Seal selection.

[Mitesh87]

As per API 682 , In seal Types A,B,C. Type B flexible element normally rotates.and in Type C flexible element is normally stationary.

As I understand - if seal seal-face surface speed is below 23 m/s than flexible element rotates and if seal- face surface speed is more than 23 m/s than flexible element is stationary.

I have 2 question regarding this,
1) Is my understanding is OK? is this only criteria to choose seal type?
2) How can i calculate seal-face surface speed?

Thank you in advance.

 

[RHurst]

Well, I should start by saying that the 23 m/s (~75 ft/s) is not TOTAL gospel with regards to seal design. Some seal designs have a lower surface speed threshold, while there are others (such as sundyne seals) that are far greater. I will say that we tend to be concerned in certain applications around 18-20 m/s. It just depends on a lot of different factors.

Calculating seal face surface speed is relatively simple. A good explanation is given in this article from Texas A&M's Turbo Lab. It's old, but the information is still relevant for the purposes of this conversation.

http://turbolab.tamu.edu/proc/turboproc/T12/T129-14.pdf

v = (η * π * D) / 60,000

For D, use the seal face diameter (or simply the published seal size for a quick and easy evaluation).
η is your shaft speed