V-Packing chevron type PTFE sealing system: how much must be compressed?

[fabiobs]

Hello, everyone. I am testing a valve in which a PTFE chevron-type sealing system is used on a sliding stem. Is there any way of calculating even indicatively the necessary compressive force to be applied to the seals? If I increase or decrease the number of elements (e.g. from 4 to 5 or vice versa), do I have to change the load?
Thank you all!

 

[CptMaaB]

Just ask the manufacturer of the sealing system.
They will give you detailed information on how to adjust the packing.

 

[fabiobs]

Ok but the problem is that is not a standard sealing and I'd like to know something more...

 

[TugboatEng]

Tell us more. What makes it non-standard sealing? Are the gland dimensions incorrect?

 

[fabiobs]

The profile was designed 20 years ago by my colleagues but with experimental tests and I am not sure if the chevron pack works correctly. The lower angle is 60°, the upper 90° (inner diameter 16mm and outer 25mm). The pack consists of 4 V-elements plus the male and female on one side of the spring, and 2 V-elements plus the male and female on the other. I believe that the spring does not have enough force (about 500N) to make all these elements work properly.

 

[Compositepro]

The force is not what is of importance. It is the amount of compression of the rings that is important. The rings must expand radially as the packing is compressed lengthwise. Start with the original ring diameter, the slope of the Vee, and the final outer diameter.