Small Rod Wipers? (Or other reliable gasket material?)

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Discussion Overview

The discussion revolves around finding a suitable sealing solution for a 1/8" diameter steel rod that needs to slide slowly past a wiper while maintaining cold oil at around 0 degrees Celsius on one side and standard pressure air on the other side. The focus is on identifying appropriate gasket materials or seals that can handle several hundred psi of pressure.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant seeks a reliable rod wiper or gasket material for a specific application involving a steel rod and pressurized fluids.
  • Another participant clarifies that rod wipers are not designed for sealing and suggests alternatives such as O-rings, urethane cups, and Teflon U-cups.
  • A participant questions the suitability of O-rings for use under 1,000 psi pressure.
  • Discussion includes considerations about O-ring performance based on material properties, hardness, and extrusion gaps at high pressures.
  • A reference to the Parker O-ring Handbook is provided for further information on O-ring specifications and performance.

Areas of Agreement / Disagreement

Participants generally agree that rod wipers are not appropriate for sealing purposes and that O-rings or similar seals are more suitable. However, there is uncertainty regarding the pressure limits of O-rings and the specific material choices that would be optimal for the application.

Contextual Notes

The discussion does not resolve the specific pressure limits for O-rings in this context, nor does it clarify the best material choice for the sealing application. There are also assumptions about the pressure conditions and the compatibility of materials that remain unaddressed.

BasketDaN
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I'm looking for a 1/8" diameter rod wiper, or anything else that could be reliably used to allow a 1/8" diameter steel rod to slide very slowly past it while maintaining cold oil (at about 0 celsius) on one side at several hundred psi, and standard pressure air on the other side.

Anybody know of somewhere I could find such a setup? I can't seem to find anything that small

Thanks
Dan
 
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Hi Basket. Rod wipers are typically not meant for sealing purposes. They're made to wipe dirt and other solid particulates off a rod prior to the rod going through a seal so as not to damage the seal. What you want is a seal of some kind.

Rod seals like this are typically O-rings, urethane cups, quad seals, Teflon U-cups or similar types of seals. They can also be purchased with Teflon wear bands if wear rate is a concern. Since you have oil on the pressurized side, and pressure is relatively low, you probably don't have to worry too much about wear of the seal.

If you need a specific recommendation, the first thing that comes to mind is to look on McMaster Carr. They don't have the urethane cups that small (I'm sure other places do) but they have various O-rings. I'd suggest part number 90025K513.
http://www.mcmaster.com/#90025k513/=2qxpr7
 
Thank you very much! Good thing I didn't waste more time looking around for rod wipers.

O-rings are pretty easy to find; will they be fine for under 1,000 psi?
 
The pressure that O-rings can be used at is primarily dependent on the material, how soft/hard it is, and any extrusion gap between the moving parts. O-rings at high pressure can be thought of as being a bit like a fluid in that they conform to whatever pocket they are contained in and will try to extrude into small clearances. Attached is a typical graph of extrusion gap versus pressure and hardness.

Also, the bible for O-rings is the Parker O-ring Handbook. Lots of great information in there, but it's a fairly large download.
http://www.parker.com/literature/ORD 5700 Parker_O-Ring_Handbook.pdf
 

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