#power sprayers

Spray Away!  Selecting the perfect spray pump

The pump is the heart of power-spray systems used for pest and weed control, landscaping, golf courses and tree fertilizers. The right pump can make the job a breeze; the wrong pump will quickly ruin your day. And a high-quality pump in the wrong application is a waste of money.

Selecting the right sprayer pump requires answering some important questions:

What is the application?

What is the material being sprayed?

How hard will the pump be used?

What is the skill level of the applicator?

What is the ability of the maintenance staff?

What is the availability of repair/replacement parts?

What is the budget?

What is the total ownership cost of this pump?

If you are unsure of any of the answers, get input from staff, colleagues and vendors. NOTE: For this article, I will focus on gas-powered pumps.

1. What is the application?

What volume and pressure are required to do the work? For example, applying a weed pre-emergent doesn’t require much pressure, but significant volume may be required to treat large areas. Spraying 60-foot trees requires high volume and high pressure. Cleaning picnic tables requires pressure, but not much volume.

Higher-pressure pumps are required to reach extreme heights, push material through long hoses, and/or throw material over some distance. Higher-volume pumps may be required to drive booms or boomless nozzles.

Piston/plunger pumps provide high pressure, but not much volume. Roller pumps are great for volume at moderate pressure. Diaphragm pumps can supply both volume and pressure. Centrifugal pumps can provide volume, but not much pressure.

Design your sprayer for its most common use. Many organizations waste money designing a sprayer that handles all situations, but in the field doesn’t handle any application well.

All pump manufacturers provide volume- and pressure-output specifications. Remember that these spec charts are usually maximums at the pump, and actual results at the end of the hose will be lower. Plumbing fittings, valves, constrictions, hoses, distance, pump wear, and extreme temperatures will reduce output. Charts are available to calculate pressure loss through a given size and length of hose. Spec charts also provide horsepower requirements. Be sure to select an engine that can power the pump to provide the results you need.

If using jet agitation in the tank, be sure to consider this when determining the required pump output.  Click here for more on jet agitation at Sprayequipmentblog.com.

2. What is the material being sprayed?

If you are just spraying water, this is not really a concern. Generally speaking, granular fertilizers and herbicides are tougher on pumps than other products, such as pesticides. These materials can be corrosive or abrasive, and will significantly reduce pump life if an appropriate pump is not used. If the material is not corrosive or abrasive, there is a lot of flexibility. Diaphragm, piston, plunger, gear, roller or centrifugal pumps may all be appropriate.

If spraying herbicides, the best choice may be a diaphragm pump or a high-end roller pump. If applying granular fertilizers, a diaphragm pump or poly-centrifugal pump may be the best bet. If a pump is not appropriate for the material being applied, you will know it quickly, and the boss will ask why you need another pump so soon.

3. How hard will the pump be used?

If the pump will be subjected to rigorous use, either through long operating hours or by technicians who are tough on equipment, you may want to upsize the pump.

If the pump is barely large enough to provide the required output, it may be running at the high end of its operating range. Most pumps are designed to run “in the red” for short periods only. Running the pump full-out for extended periods will significantly reduce pump life.

My experience is that spray technicians tend to run pumps fast to get the jobs done quickly. If you have a slightly larger pump than needed, you may be able to get longer life and better results. For example, a six-roller pump may provide the output required, but for slightly more money, an eight-roller pump will provide the required output at a much slower speed.

4. What is the skill level of the applicator?

Some pumps are more sensitive than others, so technician skill is critical. For example, a diaphragm pump may be run dry for a short time without causing much damage, but a roller pump run dry will be destroyed in no time. Similarly, gear pumps can be great general-purpose pumps for many applications, but require periodic field adjustment. If you don’t have confidence in spray techs to perform this operation, then a gear pump is not the right choice. Be sure you understand operating requirements before buying a pump.

5. What is the ability of maintenance staff? What is the availability of repair/replacement parts?

A pump requires maintenance, and if not well maintained, it will require repairs. Be sure to understand the maintenance requirements of a pump.  What tools are needed?  What skills are required?  Where does one buy spare parts?  Ask these questions in advance, and you will save time, money, downtime and lots of aggravation.

Read the pump owner’s manual to understand and plan for the recommended maintenance. Make sure the required parts are in stock or readily available.  I recommend a rebuild on a pump once a year. If a pump is used constantly and you can’t afford downtime, perhaps more frequent rebuilds are in order.

Rebuild a pump at the end of the season or before the start of the next season. Too many organizations wait for the pump to break before doing the repair, which costs time and money and can turn an inexpensive maintenance job into a complete pump replacement. Ouch!

6. What is the budget? What is the total ownership cost of this pump?

Obviously, the above criteria are meaningless without a budget to support them. Generally speaking, diaphragm pumps are the most versatile and the most expensive. If there is not enough money in the budget for everything you want, try to find somewhere else to save money, including talking to an equipment provider. Don’t skimp on the pump--it will cost you. Also, some pumps require larger engines, which can quickly raise the total package price.

Remember, the cost of the pump is not just the price. Consider productivity, maintenance/repair cost, downtime, etc. If you buy the wrong pump and it takes a spray tech twice as long to do a job, have you saved money? Conversely, you may be able to use increased productivity to justify the purchase of a larger pump. If you buy too small a pump or the wrong pump and it always breaks down, you will pay in the long run.

Choosing the wrong truck for your power spray equipment can impact profitability and productivity. Be sure to consider some of the following factors when buying a truck to install your  power sprayers.

Many new trucks have features that can impact installation and use of power spray equipment.

Payload Capacity – The truck must be able to safely haul your power spray rig. The heaviest component is usually your full chemical tank. Water weighs approximately 8.4 pounds per gallon. Too big a truck means higher purchase price, insurance and gas expense. Too small a truck can mean increased expenses for tires, brakes and transmission repairs.

New Versus Existing Power Spray Equipment

Truck Bed Size – Obviously the bed must be large enough to hold your equipment in the configuration you want.  It is not a good idea to assume that equipment that fit exactly the same way in a given truck make and model will fit in the current year truck of the same make and model.

There are fewer issues with the installation of new equipment since there is more flexibility than with installing existing equipment.

Truck Bed Depth – The depth on the new Ford F-150 is greater than on prior year trucks. This can impact access to engine pull starts, hose reel and electric switches for pumps, reels, etc.

Bed Material – Some smaller trucks now have beds made entirely of plastic. Bed strength is provided by plastic ribs molded in the underside of the bed. More care is required when fastening equipment to these beds in order ensure stability and strength. Piercing a support rib might impact bed strength.

Gas Tank – The size, location and position of some gas tanks has changed. For some smaller trucks, it is not possible to access the bed above the tank. This can impact installation.

Clearance – Ground clearance on some smaller trucks has been reduced. Getting under the truck to bolt equipment or wire electrical components is a little more challenging. These trucks must be put on a lift or jack to gain access.

Electrical System – The electrical system of many vehicles is becoming more complex. Many vehicles have computer controlled electrical systems making wiring electrical components more complex and time consuming.

I am often asked by my customers, which type of pump should I use for pest control / weed control power spray rig, gas or electric?

There is no right answer to this question.  The answer depends on your company strategy, service strategy, budget and technician preferences.

Here are some things to consider:

Gas-Powered:

Pros: More Volume Higher Pressure Complete large jobs faster More expensive to purchase, plumb & maintain

Cons: Noise Safety – moving parts Safety – carrying gasoline on truck More weight Requires more space

Electric Powered:

Pros: Quiet Safety – moving parts, gasoline Less Space Required Less weight Less Expensive purchase, plumb & maintain

Cons: Lower volume Lower pressure Slower on large jobs

Gas power spray rigs cost more, because the pump and engine are usually more expensive (then electric), additional plumbing (pressure relief valve, pressure gauge, etc.) and steel (for the skid) are often required.

If your service strategy calls for mostly IPM with only occasional power spraying, electric pumps are a great choice.

If you are treating smaller properties (such as residences), electric may work for you.

If you your service strategy calls for power spraying on every stop and you are servicing large properties that require higher spray volumes or pressures, gas may be the better solution.

We have found is that if your technicians are used to using a gas-powered rig and you switch to electric, they will complain about the volume and pressure.  If using electric, start with electric.

Discuss your strategy with your equipment supplier so that you get a solution that works long-term for your Company.  Do not settle for a standard solution if it will not support your strategy.

Polyethylene (Poly for short) is the plastic used to make many tanks for power sprayer applications should as pest control and weed control.

Poly tanks are lighter and less expensive than most other types of tanks. They are easy to plumb. Most come with lids and output fittings already installed, which saves time and money. They are usually opaque so the technician can see how much water is in the tank.

On the downside, the tanks generally do not have the life of fiberglass or steel tanks. In my experience, these tanks should last 5 years or more, even in extreme conditions like the AZ sun. The most common problem we see is operator error. For example, when a technician throws a tool in the truck and cracks the tank.

Poly spray tanks are usually one of three styles:

Leg Tank - Designed to bold directly to truck or trailer. Usually comes with steel bands for this purpose. No frame is required, which saves money. Downside - it is difficult to fully drain these tanks because water sits in the legs.

PCO Tank - PCO stands for Pest Control Operator. These tanks are usually square or rectangular. They usually require a frame or some other type of support. The are usually the lowest cost tank.

Elliptical Tank - These tanks are popular because they can be fully drained. The tanks usually sit up in a saddle and are plumbed from the bottom. Many have a sump. These features are beneficial if you are changing materials and need to fully empty the tank.

Power sprayer tank agitation can be either jet or mechanical.  Jet agitation utilizes a portion of the pump’s output to stir up the tank.  Mechanical agitation, utilizes paddles (usually of stainless steel) on a shaft that is turned by belts and pulleys connected with the engine.

Jet agitation is cheaper to install and service, and is sufficient for most applications.  Mechanical agitation, which can add $500 - $1000 to the cost of your rig, is best for mixing heavy granular, or non-soluable, materials.

This entry will focus on jet agitation.  We will discuss mechanical agitation in a future blog.

Volume:

Jet agitation requires a pump that has output volume sufficient for your spray application PLUS the volume required to agitate the tank.

Rule of Thumb – Most liquid materials require 8% of tank volume for agitation.  Most granular or non-soluable materials require 12%.  For example, to agitate a 200-gallon tank that you will be mixing a liquid concentrate into, you need 8% times 200 gallons, or 16 gallons per minute (gpm), for agitation.

Agitation boosters reduce the volume required by creating jet action.  Most commonly used boosters are 3X (5X are also available).  This means that instead of 16 gallons per minute, we need 16 divided by 3 or 5.33 gpm.

You need to select a pump with output equal to the desired spray volume PLUS the required agitation volume.  If you need to spray at 5 gpm, you need a pump that will provide at least 10.33 gpm (5 gallons for spray plus 5.33 for agitation in this example).  You actually want a pump that will do more than this because the rated output is for a new pump with no restrictions.  Actual output will almost always be lower.

Plumbing:

Some power spray equipment providers plumb the agitation on the pump return.  We strongly believe this is a bad idea.  Some pump manufacturers (e.g., Hypro, Udor) specifically warn against this as it creates back pressure that can affect the pumps performance.  Regardless, it is a bad idea because return lines cannot have shut off valves on them (Note – centrifugal pumps are the exception).  Because you can’t shut off the line, if the pump requires service when the tank is full, you will have to dump the tank since you  can’t shut off the line.  We recommend separate lines with the return to the top of the tank and the agitation to the bottom.  It is sometimes helpful to put a gate valve on the agitation line so that the agitation can be easily adjusted.  This is also an easy way to adjust the pressure of your spray line.  More agitation means less pressure on the spray line.

Agitation Jets:

Jets must be positioned to ensure that the entire tank is agitated and no dead spots exist for material to settle.  Be sure to fill the tank and observe the agitation pattern before accepting the rig from your supplier.

The biggest secret in spray equipment is "check your filter". There is nothing you can do with your spray equipment that will save you more money than this simple activity.  We repair and replace more pest control spray equipment (and weed control spray equipment) because of clogged filters than for any other reason.  We tell the boss that if his techs would have checked the filter, the repair and downtime could have been avoided.  It doesn't seem to do any good.  The next month they are back for the same reason.

Check, and clean, your spray equipment filter.  Its money in the bank.