everything under control. Contact: Email: [email protected] Tel: +44 (0) 1884 232232 The Rotolok Group - core engineering companies Rotolok Ltd UK everything under control. Rotolok Valves Inc US everything under control. Sautelma Rotolok S-A - France Blo-Tech Ltd - UK from conception to completion. Roots Systems Ltd - UK at the centre of your system.
AMD-Rotolok Pty Ltd South Africa your plant needs roots everything under control. Solitec Engineering Ltd - UK Rotolok Asia Pacific Pty Ltd Singapore a tradition of innovation. everything under control. EDL John Quinn Packaging Ltd - UK shrinking your problems. Rotolok Valves Private Ltd INDIA everything under control. Valve Basics What is a rotary airlock valve? A rotary airlock is a valve that consists of a body, rotor and drive package. The rotor is a shaft with six to ten vanes welded to it, similar to a paddle wheel on a steam ship. The body has an inlet and outlet flange. The rotor rotates inside the body by chain drive or direct coupling to the drive package. Material is dropped into the inlet, the turning rotor then carries the product to the outlet where it is dropped out.
How is an airlock provided? Clearances between the rotor and housing are 0.10mm / 0.15mm (0.004 / 0.006) for the standard valve. Tight clearances allow minimal air escape through the valve. This way product can be transferred between areas of differing pressure or vacuum. ROTARY VALVE Valve Basics Vacuum Pressure Pv SOLID MATERIAL PARTICLE Pa > Pv AIR PARTICLE Rotary Airlock LOK O T RO
Atmospheric pressure Pa Valve Basics What is the difference between a rotary feeder and rotary airlock? All Rotolok rotary valves are machined to very tight tolerances as mentioned above, and are suitable for both feeder and airlock applications. Only valves with tight tolerances are suitable for airlocks. How the product feed rate controlled? The feed rate of product is controlled by two things: valve size and valve speed. The volume of the valve is calculated as the empty volume between the rotor pockets. The larger the rotor, the more capacity it has and greater feed rate. The feed rate is additionally controlled by the speed the rotor is turning. Applications What are typical applications? Controlling the feed rate from a hopper or silo Providing an airlock on the bottom of a dust collector Providing an airlock on the bottom of a filter/receiver Providing an airlock on the bottom of a cyclone Providing an airlock into a pneumatic conveying line Providing an airlock into a vacuum conveying line
Why Rotolok Advantages Rotolok valves have several features that need to be considered when comparing our valves to the competition. Construction Robust cast bodies and end covers. Bodies, end covers and rotor precisely machined on CNC machines. Spigot Located End Covers insures concentricity and tight clearances. All bodies can be drilled and tapped for body vents. All end covers can be drilled and tapped for air purge shaft seals Rotors are available with open or closed ends. Fixed bladed rotors are standard (beveled blades optional) which have less drag and have less product degradation. Larger rotor shafts insures rotor does not deflect under product and/or pressure loading Bearings are sealed for life ball type rigged outboard and for high temperature above 250 C; ZZ bearings with kluber grease are fitted. Gland type shaft seals eliminates leakage and allows adjustment and various types of packing material. Gland follower will withdraw sufficiently to allow the packing to be changed without
disassembling entire valve. All threads and fasteners are metric. Why Rotolok Drive Package Helical gearboxes 25% to 30% more efficient than right angle gearboxes, more compact design Motors universally available, easy and quick changeovers or replacements Chain drive allows changes in rotor speed by changing the sprocket ratio. Taperlock Sprockets allows easy removal and adjustment of sprockets, will not slip or strip shafts.
Steel Guards more robust than plastic or fiberglass The Gland Follower Rotolok offers a very unique design for the Inline and off-set valves Rotary Airlocks Shaft packing has to be maintained properly to prevent product from leaking from the valve, especially in positive pressure applications. Maintenance personnel will confirm how difficult this can be on the standard valve. Limited space typically requires the valve to be disassembled and the end cover removed for packing to be replaced. Why Rotolok Valve Temperature
Product temperature is the most important question when selecting a valve for an application. Anything above ambient 21C (70 F) must be specified. Standard valve clearances are 0.10mm/0.15mm (0.004/0.006). These tight clearances are required to insure the valve provides a good airlock in pressure differential situations. If the product is hot the valve warms, and the rotor grows due to thermal expansion. The change in rotor diameter and length is directly proportional to the change in temperature. This also means that the larger the valve, the faster the rotor expands. Once rotor expansion exceeds the 0.10mm/0.15mm (0.004/0.006) clearance, the rotor blades will start rubbing against the housing. This will cause excessive wear, noise and possible valve seizure/failure. For this reason, the temperature must be specified on each and every application. Closed rotors are preferred on high temperature applications whenever possible, as the gap between the end
shrouds and end covers eliminates any concerns with thermal expansion along the length of the rotor. For temperatures above 250C (482 F), we supply high temperature, bearings packed with kluber grease. We also switch to high temperature packing and closed end rotors. For temperatures above 400C (750 F), we have to supply all stainless steel valves, higher temperature bearings and heat shields between the valve and drive. In all cases, refer back to Rotolok for assistance in selecting a valve for applications greater than 200C (400 F). Valve Selection BULK MATERIAL PROPERTIES POWER SIZE DIFFERENTIAL PRESSURE SPEED VALVE TYPE & CONFIGURATION
CAPACITY DUTY TEMPERATURE Valve Selection Ideal condition Practical Valve Selection Inline Rotary Valve (RV) Inline rotary valve is the standard unit and used in most applications. Available with round or square flanges, and are available in sizes from 50mm to 900mm.T Designed for heavy duty applications. Ball bearings are mounted outboard and have gland type shaft seals. Numerous rotor options are available; please refer to the Rotor
Selection guide. Applications vary from bottom of dust collectors to pneumatic conveying systems. Valve Selection Offset Rotary Valve (RV) Off-set valve is used in applications where product shearing is a concern. Valve name derives from the offset inlet and outlet flanges, where the product enters the side of the rotor instead of the top. On a normal valve, shearing takes place as the rotor rotates into the housing. These two straight edges meet on a typical drop thru, this provides a pinch area where the product can shear and/or jam. With the side entry, the product is caught on the upswing of the rotor blades so that the product is constantly falling away from the shear point. Rotor pockets also do not fill up as completely, additionally reducing the likelihood of shearing. Lastly, the throat has a V shape which helps push product out of the way Valve Selection Blowing Seal (BS)/ Blow Through Valve The blow thru valve is used in pneumatic conveying applications only, both positive pressure and vacuum.
Instead of a typical outlet, the blow thru includes two ports on the sides of the valve near the bottom. Conveying line pipe connects directly to the valve, with the air stream flowing through the rotor pockets. This design is very efficient, and works well on materials that tend to hang up in the rotor pockets. However, this valve is not recommended on abrasive products as the vanes will quickly wear. This valve is also very helpful in applications that have height limitations. Valve Selection Rotary Dust Valve (RDV) Standard duty valve is designed specifically for lighter duty applications, such as gravity flow or bottom of dust collectors handling light loads and non-abrasive products. These units have a direct drive right angle gearbox, inboard bearings and lip seals; making them very cost competitive. Rotor Selection & Options Rotor Selection Proper rotor selection is the most important part of selecting a valve that will suit the intended service. This will make a significant difference in the life of the valve and overall performance.
Rotor Options Materials: Mild and Stainless Steel Style: Open, Closed, Open/Closed Combo Vanes: Adjustable or Fixed Tips: Mild Steel, Stainless Steel, Abrasion Resistant, Bronze, Brass, Polyurethane, Treatments: Beveled Edges, Scraper Blades Pockets: Scalloped, Reduced Volume Coatings: Nickel, Stellite Tipped Blades, PTFE, Chrome, Plasma Finishes: Mill to polish. Standard: Open End, Fixed Blades with Beveled Edges (optional) Viton, PTFE, Rubber, etc. Rotor Selection & Options Open vs. Closed (Shrouded) Open Rotor As a rule of thumb, 2 psi is the cutoff point between closed end and
open end rotors. The open end rotor provides a better air seal due to the vanes extending all the way to the end covers. Sealing capability is a matter of surface area between the rotor and housing. This is maximized with an open end rotor. The open rotor has its drawbacks as the material is in contact with the end covers. For abrasive products this leads to wear problems. In higher temperature applications, this adds to the tolerances that need to be carefully machined. Fine materials tend to leak out through the shaft seals if not properly maintained. Rotor Selection & Options Open vs. Closed (Shrouded) Closed Rotor
The closed rotor is not to be used in applications where the pressure differential exceeds 2 psi across the valve. (Difference in pressure/vacuum above and below the valve) It is primarily intended for gravity flow applications or the bottom of dust collectors. When allowed, the closed end rotor is ideal for abrasive and high temperature applications. In abrasive applications, the product is kept away from the end covers where most wear takes place.
In high temperature situations, the gap between the end cover and rotor eliminates any expansion concerns, leaving only the diameter to be machined. Rotor Selection & Options Fixed Blades vs. Adjustable Tips Fixed Blades Fixed blade rotors are Rotoloks standard. With fixed blades there is no concern with rotor tips coming loose or hardware falling off into the material stream. Fixed blades are also thicker and more rigid than adjustable tips. As product can become trapped under the adjustable blades, fixed blades are also preferred in sanitary type applications such as food and pharmaceutical.
Some products are also sticky or sluggish, and the fixed blade rotor allows these products to more easily leave the pocket. Adjustable Tips Adjustable tips are required for applications in which special tips are required. This is discussed in more detail below. Some people also prefer adjustable tips as they believe the tips can be adjusted up as they wear. Usually though wear is uneven, and impossible to bring the tip up to the original tolerances when new.
Rotor Selection & Options Rotor Tips Rotor tips can be either rigid or flexible, and are available for both open and closed end rotors. Rigid rotor tips should be used in all applications where the pressure differential exceeds 2 psi. Rigid rotor tips include mild steel, stainless steel, bronze, brass, and abrasion resistant steel. Standard tip is mild steel or stainless steel, depending on the general construction. Brass or bronze tips are often requested when handling materials that are explosive or easily ignite.
Abrasion resistant tips are used obviously for abrasive materials. Flexible tips are generally used only in gravity flow applications. They will have a tendency to wear faster. Rotor Selection & Options Rotor Tips In higher pressure differentials, they can also flex causing additional leakage. Flexible tips include Polyurethane, Viton, Neoprene, Rubber, PDFE, EPDM etc. Flexible tips are generally used on larger particle size products. The idea being that any material that becomes trapped between the rotor tips and housing will not jam the valve.
Polyurethane is the most widely used flexible tip. Other materials are specified due to temperature, chemical resistance, and food quality or customer preference. Maximum temperatures for Polyurethane : 100 C, PTFE: 150 C, Viton : 275 C. Flexible tips should not drag on the bore and end covers. Drag will increase the torque, possibly causing the motor to overheat. Drag may also cause the tip to tear or crack due to constant flexing. Rotor Selection & Options Vane Options
The most common vane treatment is beveled edges. Some products have a tendency to smear or build up on the bore. This will cause additional drag and may even lead to valve seizure. By beveling the trailing edge of the vane, this relieves the drag by reducing the surface area of the rotor Scraper blade rotors are primarily used in Salt Cake applications. Two opposing vanes have adjustable tips with notched out edges.
Notches are opposite of each other on opposing blades. This effectively scrapes of material buildup. (Note that the bore is not scraped clean, only enough to allow the rotor to keep turning.) Rotor Selection & Options Pocket Options A scalloped rotor pockets is where the bottom of the rotor pocket is rolled out and ground smooth. This is desirable in both sanitary and sticky applications. The idea is to get the material to discharge completely from the pocket.
Reduced volume is used to reduce the capacity of the rotor. Smaller valves will often cause the material to bridge above the valve. The reduced volume rotor allows a larger valve to be used that will not cause bridging, but allow the lower capacity. Reduced volume is also used when trying to accurately feed material. Material tends to discharge from a rotary valve in clumps. The reduced volume rotor allows more even flow. Rotor Selection & Options Coatings
Coatings are not often used, but sometimes requested by the customer. Coatings are usually applied to fixed blade rotors only. Nickel has some increase wear resistance, but is primarily used as a less expensive alternative to stainless steel. PTFE is used on sticky materials that have a tendency to build up in the pockets. Stellite is a highly abrasion resistant material that is sometimes specified or requested by the customer. Stellite is welded onto the outer edges of the rotor, then machined down to required tolerances. Rotors can also be chrome plated for abrasion resistance. Finishes
This only applies to the stainless steel rotors. Polishing is left up to the customer, but can be supplied all the way to a mirror finish. Usually this is an open end type rotor. Valve Selection Double Dump Valve Suitable for discharge dry dust, powder, granules and fibrous materials from cyclones, filters, hoppers etc., whilst maintaining an effective gas seal. The valve consists of two flaps connected by counterweights or spring loaded spindles, which are operated by means of a motor driven cam.
The cam alternately opens each flap allowing materials to pass through the separate chambers in batch form and thereby ensuring a gas seal. After cam release, the counterweights (or springs), return each flap to the upper (sealed) position and are designed and sized so that a clapping action at the flaps is obtained, aiding material flow and preventing build up at the seal plate. The unit is suitable for pressure differentials of up to 500mm W.G. This can be increased with special features. A fabricated steel body caters for sizes and specials that fall outside the standard 150, 200, 250 and 300mm cast iron body range as well as offering stainless steel construction.
Optional hardened steel flaps and inlets can help prolong the valve life in particularly arduous or abrasive applications. Bulk Material Properties & Behaviour Bulk Material Properties & Behaviour Sample Applications Each application has to be considered on its own, but typical selections are as follows: Characteristics Fine, Free Flowing, Nonabrasive Powder or Dust Typical Lime, Flour, etc. Fine, Free Flowing, Abrasive Powder or Dust Sand, Silica, Fly Ash, Cement, Alumina, Limestone, Coke, Perlite, Iron Oxide, etc.
High Temperature Smears or Cakes Salt, Sugar, Salt Cake, Starch, Soda Ash, etc. Rotor Open or Closed End, Mild Steel, Fixed Blade Rotor (Standard Design) Closed End Rotor with Abrasion Resistant Tips (2psi max.) Closed End Rotor preferred, but open end will work Open end rotor only. Beveled edges are a must. Some situations require scraper blades. Closed rotor must not be used as product will build up between end covers and shrouds causing valve seizure.
Sample Applications Characteristics Typical Rotor Sticky Sludge, Titanium Dioxide, etc. Beveled Edges, Open rotor with fixed blades only. Scalloped pockets. PTFE coating would benefit. Other valve options: Pocket Purge, Blowing seal Sanitary Applications Food, Pharmaceutical, etc. Open rotor with fixed blades, stainless steel typical. Scalloped pockets may
require polishing. Larger Particle Size Beads, Pellets, Wood Chips, Etc. Flexible tip rotor if gravity flow application. If all of the product will consist of larger particles then an offset rotary valve is recommended. Rotor Selection & Options Large Particle Size Very large particles will always be a problem and unless friable should be avoided. Remember that flex tips are only good up to 2 psi. Some large flat pieces, such as shredded plastic, require a closed rotor to prevent the product from getting
hung up on sides. In any case the object is to eliminate shearing and avoid the product from getting caught between the rotor and housing. Typical results of a jammed valve are: bent rotor blades, broken chain, motor burnout, feet broken off gearbox, etc. Hence this a major concern when selecting a valve. Options to consider: Offset Body Design, Shear Pin Sprocket, Beveled Edges, and Shear Plate Deflector everything under control. Contact: Email: [email protected] Tel: +44 (0) 1884 232232
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