Are your valves compliant with NFPA?

Rotor Assembly Tolerance Check

Here at ACS, we only like explosions in the form of really cool ones in Michael Bay movies we watch from the comfort and safety of our own homes.

We emphasize the word safety here, because in real life, explosions can have serious consequences and precautions must be taken to prevent them. This means staying compliant with NFPA in your plant or facility.

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.

That’s why we’ve put together this nifty video guide 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.

Watch the video

What steps should I take?

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.

1. Loosen and remove chain drive guard
2. Loosen and remove bearing lock-collars
   1. Remove allen set screw from collar and peen down groove formed by set screw using a small flat punch
   2. 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.
   3. Slide collar off shaft.
3. To measure the clearance between the rotor and the endplate, attach an indicator to the end of the shaft, and set it to zero.
4. 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.
5. Next, take all the bolts out of the tail side endplate
6. Remove the endplate off the housing by using a wheel puller tool and take out your set of feeler gauges.
7. Stick the gauges between the housing and both the bottom and top rotor blades until you feel friction from both feeler gauges.

If your tolerance is higher than 0.0079”, it is time to replace your rotor. You can find a replacement kit here.

Things to remember to stay compliant

• Two vanes must be in contact with the housing at all times. We recommend 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

More reading about NFPA

We’ve done a number of blogs about keeping your plant compliant with NFPA. Check out the blogs below to learn more:

OSHA is sweeping combustible dust under the rug

Everything you need to know about NFPA 652

ACS deconstructs deflagration