Paint and coating lines have two different dosing jobs, and one flow meter rarely covers both well. For low-viscosity solvents such as toluene or xylene used in dilution and gun cleaning, a micro positive displacement meter like the Silver Instruments LC-M series measures accurately down to 0.5 ml/min. For resin, pigment paste, or additive dosing at higher viscosity, a Coriolis meter such as the SH-CMF-FE gives mass-based accuracy plus density output for recipe checks. Standard oval gear meters (LC series) cover higher flow and higher viscosity than LC-M. But they lose accuracy at the low-viscosity, low-flow end, so check the range table before specifying one for solvent service.
Two dosing jobs, not one
A coating production line usually has two distinct flow measurement points, and they call for different meter types.
- Solvent and diluent lines: thin fluids, often under 5 cP, used for viscosity adjustment, line flushing, and gun cleaning between color changes
- Resin, pigment paste, and additive lines: thicker fluids, often 100 to 2000 mPa·s, where the exact quantity added changes the final formula
Specifying one meter type for both jobs is where most selection mistakes happen. A meter sized for pigment paste will read solvent flow poorly, and a meter tuned for thin solvent will choke on paste.
Why solvent lines break oval gear accuracy at low flow
An oval gear meter measures volume by counting how many times a pair of gears rotate as fluid pushes through them. The gears seal against the housing using the fluid itself as a lubricating film. Thick fluid holds that seal well. Thin fluid, including water-like solvents, lets some volume slip past the gears without turning them. That slip shows up as a low reading.
The Silver Instruments LC series oval gear flow range table shows this clearly. At 0.3 to 0.6 mPa·s viscosity, the LC-15 (DN15) has a minimum measurable flow around 0.75 m³/h. At higher viscosity bands the same meter reads down to roughly a third of that. In practice this means an oval gear meter sized for a solvent line has to run at a higher minimum flow than the same meter would need on a heavier fluid, or the reading drifts low.
If your solvent line runs below the minimum flow for its viscosity band, oval gear is not the right technology, regardless of pipe size.
LC-M micro PD meter: the fit for low-flow solvent dosing
The Silver Instruments LC-M series is built for exactly this gap. It uses the same positive displacement principle as oval gear, but at a much smaller scale, and it lists painting industries by name among target applications, along with toluene as a compatible fluid.
Key numbers for the LC-M series: accuracy ±0.5% F.S, viscosity range up to 2000 mPa·s, flow range from 0.5 ml/min on the smallest model (LC-M2) up to 100 L/min on the largest (LC-M25). Standard pressure rating is 5 MPa (725 PSI), with an Exd explosion-proof option available. Body material is 316L stainless steel or aluminum, gears in 316L, PPS, or aluminum depending on model. Output is a Hall effect pulse signal, NPN or PNP.
This is the meter to specify on a diluent metering skid, a gun cleaning solvent line, or any point where the fluid is thin and the flow is small. It is not the meter for a bulk solvent transfer line running at higher flow, where a standard LC oval gear or a turbine meter fits better once flow is above the low-viscosity minimum. For full dimensional drawings and the complete model code table, see our ink and paint flow meter product page.
Coriolis for resin, pigment paste, and additive dosing
When the dosing point needs mass accuracy rather than volume, or when the operator wants density fed back to confirm the batch recipe, Coriolis is the better technology regardless of viscosity.
The Silver Instruments SH-CMF-FE micro Coriolis line covers 40 g/h to 1000 kg/h with ±0.25% F.S accuracy on liquid, simultaneous density and temperature output, and an integrated PID controller for closed loop dosing. For larger resin or paste lines, the standard SH-CMF series scales up to DN300, with flow accuracy down to ±0.1% and wetted parts in 316L stainless steel or hastelloy C for aggressive solvents.
Coriolis does not care about viscosity the way oval gear does, so a pigment paste that would clog or slip past oval gear internals passes through a Coriolis tube without a separate calibration step. The trade-off is cost, and a straightforward toluene dilution line rarely justifies it.
Color change and gun cleaning: what actually gets measured
We do not have a documented, named installation to cite here, so this is a general pattern rather than a specific project. A common inquiry shape looks like this: a coating line tracks solvent consumption during color change flushing to control cost and emissions reporting, and the existing meter either under-reads at low flow or cannot survive repeated exposure to ketone or ester-based cleaning solvents.
Check wetted material compatibility against the actual solvent blend, not just a general “solvent resistant” claim, before ordering. Send us the solvent composition and we will confirm material fit.
Why not electromagnetic or turbine meters for solvent lines
Electromagnetic flow meters need a conductive fluid to work at all, typically above 5 µS/cm. Toluene and xylene are practically non-conductive, and acetone sits far below that threshold too. Put any of these through a magnetic meter and you get no signal, not just a bad reading. This rules out magnetic flow meters for most solvent dosing lines in a coating plant, regardless of flow rate or pipe size.
Turbine meters are harder to rule out. The Silver Instruments SLW series is rated for clean, low-viscosity, non-corrosive liquid with kinematic viscosity under 5×10⁻⁶ m²/s. Most solvents fall under that limit, so viscosity itself is not the blocker.
Two practical problems come up instead. First, a turbine only measures volume, so any application that needs mass-based dosing accuracy or density feedback still points to Coriolis. Second, if the working viscosity or temperature drifts from the calibration point, the SLW series needs a wet calibration in the actual fluid before use, which adds a step most solvent dosing skids do not budget for. A turbine meter still works well for bulk solvent transfer or tank filling where volume alone is the answer and flow stays fairly steady.
That leaves three real options for solvent and paste dosing: LC-M, LC oval gear, and Coriolis. This article sticks to those three.
A worked sizing example
Take a DN15 toluene flushing line running at an expected 30 L/min, roughly 1.8 m³/h. Toluene at room temperature sits around 0.6 mPa·s, which lands in the lowest viscosity band on the LC oval gear range table, 0.3 to 0.6 mPa·s.
The Silver Instruments LC-15 at that viscosity band has a range of 0.75 to 1.5 m³/h. The line’s expected flow of 1.8 m³/h sits above that range, so an LC-15 oval gear meter would actually be oversized on the high side for steady flushing flow, and undersized if flow ever drops toward the low end of a batch cycle. Step up to the LC-20 model, rated 1.5 to 3 m³/h at the same viscosity band, and 1.8 m³/h sits comfortably inside range with margin on both ends.
Now take the same toluene, but on a smaller gun cleaning line running at 400 ml/min, about 0.024 m³/h. No oval gear model in the LC series reads that low at 0.3 to 0.6 mPa·s viscosity, since even the smallest LC-10II model starts at 0.08 m³/h in that band. This is exactly the gap the LC-M series fills. The LC-M9 model, rated 6 to 600 L/h (0.006 to 0.6 m³/h), covers 400 ml/min with room on both sides.
The rule holds across the board: check expected flow against the datasheet range for the actual working viscosity, not just the meter’s nominal pipe size. A DN15 line does not automatically mean an LC-15 meter once the fluid is thin and the flow is small.
Flow meter or flow controller: which one the dosing point needs
Both the LC-M and SH-CMF-FE lines come in a plain meter version and a controller version, and the choice depends on what happens after the reading.
A meter version reports flow and totalized volume, and something else in the system, a PLC or a manual valve, decides how much fluid actually goes through. This fits a manual dilution station or a line where an operator watches the total and shuts a valve at the target quantity.
A controller version closes the loop itself. The Silver Instruments SH-CMF-FE controller variant integrates a PID function and a batch function, so it reads the mass flow and adjusts its own regulating element to hit a set point without a separate PLC loop. The LC-M series controller variant works the same way on the positive displacement side, with a turndown ratio of 50:1 against 100:1 on the plain meter version, since the added valve and control electronics narrow the usable range somewhat.
For automatic tinting or resin dosing where the recipe has to hit a target quantity unattended, a controller version is worth the extra cost. For a solvent flushing line where an operator or a simple timer handles the shutoff, a plain meter version does the job at a lower price point.
Turndown ratio and batch size accuracy
Turndown ratio matters more in dosing than in continuous flow measurement. A coating plant often runs the same line for big production batches and small color-matching test batches on the same equipment.
A meter with 100:1 turndown, like the LC-M series at its standard rating, holds its stated accuracy from full scale down to 1% of full scale. Below that point, accuracy degrades. If a DN25 LC-M25 model rated for 0.5 to 100 L/min is used for a 200 ml test batch, the flow rate needed to stay inside range would be a fraction of a liter per minute, well under the meter’s low end, and the reading becomes unreliable.
The fix is not a more expensive meter. It is the right size meter for the actual batch range. A smaller LC-M model sized for the test batch volume keeps that job accurate. Keep it separate from the production-scale meter.
Side by side comparison
| Model | Flow range | Viscosity | Accuracy | Best fit |
| LC-M series | 0.5 ml/min – 100 L/min | up to 2000 mPa·s | ±0.5% F.S | Low-flow solvent, dilution, gun cleaning |
| LC oval gear | Model dependent, DN10–DN200 | up to 2000 mPa·s | ±0.5% / ±0.2% | Larger solvent or oil lines above the low-viscosity minimum flow |
| SH-CMF-FE | 40 g/h – 1000 kg/h | not viscosity limited | ±0.25% F.S (liquid) | Resin, paste, additive dosing with density feedback |
| SH-CMF standard | up to DN300 | not viscosity limited | ±0.1% – ±0.5% | Larger resin or paste transfer lines |
Frequently asked questions
These five questions reflect what shows up repeatedly across ranking articles on this topic. A web search cannot pull Google’s own People Also Ask panel directly, so this list is a distilled substitute rather than a verified export of PAA data.
What to send us for a fast quote
Send us these details and we can tell you within a day whether LC-M, LC oval gear, or SH-CMF-FE fits your dosing line, and quote accordingly:
- Fluid type and viscosity (mPa·s or cP)
- Expected flow range (ml/min, L/h, or kg/h)
- Line pressure (MPa or bar) and process temperature (°C)
- Wetted material preference or known incompatibilities
- Hazardous area classification, if the meter sits in a paint booth or solvent room
