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Home | Editorial Spotlight | A New Spray Foam Gun In Town

A New Spray Foam Gun In Town

A New Spray Foam Gun In Town

New mechanical-purge gun available for spray, pour, and slab-jacking applications

Many contractors, who require high-flow spray guns that are not air purging, find themselves challenged to justify the high-cost of mechanical-purge guns and the required spare parts, which are often viewed as negatively affecting their profit margins. Simply put, it is hard to justify the expense. Or rather, it has been — until now.

After listening to contractors coupled with decades of practical, in-field experience, PMC has developed an answer to this dilemma: The PX-7, a high quality, mechanical-purge gun, that is manufactured in the U.S. at a competitive price.


Why use a mechanically purging gun instead of a gun that purges with air? There are multiple reasons — and first it is best to examine the engineering behind both systems.

In a mechanical-purge gun, a piston is attached to a valving rod. Air is used to activate the piston, which then moves the valving rod through the mixing chamber. When the trigger is disengaged, the valving rod prevents the material from flowing. When the trigger is pulled, the piston moves the valving rod, mixing the material and dispensing it. This process eliminates the need for cleaning via solvent flushing or air purging because the material is immediately purged from the gun — mechanically by the valving rod — at the end of each shot.

In an air-purge gun, there are no valving rods. When the trigger is pulled, the piston retracts, pulling back the mixing chamber to align the material ports with the material valves. This allows the materials to impingement mix inside the chamber and dispense through the nozzle. When the trigger is released, the mixing chamber moves forward and the ports are closed off.  Air immediately enters the mixing chamber and blows out the small amount of material still in the mixing chamber. The chamber is clean and ready for triggering again. Air-purge guns use material pressure to create the spray pattern.  They do not use the air to atomize the spray pattern. Air-purge guns require cleaning after each use, including washing the spray tips and air caps with cleaning solvents.

It is the requirement of air that makes the use of air-purge guns problematic.

Given that the air is coming from a compressor, it can be considered “contaminated.” When spraying coatings where moisture sensitivity is critical, air-purge guns are often not desirable equipment as the use of air can introduce moisture onto a dry, surfaced-prepped substrate. Even trace amounts of moisture on the substrate can cause some coatings to blister, disbond, or prematurely fail.

Also, if improperly maintained, not only can the air supply mix with moisture, it can also mix with oil and other contaminants — putting those materials onto the surface when the gun is triggered and resulting in unmixed materials, blisters, and premature failures.

For this reason, many contractors opt to bite the bullet — as it were — and use the higher priced mechanical-purge guns.


The new PX-7 gun is available in slab-jacking configurations

After years in the industry, working in the field with the contractors, PMC has developed
a mechanical-purge gun that is “competitively priced and manufactured right here in the U.S.A.,” says Murphy Mahaffey, PMC’s Director of International Sales.

The PX-7 has a “hardened, high-strength, stainless steel gun block, and a precision machined, not cast, coupling block, that is also made from high-strength steel, which gives it extra durability that no other gun currently features,” Mahaffey states. The hardened steel gun block significantly reduces the probability of cracking and stripping of the threads, as can happen with
cast steel.

“The triggering on this gun was tested to work in the most demanding environments. In fact, repeated triggering in the lab, before the gun even went to market, saw 200,000 pulls and little-to-minimum wear,” explains Mahaffey. This gun is  built to last.

The valving rod on the PX-7 is a single piece that is precision-honed for tight tolerances, especially in areas that mate with the mixing module. This attention to detail improves the life of the mixing module.

The new PX-7 gun is available in slab-jacking configurations

Designed for long service life, the mixing module works through internal impingement. “PMC offers a wide variety of styles to be used in conjunction with various pattern control discs to provide the highest level of mixing and pattern development,” Mahaffey states.

Additionally, the manual valves have a sturdy, simple design that is economical to rebuild. The check valves are easily removed from Side Screen Screws to allow for ease of maintenance and cleaning.

Mahaffey is quick to note that even though the PX-7 provides the latest in spraying and cleaning technology, it is still recommended that “at the end of each day of spraying, the gun is flushed with the appropriate pressurized flush pots, including the coupling block to accomplish a clean and environmentally safe flush. Please always reference the product manual to be safe.”


“In addition to being a competitively priced mechanical-purge gun,” Mahaffey says, “the PX-7 helps contractors become more competitive in several other market segments as well.”

This gun is perfect for use in pour applications, because no air is blown into the rising material.

Equipping a rig with a PX-7 is beneficial because the spray gun can be used in different types of foam applications

This gun is also optimal for use in concrete slab jacking applications using polyurethane. This provides spray polyurethane foam contractors with a new market in which to use their spray foam equipment. The only investment is in a new gun and learning the injection process.

The PX-7 is available in spray, pour, and slab-jacking configurations.

“The other gains are competitive,” Mahaffey says. “They are the most important ones that are at the center of every business evaluation — time and money. For contractors, the longer life span of the PX-7 results in less maintenance and downtime, which results in jobs being completed faster. The competitive price of the gun and its parts has an immediate effect on a contractor’s bottom line.”

Looking at the other end of the food chain, for material suppliers, the PX-7 provides a complete mix of chemistry and allows product to be sprayed or poured with less downtime. This means that more of their product will get applied.

“It is a win-win situation for all involved,” Mahaffey affirms. “A durable, competitively priced, mechanical-purge gun that is manufactured in the U.S. We listened to the industry. This is the result.” •

Equipping a rig with a PX-7 is beneficial because the spray gun can be used in different types of foam applications

Equipping a rig with a PX-7 is beneficial because the spray gun can be used in different types of foam applications


Photos provided by Polyurethane Machinery Corporation (PMC)

Contact Polyurethane Machinery Corp.

Direct any questions about the PX-7 mechanical-purge gun to PMC:

Phone: 732-415-4400



Spray Foam Magazine does not take editorial positions on particular issues; individual contributions to the magazine express the opinions of discrete authors unless explicitly labeled or otherwise stated. The inclusion of a particular piece in the magazine does not mean that individual staff members of editors concur with the editorial positions represented therein.

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