# Tri-clamp diaphragm membrane: flat, 1.5 and 2 in clamped size

> What size membrane does a 2 inch tri-clamp diaphragm need?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: ISO 2852 Type B gasket section for the clamped ring (bead 5.5 to the groove diameter, web 1.7), ASME BPE bore for the free span; free-span thickness and stretch are design values
- Page: https://xemstudio.com/objects/tri-clamp-diaphragm-membrane/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-diaphragm-membrane · Plain text: https://xemstudio.com/objects/tri-clamp-diaphragm-membrane/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- The membrane is drawn flat, as it sits at mid-stroke. Outside the bore it has the Type B gasket section, so it is clamped like a gasket: bead 5.5 thick from the bore out to the groove diameter (Ø43.5 / Ø56.5), web 1.7 out to flange − 1. Inside the bore it is a 1.0 mm free span.
- Free span: from the centre-disc edge to the bore, 8.90 mm (1.5 in, Ø17 disc) and 13.75 mm (2 in, Ø20 disc). At the design stroke the span forms a cone of 29.3° / 28.6° and stretches 14.7 / 13.9 %.
- Swept volume with a rigid centre disc is the frustum between the disc edge and the bore: V = s · π/3 · (R² + R r + r²); see the table.
- Three Ø2.4 holes for the M2 screws that clamp the centre and backing discs.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| bead | 5.5 thick, Ø34.8–Ø43.5 / Ø47.5–Ø56.5 | face recesses of the ferrule and the head (ISO 2852 Type B section) | clamp | membrane-* |
| web | 1.7 | between the two lands | clamp | membrane-* |
| free span | Ø34.8 / Ø47.5 × 1.0 | moves with the centre disc | designed | membrane-* |
| screw holes | 3 × Ø2.4 | M2 screws | designed | membrane-* |

## Sizes

| size_in | od_mm | bead_to_mm | free_span_dia_mm | free_t_mm | bead_mm | web_mm | disc_dia_mm | annulus_mm | stroke_mm | cone_deg | stretch_pct | swept_ml |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2 | 63.0 | 56.5 | 47.5 | 1.0 | 5.5 | 1.7 | 20.0 | 13.75 | 15.0 | 28.6 | 13.9 | 14.16 |
| 1.5 | 49.5 | 43.5 | 34.8 | 1.0 | 5.5 | 1.7 | 17.0 | 8.9 | 10.0 | 29.3 | 14.7 | 5.48 |

## Where the files are

- ISO (via iTeh sample): [ISO 2852 clamp liners: face profile and flange / groove diameters](https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf) — PDF — standard excerpt; dimensions are facts
- ASME: [BPE Bioprocessing Equipment (clamp fitting dimensions, tube OD and wall)](https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment) — standard — ASME; dimensions are facts (verify at link)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/tri-clamp-diaphragm-membrane/index.json

- membrane-2in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-diaphragm-membrane/membrane-2in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-diaphragm-membrane/membrane-2in.stl) — 2 in flat membrane: Ø63 OD, Type B bead 5.5 thick from Ø47.5 to Ø56.5, web 1.7 out to the OD, free span Ø47.5 × 1.0, 3 × Ø2.4 on Ø13
- membrane-1.5in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-diaphragm-membrane/membrane-1.5in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-diaphragm-membrane/membrane-1.5in.stl) — 1.5 in flat membrane: Ø49.5 OD, Type B bead 5.5 thick from Ø34.8 to Ø43.5, web 1.7 out to the OD, free span Ø34.8 × 1.0, 3 × Ø2.4 on Ø12

## Questions

**How much volume does a 2 in tri-clamp diaphragm sweep?**

14.16 mL at 15 mm stroke with the Ø20 centre disc (frustum between Ø20 and Ø47.5).

**Why is the membrane drawn flat?**

That is its shape at mid-stroke; at the ends of the stroke the free span is a shallow cone either side.

## Fits with

- [Tri-clamp diaphragm head: 1.5 and 2 in, membrane in place of the gasket](https://xemstudio.com/objects/tri-clamp-diaphragm-head/)
- [Tri-clamp diaphragm centre disc and backing disc: 1.5 and 2 in](https://xemstudio.com/objects/tri-clamp-diaphragm-disc/)
- [Tri-clamp gasket, ISO 2852 Type B: 1.5 and 2 in](https://xemstudio.com/objects/tri-clamp-gasket/)
- [Tri-clamp clamp, two-bolt: every flange size ½ to 4 in](https://xemstudio.com/objects/tri-clamp-clamps/)