OT- Pressure transmitter

Lemming · Jun 3, 2014

Hello

Have an application where I need a few pressure transmitters for a 90°C, 25% saline solution. Have no experience with this, but am told it eats 316SS.
Was thinking ceramic diaphram and Hastealloy wet end, but wondered if a more cost effective option is available ?? Need a few for tank levels, so only 0.4 bar span, but 2 need to live in an evaporator down to -0.9 bar..

Cheers Chris

nwboson · Jun 3, 2014

Yes, transmitters are quite susceptible to damage from the fluids they are exposed to. Is a bummer to have to drain tanks and keep replacing xmitters: gets expensive replacing them over and over.

Have you thought about a pulsed bubbler instead of a pressure transmitter? My recollection is they are roughly in the same price range as a high end transmitter?? With a bubbler you just place a piece of tubing in the fluid and the bubbler blows a little bit of air through the tube, measuring the pressure. The level is directly related to the pressure and specific gravity of the liquid. With a bubbler, there is no electronics in the tank (can be hundreds of feet away) so there is no transmitter to go bad. Try googling 'pulsed bubbler level indicator'.

Tom Jenkins · Jun 3, 2014

Another option is an isolation diaphragm - they should be available from your transmitter supplier and as the name implies keep the sensed fluid from direct contact with the transmitter.

Lemming · Jun 3, 2014

nwboson said:
Yes, transmitters are quite susceptible to damage from the fluids they are exposed to. Is a bummer to have to drain tanks and keep replacing xmitters: gets expensive replacing them over and over.

Have you thought about a pulsed bubbler instead of a pressure transmitter? My recollection is they are roughly in the same price range as a high end transmitter?? With a bubbler you just place a piece of tubing in the fluid and the bubbler blows a little bit of air through the tube, measuring the pressure. The level is directly related to the pressure and specific gravity of the liquid. With a bubbler, there is no electronics in the tank (can be hundreds of feet away) so there is no transmitter to go bad. Try googling 'pulsed bubbler level indicator'.

Seen these in a well / bore scenario, but not sure they would be a good fit for a tank, or especially a vacuum..

Lemming · Jun 3, 2014

Tom Jenkins said:
Another option is an isolation diaphragm - they should be available from your transmitter supplier and as the name implies keep the sensed fluid from direct contact with the transmitter.

Am looking into this, but a Hastealloy diaphragm + PT is as expensive as a ceramic / Hastealloy transmitter, and not as accurate.. A PVC diaphragm is ideal, but accuracy suddenly blows out to +/- 10%...

Plan A may have been the best option...

Thanks for the suggestions

nwboson · Jun 3, 2014

Lemming said:
Seen these in a well / bore scenario, but not sure they would be a good fit for a tank, or especially a vacuum..

Yes, the vacuum is not a good fit for a pulsed bubbler. Tanks would need to be ventilated for the bubbler to work. Sorry I missed that in your post. I've seen the bubblers used in lots of tanks for marine applications (salt and nasty chemicals), wells, sewage tanks, and even in a liquid asphalt tank application: they are a slick fit for the nasty chemicals.

Lemming · Jun 3, 2014

nwboson said:
Yes, the vacuum is not a good fit for a pulsed bubbler. Tanks would need to be ventilated for the bubbler to work. Sorry I missed that in your post. I've seen the bubblers used in lots of tanks for marine applications (salt and nasty chemicals), wells, sewage tanks, and even in a liquid asphalt tank application: they are a slick fit for the nasty chemicals.

The tanks are ventilated, but was more concerned about air supplies etc.. Package heading over seas, so want it to be as un-complicated as possible..

Lemming · Jun 4, 2014

If anyone is interested, Signet do a plastic body PT with ceramic diaphragm...

OT- Pressure transmitter

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