How well does a thread function as a labyrinth seal?
How well does a thread function as a labyrinth seal?
(OP)
I am working on a hand-operated hydraulic device which involves a shaft being forced into a closed cylinder by a screw thread thereby creating the hydraulic pressure. This is hardly patentable, but it created an interesting problem.
For the purposes of sealing around the shaft, the original concept involved a simple O-ring. It soon became apparent that the diameter of the housing around the shaft itself added to the diameter of the thread that holds the housing in the cylinder head conflicted with the internal diameter of the cylinder. In other words, you can't make it. There's not enough room. That leaves the option of simply driving the screwed shaft into the cylinder - winding a bolt into the cylinder cavity if you like. My question is, how badly would that leak?
Internal pressure would force the lands of the male and female threads into tight contact and a seal, but there would still be the inevitable root gap of the thread to consider. My thinking is that the fine, capillary-like passage created by the root gap would sufficiently restrict passage of the hydraulic medium, probably heavy grease, so that leakage would not be a problem - even at 100+ MPa.
I'd appreciate experienced advice on this.
Thanks
For the purposes of sealing around the shaft, the original concept involved a simple O-ring. It soon became apparent that the diameter of the housing around the shaft itself added to the diameter of the thread that holds the housing in the cylinder head conflicted with the internal diameter of the cylinder. In other words, you can't make it. There's not enough room. That leaves the option of simply driving the screwed shaft into the cylinder - winding a bolt into the cylinder cavity if you like. My question is, how badly would that leak?
Internal pressure would force the lands of the male and female threads into tight contact and a seal, but there would still be the inevitable root gap of the thread to consider. My thinking is that the fine, capillary-like passage created by the root gap would sufficiently restrict passage of the hydraulic medium, probably heavy grease, so that leakage would not be a problem - even at 100+ MPa.
I'd appreciate experienced advice on this.
Thanks
----------------------------------------
Artificial Intelligence is no match for Natural Stupidity





RE: How well does a thread function as a labyrinth seal?
RE: How well does a thread function as a labyrinth seal?
Put a 'wiper' portion on the front end of the thread made of PTFE or something with an interference thread in it? Doubt you'd get a good enough interference thread for acceptable cost to really make it work but maybe.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: How well does a thread function as a labyrinth seal?
A more professional approach would be a rubber plug in a smooth bore pushed by screw. The tip of the screw would be turned down to remove the threads and match the diameter of the bore (sometimes called gib screws).
RE: How well does a thread function as a labyrinth seal?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: How well does a thread function as a labyrinth seal?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: How well does a thread function as a labyrinth seal?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: How well does a thread function as a labyrinth seal?
----------------------------------------
Artificial Intelligence is no match for Natural Stupidity
RE: How well does a thread function as a labyrinth seal?
Similarly, you could use ptfe tape, paper towels, or Saran Wrap to seal your bolt in even a loose fitting threaded hole.
Mike Halloran
Pembroke Pines, FL, USA