I'd always have it backed up to something if at all possible. As much to provide a loop easy to clip in to protect people on approach than as safety thing if the scaff pole failed. Wrap a short sling round it enough times to get the knot at a satisfactory height. Depends what if anything there is for people to stand on in the shaft where that is. Then, krab in to the ends of the sling and knot in to that. You can tie the climbing rope directly round he scaff bar if it is removable, like at the top of Oxlow, or Eyam Dale House. Nice big radius around the tube. If the tube is fixed, this makes judging how much rope to leave to go to a backup tricky and leads to time wasted adjusting lengths. Slings are cheap, so take one with you. The sling wound round the tube will also keep it in position. There may be parts of the tube that if the suspension point slides along will give a rope rub lower down.
Just what I do.
Jen