Pressure Coating Issues: Even Layer Not Achieved

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    Coating Pressure
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Discussion Overview

The discussion revolves around the challenges of achieving a uniform coating of thread sealant on external threads using a roller transfer mechanism and the effects of pressure on the application process. Participants explore the mechanics of fluid behavior under pressure and the effectiveness of different application techniques.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant describes a roller transfer mechanism for applying a thread sealant but notes that the coating is uneven despite using a pressure vessel at 3 kg/cm2.
  • Another participant questions the nature of the sealant, suggesting that external pressure might affect fluids containing gas bubbles, while noting that the thread sealant is an incompressible liquid without gas bubbles.
  • A suggestion is made to use vibration, possibly ultrasonic, to encourage the fluid to flow and wet the thread surface more effectively.
  • Concerns are raised about the roller applicator's design, with a proposal that differential rotation between the bolt and the application roller could lead to a more uniform coating.
  • A participant questions the assumption that pressure would help the grease spread uniformly, asking for clarification on how pressure would affect the geometry of the grease blob.
  • One participant expresses uncertainty about their previous assumptions, suggesting that a pressure differential may be necessary for the grease to change shape.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether pressure alone can achieve a uniform coating of the sealant, and there are multiple competing views regarding the mechanics of fluid behavior under pressure.

Contextual Notes

There are unresolved questions regarding the assumptions about fluid dynamics under pressure, the specific properties of the sealant used, and the design of the application mechanism.

P K Pillai
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I have assembled a simple roller transfer mechanism for applying thread sealant ( toothpaste consistency ) to external threads. Since I did not get uniform coating, I placed the unevenly coated component in a small pressure vessel at 3 kg/cm2, hoping that the pressure would even out the uneven layer.However, the coating remains unchanged. Why is this so ?
 
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Is it a commercially available sealant, manufacturer, product name ?

I would expect external pressure to have an effect on a fluid that contained gas bubbles. The thread sealant I use is an incompressible liquid without gas bubbles.

You might get the fluid to spread by vibrating the bolt, maybe ultrasonic. That could encourage a liquid to flow and wet all the thread surface.

If your roller applicator rolls with the bolt then a fluid may not be spread evenly on the roller or bolt. By having a differential rotation between the bolt and the application roller you should paint a more uniform coating by equalising the fluid distribution on the application roller(s).
 
Thank you.
Yes, Vibraseal.
The bolt rotates freely on it's axis & moves against a (fixed) rubber roller axially rotating in the opposite direction.
The point is,if an irregular blob of grease is placed in a small pressure chamber & pressurised at, say 3 kg/cm2,would it not spread itself uniformly against the inner walls?This does not seem to be happening.
 
I think you should try to explain why you think the grease would somehow find internal surfaces when under pressure, when it could not find them at atmospheric pressure.

What is it about the geometry of the grease blob that is effected by pressure ?

Where have you seen environmental pressure spread a grease ?
 
Perhaps my thinking has been very wrong on this & a pressure differential is required for the grease to change shape.Thanks for making me think.
 

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