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Smart spraying with Wilhelm Wagner

07th August 2013

Changes in coating technology are calling for smarter and more advanced paint application equipment for marine and offshore structures

Smart spraying with Wilhelm Wagner
Higher paint viscosities means technology used in coatings applications has had to adapt

Offshore and marine structures are exposed to highly aggressive environments, which provide a severe test of the coatings used on their exterior and interior components. 

The coatings technologies used to provide the corrosion protection to meet these environments have various proprieties.  These have generally moved to high and ultra-high solids ranging from 80 to 100 per cent solids materials, solvent free, and possessing an extremely short pot life - sometimes just minutes and even seconds of pot life.

 

Coatings technologies driving equipment changes

 

As coatings technology has advanced, equipment used to apply coatings has also had to evolve.   The function of the equipment is to process the material and provide the coatings applicator with a consistent and effective flow of material. Equipment nowadays has to meet the requirements of higher paint viscosities and the challenges posed by both single and plural component paint applications.   

 

The challenge of overcoming the higher viscosities and their associated pressure losses is accomplished by various means. Typically higher operating pressures and heating systems are used to reduce the viscosity without the addition of solvents.

Currently, there are two categories of equipment used in coatings application - single component systems and dual component systems.

 

Single component systems

 

Single components systems are typically used for two types of paint application. Firstly, they can be used to apply coatings that do not consist of more than one component. Secondly, they can be used for dual component paints that, when mixed together, have a pot life or reaction time slow enough to spray through the system before the pot life has been exceeded.   Once completed, this system can be cleaned with the proper cleaning agent, a solvent or water. 

 

These systems can also be modified to meet certain application requirements.  Such modifications can include a hopper or tank to feed the paint into the fluid section of the pump if it is too viscous. Additionally, the pump can be mounted on to an elevator or ram-style frame to drop into a container to ease the paint into the fluid section of the pump.

 

Additionally, these systems can be supplied with a flow heater to lower the viscosity of the paint to support its efficient transfer from spray device to substrate.

 

Dual component systems

 

Dual component systems are a method of coating application in which two-component, catalysed coatings are mixed proportionately and automatically by the spray equipment system.  Dual component is used to spray very high and 100 percent solids coatings with pot lives that are very short and fast reaction times that do not allow for the use of single component systems.

 

These systems are designed to deliver the dual component materials separately to a mixing station that is convenient for the applicator.  At this point, the two materials are combined and mixed, and then delivered to the spray device.   An additional advantage of this system is that the two materials are mixed only at the point closest to the application; this reduces the waste of useable material and use of cleaning solvents required at the end of an application.

 

Dual component systems consist of several different configurations.  There are three basic design options; fixed ratio proportioning, variable ratio mechanical proportioning and electronically-controlled proportioning.    

 

Fixed ratio proportioning is a system configuration that is only able to deliver the paint in a component ratio such as 1:1 or 2:1.  These systems can be configured to achieve different ratios by changing the fluid section.

 

Variable ratio mechanical proportioning is a system configured to allow for a ratio to be set with the fluid section mechanically locked in place.  Later, the ratio can be changed by unlocking the fluid section and moving it to a different position.   Some of these systems still require the changing of the fluid section to achieve different ratios.

 

Variable ratio electronically-controlled proportioning allows for different ratios to be achieved by changing the settings on an electronic control panel that operates the system’s functions.

 

Additional equipment required for a dual component system to process the paints include but is not limited to storage containers that control material temperatures and environmental requirements of the coating specification and heating systems that process the paints in preparation for mixing and applying to the substrate. There will be many options available to meet the requirements of each particular application.  Working with material and equipment suppliers to match the specific needs of the application is critical to achieving a proper solution in a corrosion protection project.

 

This article was written by John Berry, general director of sales for Wiwa LP, Latin America.