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Join Date: Mar 2016
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PTFE Coating for Vibrating Forks Level Switch

03/31/2016 12:38 PM

One of our process involves measuring the level of a highly slurry product, the application is to use the EH FTL71 vibrating forks level switch, due to stickiness of the product we have EH to coat the forks with Teflon (PTFE) and this has worked great for us, however recently we have cracks already appearing in the Teflon coating and the problem is gradually appearing again.

Is there a way to recoat this forks without sending it to the manufacturer, I mean DIY kind of recoating as the plant is in a very remote location away from the manufacturer? Otherwise is there any other material we could use which will be better of than PTFE and will withstand a temperature of about 400oF.

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#1

Re: PTFE Coating for Vibrating Forks Level Switch

03/31/2016 1:35 PM

Maybe there could be a way to make slip-on sleeves of PTFE, and renew them periodically. Maybe the vibration frequency could be adjusted to avoid a resonance. Why not call EH, eh?

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#2

Re: PTFE Coating for Vibrating Forks Level Switch

03/31/2016 1:51 PM

You might take a look at this process, or maybe a ceramic coating of some sort...

http://www.suncoating.com/why-excalibur.html

http://www.plasmacoatings.com/releaseandcleanability.html

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#3

Re: PTFE Coating for Vibrating Forks Level Switch

03/31/2016 2:26 PM

Any DIY solution will require the process to be down (or at least without the reading) during prep/application/curing time on the old fork.

It might be a better idea to order a new fork from E&H, replace the old one, then send it back to them for recoating. That way when it gets back from them, you will have an on-hand spare to do an immediate replacement - send back for recoating...

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#4

Re: PTFE Coating for Vibrating Forks Level Switch

03/31/2016 5:48 PM

Instead of asking, "Otherwise is there any other material we could use which will be better of than PTFE and will withstand a temperature of about 400oF."?

Ask, "Otherwise is there any other material sensor we could use which will be better of than PTFE and will withstand a temperature of about 400oF.

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#5

Re: PTFE Coating for Vibrating Forks Level Switch

04/01/2016 4:31 AM

http://www.rjchase.com/application_guidelines.pdf will provide step by step procedure for coating Teflon.

The process is no more complicated than a industrial powder coating. I see dozen of small scale industries doing PTFE coating in Bangalore industrial suburbs.

Of course it is important to scrupulously adhere to coating manual instructions on substrate surface preparation and method of spray application.

Best advice would be get the coating done from a DuPont approved firm and it would not be economical to attempt in situ coating for one off applications.

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#6

Re: PTFE Coating for Vibrating Forks Level Switch

04/01/2016 8:23 AM

The tuning fork solution is a switch, not a measurement. If a measurement is required, then consider a non-contact method such as ultrasonic or radar, or place the vessel on weigh cells instead.

This is the wrong place to look for a solution, for a home-brew one will obviate any equipment manufacturer's warranty remaining on the product.

The correct place to look is the equipment manufacturer's telephone number. The manufacturer will be interested to learn of long-term issues with the equipment for the purposes of product improvement. Further, it may well have experience with other users that it can bring to bear on this particular issue. So, ring the local Sales Engineer without further delay.

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#7
In reply to #6

Re: PTFE Coating for Vibrating Forks Level Switch

04/01/2016 9:17 AM

Thanks for your contribution, agreed totally that its not a measurement but a switch, I have started engaging the vendor and I want to seek other opinion and if there is actually a DIY solution anyone has tried and it worked out as we may not have the luxury of buying another set of these switches neither could we afford downtime due to waiting on the manufacturer to re-vamp the switches just incase we are stuck with the Teflon solution.

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#8
In reply to #7

Re: PTFE Coating for Vibrating Forks Level Switch

04/01/2016 10:37 AM

<...afford...> Is business that tight, then (rhetorical question - NNTR)?

<...neither...> Simply choose the less worse solution.

<unsubscribes>

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