The short answer
A water-based flow reference does not establish throughput for a viscous process liquid. Obtain the test conditions behind the reference, characterize the actual fluid and measure pressure loss and acceptable output across the relevant operating range.
Read the conditions behind the number
Before comparing quoted flow rates, identify the test liquid, temperature, viscosity, media grade and whether the stated loss includes the housing. Ask whether the value describes clean media, a recommended working point or an upper reference. Eaton's PROGAF sheet explicitly identifies water-based conditions for its own data. That is a useful documentation example, not a correction factor for another bag or a promise about a resin, syrup or oil.
Describe viscosity as an operating condition
Report the viscosity unit and measurement temperature. Dynamic viscosity in mPa·s and kinematic viscosity in mm²/s are different quantities; converting between them requires density at compatible conditions. For a shear-dependent liquid, report the measurement method and relevant shear conditions instead of presenting one number as a universal property. Note aging, concentration and mixing history if these change the liquid during a batch.
Define the coldest approved startup and normal transfer conditions. A warm sample taken after several hours may not represent the first liquid entering the filter. Temperature changes may also affect chemistry and product quality, so heating is not an automatic remedy for poor flow. Obtain approval for any proposed temperature adjustment before testing it.
Separate clean resistance from loading and system limits
Use simultaneous flow, temperature and pressure readings. The table offers a way to sort evidence before requesting a different bag.
| Observation | Question to resolve | Useful evidence |
|---|---|---|
| Low flow and high initial filter pressure loss | Is clean resistance excessive for this fluid? | Actual viscosity and matched clean-start comparison |
| Low flow but little filter pressure loss | Is the restriction elsewhere? | Pump, valve and piping review within approved procedures |
| Flow declines as filter pressure loss rises | Is solids accumulation limiting the run? | Volume, solids and pressure timeline |
| Flow changes with temperature or mixing | Is fluid behavior changing? | Time-matched temperature and viscosity measurements |
Design a representative trial
Choose a trial liquid and batch history that represent production, not an easier substitute without justification. Keep the filtrate requirement unchanged and record accepted volume, process time, changeouts and end conditions. Repeat at the difficult but approved operating condition. Define a minimum usable flow and quality requirement before the trial, with limits approved by the responsible engineering team. A successful warm-water check confirms only that check, not production suitability.
For an unchanged clean porous structure and a Newtonian liquid in a low-velocity regime where Darcy's law applies, pressure loss is approximately proportional to viscosity and flow. Treat this as a screening relationship, not a validated sizing rule. Housing losses, wetting, non-Newtonian behavior and a growing cake can invalidate a simple scaling exercise.
Ask for a bounded proposal
Give the supplier the fluid data, required batch completion time and measured clean and loaded behavior. Request the assumptions behind any projected flow and an explanation of how they will be verified. IFM identifies viscosity among process-dependent flow variables; it does not supply a universal conversion. Compare proposals against the same duty envelope. If no supporting test exists, describe the proposed operating point as a trial target, not a guaranteed production capacity.
Your review checklist
- Viscosity quantity, units, method and temperature stated.
- Cold-start and normal process conditions distinguished.
- Pressure measurement boundary and housing contribution identified.
- Required accepted volume and batch time defined.
- Filtrate quality and minimum useful flow agreed before testing.
- Pump constraints and engineering-approved stop limits recorded.
Limits of this guidance
General interpretation guidance, not a JINLV viscosity correction chart. Pressure, temperature, pump and process modifications require engineering approval; trained operators must follow the approved operating and chemical-safety procedures.
Questions buyers ask
Can I divide a water flow rating by the viscosity ratio?
Not as a general selection rule. That shortcut assumes unchanged conditions that may not apply. Use a supplier-supported model within its limits and verify the proposed duty with representative fluid.
Would a larger pump solve slow filtration?
Not necessarily. It may increase pressure or move the system beyond approved limits without resolving loading or retention problems. Review the pump-system operating point and filter assembly together before making changes.
Technical references
References support general principles or the named supplier's own products; they do not certify or validate a JINLV configuration.
- PROGAF Filter Bag Range — US Technical Data Sheet
- Frequently Asked Questions — Industrial Filter Manufacturing
- Modeling Darcian and Non-Darcian Flow in Porous Media
AI-assisted technical synthesis of the references below, with editorial checks. This is general procurement guidance, not an independently signed engineering review or a product validation report.
English is the indexing version. Chinese and Indonesian are reading translations of the same article.