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West of I-95 in Virginia: Joe Polito - joe@vaheat.com (804-350-8829)
            
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Positive and Negative Pressure


POSITIVE PRESSURE - DILUTE PHASE

Positive pressure systems are normally utilized for conveying product from a single entry point to one or more destinations. The positive system uses a minimum air quantity to move a given amount of product. Material can be transported over relatively long distances using the positive pressure system. When required, step line conveying systems can be employed to provide relatively constant conveying velocities to minimize product degradation during the conveying cycle.

NEGATIVE PRESSURE - DILUTE PHASE

Negative pressure pneumatic systems are well suited for conveying material from a number of inlet points such as unloading rail cars, transporting and discharging product into a single point. Pneumatic systems are used when a variety of feed configurations may be required, and are almost always used when handling toxic materials to avoid accidental discharge to the atmosphere. When required, step line conveying systems can be employed to provide relatively constant conveying velocities to minimize product degradation during the conveying cycle.

COMBINATION NEGATIVE/POSITIVE PRESSURE -DILUTE PHASE

The pull-push system incorporates the advantages and benefits of both negative and positive pressure arrangements in a single system. Systems are used where there are multiple material entry points, and multiple delivery points. Typical applications include drawing materials from several points for batching before entering process and unloading from several points such as rail cars with delivery to bulk storage. When required, step line conveying systems can be employed to provide relatively constant conveying velocities to minimize product degradation during the conveying cycle.

CLOSED LOOP- DILUTE PHASE

Closed loop systems are used for handling hazardous chemicals, hygroscopic materials and extremely dusty products. Products such as TPA, caustic soda, and IPA require protection from atmosphere and particularly oxygen. These materials may be transported pneumatically in a closed loop system using an inert gas as the conveying medium. Both negative and positive pressure conveying systems are adaptable to closed loop design. This type of system is especially adaptable to edge trim conveying applications and for use in conjunction with rotary knife cutters, reduction mills and similar process machinery which require an air draw for proper operation.


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