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How to Spec Aircraft Fluid-Zone Seals: What to Send H-O for a Quote
Fluid-zone seals attract underspecified quote requests because the gasket looks like the whole story: a flange ring, a face seal, a strip of tape. What the quote actually prices is the duty behind it, every fluid the joint can see, the phosphate-ester answer, the service temperature, and the designation call-outs that are the contract. This is the ten-item checklist the H-O applications team works from, what engineering does with each item, and what comes back.
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The ten things to send, and what each decides
Fluid-zone seals attract underspecified RFQs because the gasket looks like the whole story: a flange ring, a face seal, a strip of tape. What the quote actually prices is the duty behind it: every fluid the joint can see, the phosphate-ester answer, the service temperature, the construction, and the designation call-outs that are the contract.
This is the ten-item checklist the H-O applications team works from for fuel, hydraulic, gearbox, de-icing, and chemical-zone seals, drawn from the parent application page's own selection factors, plus what engineering does with each item and what comes back.
| Send this | What it decides |
|---|---|
| 1. Every fluid the joint can see | The family, by the worst fluid. List them all, including the cross-contamination leak that has not happened yet, and spec to the most aggressive. |
| 2. The phosphate-ester answer | Which world you are in. Phosphate-ester present means EPDM or butyl and rules out the fuel-zone fluorocarbons; absent means the FKM, nitrile, and HNBR world. |
| 3. Service temperature, highest credible | The governing case for ASTM D471 immersion behavior. Compatibility read at the bench temperature is optimistic at a hot joint. |
| 4. Construction: sponge, solid, or sheet | Follows the closure. Sponge for conformable low-force joints, solid for bolted faces, ePTFE sheet where chemistry defeats every elastomer. |
| 5. Designation call-outs | The contract. AMS 3215, AMS 3216, AMS 3323, AMS7257, MIL-R-83248, or MIL-R-83285 on the print are honored verbatim, with the TDS reference as screening evidence. |
| 6. Durometer and compression target | Hardness per ASTM D2240 and set per ASTM D395 to the joint's bolt load and gland. |
| 7. Oxygen-system interface flag | The special case. An oxygen interface has its own cleanliness and material rules and is called out explicitly, never assumed. |
| 8. Cross-contamination scenario | Where two systems share a space, the seal is chosen for both fluids; name the credible leak so the worst-fluid rule covers it. |
| 9. Geometry and presentation: DXF, STEP, or PDF | Flange or face profile, bolt pattern, thickness, and kiss-cut-on-liner format, plus bolt-load practice for ePTFE. |
| 10. Prototype and production volumes | Converting method and price structure. Every part is made to order; prototype quantities through production runs are equally accepted, and MOQ varies by material and part. |
What engineering does with the list
Items 1 and 2 pick the world: FKM, nitrile, or HNBR for fuel and oil, or EPDM and butyl if item 2 says phosphate-ester. Item 3 reads the immersion behavior at the service temperature, and item 4 picks the construction, with fluorosilicone sponge for conformable fuel joints or an inert ePTFE sheet for the joints chemistry cannot solve. Item 5 matches the designation, stepping to FFKM for mixed chemistry.
Items 6 through 8 set the durometer, the oxygen flag, and the cross-contamination case; items 9 and 10 become the converting plan and the price structure.
What happens after you send it
- Drawing review. Engineering reviews the joint against the vendor TDS and the program fluid spec: the fluid list, the phosphate-ester answer, the service temperature, the construction, and the designation call-outs.
- Material direction and quote. A family and grade direction with the TDS, the converted format (die-cut flange ring, face seal, kiss-cut on liner, ePTFE sheet to bolt-load practice), and pricing at your quantities.
- Samples. Typically 3 to 5 business days for common die-cut configurations on materials we keep on hand.
- Production. Standard runs ship about two weeks after drawing approval, including kiss-cut-on-liner configurations; expedited service is available. Ongoing parts run with material traceability and lot-code TDS records.
Documentation available on request: material technical data sheet, certificate of conformance, and lot traceability, under our ISO 9001:2015 certified quality management system. H-O is a die-cut converter, not a raw-material producer: we do not manufacture the raw elastomer or ePTFE, we do not independently certify fluid compatibility, and the fluid-spec qualification and oxygen-system clean handling requirements belong to the OEM.
The mistakes this checklist prevents
| Spec mistake | What it causes | Checklist item that catches it |
|---|---|---|
| FKM carried into a phosphate-ester bay | Fluorocarbon degrades in the wrong fluid | Item 2, phosphate-ester answer |
| EPDM in a bay a fuel leak can reach | EPDM destroyed by fuel | Items 1 and 8, worst-fluid rule |
| Compatibility read at the bench | Seal ages out of its window hot | Item 3, service temperature |
| Silicone in a wet fuel zone | Swelling, lost seal | Item 1, fluid owns the joint |
| ePTFE treated like an elastomer | No recovery, joint loosens | Items 4 and 9, bolt-load practice |
| Oxygen interface assumed, not flagged | Wrong material and cleanliness | Item 7, oxygen flag |
Frequently asked questions
What information do I need to send H-O to quote a fluid-zone seal?
Ten items turn the gasket into a quotable drawing: every fluid the joint can see, the phosphate-ester answer, the highest credible service temperature, the construction (sponge, solid, or sheet), the designation call-outs, the durometer and compression target, any oxygen-system flag, the cross-contamination scenario, the geometry and presentation as DXF, STEP, or PDF, and the volumes. Send what you have; engineering frames the rest, including reading the immersion data at your temperature, and flags any assumption.
What does an AMS or MIL designation on the drawing actually require?
It is the contract: a specific qualified material with defined properties, not a generic family. An AMS 3216 or MIL-R-83248 FKM, an AMS 3215 nitrile, an AMS 3323 fluorosilicone, an AMS7257 FFKM, or a MIL-R-83285 silicone names a material whose matching TDS reference is the screening evidence.
H-O honors the designation verbatim and cross-references it against the lines we convert, with the TDS reference confirming the alignment, verified against the program fluid spec before quoting. The qualification to the designation belongs to the material maker and the OEM.
How should I spec gaskets for oxygen system interfaces?
Flag the oxygen interface explicitly on the drawing; never let it be assumed. Oxygen-system interfaces carry their own cleanliness and material rules that differ from ordinary fuel or hydraulic joints, and the special-case handling has to be called out so the material selection and the cleaning and packaging are done to the right requirement. H-O converts to the program's oxygen-service requirements when they are stated; the determination of those requirements and the clean-handling specification belong to the OEM and are not assumed by the converter.
Can H-O cut FKM and EPDM gaskets from my drawing, and in what thicknesses?
Yes. H-O die-cuts and kiss-cuts FKM, nitrile, HNBR, fluorosilicone, EPDM, butyl, FFKM, and ePTFE sheet to your drawing in the thickness and durometer the joint needs, as flange rings, face seals, and gaskets, with material traceability and lot-code TDS records. The available thickness and durometer range depends on the stock each material maker offers, confirmed at quote against the current TDS. Send the geometry and the fluid and temperature duty, and engineering recommends a grade and converts it; the compatibility finding stays with the OEM.
What lead time should I expect for fluid-zone gasket samples and production?
Every fluid-zone seal is made to order, including samples. Samples typically ship in 3 to 5 business days for common die-cut configurations on materials we keep on hand; standard production runs ship about two weeks after drawing approval, including kiss-cut-on-liner configurations; expedited service is available when timing is critical. MOQ varies by material and part, and prototype quantities through production runs are equally accepted.
Send the checklist, get a fluid-zone seal quote
Attach the geometry and as many of the ten items as you have. If something is unknown, say so; the review proceeds with the assumption flagged.
Samples typically ship in 3 to 5 business days for common die-cut configurations on materials we keep on hand; standard production runs about two weeks after drawing approval; expedited service is available. MOQ varies by material and part.
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Related reading
Request a quote for your fuel, hydraulic & chemical-zone sealing part
Send H-O your drawing or describe the part—engineering reviews every RFQ and converts samples on your geometry.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
References
- ASTM D471 (rubber property change in liquids, read at the service temperature); ASTM D2240 (durometer); ASTM D395 (compression set).
- AMS 3215 (nitrile), AMS 3216 (FKM), AMS 3323 (fluorosilicone), AMS7257 (FFKM), by designation.
- MIL-R-83248 (FKM) and MIL-R-83285 (silicone) families, by designation; the program fluid specification governs compatibility.
- Manufacturer technical data sheets for the FKM, nitrile, HNBR, fluorosilicone, EPDM, butyl, FFKM, and ePTFE grades named on the parent application page.
This article summarizes fluid-zone sealing material-selection principles for aircraft fuel, hydraulic, and chemical systems using the families and published test methods cited on the parent application page. Comparisons are qualitative; per-grade values and immersion behavior quoted are maker-TDS figures and must be confirmed on the manufacturer's current technical data sheet and against the program's fluid specification at your temperature. Standards (ASTM, AMS, MIL) are cited by designation for context, not as a claim of qualification.
H-O is a precision die-cut converter, not a raw-material producer, and does not certify fluid compatibility, qualify seals to the fluid specs, or hold aerospace approvals; those belong to the OEM and its test houses.