Syphons
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If there were only one kind of rotating cylinder, and only one set of operating conditions, choosing the right syphon system for optimum performance would be a simple matter. But that's not the case. In order to end up with the most effective syphon system, a great deal of care must be taken to ensure efficient and reliable syphon system is selected. Operating conditions such as machine speed, steam pressure, condensing loads and dryer fabric configurations all have an effect on syphon selection. 
Stationary Syphons
With more than 15,000 cantilever stationary syphons sold, Kadant is the preferred supplier and global leader in stationary syphon technology. Stationary syphons are preferred for medium and high speed applications because stationary syphon differential pressure requirements do not increase with speed, as is the case with nearly all rotary syphons. This gives stationary syphons a great advantage in operating efficiency.
The locking mechanism in the joint housing secures the horizontal support tube in place to resist lateral loading while the vertical support provides rigid support to the vertical legto minimize vibration and deflection. To design out the weak spots, Kadant analyzes the natural frequency of each syphon design and the rolls on the paper machine to prevent large amplitude vibrations.
To optimize heat transfer and consistency of the cross-machine temperature profile, the cantilever stationary syphon is generally used with Turbulator bars which ensure the highest level of heat transfer through the shell.
Applications for stationary syphons are found with nearly all machines operating at speeds above 500 mpm (1500 fpm). Kadant Johnson has designed high speed cantilever stationary syphons for both open gear and enclosed gear machines.
While cantilever stationary syphons are the ultimate in stationary syphon design, the advanced locking syphon elbow from Kadant Johnson addresses the slow speed applications currently using bent pipes or conventional syphon elbows. The patented design locks the elbow in place and withstands heavy vibration and stress. Conventional syphon elbows or bent pipes are not designed to handle high levels of stress and these components are generally the most frequently replaced component. The locking elbow gives maximum reliability and performance from a syphon elbow.
Rotary Syphons
Rotary syphons have many advantages that permit their use at slow to moderate speeds. Since a rotary syphon moves with the rotating cylinder, it can be placed closer to the cylinder shell thereby reducing the 
level of condensate inside the cylinder. Kadant Johnson offers various types of rotating syphons including the conventional single syphon, the Rotocurve bent pipe rotary syphon and the LDR low differential rotary syphon.
For applications with moderate speeds,
a system using a properly sized conventional rotary syphon is extremely effective. Kadant Johnson rotary syphons have
a minimum of components. At the inlet of the syphon, a stainless steel pickup foot is welded to the vertical condensate pipe. At the opposite end, a spring-loaded pressure plate secures the syphon in place. Testing in the Kadant Johnson R&D center and field results show the operating life of these syphons to be more than 10 years with no maintenance requirements.
The latest rotating syphon technology for non-rimming cylinders is the Rotary Scoop Syphon.
The Rotocurve syphon is designed for small diameter dryers that do not have access inside the dryer via a handhole or manhole. It is installed from outside the dryer and is maintenance-free. The close clearance is preset at the factory and requires no additional adjustment. The most common applications for the Rotocurve are open gear paper machines operating at slow to moderate speeds.
| Syphon Design | Type | Speed (fpm/mpm) | ||||
|---|---|---|---|---|---|---|
| 0-500 0-150 |
500-1000 150-300 |
1000-2500 300-750 |
2500-4000 750-1200 |
>4000 >1200 |
||
| Bent Pipe/Syphon Elbow | Stationary | Fair | No | No | No | No |
| Spring-Lock Syphon Elbow | Stationary | Good | No | No | No | No |
| 45° Locking Elbow | Stationary | Good | Good | Fair | No | No |
| Internal Supported | Stationary | Good | Good | Fair | No | No |
| Cantilever Syphon | Stationary | Good | Good | Good | Good | Good |
| Rotary Scoop Syphon | Rotary | Good | Fair | No | No | No |
| Rotocurve | Rotary | Good | Good | Fair | No | No |
| Conventional Rotary | Rotary | Fair | Good | Good | Fair | No |