The short answer
Treat an old sample as evidence, not as the finished specification for custom liquid filter bags. A controlled drawing must separate observed features from confirmed requirements, identify the mating housing and basket, and define how the first replacement will be accepted.
Start with the sample's history, not a promise to copy it
A used bag may have stretched, shrunk, collected deposits or been repaired. Even an unused bag may belong to an obsolete order. Give each sample an identifier and record whether it is new, used, cleaned or damaged, together with its packaging, previous part number and known service. Photograph the ring, body, seam and bottom before any destructive examination. Do not send contaminated samples without an agreed safe-handling arrangement.
Keep the original available as reference. If only one sample exists, agree which investigations may consume it. The practical objective is to reproduce the required function, not every wrinkle or discolored patch.
Create an evidence ledger beside the drawing
For every important feature, record its source and status: observed, supplier-declared, independently checked or unresolved. Fabric color is an observation; polymer identity, filtration performance and temperature suitability need separate evidence. Pentair's ordering sheet illustrates that size, media, ring and construction are separate selections, not one interchangeable label.
A drawing should have a part number, revision, units, referenced documents and a change description. Identify who may resolve open requirements. Avoid a note such as 'same as sample' as the only acceptance rule: it leaves the inspector guessing which differences matter.
Decide what the old sample can actually establish
Use this decision matrix during the drawing review. It is a proposed purchasing worksheet, not a claim that any particular supplier has completed the checks.
| Sample evidence | What it can support | What must remain open |
|---|---|---|
| Visible ring profile and seam route | A reference sketch and comparison photographs | Material grade, allowable distortion and housing compatibility |
| Used body length | A recorded observation with stated measurement references | Original manufactured length and allowable tolerance |
| Old label showing a micron value | The previous ordering designation | Test method and retention performance of the replacement |
| Known successful installation | A candidate housing and basket combination | Suitability after any change in liquid, temperature or operating cycle |
Define acceptance before asking for a production quantity
Mark the drawing's functional interfaces separately from cosmetic features. The ring-to-seat relationship, supported body envelope and bottom arrangement deserve explicit review. Agree tolerances and measurement conditions with the parties responsible for design and inspection; do not derive tolerances from a single worn article. NIST's metrology guidance distinguishes a measured result from the instrument used to obtain it.
For a hypothetical project, a sample may have an intact ring but a stretched bottom. The sensible release path is to retain the ring observation, resolve body geometry against the identified basket, and mark the old length as non-controlling. Ask the supplier to return a first-article report against the proposed drawing, recording deviations individually.
Close the loop from prototype to purchasing record
Separate dimensional conformity, safe installation and filtration-duty acceptance. A prototype fitting the basket does not demonstrate particle retention or chemical durability. Define a supervised trial with the process owner, including the relevant operating conditions, observation points and stop criteria. Housing access and operation belong to trained personnel using the approved site procedure.
When a change is accepted, update the drawing and order reference together. Retain a clearly identified approved reference sample where useful, but make the controlled document the purchasing authority. Quarantine rejected versions so an attractive prototype cannot accidentally become the repeat-order master.
Your review checklist
- Assign sample ID, condition and safe-handling status.
- Identify housing, basket and previous order references.
- List confirmed features and unresolved assumptions separately.
- Set drawing revision, units, references and agreed tolerances.
- Define dimensional, installation and duty acceptance records.
- Link the accepted revision to the purchase order and retained sample.
Limits of this guidance
General procurement guidance, not a dimensional reverse-engineering procedure or engineering approval. Material identity, tolerances, filtration performance and compatibility remain order-specific; uncertain functional features require review by the responsible technical parties before release.
Questions buyers ask
Can a supplier quote before every uncertainty is closed?
Yes, as a conditional proposal listing assumptions, exclusions and the evidence needed for release. A quotation is not proof that the reverse-engineered design is acceptable.
Should the replacement look exactly like the old bag?
Only where appearance is a defined requirement. A change in handle or seam position may matter functionally, while discoloration may not; classify each difference rather than accepting or rejecting by resemblance alone.
Technical references
References support general principles or the named supplier's own products; they do not certify or validate a JINLV configuration.
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.