NFPA Rotary Valve

Is your valve NFPA compliant?

The Ultimate Guide to NFPA Rotary Valve Compliance

NFPA Fact Sheets

Over 37,000 fires each year

According to NFPA reports, more than 37,000 fires in U.S. industrial and manufacturing properties were reported each year between 2011 and 2015. [1]

$1.2 billion in property damage annually

An estimated $1.2 billion in property damage annually caused by these fires.

The National Fire Protection Association (NFPA) provides regulations to protect your manufacturing plant from fires, deflagrations, explosions, and other safety risks. NFPA compliance is a complex, ongoing effort. But the potential cost to your plant and your operations — not to mention your employees’ health and safety — means it’s worth examining from every angle.


Rotary valves help or hinder your fire safety efforts, depending on how they’re made and maintained. Before you learn how valves impact NFPA compliance, it’s important to understand how fires and deflagrations start in a manufacturing facility.

Manufacturing and processing properties tend to be more prone to structural fires, and conveying systems are rife with combustible materials. Fires start when fuel, an oxidizer and an ignition source come into contact with each other. Deflagrations are more complicated — and more dangerous. [2]

When a heat source moves over and ignites cold materials, it creates a form of combustion called deflagration. This is a fast-moving fire that can spread across manufacturing lines and consume more material as it progresses, creating a chain reaction that is difficult to contain.

Read the entire article at
[1] Fires in US Industrial and Manufacturing Facilities
[2] Industrial FactSheet


What to do if your valve becomes uncompliant?

What to do if your valve becomes uncompliant




Explosion Prevention & Mitigation

Guide: How to check rotor-to-housing tolerances

Though you can’t stop explosions by using a rotary valve, they can help stop the spread of flames along your conveying line, should an explosion happen.

Watch this video guide ACS Valves put together on how to check your rotor-to-housing tolerances to ensure that they stay below the compliant 0.0079”. Check it out, and a summary of the steps required, below.

If the inlet or outlet of the valve is accessible, the clearances can be measured directly through this opening. If the inlet or outlet is not accessible, inspection is performed with the endplate removed. It’s easier to do this tail side because it’s not necessary to remove your drive package.

  • Loosen and remove chain drive guard
  • Loosen and remove bearing lock-collars
    • Remove allen set screw from collar and peen down groove formed by set screw using a small flat punch
    • Loosen collar by rotating collar in the same direction as the shaft rotation. Use drift pin in the through hole (not threaded set screw hole) and tap with hammer to rotate collar.
    • Slide collar off shaft.
  • To measure the clearance between the rotor and the endplate, attach an indicator to the end of the shaft, and set it to zero.
  • Plush the shaft towards one endplate, and the indicator will show what the clearance is. There should be a minimum of 0.0079" on each side of the rotary valve.
  • Next, take all the bolts out of the tail side endplate
  • Remove the endplate off the housing by using a wheel puller tool and take out your set of feeler gauges.
  • Stick the gauges between the housing and both the bottom and top rotor blades until you feel friction from both feeler gauges.

Keep your rotary airlock valve NFPA compliant

  • Two vanes must be in contact with the housing at all times. ACS recommends using a rotor with 8 or more vanes
  • 6 vane rotors are uncompliant with NFPA
  • Rotor vanes must be 3 mm thick
  • Rotor tips must be of metal construction. Rubber or plastic would not be able to handle the pressure of a deflagration

CI Series rotary airlock valve

NFPA standard rotary valve

MD Series rotary airlock valve

round NFPA rotary valve