Dislodge powder on sides of pipe (powder contains PTFE)

[PreciousPE]

What would be an effective way to (automate a) clean down of a pipe operating under a vacuum for even deposition on substance below. We currently take equipment apart and blow compressed air into the pipe every so often to remove powder stuck to the sides as when they build up, it negatively impacts deposition part of the processs. However doing this is no longer sustainable and slows down production immensely.
We cannot coat pipe with PTFE as this would only make problem worse -powder also contains PTFE.
We cannot flush pipes with liquids either.

 

[shvet]

We cannot coat pipe with PTFE as this would only make problem worse -powder also contains PTFE.

Why does powder contain PTFE if pipe is not coated with PTFE?
Why do you want to coat pipe with PTFE?

Process diagram and description might help.
More details = better comments.

 

[EdStainless]

Have you looked into other coatings?
Be careful with coating as you will likely need something either static dissipative or conductive.
Do you very the flow conditions?
Can you engineer an integral 'blow down' that could be cycled periodically?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Latexman]

The old school solution is a few pnuematic vibrators at key spots along the pipe. Periodically when flowing solids they would be activated to give the pipe a good "shaking". Be careful though, this solution comes with it's own problems.

Good Luck,
Latexman

 

[shvet]

Be careful - PTFE has low adhesion to metals so most PTFE lined pipes are not designed to withstand vacuum.

 

[MortenA]

@PreciousPE, is the powder explosive?

--- Best regards, Morten Andersen

 

[georgeverghese]

What is the pipe material, and what is the material in this powder that makes it stick to xxx pipewall?
Or is it sticking due to electrostatic buildup? - if this is the case, would electrically grounding the pipe be the solution ?

 

[pierreick]

Hi,
You may want to consider a pigging system to clean your pipe.
More details better answer.

Pierre

 

[PreciousPE]

Thank you all so much for your replies.
To clarify:
PTFE in catalyst powder is needed for process.
PTFE not coated on pipe as that would aggravate existing problem causing more sticking issues.
I mentioned coating with PTFE not being an option as it came up in some literature as a possible solution but cannot be applied to this process.
Powder is not explosive.
Pipe material is stainless steel I believe and working theory is powder sticks due to PTFE- although another possibility might be due to the moisture content level of the powder.
Pigging in the pipe might not be feasible due to powder deposition under vacuum. Cannot have fixtures inside that would alter shape/area powder is deposited.

 

[TiCl4]

PTFE has an extremely low surface energy. It is unlikely this is the source of the deposition. What is the moisture content of this catalyst? Water sometimes plays havoc with powders and causes clumping. Another thing to check would be the grounding of the pipe. Flowing powder usually develops some level of static charge, which could also cause the powder to adhere to the pipe. Have operators or maintenance every reported slight static shocks when touching the pipe?

It's hard to posit any solutions without a better understanding of the issue.

It would not be difficult to try pneumatic or electric vibrators - there are several kinds you can strap on to the pipe. Be cautious with pneumatic vibrators - they can be quite powerful when turned up high. You'll want to take frequency measurements if you go this route. Running near mechanical resonant frequencies is VERY likely to cause failure of small-bore connections due to the very high stress risers in the weld of the connector to the main pipe. I've seen this first-hand.

 

[georgeverghese]

Not clear to me what's causing this catalyst powder to stick to the SS pipe walls - may be some residual ongoing chemical reaction that heats up the powder and causes clumping?

Cosasco make access fitting for inline / online access into pipes in the oil/gas business. Speak to them and see if they can help find some kind of inline rodding device.

https://www.cosasco.com/products/access-systems

 

[pierreick]

Hi,
So far, we have no indication about the pipe, the length, the internal diameter, the roughness of the pipe, the layout, the material itself and its properties .... How this is affecting the cycle time of your operation. BTW what is the current process?
Nothing very encouraging.
Pierre