Why Remove the Internal Bead?    
 

The first question everyone asks is how severe does the fusion beads affects flow reduction or pressure loss in HDPE pipe systems. The answer is, very little. One of many great attributes of HDPE pipe is its low friction factor. HDPE pipe is less impaired by flow reduction or pressure loss from the fusion beads than the turbulence in a comparable system made of PVC push joints.

So then the question "Why remove the beads at all?" arises. Well, using a material that has less flow reduction and pressure loss doesn't mean that there isn't impairment. It is this impairment that we are completely removing. Excluding the issue of flow reduction there are four additional reasons why bead removal is important:

  
1. Flow Restriction:
 

Even though flow reduction is virtually nonexistent. There is still a restriction at the bead location. Among other reasons this can be a problem when pigging for blockage and biofilm or when HDPE is used as a casing for telecommunication conduits.
  2. Stimulated Blockage:        
It's easy to understand how sediment can build against a bead during a slow flow rate. This is the beginning of blockage as large debris become embedded in the sediment. Think about push joint piping systems and how every 13' or 20' this problem occurs compared to thermoplastic fused pipe where welds at lengths of 40 feet or more in distance is the standard along with complete internal bead removal.
3. Biofilm & Bacteria Entrapment:

In the potable water industry biofilm can stage a footing from under the fusion bead. In addition bacteria or other particle entrapment is of great concern in industries where it's common to use fusible plastics in de-ionized water systems. Most entrapment concerns are strongest in systems where chemical purification isn't an option because of other reaction problems it brings to the system. In push joint piping systems the bacteria entrapment can't be removed and is always a concern.
4. Turbulence Wear:
 
 

With increased flow the bead creates a turbulence that generates wear when slurries of abrasive materials flow through the system. Even though the bead will finally wear away and turbulence decreases, the final effect is a thinner wall cross-section in that location. In push joint pipe systems this turbulence can never be removed.

In thermoplastic piping systems engineers recognize the efficiency and advantages of having the internal weld bead removed from a system compared to a system that is not. Whether the issue is flow Reduction, or flow Restriction, or Stimulated Blockage, or Biofilm/Bacteria entrapment or Turbulence Wear. The concept of bead removal is an advancement in the thermoplastic piping industry that needs to be utilized, if for no other reason than higher efficiency.

   
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