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Are there any instruments available to measure tank level from outside by touching the tank wall like hand held IR gun.

Not really.

There are so many different configurations of tank, wall thickness, insulation, heating/cooling jackets, and so many different fluids in tanks, not to mention the conditions inside the tank (swirling, sparging, fill showers, etc.) that it is nearly impossible to conceive of an instrument that will work.

Except one.

The old Texas Nuclear produced for a while something we called a "source on a stick." It was a neutron backscatter level sensor mounted on the end of a very long wand. The operator ran it up and down the tank wall until it found an end-point in the thermal neutron count. It only worked on hydrogenous material, and it was an unshielded neutron source on a stick... and it had most operators and most companies scared of it... so it never took off. It was expensive too.

But it worked pretty darn well.

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Ever tried tapping on it?

Actually in our plant we have 10 different chemical storage tanks with ultrasonic level transmitters. But we don't have any other provision to cross check this level and no provison to take manual dip. For this reason I'm looking for a portable level measuring instrument to measure from outside the tank. I can get the tank dimensions and type of chemicals. We ar using HCL, H2SO4, caustic, antiscale, antifoam, cacl2, etc.

The ultrasonics should be quite accurate and reliable, they might be effected by the vapour above the fluid as this effects the speed of sound.

If you have a drain on the tanks you could attach a tube running up the side of tank, crack the drain valve and the fluid in tube will reach the same level as inside contents.

Once you have taken the reading apply gas pressure to the top of tube and blow the fluid back into the tank.

The chemicals you have are quite nasty so you would need to be VERY careful, make sure the tubing is compatible with the fluid, just crack the valve. DON'T LEAVE THE GAUGE ON-LINE - use as a check only.

The company I work with uses a lot of similar fluids in glass lined vessels. We use Tantalum bubble tubes for level, interface and density.

Hope this helps,

Roy

Hi,

Question: are the vessels pressurised or open to atmosphere? On open vessels I use pressure transducers to determine levels, connected at the same point I fit a manual 150mm mechanical gauge calibrated in mmH2O. I am only on water so I don't use process isolation diaphragm assemblies.

There are pressure differenial transducer options, but I've never seen a manual gauge (but never had to ask). Ask lots of questions before making a decision.

Cheers,

JAS

Suresh,

I was serious about tapping on the tank, provided it's non insulated you will get a different sound above/below the surface.

If you have access to the top of tank and the solution is mildly conductive one of my co-workers came up with an attachment for a regular tape measure using a 9V battery, LED, transistor and a ground clip. Clip to ground and run the tape down to surface which causes the LED to light (very accurate). We were faced with about 60 tanks where the level transmitters all failed within a month. This got us out of trouble until we could replace the transmitters.

If you don't have top of tank access and the tanks aren't agitated perhaps you could make a float and pulley device similar to what you sometimes see on large outside tanks.

Give us a better description of the tanks and process and I'm sure someone has the solution you are seeking.

Regards,
Roy

Some fabricators/construction workers provide a glass tube outside the tank to serve as level indicator. Inside that tube a thermocol ball can be put to make level of transperent liquid clearly visible.

Pranav,
Yes but I think the tank contents are a little too dangerous in this case. Reading the post again the author asked for hand held device. A good pressure gauge or pressure calibrator might fill the bill. I would still purge with gas to prevent fluid entering the gauge and it would also give a good reference point at the valve.

It's only to check the ultrasonics, not replace.

Roy