Viscosity picks the meter. Not the line size.

Inside a Coriolis sensor the flow splits into two thin tubes that bend around and come back. Those tubes are narrower than the line feeding them, and thick fluid squeezing through narrow tubes burns pressure fast.

This plant had 80 psi to work with. That 80 psi has to cover the pipe run, the valves, the fittings and the meter. A sane share for the meter is about 15 psi. Once the flow is fixed at 40 lb/min, the only thing left that moves the number is how thick the product is.

So every product lands somewhere on one scale, and the scale tells you the size. This is the single most useful chart on a multi-product dispensing job, and almost nobody draws it.

The thickest item in the book is a 45 % actives biocide dispersion. Its safety data sheet gives a measured viscosity of 27,714 mPa·s at 68°F, tested to OECD 114. That is roughly three times thicker than honey. The sheet is a scanned-and-rebuilt document, so we rendered the page and read it directly rather than trusting a text extraction.

At that thickness the meter is not the problem. The pipe is.

No. Not at 68°F, which is the temperature the number on the sheet was measured at.

A 2″ meter on its own burns 217 psi at 40 lb/min against an 80 psi supply. And the meter is only part of it, because the pipe has to grow with it. A 2″ meter fed by a 1″ line is pointless, since that line alone eats 877 psi over a 30 foot run.

Here is the whole ladder. Meter plus a matched 30 foot pipe run, at 68°F and 40 lb/min.

So, in order

• Get the shear rate curve first. If the product thins under flow, which the 20x temperature drop suggests, none of the rest is needed and a 1½″ meter handles it cold.
• If it really is 27,714 cP in motion, heat the line to about 100°F. That buys a 1½″ meter at ±0.36 %.
• If heat is off the table, slow it down. At 10 lb/min and 68°F a 2″ meter on a 2″ line totals 69 psi and just fits, at four times the dispense time.
• Do not go to 4″. It works and it is the worst option on the list.

And the honest conclusion. If that product is genuinely that thick in motion and cannot be heated, Coriolis is the wrong tool for that one line. A positive displacement meter or a loss in weight scale handles thick product far better. The other seventeen positions are still a clean Coriolis job. Part of sizing well is knowing which line to take out of the scope.

Every line runs the same mass flow, so the volumetric flow varies only with density. Products are listed by chemistry rather than by trade name.

The instinct is to go small. A smaller Coriolis is more accurate at low flow, because the fixed error inside the meter is a bigger share of a small number. That instinct is correct, and on this job it is worth about three hundredths of a percent.

Read that table left to right

Going from ½″ to 1″ costs 0.03 percentage points of accuracy. It buys six times the viscosity headroom and takes the CIP flush from 74 psi down to 8 psi.

The ½″ meter tops out at 42 cP. Four of the seven measured products are already above that, and the eleven unmeasured ones are a coin flip. A ½″ meter would be starving on half the book.

That is the whole argument. A meter that runs out of pressure is not accurate in the real world no matter what its spec sheet claims. Accuracy over economy means buy the premium meter and give it room. It does not mean buy the smallest one.

This has nothing to do with meter sizing but it bites first. The system was specified for ambient service, 32 to 100°F. Five of the eighteen products carry a storage temperature limit on their own sheet that the range violates.

If the room is not heated, two of those lines need heat trace and insulation at minimum, and three more want the space held above 40°F. Settle it before anyone quotes meters, because heating the room may also solve the viscosity problem on the thick lines and change the sizing.

Reading eighteen sheets for corrosion risk is not a formality. What came back:

• No chlorides or bromides in any composition section. Chloride is what pits 316, and there was none in this book.
• No product carried a GHS “corrosive to metals” classification.
• One biocide contains 0.5 to 1.5 % sodium nitrate, which is a corrosion inhibitor. That helps rather than hurts.
• pH ran from about 2 up through 45 % caustic potash. 316L handles that whole span at ambient.

One caution. Caustic potash at 45 % can cause caustic stress corrosion cracking in austenitic stainless, but only above roughly 120°F. With a 100°F ceiling that line is clear, as long as nobody heat traces it hot.

PTFE for every gasket and seal. It is the one material that covers 45 % caustic, a phosphate ester surfactant and a fluorosurfactant without a separate compatibility check per line.

These came out of this project, but they generalize to any mini bulk or multi-product dispensing system.

Every density and viscosity came off the eighteen supplied safety data sheets. Nothing was assumed where a sheet had a number. Where a sheet gave a range, the thick end was used, which is the conservative choice for pressure drop.

Scanned sheets get read, not skipped. One sheet was a scanned image with no extractable text. It was rendered and read by eye rather than dropped from the study.

Extraction errors get caught. Six sheets sharing one common SDS template had labels and values misaligned when the text was pulled out of the PDF. Taken at face value that would have assigned the wrong density to six products. The correct alignment was verified by rendering one of those pages and reading it directly, then applied to the rest.

Pipe pressure drop is exact. 1″ Schedule 40, 1.049″ inside diameter, Hagen-Poiseuille below Reynolds 2100 and Darcy with Blasius friction above it. That arithmetic is checkable.

Meter pressure drop is an estimate, and we say so. A Coriolis sensor is two tubes with a developed length, and manufacturers do not publish the geometry. We used a dual tube model calibrated so a ½″ sensor at its nominal water flow lands at 14.2 psi, inside the 10 to 15 psi band vendors publish. That makes the comparison between sizes solid, because pressure drop scales as the fourth power of tube diameter and that ratio holds regardless of exact geometry. It does not make the absolute numbers exact.

Final numbers on any job go through the manufacturer's own sizing program before a quote goes out. The value of the work above is knowing what to type into it, which inputs are missing, and which ones to argue about first.