Sensor for grease application

[TConnolly]

Beckhoff has an oscilloscope card that will go on device net. We considered using one in an acoustic emission application (similar to whats usde on boilers) but decided we needed something a little faster. But coupling it with a piezelectric ultrasonic transudcer might work. But it will requier quite a bit or engineering and development work. You would be looking for brief input spikes on the o-scope card that rise above a specific threshold trigger. Some number of events occuring in some short time span, emperically arrived at, would signal the presence of air bubbles.

 

[Stationmaster]

Thats precisley why I suggested pressure DROP across an orfice near the grease dispenser combined with pump stroke.

Yes, you did. And when the liquid is moving, during the stroke, I can see the (theoretical) possibility. I'm guessing you are thinking about an "upstream" xdcr and a "downstream" xdcr relative to the orifice?

Stationmaster

 

[TConnolly]

A differential pressure trasnducer might be required - we don't know enough about the grease application yet. If its to an open surface then we can just assume atmospheric pressure. If its to a cavity through a zerc fitting then a DP may be required.

 

[OkiePC]

Thats precisley why I suggested pressure DROP across an orfice near the grease dispenser combined with pump stroke...

I don't know what you mean by pump stroke. I think the pump stroke variability in normal operation would be as large as some small bubbles.

that all depends on the relationships between pump stroke volume, dispense volume and bubble size.

If the pressure is supposed to be consistent, and it has dips and spikes in it (single transducer as close to the dispensor as possible) and a fast 'puter watching it and comparing it's signal over time to a standard, then a deviation alarm could be set up...

The acoustic monitoring thing sounds fascinating. Someday maybe we'll replace all our photocells and proximity switches with digital cameras and microphones...

Stirring the Pot,
Paul

 

[Stationmaster]

So....

FIRST the idea would be to PREVENT air bubbles.

So far my favorite DETECTION concept would be an orifice combined with a directly coupled acoustic device to listen for the "crackling" sound as the grease is going through the orifice. And analyze the "crackling" with a Cray super computer with software similar to "vibration analysis " applications, compared to a "non-crackling" standard.

And as previously mentioned, "then what?". Alarm? Stop production? Scrap the batch?

[OT on]
Now about OakiePC's "pot stirrer". Servos? VFD? The stirring device will have to move in some random but limited fashion or we may have lumps. We will have to sense viscosity and vary the speed to prevent "WHIPPING" which as we all know is not an interchangeable term with "stirring".

How large is this pot OakiePC? More info may be required to provide an appropriate answer.

And how do we detect when the pot is sufficiently stirred?
[OT off]

; )

Stationmaster

 

[leitmotif]

On submarine there were grease lines going to inaccessible equipment ie valves outside the pressure hull etc. Also in steel mill we had long grease lines to inaccassible (at least when rolling hot steel) equipment.
We had no detectors and were only able to rely on proper filling of the line before placing in service. When able we visually verified proper operation.

I keep wondering why go to the expense of installing a detector when a pair of Mk 1 eyeballs and a wrench or vent valve could do the same thing? It is without doubt an interesting concept and I am curious if it could be done.
BUT my curiosity is getting high --
what kind of equipment is this being implemented on?

Dan Bentler