Fire is good when you use it to toast marshmallows, light a candle, or compliment a Gen Z friend (“Your t-shirt is straight fire!”). Otherwise, you probably want to avoid it.
To prevent fires in your processing plant and avoid fines for noncompliance, it pays to understand NFPA rules and regulations. That means PPE, equipment, and even the layout of your plant must be designed for safety.
Valves are no different. Find out what makes a rotary airlock valve NFPA compliant and why it’s so important.
What are the requirements for rotary valves?
Certain rotary valve features are essential for NFPA compliance. If your valve checks all of these boxes, you’re in the clear.
- The valve’s rotor-to-housing clearances must stay under 0.0079’’ at all times.
- To be extra safe, a range of 0.004’’–0.006’’ is best.
- Two or more rotor vanes must be in contact with the valve housing at all times.
- That means rotors with 8, 10, or 12 vanes are ideal.
- Rotor blades must be 3/8’’ thick.
- The rotor tips must be made of metal, not rubber. Steel is the standard.
Why do valves need to be NFPA compliant?
NFPA compliance is mandatory, and processors that don’t follow the regulations could face fines. Compliance keeps your workers and facility safe from fires and deflagrations, which are fast-moving fires that can result in explosions.
When it comes to rotary airlock valves, compliant features allow the valve to work as isolation devices. That means in the event of a fire or deflagration, the airlock prevents the flames from spreading further down the conveying line.
Does everyone need to worry about NFPA compliance?
If your material generates combustible dusts, you’ll need to be well-versed in NFPA regulations as they apply to all areas of your facility, not just valves. NFPA 652 and NFPA 654 have information on how materials are screened and tested for combustibility, as well as thorough guidelines on how to identify and mitigate fire and explosion hazards.
Side note: These standards, along with a handful of other related codes, will be consolidated into a new standard in 2025, so keep an eye out for news from the NFPA.
How do I know if my dusts are combustible?
If you’re not sure whether your plant generates combustible dusts, it’s your responsibility to contact a qualified laboratory to test your materials. Those who do handle combustible dusts will be required to perform dust hazard assessments (DHAs) every five years, which will help you further identify potential dust hazards in your facility.
Do valves stay compliant forever?
A valve designed for compliance can become uncompliant over time. Abrasion from everyday use causes the rotor tips to gradually wear down, eventually increasing the clearances above the required range of 0.0079’’ or lower. We highly recommend keeping a historical maintenance log, which makes it easy to keep track of prior inspections and rotor replacements.
Our how-to blog provides a step-by-step guide to checking your rotor-to-housing tolerances. Feel free to follow along whenever you need to inspect the rotor.
What else needs to be maintained?
Along with rotors, your valve’s shaft seals and bearings must be replaced periodically to maintain NFPA compliance. To avoid downtime, we recommend keeping an NFPA kit on hand, so you never need to take valves out of commission while you wait for replacement parts to arrive.
That’s a lot to remember!
We understand, so we created this NFPA Pocket Guide as a quick reference to NFPA compliance rules. Bookmark it or print it out — it’s designed to fold up and fit nicely in your pocket.
To order an NFPA kit with all the replacement parts you need, contact the ACS Valves team today. We’re happy to answer any questions you might have about rotary valve safety and compliance.
