INTRODUCTION: The use of variable flow pumping systems on ULV sprayers can provide many benefits for the right application. The Pro-Nar ultra-sonic ground speed sensor keeps the speed sensing abilities of the variable flow pumping system with the sprayer itself rather than the spray vehicle, which improves versatility, flexibility, and accuracy.
MAJOR POINTS
* Difference between variable flow and fixed flow pumping systems
* Benefits of variable flow - Application accuracy maximized - Monetary, chemical & time savings
* Problems associated with older variable flow systems and transducers used for ground speed sensing
* The Pro-Nar sensor and how ultra-sonic technology works
* The specifications and requirements for using the Pro-Nar sensor
DIFFERENCE BETWEEN VARIABLE FLOW AND FIXED FLOW PUMPING SYSTEMS.
Within the ULV equipment industry, manufacturers produce sprayers that typically offer two types of pumping system operation.
Fixed-flow, aka constant flow, is a system that has it's pumping system calibrated and set to deliver a fixed or constant flow rate of product to be applied ata pre-determined application speed. Thusly, regardless of the spray vehicle's speed while spraying the pump will deliver a constant amount of product.
In other words, with a product labeled to be applied at 4 ounces per minute at 10 MPH, after the pump is properly calibrated it will deliver 4 ounces per minute, every minute of it's operation. The operator will then spray when spray vehicle application speed is 10 MPH, but the flow rate will be 4 ounces per minute regardless of application speed.
Variable, aka synchronized flow, is a system that has it's pumping system calibrated and set to deliver the proper flow rate of product that can be applied at any application speed, typically between 5-20 MPH, proportionally varying flow rate in accordance with application speed.
In other words, with a product labeled to be applied at 4 ounces per minute at 10 MPH, after the pump is properly calibrated it will deliver 4 ounces per minute at 10 MPH, 6 ounces at 15 MPH, 8 ounces at 20 MPH, etc., all based on how fast the spray truck is moving while spraying.
BENEFITS OF VARIABLE FLOW
Variable flow may not be for every ULV application, but use of a variable flow pumping system has several benefits to offer practically any ULV program. These benefits should be considered to determine if the cost of adding variable flow capabilities to your ULV sprayer will pay for itself in money and accuracy. Most adulticide programs that cover residential areas from the street can greatly benefit from variable flow.
APPLICATION ACCURACY MAXIMIZED
The first benefit of variable would be improved application accuracy. As previously mentioned, fixed flow systems are set for one application speed. If a ULV system is delivering a constant 4 ounces per minute at 10 MPH, and the applicator drops speed to 9 MPH, the result is an over application of product by 10%, and if the applicator increases speed to 11 MPH, the result is an under application by 10%.
While this amount may seem minuscule in the overall realm of application efficiency, it does add up. At the flow rates used in this example, a 10% over application equals an over application of 24 ounces of product per hour. After 100 hours, it equals 2400 ounces, or 18.75 gallons of product.
Variable flow systems are designed to minimize this occurrence, and maximize the accuracy of application. With a variable flow system, when the application speed dropped from 10 to 9 MPH, the pump flow would have automatically adjusted from 4 ounces per minute to 3.6 ounces to compensate for the difference, keeping the pump flow output in complete proportion to changing vehicle application speed.
Using a variable flow system, the applicator need only keep application speed between 5-20 MPH, the pump adjusts automatically. The variable system also keeps consistency between applications, and eliminates possible variations in application speeds that may be seen between different ULV applicators. With concern given to possible resistance created by under dosage of product, variable flow certainly minimizes that concern as well.
MONETARY, CHEMICAL & TIME SAVINGS
The second benefit is the monetary savings this system offers. Going back to the same scenario we examined, a minimally potential savings of 18.75 gallons of product saved every 100 hours adds up. At $50 gallon, the savings would be $937.50.
Tied to the above benefit is the chemical savings. At four ounces per minute, the 18.75 gallons of product saved would be enough for another 10 hours of application.
With the varying costs of ULV products, it's quite conceivable that adding variable flow capabilities to your ULV sprayer can pay for itself rather quickly, all depending on the cost of the product.
The next benefit is time savings. On a fixed flow system, a 40 mile spray route with a 4 oz/min @10 MPH application rate will take 7.5 gallons of product and four hours to complete the route treating about 1454 acres.
If conditions allow the applicator to apply at any speed up to 20 MPH, and increased application speed can reduce the time to complete the route by 25%, the same application that took four hours could be completed in 3 hours.
There are problems associated with older variable flow systems and transducers used for ground speed sensing. While all the benefits we've just mentioned seem to make variable flow so appealing, the problems associated with keeping our industry's earlier variable flow systems calibrated accurately seemed to create more work than it was worth.
Originally, pre-1988 or '89 trucks allowed placement of a magnetic sensor transducer "tee" placed between the speedometer cable and transmission to read truck speed and send a signal to the pumping system, which in turn adjusted the flow rate proportionally.
Wheel or driveshaft mounted magnetic sensors, or transducers as we call them, offered the advantages of low price and simple design. However, variations in wheel slippage, wheel distortion under varying loads, tire size and inflation may produce inaccurate speed readings. In addition, changing brands of truck, like from a Ford to a Chevy, required a new transducer.
The new electronic speedometers introduced in the late 80's created a new compatibility problem for variable flow systems. The electronic speedometer cables weren't compatible with transducers, and as mosquito control districts replaced their older spray vehicles, costly adapters or converters were now required in order to keep the variable flow features intact on any new spray truck.
There were other problems to considered. I know of at least one district who zapped their brand new truck's computer system while trying to tie a variable flow system into the electronic speedometer cable. I don't need to tell you how expensive it is to replace a computer system, so be sure to examine your new truck's warranty before attempting to tie in any speed reading device to it.
As a ULV equipment manufacturer, we saw the growing limitations of the transducer connection and in 1993, became the first ULV equipment manufacturer to produce a ULV variable flow pumping system using sonar technology to read ground speed in place of a transducer.
This allowed the incorporation of the speed reading function into the sprayer itself, rather than isolate that function of the ULV sprayer into the spray vehicle, separate from the spray unit and pumping system.
THE PRO-NAR SENSOR AND HOW ULTRA-SONIC TECHNOLOGY WORKS
Based on the technology available then and today, sonar technology has proven to be the most compatible with the requirements of a ULV variable flow pumping system.
Sonar technology works on the principal of emitting sound signals back and forth to the ground. With the Pro-Nar sensor, we're talking about 62,500 signals per second. The sensor processes these signals, averages out speed over a certain number of signals, then relays the speed signal to the pumping system, which varies flow rate accordingly.
The Pro-Nar ultrasonic speed sensor fits the requirements needed in a variable flow system in that it is extremely accurate at speeds up to 40 MPH, twice the speed of the highest ULV application speed used, emits harmless high frequency sound waves, the safest technology used in the ground speed sensing industry, and it reads ground speed in forward and reverse, giving the sensor the ability to be used in conditions where field debris or waving weeds can cause false signals with other sensors. This makes the Pro-Nar suitable for use under any type of off-road condition, such as the ability to have variable flow capabilities from an ATV or Argo-type vehicle that doesn't even have a speedometer, and is used in an heavily vegetated environment.
In addition to the variable flow capacity the Pro-Nar gives to such diverse applications as from an ATV or Argo, there's more to consider in the overall picture.
In the age of continual budget cutting, this sensor gives more flexibility to mosquito control programs. A ULV sprayer with this sensor can be removed, freeing vehicles for other duties, while not losing calibration. In fact, with this system, you can pull the sprayer off of one truck and put it on another, or on the shelf, and never lose speed sensing calibration.
In addition, initial flow calibration is quite simple. With the Pro-Mist ULV sprayer, the pumping system is simply calibrated to the 10 MPH flow rate that will be used, typically in less than 3-5 minutes. After flow calibration, a keylock switch on the Pro-Mist 6CS cab control system is turned to "VF" (variable flow) mode. This activates the Pro-Nar sensor and alerts the pumping system to use the speed input from the sensor to adjust flow in relationship to ground speed.
THE SPECIFICATIONS AND REQUIREMENTS FOR USING THE PRO-NAR SENSOR
The Pro-Nar sensor has minimal requirements to ensure correct use. The first is the mounting height. The sensor must be mounted 20-40" from the ground in order to work properly. We have found most pickup truck beds to fall within this category so the sensor can be mounted directly to the ULV sprayer. Some districts have elected to separately mount the sensor directly to the truck frame underneath the truck body. The sensor must also be level to the ground in order to read the ground speed correctly. This can be easily accomplished with a level.
The sensor is calibrated from the manufacturer, and requires no additional calibration, ever. It does offer field-calibration capabilities but that process requires another known completely accurate speed control device to measure the sonar sensor against. The factory speed resolution specification is .04 MPH, and the accuracy is +/- 1.5% + .04 MPH.
The only limitation of this technology may be it's potential to not work properly on roads that are holding standing water, which create a smooth, mirror-like surface the sensor cannot read properly.
With 62,500 signals per second being used to read ground speed, the sensor processes a certain number signals into an average signal, which is then fed to the system processor. This process occurs hundreds of times each second, so the system is quick to regain a clean signal after crossing over a pothole, puddle or standing water.
We have built in technology into the Pro-Mist to recognize extreme instances and allow the operator to switch to fixed-flow mode and resume spraying in case of a situation which causes the sensor not to operate properly for an extended period of time.
As a equipment manufacturer using newer technology, one of our concerns was the potential of our customers spraying immediately after a rainfall, where the most chance of large amounts of standing water would happen. But based on our continual communication with our Pro-Nar users, which are located worldwide, any spraying done immediately after rainfall seems to be the exception rather than the rule.
As a result, we have had 100% satisfaction with the Pro-Nar performing exactly as promised. In fact, 1 of every 4 Pro-Mist sprayers shipped so far in 1996 have been ordered with the Pro-Nar sensor option, so I'd say the success of the Pro-Nar sensor speaks well for itself. A list of users can be provided upon request.
Lastly and very importantly, the Pro-Nar sensor, in fact all variable flow systems in general, should be used with a ULV sprayer capable of meeting the label droplet size requirements of the product being used, at all flow ranges experienced during application, from the 5 MPH rate to the 20 MPH rate.
In the world of ULV sprayers, the Pro-Mist HD6 offers that built in capability. Other than calibrating flow rate, there are no other adjustments made to not only meet droplet size but produce the optimum ULV droplet spectrum, at any flow rate within sprayer specification.
This ensures correct and optimum droplet size is being met at all flow rate levels and application speeds used while spraying. This ability should be in any ULV sprayer used in variable flow applications, and is critical to the success of your ULV applications.
As an equipment manufacturer, I believe that companies like Beecomist have a responsibility to continually seek new technology to produce the most application efficient equipment in the ULV industry. The use of the technology used in the Pro-Nar sensor is exciting, and just the beginning of more innovations you can expect from ULV industry leaders like Beecomist.
Questions or Comments? Call Karl Kutzner @ Beecomist: 800-220-0787, or write to:
Beecomist Systems
3255 Meetinghouse Road
Telford, PA 18969 USA
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