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Factors to consider selecting the best foam spray rig

by Donny Stock

Polyol and isocyanate resin react with each other and expand to form spray foam. Spray foam is widely used to insulate buildings. Spray foam can be used for both walls and roofs of buildings. Apart from insulation, spray foam prevents entry from water and allergens into the buildings through cracks, prevents the growth of moulds and also reinforces the strength of the walls. Spray foam is applied using a spray foam rig. Spray foam rig houses all the components for application of spray foam such as spray foam machine, compressor, storage area, generator and others.

In order to select the most suitable spray foam rig as per your specific requirements, the following factors should be taken into account.


Purpose of using the spray foam rig is a major consideration. Spray foam rigs are used for roofing jobs as well as for insulation in residential and commercial buildings. Thus, you need to pick one as per your specific purpose. Spray foam rigs for residential projects do not need to have high outputs. This is because residential applications require just 5-8 pounds per minute or PPM of foam output. Thus, a spray foam rig having output lower than 15-20 PPM is suitable for residential contractors. Air-driven machines work best for residential projects. In the case of commercial contractors dealing in large scale commercial projects, spray foam rigs having a high output and pressure ratings are essential since the volume of materials used is much higher as compared to residential projects. Hydraulic machines are recommended for commercial works.

In the case of roofing jobs, spray foam rigs of mechanical purge varieties are considered to be the best.


Whether you want to spray foam only or intend to spray coatings as well is an important factor to consider while choosing a spray foam rig. Air-driven closed-cell spray foam rig is an appropriate choice for spraying foam only for small scale residential projects. On the other hand, a heavy-duty hydraulic spray foam rig is most suitable for spraying both foam and coatings. The hydraulic machine also ensures uniform application of foam and coatings over even thousands of square feet of the surface.


The spray foam rig must be properly insulated so that the chemicals which combine to produce the foam are maintained at a temperature ranging between 60 and 75 degrees Fahrenheit. Otherwise, the chemicals will fail to produce proper foam. To this end, the spray foam rig must be equipped with an air conditioner if it is to be used in a warm place or a heater if it is to be used in a cold place.

Types of mechanisms

Air purge spray foam rig has an air compressor which generates air pressure to expel the foam from the machine. The rating of an air purge spray foam rig needs to be checked to ensure that it matches the pressure required for your specific purpose for spray foam application. Spraying coatings require high-pressure ratings. Residential contractors widely use air purge machines.

Solvent purge spray foam rig uses a chemical solvent which removes any residual material left inside the chamber. This type of spray foam rig is most suitable for coatings. Spraying time is more for a solvent purge machine.

Mechanical purge spray foam rig has a valving rod which separates the chemicals from each other. When the valving rod is withdrawn, the chemicals mix and create foam and after spraying is complete, it falls back into position and flushes out residual chemicals from the chamber. This type of spray foam rig is capable of generating different flow rates and is widely used for large scale commercial projects.

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