Nozzle Wear `N' Tear

Spray tips are the most neglected component in today's farming, yet they're among the most critical of items in proper application. Sprayer calibration clinics conducted in Ohio revealed that a considerable number of the sprayers surveyed were overapplying chemicals.

The major reason: worn nozzles. And that can be costly, for both dealerships and growers. For example, based on today's chemical investments of $10 to $50 per acre, a 10% overapplication on a once sprayed 1000-acre farm could represent an additional cost to the farmer of $2000 to $5000. This, of course, doesn't take into account any potential crop damage.

The best way to determine if a spray tip is excessively worn is to compare the flow rate of the used tip to the flow rate of a new tip of the same size and type. Spray tips are considered excessively worn and should be replaced when their flow rate exceeds the nominal flow rate of a new tip by more than 15%.

But, what causes nozzle wear, and how can it be managed? Here are a few hints.

A number of factors influence nozzle wear, including:

• Spraying pressure duration.
• Type and concentration of material used in the spray mixture.
• Type and size of nozzle.
• Shape and material of the orifice.
• Differences in operating conditions.

Nozzle wear affects flow rate, droplet size, and spray pattern, and the relative wear rates of nozzle tip materials can be greatly difference at different times of usage. Still, there are some predictable patterns.

It's been found, for instance, that flat fan nozzles-new and worn-show little visible difference in the width of spray deposit patterns. However, there are greater differences in volumes of liquid collected in the centers of the spray patterns than at the edge of the patterns.

The type of material the nozzle is made of also can affect wear. Research at Ohio State University and at USDA-ARS in Wooster, OH, has found that the wear rate-how quickly a nozzle's output increases to 10% more than its original rate-was lowest for stainless steel tips, highest for brass tips.

Of course, the relative wear rates of tip materials vary greatly with different usage or time. But for all nozzle capacities, stainless steel tips had average usage times 5.6 and 2.1 times longer than brass and nylon tips, respectively.

Research also has shown that flow rates of some plastic tips decreased slightly with usage time before beginning to increase. At a 10% increase in flow rate, some plastic tips had longer usage times than stainless steel tips. In fact, if accurate sprayer calibration is maintained as nozzle flow rate increases, plastic tips may provide the most uniform spray distribution with continued use.

How Well They Wear -- 
Wear lives of spray tip materials
----------------------------------------------------------
Ceramic		 Superior wear life; highly resistant to 
		 abrasive and corrosive chemicals.

Hardened	 Very good wear life; good durability and
Stainless Steel	 chemical resistance.

Stainless Steel	 Good wear life; excellent chemical 
		 resistance; durable orifice.

Polymer		 Medium to good wear life; good chemical 
		 resistance; orifice susceptible to damage 
		 when cleaned.
	
Brass		 Poor wear life; susceptible to corrosion, 
		 especially with fertilizers.
----------------------------------------------------------
Source: Spraying Systems Co.

Safety

Accidents Can Happen

The other night my 9 year old daughter began screaming in pain and running down the stairs. She had accidently gotten fingernail polish in her eye. In the past few years I have told hundreds if not thousands of pesticide applicators what to do if pesticides got into a persons eye. This incident proved to me the value of that information.

My daughter was in panic and in pain. She was not agreeable to running water into her eye for at least fifteen minutes. She also was much stronger than I remember her being. After much effort on the part of both myself and her mother we were able hold her down and irrigate the eye for over fifteen minutes by using a squirt bottle to gently force the water into her eye.

I contacted the North Dakota Poison Center when my daughter had started to settle down and become more accepting of the procedure. I visited with the poison center staff person who provided helpful information, made suggestions, shared opinions with me and assured me that they would follow up on the situation.

Based on the symptoms (and lack of symptoms) we decided after the eye flushing that a trip to the emergency room was not required and the best course of action would be to monitor her to see if symptoms would develop.

One thing that irritated me was that fingernail polish which is not a pesticide has no label. It did have an ingredient statement which was helpful, but it would have been nice to have had label information to tell what to do in case of an accident.

My daughter's eye has recovered nicely and there were no lasting effects. The North Dakota Poison Center did call back the next day as they had promised. My sincere thanks to the North Dakota Poison Center (800)732-2200.

Are you prepared for an accident? Accidents can happen.

(Submitted by Greg Dahl, Extension Pesticide Program Specialist)