Operating problems:Vacuum nozzles and Flow control.

Vacuum nozzles

Vacuum nozzles are widely used for feeding negative pressure, or vacuum systems, since they enable material to be transported from open storage, such as from stock- piles and from the holds of ships. They can equally be used in hoppers as an alternative to rotary valves and screw feeders as illustrated in Figure 3.25.

Flow control

Vacuum nozzles, unlike rotary valves and screws, are not positive displacement feeders. Their control, therefore, is based on proportioning of the air, in a similar manner to that of a blow tank. The main requirement is that primary air should be provided at the pick-up point and that this should be sleeved to provide a free passage of air directly from the atmosphere, as shown in Figure 3.22. For continuous operation the nozzle needs to be plunged into the material. Air may permeate through the material but it is unlikely to be sufficient for conveying alone.

The primary air, together with any that might permeate through the material, will pick the material up and transfer it into the conveying line. If the concentration of mater- ial is too great, the secondary air can be used to provide the necessary dilution. This proportioning of the air is essential if the pipeline is to operate at the maximum mater- ial flow rate with the available pressure drop generated by the exhauster. The location of the outer sleeve in relation to the pipeline (see Figure 3.23) is also important in terms of feed rate control as illustrated in Figure 3.24.

Related posts:

Benefits, drawbacks and operational issues:Resonant vibrations in vertical pumps
System and process requirements:Process requirements
System and process requirements:Introduction to variable speed concept
Compressed Air Transmission and Treatment:AIR DRYERS
Introduction to pneumatic conveying and the guide:Information provided ,Availability of design data ...
Fine material:Dense phase conveying of cement
Pipeline scaling parameters:Scaling requirements
ROUBLESHOOTING PNEUMA TIC CIRCUITS:Rotary Screw Compressors
CONTROL VALVES:VALVE CLASSIFICATIONS
LINES, FITTINGS, AND SEALS:FLEXIBLE HOSE
BASIC DIAGRAMS AND SYSTEMS:DIAGRAMS
A brief system comparison: An electrical system ,A hydraulic system ,A pneumatic system and A co...
Fundamental Principles:Pressure measurement
Fundamental Principles:gas laws
THE SECOND LA W OF THERMODYNAMICS:INTRODUCTION TO THE SECOND LAW

Leave a comment

Your email address will not be published. Required fields are marked *