Need Transducer Advice
September 22, 2008 12:45 PM   Subscribe

I need suggestions on how to Mount a 20K pressure transducer in a line that is carrying an abrasive media solution (25 Micron garnet in suspension.) This is not the operating pressure. This value is used so that the run pressure will be somewhat close to the middle of the transducer range and to use some units that are allready on our shelf.

I am worried about the transducer fluid entry acting as a trap and plugging. I also need to be confident that the transducer output will not degrade over time due to damage from exposure to the abrasive. This would be used in a abrasive machining process where a certain pressure value will be used to determine the process cutoff. One possibility would be to mount the transducer in a wye fitting that would allow the transducer port to face away from the direction of flow. Any ideas out there?
posted by Raybun to Technology (3 answers total)
Couple options:

1: Set up a sample configuration using a clean fluid to check if orienting the transducer differently will augment the reading. If it does, then that option is out.

2: Check if you can find a mesh that is smaller than the particulate matter and hide the transducer behind it (it may still clog, but it would have to clog quite a bit to alter a reading I would think)

3: Put a tank in line with the supply, and orient the transducer off of the tank (the decreased flow rate of this orientation might save the transducer from the abrasion)

4: Call the transducer's manufacturer and see what they have to say about it. Those people answer crazy questions like that for a living. If they are worth their salt, they should at least give you a 'no' and a reason.

5: Some combination of the above

It may just turn out that you need to get something special (piezo instead of thin-film or something) to make this work. The steps above would be the first things I might look into.

Good Luck
posted by milqman at 1:15 PM on September 22, 2008

What about using some sort of pressure isolator? I am not familiar with pressures as high as you need, but I know for automotive use one can use a pressure isolator to keep a volatile fluid, such as fuel, outside the cockpit of a vehicle, and use a mechanical isolator to transfer pressure readings via an inert fluid to a gauge mounted inside the cockpit.

Something like this, for example.

Perhaps someone makes such a pressure isolator for use at the pressures you will be using? This would keep the abrasive material away from the transducer.
posted by mosk at 3:18 PM on September 22, 2008

As long as the transducer isn't in the flow, it won't wear that quickly from the garnet. If the pipe is constantly full, the transducer column can face the flow (off a wye) or be perpendicular because once the small section of tube containing the transducer fills, it's not going to have any real movement of the liquid. The volume of liquid in the transducer section will act like a pressure isolator.

This assumes that the sensor is located sufficiently away from the main flow that turbulence doesn't scour out the volume of solution in the transducer column. And that the pipe carrying the solution isn't empty.

Position is pretty important, though. Depending on what you're using to suspend the garnet, if you mount the transducer 'above' the main flow: the garnet may settle out of the transducer column over time and you'll end up with just the liquid portion in that column. You'll still get accurate pressure readings but not a large volume of garnet in the solution. And it'll be self cleaning.

All things considered, a wye that points downstream at a sufficient angle to allow particulate settling out to rejoin the main flow. If the pipe drains, so will the transducer column and on refill, it'll be less exposed to abrasive turbulence than a wye facing upstream or a 90 degree column.
posted by jdfan at 9:06 AM on September 23, 2008

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