Equipment selection is critical to the success of airless spraying of industrial coatings. No matter what market you serve, the equipment must be capable of dependably delivering a select coating type at the right application rate, under various operating conditions. If equipment is not properly suited for the job, quality issues and equipment failures can result, often leading to budget overruns, schedule delays and unhappy customers.
The key to airless spraying is providing enough fluid pressure at the gun to atomize the material into a pattern that provides consistent coverage. In selecting airless spraying equipment, many factors need to be considered, including: available power source, coating type, application demand, distance between pump and spray gun, operating environment, portability and maintenance requirements.
Airless pumps can be powered by air, electric or gas power sources. The selection of power is often determined by the operating conditions and availability of power sources. Key considerations of each source are shown below.
Power Source Pros Cons
Convenient for contractors using air-compressor-driven blasting equipment
Safer in explosive atmospheres
Capable of using large tip sizes
Capable of employing multiple spray guns
Easily handles long spray hoses
Noisier than other types
Can be prone to icing in cold environments
Requires large compressor
Quieter than other sources
Reduces energy costs
Less prone to icing
Does not require large compressor
Handles long spray hoses
Need 240V on-site as well as an electrician
Only supports smaller tip sizes (not able to use for heavier-
Capable of high production rates
Helpful in handling heavier, thicker coatings
All-in-one power source (does not require electricity or compressor)
Not allowed in hazardous environments
May need permits for fuel on jobsite
MATERIAL & APPLICATION
Material Being Sprayed
Coating type also plays a key role in spray equipment. Industrial coatings are typically epoxy or polyurethane based, which are highly viscous materials (i.e., thick and resistant to flow). Higher pressure pumps allow pumping more viscous materials and optimizing pressures for less viscous materials.
If solvents are used to lower viscosity, one key factor to consider is the length of time the material needs to be sprayable after being hand mixed (hot potted). The proportion of solids in the coating is another key factor. As the solids percentage increases, the amount of solvent decreases and pot life decreases.
The rate at which coating is to be sprayed, or application demand, is also a key factor in selecting spraying equipment. The pressure required to atomize the material often determines the appropriate pump. Tip size required for proper coverage, the number of guns, duty cycle and pump flow rate also need to be considered.
A combination of both pressure and flow of pump determine the application rate. Many pumps have enough pressure to spray a coating, but they’re offered in different sizes (or flow rates).
The flow rate that the pump is capable of achieving also needs to be considered. For example, a sprayer with a larger pump fluid section can handle more demanding applications because it cycles slower.
External pipe coatings application
DISTANCE & ENVIRONMENT
Distance from Pump to Gun
To properly atomize and apply coating material, the pump must overcome pressure drop in the hose. As hose lengths increase, pressure drops increase, and additional pumping pressure is needed.
The diameter of spray hose also affects pressure drop. By increasing hose diameter, pressure drop can be reduced. Elevation of the application area can also affect pressure drop. If the application area is higher than sprayer, a larger pressure drop will occur through the hose. Coating suppliers and product data sheets can provide additional information on pressure required.
Different operating environments require different spraying equipment. Temperature and humidity are often key factors to consider. Air motors can experience icing issues, as ambient air is compressed and exhausted out of the pump at a colder temperature. A good motor design will mitigate icing and possible pressure loss. Some advanced sprayers feature thermally isolated poppets on the motors that are insulated from motor castings to virtually eliminate pilot valve freezing.
If sprayers are used in hazardous locations, pump type must be considered. Gas pumps are generally not allowed in these areas. If an electric pump is being used, agency approval is needed for operation in a hazardous location.
Portability is another factor to consider. Most sprayers are typically available on carts, and may be moved around a job site. Pump size can also affect portability. While larger pumps often help achieve higher application rates, the pump size should also be optimized to maximize portability. In industrial environments and smaller projects, if a sprayer can be maneuvered by one person, a smaller unit at a lower cost may make sense.
A sprayer that’s easy to troubleshoot and maintain will make life easier – and jobs more profitable. The equipment dealer can advise on ease of maintenance, regular maintenance tasks and anticipated lifespan of wear items for various sprayers. Some key maintenance questions to ask:
Are common items easily accessible, or is disassembly required?
Are any special tools required, or can common tools handle most maintenance tasks?
How easy is it to remove the cover?
Is there a convenient place on sprayer to store essential tools and parts?
Are replacement parts reasonably priced and readily available?
Each of the factors discussed in this article (power source, coating type, application demand, distance between pump and spray gun, operating environment, portability and maintenance requirements) play a key role when selecting an airless sprayer.) In addition, here are some general items to consider when selecting equipment:
Make sure you have sufficient fluid pressure at the gun to provide consistent coverage.
A dependable, high quality sprayer may have higher initial cost, but successful completion of more jobs on time is possible if you consider all the right factors.
Rugged sprayers can perform in a variety of environmental conditions and make the difference between a good day’s work and a day of frustrating delays.
Work with a qualified technical representative to make the right choice