How to select an airless sprayer for industrial coatings

What to consider when choosing an airless coatings sprayer

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 selected 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 atomise the material into a pattern that provides consistent coverage. When selecting airless spraying equipment, many factors need to be considered, including: the available power source, coating type, application demand, distance between the pump and spray gun, the operating environment, portability and maintenance requirements.
 

Power sources

Airless pumps can be powered by air, electric or gas power sources. Selection of what kind of power to user is often determined by the operating conditions and availability of the power sources. Key considerations concerning each source are shown below.

Power Source Pros Cons

 

Air (pneumatic)

  • Convenient for contractors using air-compressor-driven blasting equipment
  • Safer when used in explosive atmospheres
  • Allows use of large tip sizes
  • Allows use of of multiple spray guns
  • Easily handles long spray hoses 
  • Noisier than other types
  • Can be prone to icing in cold environments 
  • Requires a large compressor

 

Electric power

  • Quieter than other sources
  • Reduces energy costs
  • Less prone to icing
  • Does not require a large compressor
  • Handles long spray hoses
  • Needs 240V on-site as well as an electrician to install it
  • Only supports smaller tip sizes (one is not able to use it for heavier-bodied materials)

 

Gas

  • Greater portability
  • Capable of allowing high production rates 
  • Helpful in handling heavier, thicker coatings
  • An all-in-one power source (does not require electricity or a compressor)
  • Not allowed to be used in hazardous environments
  • May need permits for use of the fuel on a particular jobsite
     

The material & its application

Material being sprayed

The coating type also plays a key role in selecting 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 of more viscous materials and optimisation of pressures for less viscous materials.

If solvents are used to lower the 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 the pot life decreases.
 

Application demand

The rate at which a coating is to be sprayed, or the application demand, is also a key factor in selecting spraying equipment. The pressure required to atomise the material often determines the appropriate pump to use. The tip size required for proper coverage, the number of guns, the duty cycle and pump flow rate also need to be considered.  

A combination of both the pressure and the flow of the pump determine the application rate. Many pumps have enough pressure to spray a coating, but they are 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.
 

Application of external pipe coatings



Distance & environment

Distance from the pump to the gun

To properly atomise and apply coating material, the pump must overcome the pressure drop in the hose. As hose lengths increase, the pressure drops increase and additional pumping pressure is needed. 

The diameter of the spray hose also affects the pressure drop. By increasing the hose diameter, the pressure drop can be reduced. Elevation of the application area can also affect the pressure drop. If the application area is higher than the sprayer, a higher pressure drop will occur through the hose. Coating suppliers and product data sheets can provide additional information on the pressure required.
 

Operating environment

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 lower 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 the motor castings to virtually eliminate pilot valve freezing.

If sprayers are used in hazardous locations, the 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

Portability is another factor to consider. Most sprayers are typically available on carts and may be moved around a job site. The pump size can also affect portability. While larger pumps often help achieve higher application rates, the pump size should also be optimised to maximize portability. In industrial environments and for smaller projects, if a sprayer can be manoeuvered by one person, a smaller unit at a lower cost may make sense.
 

Maintenance

A sprayer that is 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 the 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 commonly available tools be used for most maintenance tasks?
  • How easy is it to remove the cover?
  • Is there a convenient place on the sprayer to store essential tools and parts? 
  • Are replacement parts reasonably priced and readily available?

Summary

Each of the factors discussed in this article (the power source, coating type, application demand, distance between the pump and the spray gun, operating environment, portability and maintenance requirements) play a key role when selecting an airless sprayer. Furthermore, there 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 a higher initial cost, but successful completion of more jobs on time is possible if you consider all of 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

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Video: Benefits of an electric sprayer

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