​What is "Axial" and "radial" diaphragm seal connection?

The basics:-What is the difference between Axial and Radial  movement mean?
 
Axial movement
Imagine a circle an you are in the middle of the circle.
Now you start jumping, this is axial movement.
 
Radial movement
From the center of circle you move to the end of circle.
This is radial movement.
In other words movement along the radius of the circle is called radial movement.
 
A Practical example:-
 
Let’s take a case study of the vendor Badotherm
 
This vendor has a seperate model number code to choose whether we want an axial or radial entry.(Reference :- GS 06P01Y01-E-E 7th Edition)

Model code C1/C2

Note:- A majority of vendor by default provide Radial capillary entry.
 
 
Now the difference can been seen from the picture below.

Axial Connection

Courtesy:-Yokogawa

Radial connection

Courtesy:-Yokogawa

How is this useful ?

Clearance space requirement

​Axial diaphragm seal requires clearance space in the X-Y plane.
 
While the Radial diaphragm seal clearance space in the Y-Z plane.

Also the capillary requires bending radius hence as per space consideration the appropriate connection must be selected.

Type of diaphragm seal

The type of diaphragm seal also dictates the connection type.
 
Example “Pancake” diaphragm seal requires a radial entry diaphragm seal.
 
Since a pancake diaphragm seal sits between two flanges axial entry is not feasible.
 

Wafer (Pan-cake) diaphragm seal connection

Thus depending on space consideration and type of diaphragm seal etc appropriate diaphragm seal connection must be used.
 
In conclusion the freedom of selecting radial and axial diaphragm seal connection depends on the available options with vendor, type of diaphragm seal (Pancake type supports only radial connection), Space considerations etc. 

Thanks for reading.

Hope it been of value to you.

PS:This is as per best of my current understanding