Verify a used acid-resistant tank’s material by connecting documents and any test results to the individual unit and its components. The label “acid-resistant” does not complete that check. If your project already specifies the material, establish whether the available evidence actually supports that requirement before buying.
Start by identifying the individual unit
An offer number identifies a product in the catalogue. If one offer covers several tanks, also ask how the individual units are distinguished. This might be a manufacturer’s number, the seller’s identifier or a clearly labelled set of photographs.
Gather the available information: a nameplate photograph, manufacturer documentation, material documents and details of component replacements. Do not assume every used tank has a complete set. Establish what exists, what it covers and what remains unknown.
Put an item of evidence and the component it covers beside each material claim. Look in the document for the grade designation, issuer and material identifier, such as a heat number where provided. Then ask how that identifier connects to a tank component through markings or fabrication records. A material document without that link leaves open whether it describes the unit you are buying.
The shell, heads and fittings may need separate checks
Prepare a simple material table. Include the shell, upper and lower heads, nozzles and metal parts in contact with the medium. Mark repaired or replaced components. Seals and other non-metallic parts need separate identification.
Offer 1083 — a 500 m³ tank illustrates why this distinction matters. Its description specifies AISI 316 for the shell and duplex steel for the upper and lower heads; it also mentions an option in AISI 316. This is information from the listing, not an independent test result. Confirm the configuration of the individual unit and the available documents before purchase.
| Component | Seller’s declaration | Available evidence | What remains to be clarified |
|---|---|---|---|
| Shell | Material designation | Component-linked document or test result | Link to the selected unit |
| Heads | Material of each head | Document or result for the identified head | Any differences from the shell |
| Nozzles and repairs | Component material and modification history | Work records or agreed testing | Parts of unknown origin |
You can send this table by email. Leave an empty field marked as unconfirmed instead of assigning it the grade of an adjacent component.
Hypothetical example: the seller has records for the original shell, but a nozzle was replaced later and its material is undocumented. The shell records do not fill that gap. Identify the replacement nozzle in your enquiry and request evidence for that component or agreement on further verification. This need not invalidate all the other documents; their scope needs to be clear.
What can PMI testing clarify?
PMI, or positive material identification, uses compositional analysis to check an alloy. One method is XRF, or X-ray fluorescence. Suitable surface conditions matter: contamination and coatings can affect the reading. Source: instrument manufacturer Evident.
If the documents leave a gap, agree with a specialist what question testing should answer. Then agree the method, measurement locations and reporting. Asking to “check the acid-resistant steel” is insufficient if purchase depends on the specific composition of particular components.
Before commissioning testing, consider agreeing that the report will include:
- the unit identifier and a photograph or sketch locating the measurement points;
- the method, date and testing provider;
- results for the measured elements and the measurement limitations;
- an assessment against the agreed material requirement.
This is a suggested scope useful to the buyer, not a universal legally required document template. A result assigned to one nozzle does not establish the material of the whole tank. Testing locations should follow from documentation gaps and project requirements.
Why might an XRF reading alone be insufficient?
Handheld XRF does not measure carbon content. Where a grade distinction depends on this element, a suitable method is needed, such as OES or carbon-capable LIBS. Thermo Fisher Scientific’s application note on stainless steel identification explains this difference in capabilities.
Request an explanation of what was actually measured and what the method cannot resolve. The grade name displayed by an instrument should not replace checking the criteria that matter to your purchase.
Material verification is one part of the assessment
Once the material is established, questions about condition and suitability remain. Composition identification is not a tightness test or an assessment of the entire unit. It also does not confirm food-contact suitability or approval for a particular duty.
Corrosion resistance depends on the combination of material and environmental conditions, including temperature and medium composition. The confirmed grade must therefore be assessed against the actual process, including cleaning. Source: Outokumpu — corrosion resistance.
How should you assess the evidence before deciding?
| Situation | Implication for the buyer |
|---|---|
| Documents are linked to the unit and cover the necessary components | Have them assessed against project requirements; also check subsequent modifications |
| Some evidence is consistent, but components remain unidentified | Identify the gap and agree how to close it before purchase |
| Markings, documents and test results conflict | Withhold acceptance of the material until the discrepancy is resolved |
The outcome should be a list of components with verified materials and a list of gaps. This helps the seller give a specific response and the person responsible for the project assess whether the purchase can proceed to its next stage.
What should you ask Agrotex before selecting a tank?
When browsing acid-resistant tanks, note the offer number and the material required by your project. Ask for identification of the unit, the declared materials of individual components, available documents and the possibility of resolving information gaps. The feasibility and organisation of additional testing must be agreed; a tank listing alone does not mean that PMI has been performed or included in the price.
Call +48 508 914 182 or email krzysztof@zbiornikiagrotex.pl. Quote the offer number and specify which material evidence is a condition of your purchase.
