any limits on mechanical seals?

In article . com,
wrote:

Joe Strout wrote:
Suppose you have a large space station (OK, let's say a colony) with a
rotating portion and a stationary portion, ........

An interesting problem but one I would try to avoid entirely by having
no stationary parts at all on the colony, at least not pressurized
ones.

An interesting idea but not practical, in my opinion; there are far too
many uses for a stationary portion. In addition, the problems presented
by trying to dock (especially more than one ship) on a rotating station
far surpass the problems presented by large rotating seals.

The most common supposed need for stationary parts is to allow
docking spaceships but a case could be made for keeping approaching
ships a healthy distance from the main body of the colony (remember the
re-supply ship that collided with Mir?).

A poor case, I think. Can you imagine a town where all vehicles have to
park 1 km outside the city limits, and passengers and cargo transferred
in and out of town by some other means? Yes, it's possible, but it's
highly inefficient and expensive compared to letting the ships dock
directly.

I would have tethered platforms swinging around the colony, 100m or
more away. The ships would drop landing gear and brake to a stop.

Hah! Thank you for a humorous mental image.

Best,
- Joe