Wired water level indicator

[idratherbefishing]

Hello all,

I am in need of several wired water level indicators that will be able to produce a % read out of below ground water tanks.

The environment around the sensor is going to be high in humidity, salinity, and a temperature range of 50 to 90 deg F

I have done a search on the net, have purchased and installed some of the items and have not been impressed by the reliability nor the accuracy of them. This is why I am posting here.

Any help at all will be appreciated.

 

[ScottyUK]

Vega and Rosemount (Emerson) both manufacture a range of level measurement instruments which are more than capable of surviving in those conditions. Specific technology needs more details.

Some more details on the fluid would help - is it potable or service water, sewage, oily effluent, something worse? How do you propose to mount the transducer? What power source have you got available? What signal output do you want from it? What budget are you looking at?



----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[idratherbefishing]

Scotty,

It will be mainly potable water and we have a range of 120/220V 60Hz as a power supply option.

As for the budjet side I will look at the ranges of the products and make a decision based on that.

Mounting of the transducer will be to the underside of the concrete tank tops.

I am looking for an LCD display, and an the ability to turn pumps/ valves on and off based on fluid level.

What are your thoughts?

 

[ScottyUK]

Immediate thoughts are ultrasonic or radar based sensor with a 4-20mA output, a remote 24V DC power supply fed from whatever you please, and a loop indicator to provide your LCD or LED display.

Plenty of possibilities from Rosemount.

My temptation would be to use a guided wave radar type but that's largely because they have worked well in applications where other types have been troublesome. For example Vega, just so I don't show bias toward Emerson! If I remember correctly many of the Vega instruments have built in relays for high and low thresholds where the Emerson products require an external threshold detector driven from the loop. Not a huge issue but something to check.

The loop indicators are pretty much a commodity item, I quite like these but there are plenty others to choose from.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[ScottyUK]

Ok, my mistake: the Vega GWR level detector doesn't have relay outputs either. It doesn't matter if you use an indicator unit similar to the BEKA type I noted above - that has a couple of alarm relays which could initiate pump start and pump stop. If you use the this as your pump control I'd probably install an independent high-high float switch with one or more of the following capabilities: close inlet isolation valve if possible; send an override 'run' command to all pumps; activate and audible or visual alarm.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[SteveWag]

Consider a submersible pressure transducer. Tank bottom is defined by when the transducer touches the bottom and depth is pressure x density. For $100 you get 0.1 ft. reading and for $300 you get 0.001 ft. and barometric correction. Just drop into the tank, hook up, no calibration required, easy to remove and easy to verify operation. If you don’t need continuous readout you can get sensor with internal clock and memory and download to a data collector or laptop every so often. MJK North American, Ametek and Omega make (sell) fine ones.
Steve

 

[idratherbefishing]

SteveWag,

Thanks for the info, I will chase these up.

 

[danw2]

Siemens' ULS200 is ultrasonic unit that can be used directly as a pump controller with its built-in relay, but it is designed to mount from the top via 2"NPT through the tank/cover top into the tank. I'm not sure mounting underside would be feasible, given the wiring access is through the screwcover on the top.

I had one problem with it - fog. It's on an outdoor water tank and on a late winter/spring day (Chicago area) with pea soup fog there was fog over the water in the water tank, too, and ultrasonic wouldn't operate until the temperature rose and cleared the fog. Only situation where it didn't work.

http://pia.khe.siemens.com/index-process_instrumentation-pointek_uls_200-5971.htm

As others mentioned, submersible works great for head pressure, but be aware that I've had condensation build up in the atmospheric reference tube that runs down to the sensor along with the wiring cable, particularly if the water through which the reference tube runs is below the dewpoint temperature of the surrounding air. Although there's no flow through the tubing, moist air can get in, condenses and shifts the zero point.

There's also conductivity - a couple contact metal rods mounted from the top (typically) immerse in the liquid. There immersion depth determines the pump turn-on and turn-off level points. An electronic box produces an excitation voltage and sees the conductivity of the water when the water level connects the reference rod to the level rod and flips a relay output. Quite reliable, but the turn on and off points are mechanically determined by where you cut/trim the contact rods. I think Gems sells them.

I used this panel meter with a couple relay outputs with adjustable deadband for pump-up or pump-down. It claims a sunlight readable display, although I've never used it outdoors.

http://www.predig.com/pd765/index.php

Dan

 

[ScottyUK]

If you're mounting anything plastic in an exposed outdoor location check the UV stability of the components. European IP ratings are definitely no guide, not sure if Nema 4X accounts for this effect (anyone?).

I inherited a lot of problems with A-B's Panelview 550 which really does not like UV. The LCD screens went opaque. I had a tacit admission from A-B that the PV-550 was not really suitable for outdoor service but that was an 'off the record' comment and Rockwell UK would not formally acknowledge it. Something to be aware of.


----------------------------------

If we learn from our mistakes I'm getting a great education!