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How to Spec an Oil or Chemical-Service Gasket: What to Send H-O for a Quote
A gasket RFQ that says "nitrile, 1/8 inch, see DXF" reads like a finished spec, but it is a stack of unstated assumptions: that the fluid is petroleum mineral oil, that the joint runs near ambient, that the flange can seat a solid elastomer, and that no listing applies. When any of those assumptions is wrong, the revision loop starts after tooling instead of before it.
This article is the checklist the H-O applications team works from for oil-filled and chemical-exposed equipment gaskets: the six things to send, why each one changes the answer, how to dimension the gasket on the drawing, and what happens after you hit send. It condenses the selection logic of the full application page into a quoting workflow.
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The six things to send, and what each decides
| Send this | What it decides |
|---|---|
| 1. The fluid, by name (with concentration or blend percentage) | The chemistry track. Petroleum mineral oil, ester fluids, diesel, bio-diesel blends (B20 vs. B100), glycols, acids, and chloraminated potable water each map to a different family, verified against ASTM D471 immersion data on the TDS, never assumed from the family name. |
| 2. Continuous temperature at the gasket | Whether the fluid's first answer survives the heat. Sustained elevated temperature moves NBR to HNBR, then to FKM (the 75 durometer FKM TDS lists -20°F to +400°F). State the temperature at the joint, not the room ambient. |
| 3. Flange detail (bolt pattern, available seating stress, compressed thickness) | The construction: cork-elastomer for modest bolt loads and wavy flanges (compressibility and recovery per ASTM F36), solid sheet for flat stiff flanges, cloth-inserted nitrile for large heavily bolted covers, sponge or foam where seating stress is scarce. |
| 4. Any compliance designation, verbatim | Whether the material name is really a listing: NSF/ANSI 61 (with NSF/ANSI 372), FDA 21 CFR 177.2600, AMS 3215, AMS 3216, MIL-R-83248, AMS7257. The designation belongs on the drawing exactly as written; the paperwork travels with the lot. |
| 5. Quantity (prototype and production) | Converting method and price structure. Prototype counts through full production runs are equally accepted; the cutting method (flatbed die, waterjet for thick cork and elastomer) may differ. |
| 6. The material family, or "recommend" | Where the review starts. A named grade gets verified against items 1 to 4; "recommend" is a valid callout and routes the joint through the selection sequence. |
How to dimension the gasket on the drawing
Three drawing habits prevent most fluid-seal rework. First, dimension the compressed state: state the compressed thickness (or the compression percentage) alongside the free thickness, because the seal works at its installed height, not its catalog gauge.
Second, draw the flange honestly: bolt pattern, hole sizes, and any known waviness or weld distortion, since that detail decides between cork-elastomer sheet, solid elastomer, and cloth-inserted reinforcement. Third, write the fluid and the designation on the face of the drawing, not only in the email: "transformer mineral oil, continuous 90°C at gasket" or "potable water, NSF/ANSI 61" survives every handoff the email does not.
For chemical interfaces, add the cleaning chemistry too; wash-down fluids have ended more gaskets than the process fluid they were specified for.
What engineering does with the list
The review runs the parent page's sequence. Item 1 picks the chemistry track: the transformer-oil NBR grade or cork for mineral-oil covers, the bio-diesel grade or AMS 3215 nitrile for fuels, Gore GR ePTFE sheet or FFKM for aggressive chemistry, the 576 NSF EPDM for potable water. Item 2 checks the heat path (D573 aging; HNBR and FKM as the steps).
Item 3 sizes the construction against the flange, with epichlorohydrin foam C41ECH and Viton sponge covering the low-seating-stress cases. Item 4 locks the listed grade where a designation applies. The output is a family and grade direction with the TDS attached, a footprint and thickness proposal, and a quote.
What happens after you send it
- Drawing review. Typically opened the same business day; the response is either a material direction or the specific missing items.
- Material direction and quote. Family, grade, construction, and converting plan, with grade data cited to the manufacturer's TDS and immersion data checked against your fluid per ASTM D471 / F146.
- Samples. Typically 3 to 5 business days for common die-cut configurations on materials we keep on hand, so the joint can be compression-checked on real hardware.
- Production. Standard production runs about two weeks after drawing approval, on flatbed die-cutting or CNC waterjet for thick cork and elastomer sheet; special orders are quoted to the job. MOQ varies by material and part.
Documentation available on request: material technical data sheet, certificate of conformance, lot traceability, and designation paperwork (NSF, FDA, AMS) where the grade carries it, under our ISO 9001:2015 certified quality management system. H-O is a die-cut converter, not a raw-material producer; we do not mold or extrude elastomers in-house, and molded or extruded profiles are coordinated through our partner network.
The mistakes this checklist prevents
| Spec mistake | What it causes | Checklist item that catches it |
|---|---|---|
| Fluid named by category ("oil-resistant") | A petroleum-tuned compound swelling in an ester fluid or bio-diesel blend | Item 1 |
| Room ambient quoted instead of gasket temperature | Hardening and lost recovery at the hot joint; D573 aging surprises | Item 2 |
| Construction defaulted to solid sheet | An under-compressed gasket on a wavy, lightly bolted cover | Item 3 |
| "Food-grade-looking" material in a listed duty | Failed review: the listing, not the durometer, is what the inspector verifies | Item 4 |
| Legacy brand callout left unexamined | A retired house code nobody can source; engineering cross-references on properties instead | Item 6 |
Frequently asked questions
Can H-O cross-reference the gasket material on my legacy transformer print?
Usually, yes. Legacy prints often call out cork or nitrile by a long-retired brand or house code. Send the print: engineering matches on the properties that drive the joint (construction, durometer or compressibility class, fluid duty, and any designation) and proposes the closest current grade with its TDS. It is an engineering cross-reference, not a guaranteed drop-in; where the legacy callout is ambiguous, we ask for the fluid and flange detail rather than guess.
Do you need a finished CAD model, or is a sketch enough to start?
A dimensioned sketch with the bolt pattern, the gasket footprint, and the compressed thickness is enough to open the review. The production die ultimately wants a clean DXF or STEP outline, but the material direction and most of the engineering feedback do not wait for it. A sample part works too; send what exists and the response will list what the final drawing still needs.
What if I do not know the available seating stress?
Send the bolt pattern (size, count, spacing) and the cover construction instead; engineering can estimate the seating regime well enough to pick between cork-elastomer, solid sheet, and reinforced constructions. The honest version of this estimate matters: a gasket that needs more seating stress than the joint can deliver leaks regardless of chemistry.
Can one drawing cover gaskets in different fluids on the same equipment?
Yes, and it should, as long as each gasket line item names its own fluid and temperature. Equipment commonly mixes zones: a mineral-oil cover, a diesel-exposed enclosure strip, and a wash-down-exposed junction can sit on one machine and take three different families. Listing them on one drawing with per-item fluids lets the review keep the families straight and the kit ship as one order.
Send the checklist, get a fluid-seal quote
Attach the drawing and as many of the six items as you have. Drawing review typically starts the same business day.
Samples typically 3 to 5 business days; production about two weeks; MOQ varies by material and part. Expedited service available.
Family-owned in Winsted, Connecticut since 1971 · ISO 9001:2015 certified · OEMs worldwide send us a drawing — and get back their part.
Related reading
ApplicationOil-Filled Equipment & Chemical SealingRead →
Sub-applicationRefrigerant, Oil & Coolant SealingRead →
GuideRubberized Cork vs. Nitrile vs. FKM: Choosing a Gasket for Oil-Filled and Chemical-Exposed EquipmentRead →
GuideWhy Transformer Cover Gaskets Weep Years After the Leak Test: Fluid Aging per ASTM D471Read →
IndustryElectromechanical & Switchgear hubRead →
Request a quote for your chemical & oil fluid 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 (effect of liquids); ASTM F146 (gasket-sheet fluid resistance); ASTM F36 (compressibility and recovery); ASTM D573 (heat aging); ASTM D1056 (flexible cellular rubber).
- NSF/ANSI 61 and NSF/ANSI 372 (drinking-water components); FDA 21 CFR 177.2600; AMS 3215 / AMS 3216 / MIL-R-83248 / AMS7257 (designation language for spec-driven drawings).
- Manufacturer technical data sheets on file for the cork, NBR, CI nitrile, HNBR, FKM, FFKM, ePTFE, epichlorohydrin, and NSF EPDM grades named on the parent application page.
This checklist supports a quotation workflow; it does not constitute design guidance for any specific joint. Grade-level values are confirmed on the manufacturer's current technical data sheet; compliance listings belong to the listed material, and equipment-level outcomes belong to the tested assembly. All parts are custom manufactured to order; minimum production run quantities vary by material and part. H-O is a die-cut converter, not a raw-material producer.