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Polymer Mass Flow Meter for High-Viscosity Lines: Direct Mass Measurement Without Drift
Quick Answer: A Coriolis mass flow meter is the most reliable tool for polymer process lines where viscosity exceeds 5,000 cP. It measures mass directly, ignores density shifts, and has no moving parts in the flow stream. Silver Instruments supplies SLG-series Coriolis meters that handle polyols, hot melts, silicone oils, and reactor feed up to 50,000 cP without recalibration.
Polymer plants deal with fluids that behave nothing like water. A melt at 230 °C can be 100,000 times thicker than a solvent stream at the same temperature. Gear pumps, extruders, and reactor feed systems all need a mass balance. A volumetric meter such as oval gear or turbine will drift with temperature, backpressure, and viscosity change. A Coriolis meter, by design, sidesteps all of that.
Why a Coriolis Meter Excels with High-Viscosity Polymers
The measuring tubes in a Coriolis mass flow meter are excited at their natural frequency. As polymer flows through the bent or straight tubes, the twist created is directly proportional to mass flow. Viscosity does not appear in the mass flow equation. So a change from 8,000 cP to 35,000 cP on a polyol premix line does nothing to the measurement. You still get a live reading in kg/h, with no need to recharacterise the meter.
Positive displacement meters can handle thick fluids but the mechanical wear from abrasive fillers in specialty polymers kills gear sets fast. Oval gear meters in a TiO2-loaded polyester line in Thailand were failing every four months. The plant switched to a DN25 SLG Coriolis meter and has not touched it for 14 months. The signal is 4-20 mA HART straight into the PLC, mass flow, density, and temperature all from one device.
Real Data from the Field: What Operators Actually See
Here is the thing. Polymer lines rarely run at steady state. Start-up and grade changes push the flow profile all over the map. A SLG meter with a 0.1% rate accuracy and zero stability of 0.02 kg/h catches the real mass movement even when the pipe is half empty at shut-down. No low-flow cut-off masking the true signal.
A polyurethane manufacturer in Vietnam needed to control isocyanate and polyol feed to a mix head within 0.5% of batch ratio. They used two DN10 SLG meters with PTFE lining and Hastelloy C-22 wetted parts. The density output flagged an off-spec polyol shipment before it hit the reactor, saving a five-figure USD batch. Most engineers skip the lab sample now and let the meter fingerprint the fluid by density.
SLG-Series Configuration for Sticky, Hot, and Hazardous Lines
Silver Instruments builds each Coriolis meter for the polymer line it will live on. The common build for a hot melt line includes a heated jacket or steam trace on the sensor body to keep the melt above its softening point. Process connection is usually a flanged or Tri-Clamp style, DN15 up to DN100, with PT100 temperature compensation embedded. For low-flow catalyst injection, we supply a DN06 meter body that resolves 0.15 kg/h, plenty enough for tin catalyst dosing in silicone polymerisation.
The transmitter can be remote-mounted, 50 metres from the sensor, which is critical when the line runs inside a Class I Division 1 area. For areas that require ATEX Zone 1 or IECEx, we certify the entire assembly, not just the electronics. A EPDM or FKM O-ring selection is standard, with Kalrez for aggressive monomers.
Typical specifications that engineers ask for: fl
Installation Advice That Eliminates Start-Up Surprises
High-viscosity lines do not forgive standard installation rules. Mount the sensor in a vertical pipe with flow going upward. This keeps the tubes full at zero flow and prevents solids from settling in the bends. Provide insulation on the pipe and sensor jacket, but never insulate the transmitter neck. For batch reactors, install a check valve downstream of the meter so no reverse flow spikes corrupt the totaliser.
A polymer plant in Malaysia ignored the vertical-up rule on a DMTA melt line. With the meter horizontal, the gel layer that formed during weekends airlocked the tubes every Monday. They rotated the meter 90 degrees, added a steam trace, and the Monday error peak disappeared. Zero shift went from 2 kg/h to 0.1 kg/h.
Get a Specific Quote for Your Polymer Stream
Every polymer is different: PE melt, nylon 6,6 prepolymer, silicone resin, or an ester base stock each stresses a meter in a distinct way. Send us your pipe size (DN), fluid type, normal and max viscosity at operating temperature, flow range in kg/h, process temperature, and line pressure. Our engineers will match a SLG sensor and transmitter, certify it for your hazardous area if needed, and deliver a complete data pack. We are Silver Automation Instruments, direct manufacturer for Coriolis mass flow meters, shipping to chemical, adhesive, and plastics plants in Southeast Asia, the Middle East, Latin America, and Africa.
FAQ: 5 Key Questions on Polymer Mass Flow Meters
What is the highest viscosity a Coriolis meter can handle? The SLG series operates reliably up to 50,000 cP. Above that, we reduce the flow velocity to keep pressure drop within limits. Some meters with straight tubes can pass 100,000 cP at very low flow, but for most polymer processes 50,000 cP is a safe ceiling.
Does the meter need recalibration when switching polymer grades? No. Because a Coriolis meter measures mass directly, a viscosity or density change does not alter the calibration. The density output will show the new grade instantly, but the mass flow stays accurate.
Can I use a magnetic flow meter for conductive polymer solutions? A magmeter works only if the fluid is electrically conductive above about 5 µS/cm. Many polymer melts and solvents are non-conductive. Even when conductive, a magmeter reads volumetric flow, not mass, so you still need temperature and density compensation. Coriolis gives mass and density in one step.
How do you clean the meter after a polymer block? Flush with a compatible solvent at temperature, often DMF or NMP, while the meter is still hot. The SLG sensor has no dead legs where gel can accumulate. For solvent-free cleaning, we recommend a hot oil flush through a bypass loop.
What delivery time and support can I expect? Standard SLG meters from DN10 to DN40 ship within 2 weeks. Custom alloys or ATEX/IECEx certification adds 2 extra weeks. We provide remote commissioning over video call, so your local E&I team handles the mechanical installation and we tune the parameters live.
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