The short answer
Compare differential pressure and flow at similar fluid conditions and against cumulative volume, not elapsed time alone. A bag that blocks late in a batch may be receiving concentrated tank-bottom solids; changing the micron label before checking the feed can hide the actual problem.
Define what failed before changing the bag
Write down whether the batch stopped because flow fell, differential pressure reached the approved change point, or filtrate failed its quality limit. These are different endpoints. Record upstream and downstream pressure together, actual flow, temperature, bag identity and processed volume. Use the established operating limits for the complete assembly; a pump discharge reading alone is not a measurement of pressure loss across the filter.
Build a batch timeline that exposes feed changes
Take comparable readings at startup, during stable transfer and near the end, with extra observations around agitation changes, ingredient additions or tank switching. Collect representative feed samples through approved sampling points and use the same solids method throughout. A settled tank can send a concentrated final portion even when its average solids result looks ordinary. Note whether the sample represents circulating liquid, a surface layer or the actual filter feed.
For a once-through transfer, feed concentration multiplied by transferred volume estimates incoming solids mass only when units and sampling are consistent. Sum separate intervals when concentration varies. This is not retained dirt capacity: some solids pass, settle elsewhere or remain in the vessel. Do not repeatedly count the same material in a recirculating loop.
Use a hypothesis matrix, not a single pressure alarm
The patterns below suggest checks, not proven diagnoses. Compare runs at similar flow and temperature before attributing a difference to the bag.
| Observed pattern | Working hypothesis | Discriminating check |
|---|---|---|
| High pressure loss from the first stable reading | Viscosity, wetting or installation issue | Compare temperature and clean-start conditions with an accepted run |
| Differential pressure rises gradually at comparable flow | Accumulating retained solids | Compare rise against volume and interval feed solids |
| Differential pressure rises sharply near tank emptying | Concentrated solids slug | Compare end-of-batch feed with earlier samples |
| Differential pressure falls unexpectedly while filtrate worsens | Bypass, damage or changed flow | Hold affected output and investigate the assembly safely |
Run one controlled comparison
Keep the final filtrate requirement fixed. Compare a representative batch with a documented baseline, changing only one justified variable, such as an approved feed-management practice. Log bag changes and total accepted output, not just the longest individual run. If feed variation cannot be controlled, group results by solids band and temperature instead of averaging unlike batches. A lower pressure trend is not a success if particles now pass through.
Record the replacement reason on every removed bag. Separate a scheduled preventive change from a quality failure or a reached pressure limit. Otherwise, a shortened operating shift may incorrectly appear to demonstrate lower dirt capacity.
Turn the diagnosis into a purchasing request
Send the supplier the process timeline, representative feed description, filtrate criterion and safe operating envelope. Ask for a proposal addressing the observed load pattern and for test conditions behind any capacity statement. IFM identifies several variables affecting flow; Eaton's PROGAF data is a named example with specified test conditions. Neither provides a universal batch-life prediction. Request a trial acceptance plan that records both quality and throughput before making repeat-order commitments.
Your review checklist
- Batch identity, feed tank and agitation history recorded.
- Pressure taps, instrument units and calibration status checked.
- Flow, temperature and cumulative volume logged together.
- Feed sampling locations and solids method documented.
- Bag-change reasons and affected filtrate segregated in records.
- Trial acceptance criterion and authorized stop conditions agreed.
Limits of this guidance
General diagnostic guidance, not a JINLV capacity guarantee. Trained operators must follow approved isolation, depressurization and chemical-handling procedures; engineering approval is required before changing operating limits or process configuration.
Questions buyers ask
Does a faster differential-pressure rise prove the bag is defective?
No. Higher solids concentration, colder liquid or increased flow can change the trend. Investigate a defect when comparable operating evidence and inspection support it, not from elapsed time alone.
Should I install a coarser bag to finish the batch?
Only after confirming that the resulting filtrate still meets the approved requirement. A coarser label is not a substitute for investigating concentrated feed or an unsuitable filtration arrangement.
Technical references
References support general principles or the named supplier's own products; they do not certify or validate a JINLV configuration.
- Frequently Asked Questions — Industrial Filter Manufacturing
- PROGAF Filter Bag Range — US Technical Data Sheet
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.