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Abrasive Environment Pressure Sensor

07/14/2020 8:15 AM

I am looking for a pressure sensor to install in a pipe that carries a highly abrasive material in a fluid medium. The material is Silicon Carbide powder suspended in various fluids one of which is Cyclohexane. The pressures will range from 0 to 15 PSI and 0 to 55 PSI.

I am having a hard time finding something as I think a orifice style will just clog up, I was thinking a sensor with a rugged membrane might work but I am having difficulty finding anything. Any suggestions would be much appreciated.

This work is being done in the USA if it is relevant.

Thank you for any help and suggestions.

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#1

Re: Abrasive Environment Pressure Sensor

07/14/2020 8:28 AM

It could be that no suitable instrument exists. It is worthwhile zooming-out, and stating what the signal is intended to do, lest there might be other ways of doing what is wanted. So, is the <...pressure...> signal for control or for monitoring? Why is the information of value?

One presumes that, if electrical, the unit is intended for use in a hazardous area?

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#2
In reply to #1

Re: Abrasive Environment Pressure Sensor

07/14/2020 9:17 AM

I am monitoring the pressure for data collection. I have found some that are used in concrete pumping but they do not go to a low enough pressure.

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#4
In reply to #2

Re: Abrasive Environment Pressure Sensor

07/14/2020 10:00 AM

Of what purpose is this <...data collection...>? Why is the <...data...> of value?

Please tell a story and thereby help the forum to provide the help requested.

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#10
In reply to #4

Re: Abrasive Environment Pressure Sensor

07/14/2020 12:46 PM

This will be used in an injection molding system

We want to monitor the high and low pressures present in the system as the material is pushed (and sucked) through the piping. It has to pass through a filter and valving so we are also looking for a pressure drop across the filter. The data will be used to monitor the process but also to discover all of the pressures throughout the system as the process goes through all of its steps. This data will be used to make changes if needed and once done used to monitor the health of the system.

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#12
In reply to #10

Re: Abrasive Environment Pressure Sensor

07/14/2020 11:01 PM

You've been given several good options. One other would be to purge the pressure port with a small flow of clear cyclohexane, if available.

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#3

Re: Abrasive Environment Pressure Sensor

07/14/2020 9:22 AM

pipe diameter?

temperature?

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#14
In reply to #3

Re: Abrasive Environment Pressure Sensor

07/15/2020 5:01 AM

Still missing...

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#16
In reply to #3

Re: Abrasive Environment Pressure Sensor

07/15/2020 6:05 AM

ID is about 5/8 inch, flexible pipe. I could easily make it hard pipe though where I install the sensors. Temperature is about 70 F.

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#5

Re: Abrasive Environment Pressure Sensor

07/14/2020 10:27 AM
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#6

Re: Abrasive Environment Pressure Sensor

07/14/2020 10:31 AM

Several issues - clogging, pressure transfer at low pressures, erosion of the diaphragm causing a failure.

diaphragm materials

1. Metallic diaphragm seals are
a) very thin, on the order of thousandths of an inch, and are very subject to erosion by a slurry.
b) insensitive at low pressure ranges because of their inherent rigidity.

2. Elastomers tend to hold up slightly better to erosion and being more flexible, are more sensitive at low pressure ranges.

Seal Mounting styles
1. Typical diaphragm seal process connection is through a threaded process port on the bottom.

If clogged, the two piece seal can be removed, taken apart and cleaned, and reassembled, but I do not know of any feasible repair if the diaphragm fails - diaphragm failure requires replacement of the entire seal assembly

2. The clogging graphic shows a wide diaphragm seal raised up out of the direct flow stream, subject to an eddy current movements.

3. I hear people refer to the isolation ring style seal as a donut seal.

Its circular bladder has a broad elastomeric surface for excellent pressure transfer. It's full bore in the pipe means it does not clog. Any pressure instrument can be mounted, gauge, transmitter or switch.

Mounting the gauge to the iso-ring should be done with vacuum assist, so these are frequently sold as an iso-ring/gauge/transmitter assembly. There is usually an vendor option for a quick release gauge should the gauge need replacing. Should the bladder fail, some manufacturers sell replacement repair bladders. Replacing the bladder requires vacuum evacuation of the bladder but there are vendors who do that kind of work.

4. A Spool iso-ring fits into smaller pipe sizes.


There are a variety of different elastomers offered through the various seal vendors but they'll throw the responsibility for selecting an elastomer that is compatible with cyclohexane back onto you.

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#7

Re: Abrasive Environment Pressure Sensor

07/14/2020 10:39 AM

If the forum knew more of the story, it might be able to suggest non-contact methods such as back-pressure on a bubbler; an inert gas such as nitrogen might be available, perhaps.

Materials compatibility might suggest the same material as the inside of the pipe, which would give clues as to which way to go.

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#8

Re: Abrasive Environment Pressure Sensor

07/14/2020 12:28 PM

Here's a thought: If you know the density of the slurry, what if you had a clear vertical standpipe. Would not the slurry rise in the pipe until the hydrostatic pressure equals the pressure to be measured?

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#9
In reply to #8

Re: Abrasive Environment Pressure Sensor

07/14/2020 12:41 PM

I'm not sure it would flow well enough and the pipe is actually flexible so that it can move around so it would be difficult to keep it level and straight.

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#11
In reply to #9

Re: Abrasive Environment Pressure Sensor

07/14/2020 4:40 PM

...see now that's a key piece of information....lol

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#17
In reply to #11

Re: Abrasive Environment Pressure Sensor

07/15/2020 6:19 AM

I could easily make it hard pipe where I install the sensors though.

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#13

Re: Abrasive Environment Pressure Sensor

07/15/2020 3:20 AM

Hi Rob, we used Wika pressure transducers screwed directly into the sides of coal washing jigs where the media was coal and silica suspended in liquid. For our purpose we used the stainless steel interface but at the time we researched the use of their ceramic contact surface.

The stainless steel interface gave a reasonably long lifespan for our purposes in the matter of years. The output was 4-20mA and was fed direct into Premium PLCs. They were used to measure a differential pressure between two sensors vertically separated and we used 44 for the jigs and several others on slurry tanks.

Model S11 is shown. We tried bubblers and other pressure transducers but found their response time was too slow to allow the millisecond calculations for plenum pressure detection and air admission times to change the stratification of the media.

The transducers were screwed into 32NB SS pipe couplings welded into the side of the jigs. We also screwed them direct into take offs on Poly pipe for slurry flow detection across an orifice plate.

Website: https://shop.wika.com.au/pressure_pressure_sensors_shop_en_au.WIKA?Node=85038

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#15
In reply to #13

Re: Abrasive Environment Pressure Sensor

07/15/2020 6:02 AM

Thank you, I will check these out.

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#18

Re: Abrasive Environment Pressure Sensor

07/15/2020 6:55 AM

Check out this link..they deal with abrasive media transmitters...

https://campaign.stssensors.com/blog/pressure-sensor-abrasive-media-vulkollan

You also might consider a pig tail tubing,facing UP, between your transmitter and sensor port.The pigtail will be filled with fluid,and keep the transmitter separated from the abrasive media.

KISS if possible.

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#19
In reply to #18

Re: Abrasive Environment Pressure Sensor

07/15/2020 7:45 AM

Thanks for the link. I was on there site yesterday and requested information from them.

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#20

Re: Abrasive Environment Pressure Sensor

07/15/2020 12:31 PM

I would look at a diaphragm seal. They are used to isolate the pressure sensor from the incompatible medium being measured. Since your pressure range is on the low end you need consider the diameter when choosing what will work best for you. You can check out a description of these devices at https://www.branom.com/diaphragm-seals.

This is one distributor I'm familiar with; I'm sure there are many in your area.

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#21
In reply to #20

Re: Abrasive Environment Pressure Sensor

07/15/2020 1:04 PM

Thanks, I have been thinking about the wear on the metal or ceramic diaphragms that are often used on these pressure sensors and how quickly I may have to repair / replace them.

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#22
In reply to #21

Re: Abrasive Environment Pressure Sensor

07/16/2020 12:24 PM

I would discuss it with the application engineers at the manufacturers; they should be able to provide you the best choice of materials. Another consideration, if the seal were to fail the medium used to fill the seal needs to be compatible with the material it's measuring so the application folks need to be aware to provide the appropriate fill material.

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