Pneumatic Conveying Pipe Bends
Types of pneumatic transport
Dilute Phase transport
Dense Phase transport
Airlock Rotary Valve
Product inlet / Injector
Conveying speed / velocity
Air volumetric and mass flowrate
Pipe Equivalent Length
Solids velocity in pipe
Pipe Diameter or Bore
Selecting dilute or dense phase
Bends in Pneumatic Conveying lines are necessary, it is indeed very seldom to have just a straight pipe in between the pick-up point and the receiving point. However, bends can be a source of issues not always well understood by the manufacturer.
Shortly after installing a new conveying line, the following observations may be done, if problem actually arise from bends in a conveying line :
- The line is choking (blockages)
Those issues may be avoided (experience shows that problems have sometimes several root causes) if the Conveying Pipe routing had been designed differently, with less or different bends.
2. Bend Design
Bends can take several shape, from the sharpest (simple 90 degree tee) to long radius, or with more complicated and patented design. The table below gives an overview of each design available, with some remarks on design pros and cons.
Figure 1 : Regular bend designs
Table 1 : Different types of piping connections and their advantages and drawbacks
Figure 2 : Proprietary bend designs
3. Bends effects
Bends have mainly the following process consequences :
4. Solving Problems linked to bends
Figure 3 : Product flow within a bend
Note : the drawing above is showing a flow pattern with several impact, but it may also happen, depending on the material and solids loading that the material slides on the outer part of the bend. This is what can happen in long radius bends with polymers for example and create smearing leading to angel hair when the layer of product accumulated peals off.
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