Few things will stop a spray foam job faster than seeing your A-side and B-side pressures move farther apart.

Pressure imbalance can lead to poor foam quality, inconsistent spray patterns, equipment shutdowns and wasted material. More importantly, simply increasing or decreasing pressure at the proportioner doesn't necessarily solve the underlying problem.

When spray foam pressures become unbalanced, something is usually restricting material flow or preventing the system from operating correctly.

Here's where to start looking.

What Does a Pressure Imbalance Mean?

A spray foam proportioner is designed to deliver the A-side and B-side materials at the proper ratio.

During normal operation, pressures won't necessarily be identical every second. Small fluctuations can occur.

A persistent or significant pressure difference, however, deserves attention.

The problem could be anywhere along the material path—from the drum and transfer pump all the way to the spray gun.

Instead of randomly replacing parts, troubleshoot the system logically.

1. Check the Spray Gun First

The gun is one of the easiest places to begin.

A partially obstructed mixing chamber, dirty impingement port or material buildup inside the gun can restrict flow and create an apparent pressure imbalance.

Inspect the gun for:

• Material buildup
• Restricted impingement ports
• Worn or damaged seals
• Mixing chamber problems
• Restricted fluid passages

If another properly functioning gun is available, swapping guns can also help determine whether the problem is actually at the gun or farther upstream.

Spray Foam Gear carries replacement parts, tools and equipment for contractors who need to keep their rigs working in the field.

2. Inspect the Heated Hose

Don't automatically blame the proportioner.

A restriction inside the heated hose can affect material flow and create pressure problems at the machine.

Look for:

• Kinked or damaged hose
• Material crystallization
• Internal restrictions
• Damaged sections
• Temperature problems

A hose that's beginning to fail may create problems long before it becomes completely unusable.

Contractors looking for replacement assemblies can see our heated spray foam hoses.

3. Check Your Transfer Pumps

The proportioner can't properly process material it isn't receiving.

If one transfer pump isn't supplying enough material, the machine may become starved on that side.

Check the transfer pumps for proper operation and make sure both drums have adequate material.

Also inspect:

• Air supply
• Pump seals
• Drum connections
• Material inlet screens
• Supply hoses

A supply-side problem can sometimes look like a proportioner problem.

4. Inspect the Inlet Screens and Filters

This is an easy one to overlook.

Contamination and crystallized material can gradually restrict screens and filters. As the restriction increases, the proportioner may struggle to receive enough material.

If you're troubleshooting unexplained pressure imbalance, checking the inlet filtration system should be high on the list.

5. Look for ISO Crystallization

Moisture contamination on the ISO side can cause serious problems.

When isocyanate reacts with moisture, hardened material can develop inside components and passages. Even a relatively small restriction can interfere with flow.

This is one reason keeping moisture away from spray foam equipment and materials is so important.

If you discover crystallized ISO, don't just clear the immediate blockage. Determine where the moisture entered the system or the problem may return.

6. Verify Material Temperature

Material viscosity changes with temperature.

If material isn't reaching the proper operating temperature, it may not flow through the system as expected.

Check the proportioner's temperature settings as well as actual hose and material temperatures.

Don't assume the displayed temperature automatically means everything downstream is heating correctly.

7. Check for Worn Seals and O-Rings

A tiny seal can create a surprisingly expensive problem.

Worn, damaged or incorrectly installed O-rings can allow leakage or interfere with proper equipment operation.

Inspect seals whenever you're servicing the gun or another component in the affected material path.

Keeping commonly used spray foam O-rings on the rig can prevent a small component from turning into hours of downtime.

8. Don't Ignore the Proportioner

If you've eliminated the gun, hose, transfer pumps, filters, material supply and obvious restrictions, the problem may be inside the proportioner itself.

Potential causes can include worn pump components, valves, seals or other mechanical problems.

At this point, careful diagnosis becomes especially important.

Don't start replacing expensive components simply because the pressures are different.

Work through the material path first.

A Better Way to Troubleshoot Pressure Problems

When pressures become unbalanced, think of the system as a path:

Drum → Transfer Pump → Inlet → Proportioner → Heated Hose → Spray Gun

Then work through that path systematically.

Ask yourself:

Where could material flow be restricted?

That approach can save considerable time compared with randomly adjusting settings and replacing parts.

Prevent Pressure Problems Before the Job Starts

Some pressure problems are unavoidable, but good equipment maintenance can eliminate many of them.

Before heading to a jobsite:

• Inspect your gun
• Check transfer pumps
• Examine heated hoses
• Inspect seals and O-rings
• Verify filters and screens
• Confirm proper material temperatures
• Keep common replacement parts on the rig

The cost of carrying a few spare components is usually insignificant compared with losing several hours—or an entire day—of production.

Keep Your Spray Foam Rig Ready

Spray foam equipment makes money when it's spraying.

When a small restriction, damaged seal or worn component stops production, getting the correct replacement part quickly matters.

Spray Foam Gear has supplied spray foam contractors with equipment, parts, PPE and accessories since 2007.

Browse our spray foam tools, parts, equipment and accessories and keep the parts you depend on ready before the next problem happens.