Metal product-contact parts
Hopper, cylinder, valve bodies, manifolds, pipework and nozzle surfaces should be identified by the material specified for the quoted build.
Product-contact compatibility
How to specify wetted parts and seals for a paste filling machine.
Map every component that touches the product and confirm it against normal production, cleaning chemicals, temperature, exposure time and the evidence needed for the sector.
Direct answer
What counts as a wetted part on a paste filler?
A wetted part is any surface that can contact the product during normal filling, priming, draining or foreseeable hold-up. The list can include the feed vessel connection, hopper, transfer hose, cylinder, piston seal, valves, gaskets, clamps, connectors, nozzle body and internal shut-off components. “Stainless steel machine” is therefore not a complete compatibility statement.
Elastomers and seals
Piston seals, O-rings, gaskets and valve seats can swell, soften, crack or retain product if the compound is incompatible with the product or cleaner.
Flexible product path
Hoses and liners need review for composition, pressure, bend, temperature, cleaning method and connection design.
Hidden hold-up points
Threads, cavities, dead legs, valve pockets and nozzle mechanisms can retain product even when the visible hopper and pipework look clean.
Compatibility inputs
Check the product and the cleaning regime together.
| Information | Why it matters | Evidence to retain |
|---|---|---|
| Product identity and composition | Oils, solvents, acids, alkalis, flavours, pigments and other constituents can affect metals, hoses and elastomers differently. | Approved product description and, for workplace chemicals, the current safety data sheet. |
| Normal and maximum temperature | Temperature can change product flow and accelerate material attack, swelling or softening. | Defined production and cleaning temperature ranges. |
| Exposure and hold time | Continuous exposure, overnight hold and short cleaning contact are different compatibility duties. | Production schedule, maximum hold time and drain-down plan. |
| Cleaning chemistry | Detergent, sanitiser or solvent may be more aggressive than the product itself. | Cleaner identity, concentration, temperature, contact time and rinse method. |
| Particles and abrasion | Hard or sharp inclusions can wear valve seats, seals, hoses and nozzle internals. | Largest normal particle, shape, concentration and trial observation. |
| Sector evidence | Food, cosmetic and industrial applications can require different declarations, traceability and cleaning records. | Supplier declarations and project-specific evidence listed in the approved specification. |
Food and chemical applications
Use authoritative information, then complete an application-specific assessment.
For food applications, product-contact materials need to be suitable for their intended use. The UK Government publishes an overview of food-contact materials regulations; the exact declaration or evidence required depends on the material and market.
For chemical products, a current safety data sheet helps identify hazards and handling information. The HSE explains that a safety data sheet supports, but does not replace, a risk assessment. Material compatibility and machinery risk must still be reviewed for the actual product and cleaning process.
Do not approve by colour or appearance
Ask for a controlled material schedule.
- Component name and drawing or part reference.
- Material, seal or hose grade stated by the supplier.
- Product and cleaner exposure conditions.
- Required declaration, certificate or compatibility evidence.
- Inspection and replacement criteria.
- Approved alternatives and change control.
Specification sequence
Build the wetted-path schedule before the final quotation is approved.
- Map the full path: start at the product source and finish at the nozzle outlet, including every hose, valve, seal and connector.
- Define exposure: normal product, worst normal temperature, maximum hold time, cleaner and rinse conditions.
- Review evidence: identify which supplier declarations, compatibility information or tests are required.
- Test the real application: inspect product condition, seal behaviour, cleanability and reassembly after representative exposure.
- Control replacements: retain material and part references so maintenance does not introduce an unapproved substitute.
Connect the material schedule to the cleaning and changeover guide, the risk-assessment input guide and the machine specification guide.
Buyer questions
Common questions about wetted parts and seals.
Is stainless steel alone enough to confirm product compatibility?
No. Stainless grade, finish, welds and geometry matter, and the product also contacts non-metal parts such as seals, hoses and valve seats. Confirm the complete wetted path rather than relying on the frame or hopper material.
Can a safety data sheet select the correct seal material?
A safety data sheet can identify hazards and composition information relevant to assessment, but it does not normally specify the complete machinery material solution. The equipment supplier and competent dutyholder should use it with product and cleaning conditions.
Why must the cleaning chemical be reviewed?
Cleaning exposure can be hotter, more concentrated or chemically different from normal production. A seal or hose that tolerates the product may degrade during repeated cleaning cycles.
How should material suitability be confirmed before order?
Agree the wetted-parts schedule, supplier evidence and any representative exposure or filling test in the specification. Record accepted materials and controlled alternatives in the final documentation.
Need the product path reviewed?
Send the product identity, temperature, cleaning method and required evidence with the container and fill details.
Abrasive duty
Add wear points and replacement criteria to the material schedule.
Compatibility answers whether a material can tolerate the product and cleaning regime; wear planning asks how quickly surfaces, seals and close-clearance parts may degrade under the real cycle count. Record inspection points, accepted condition and controlled replacement parts.