a specific pressure. Compare these readings to the flow rates listed in the manufacturer’s catalog or compare them to flow-rate readings from new, unused spray nozzles.
  
  For positive displacement pumps: monitor the liquid line pressure for decreases — the flow rate will remain constant.
  
  
• Spray Pressure (in spray nozzle manifolds)
  For centrifugal pumps: monitor for increases in liquid volume sprayed. The spraying pressure is likely to remain the same.
  
  For positive displacement pumps: monitor pressure gauge for decreases in pressure and reduction in impact on sprayed surfaces. The liquid volume sprayed is likely to remain the same. Also, monitor for increases in pressure due to clogged spray nozzles.
  
  
• Spray Pattern
  Visually inspect the spray pattern for changes. Check the spray angle with a protractor. Measure the width of the spray pattern on the sprayed surface. If the spray nozzle orifice is wearing gradually, you may not detect changes until there is a significant increase in flow rate. If uniform spray coverage is critical in your application, request special testing from your spray nozzle manufacturer.
  
  
• Spray Nozzle Alignment
  Check uniformity of spray coverage of flat spray nozzles on a manifold. Spray patterns should be parallel to each other. Spray tips should be rotated 10° to 15° from the manifold centerline so that the sprays do not interfere.
  
  
• Application Results
  Check for uneven cleaning, streaks, and uneven drying.
  
  If you determine that any of your current spray nozzles aren’t performing like they should, it’s definitely time to replace them — and ensure that you get maximum use from the new ones. After all, the health of your car wash business depends on it.

In next month’s issue of Auto Laundry News we will consider proper nozzle materials and methods to extend spray nozzle life.

Jerry Hagers is product specialist at Spraying Systems Co. in Wheaton, IL. He can be reached via e-mail at jerry.hagers@spray.com or by phone at (630) 665-5000. For a free copy of the Spray Optimization Handbook, call 1-800-95-SPRAY.