Rotary Airlock Feeder (Valve)

 

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Rotary Airlock Feeder (Valve)

F1: Description and Characteristics There are many types and uses for the rotary air lock feeder in our plants. Rotary feeders are in pneumatic conveying systems, dust control equipment and also volumetric feeders to maintain an even flow of material through processing systems. The basic use of the airlock feeder is an airlock transition point, sealing pressurized systems against loss of air or gas while maintaining a flow of material between components with different pressure. They are also used as a feeder for metering material at precise flow rates from bins or hoppers into conveying or processing systems. Figure F1

Keeping in mind that there are different manufactures and brand names, we will point out the main components compone nts of a standard rotary airlock feeder, along alo ng with the different end plates, rotors and casings that can be used. Interchangeable parts

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End plates 1. Flange bearing and lip seals. 2. Packing gland, separate stuffing box and cartridge bearing. 3. Packing gland, integral stuffing box and c cartridge artridge bearing.

Rotors 4. Type I open end. 5. Type II closed end with adjustable tips. 6. Type I closed end. Casing 7. Without inspection panel. 8. With inspection panel. 9. Side inlet. Figure F2

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F2: Drive Units - Rotary Airlock Feeders The drive units on the rotary feeders feeder s also vary depending on the application. application . Most of our rotary feeders are set to run at a constant speed, however there ther e are variable speed set ups as well. Most of the drive units are set up with drive sprockets and are chain driven by a motor and reducer. Note: Standard units operate clockwise as viewed from the drive side. Zero speed switches can be installed on the rotor roto r shaft to warn the operator of equipment failure. F3: Trouble Shooting - Rotary Feeders Condition:

Kicked out

1.

Check to see that all necessary equipment in front of the rotary is

2.

running. If equipment in front is okay, check to see if the rotary feeder will rotate manually.

3.

If it does move freely try to reset and restart. If it will not restart call Electrical Maintenance.

4.

If it will not move freely, check drive components and of the rotary itself for wedged material. If it cannot be taken care of by shift operator's call Mechanical Maintenance.

Figure F3  Ai r escap escap es into bin causing material to hang up.

F4: Other Tips a) Recognize that as the rotary feeder

Rotation

transfers material from above to below one side will be full of material; the other side will contain gases that are either low or high pressure. In the latter case, the gases, once reaching the space above,

Material is discharged disc harged on one side side a nd air fill s the return side.

will suddenly expand. This could cause material flow problems. (See Fig. F3) In such cases some plants employ 2 F-3

 

 

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rotary feeders in series but vent Figure F4

the intermediate chute to relieve the pressure, (Fig. F4). In this

Material Pressurized ai r from Press bel ow is siph oned off to a dus dustt coll ector. Top rotar rotary y valve should have little or no di fferential fferential pressure across it.

case a double ratary valves are used if a very high differential pressure must be sealed. Rotation

Some use special rotary valves that have vents built into that side of the casing, (Fig. F5). These are more suitable for low differential pressures, but are generally non-reversible.

Thi s arr arrangem angem ent is normall y us used ed when

Rotation

Others have built a baffle plate inside the bin closest to the

there isfferential anential extremel y extremel high di ffer pressure across the airlock.

upswing side of the rotary valve, (Fig. F6). In this case the baffle plate provides an escape route for this gas.

b) In some applications rotary feeders habitually jam due a chunk wedging itself between the vane and casing or shoe. Provided that the unit can rotate in either direction one plant used a switch to detect high motor amps at which point the valve valve is stopped then immediately reverses in direction. In this w way ay the rotary feeder became self unjamming with undetectable effects on the process.

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Figure F5 Air bled off to dust collector

Figure F6

Baffle

Air Baffle

Material Material

Rotation

Rotation

(non-reversible)

c)

Shaft sealing is a typical problem for this type of equipment. Recognize that the abrasiveness for most types of dust tears at the seal and will eventually leak.

In critical installations some plants use special grease seals w which hich

constantly pushes gritty dust away from the seal. Other units are designed with special labyrinth seals next to the packing gland which is constantly purged will high pressure air. In both cases units are of special designs. Typically the bearings are mounted well away from the casing itself. (See Figure F7.)

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Figure F7: Rotary Airlock Designed for Abrasive Material Casing Rotor Packing Gland and St uffing uffing Box

Labyrinth Seal

Inboard Bearing

Outboard Bearing Hi Pressure AIr or Grease Greas e

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