Rotor Assembly Tolerance Check

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The rotary valve assembly is at the heart of the rotary valve. It acts as an airlock for the pressure difference between what is above the valve to what is below the valve. If a rotary valve is compliant with NFPA, it can help reduce the passage of flames along a conveying line should an explosion happen.

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The following video outlines what those compliance rules are, as well as how to test your rotor tolerances.

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So check if the valve is within tolerance for the NFPA.

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You have to loosen off the set screws on the locking collars on both sides to check your side-to-side clearance first.

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After you loosen off the set screws of the locking collars, you have to either punch them clockwise or counterclockwise to get the locking collars off.

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Once they're off, remove, just loosen off the drive side cause the drive will be on there and pull it away from there.

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You have to loosen off the split locking collar on the shaft seal on both sides.

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And then get your indicator, and put it on the airlock on the end of the shaft and set it to 0.

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So once everything's loosened off there, just set your indicator. Push the valve right completely to the one side endcap, whatever side you want.

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And then push on the shaft and it'll show a reading of whatever the clearance is of the valve then.

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So right now it's saying 8-thou, so 4-thou side clearance, which is within tolerance of the NFPA.

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So after you do that, that means that the side-to-side clearances are fine for NFPA. So then you have to go about doing the outside diameter of the rotor to the housing.

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So you have everything loosened off already. You have to take all the bolts out of the tail side endplates.

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It's easier to do the tail side endplate because you won't have to take the drive off.

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After you remove all the bolts, everything will already be loosened off from your first test that you did on the side-to-side clearance, so you should be able to just pull the endplate right off the housing.

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After you do that, take your feeler gauges.

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To stay compliant, at least two rotor vanes must be in contact with each side of the valve housing at all times. We recommend valves with eight vanes, as anything lower than that would be uncompliant.

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And stick it under the rotor blade to the housing.

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And to the top of the housing, to the rotor blade.

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Until you feel friction on both feeler gauges.

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Rotor tips must be of metal construction. Rubber or plastic would not be able to handle the pressure of a deflagration.

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The housing-to-rotor tolerance must stay under 0.0079 inches wide, while vanes must be 3 millimeters thick.

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So this airlock is 6 and 6, so that's within NFPA.

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So if you're over 0.0079, then it's out of tolerance.

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So you just gotta feel light friction between the housing and the rotor blade to know what your clearances are.

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Then after you figure those two out, then you know if the airlock is within tolerance to the NFPA or not.