{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "tri-clamp-bubbler-gravity-caps",
 "name": "Tri-clamp bubbler gravity caps: measure specific gravity from the lid with two dip tubes",
 "kind": "hardware",
 "category": "Hardware",
 "group": "Sanitary clamp fittings",
 "year": null,
 "question": "How can I measure gravity in a stainless fermenter without a hydrometer inside?",
 "tags": [
  "gravity",
  "specific gravity",
  "bubbler",
  "hydrometer",
  "density",
  "differential pressure",
  "sanitary",
  "tri-clamp",
  "clamp fitting",
  "brewing",
  "homebrew"
 ],
 "aliases": [
  "measure gravity stainless fermenter",
  "bubbler gravity sensor",
  "differential pressure hydrometer",
  "tilt alternative stainless",
  "fermenter density measurement"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 6,
 "url": "https://xemstudio.com/objects/tri-clamp-bubbler-gravity-caps/",
 "sheet_txt": "https://xemstudio.com/objects/tri-clamp-bubbler-gravity-caps/sheet.txt",
 "sheet": {
  "basis": "Xem Studio design: the standard 1½ in solid cap with two Ø4.76 × Ø2.4 tubes whose open ends are a fixed Δh apart, each with a 4 mm hose barb; the method is hydrostatics, Δp = ρ g Δh",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Push a slow trickle of gas (the same gas as the headspace, CO₂) down both tubes; each tube's back-pressure equals the liquid head above its tip. The difference between the two is ρ g Δh, so specific gravity = Δp / (997 × 9.81 × Δh). The fill level and the headspace pressure cancel out, as long as both tips stay under the liquid.",
   "Read the difference with one differential pressure sensor across the two barbs. With Δh 200 mm, water gives 1956 Pa and every 0.001 of gravity adds about 2 Pa, so pick a sensor that resolves 1 Pa or better; a longer Δh gives more signal.",
   "Nothing goes in the vessel but two thin tubes: no floating hydrometer, no radio through stainless steel.",
   "Every clamp face is the ISO 2852 profile used across this site: 2.85 mm rim, flat face with the gasket groove (K 1.6 deep, R3 1.2 bottom, 23° walls, P2 0.8 edges) on C2, 20° back cone. Flange C3 / groove C2 / tube OD × wall, mm: ½–¾ in 25.0 / 20.4 (derived) / 12.7–19.05 × 1.65; 1–1½ in 50.5 / 43.5 / 25.4–38.1 × 1.65; 2 in 64.0 / 56.5 / 50.8 × 1.65; 2½ in 77.5 / 70.5 / 63.5 × 1.65; 3 in 91.0 / 83.5 / 76.2 × 1.65; 4 in 119.0 / 110.0 / 101.6 × 2.11; 6 in 166.9 (6.570 in) / 156.5 / 152.4 × 2.77; 8 in 217.7 (8.570 in) / 207.0 / 203.2 × 2.77; 10 in 268.5 / 261.0 / 254.0 × 3.40; 12 in 319.3 / 311.8 / 304.8 × 3.40."
  ],
  "table": {
   "columns": [
    "deep_tube_in",
    "dh_mm",
    "dp_water_pa",
    "dp_sg_1050_pa",
    "pa_per_0.001_sg"
   ],
   "rows": [
    [
     12,
     100,
     978,
     1027,
     1
    ],
    [
     12,
     150,
     1467,
     1540,
     1
    ],
    [
     12,
     200,
     1956,
     2054,
     2
    ],
    [
     16,
     100,
     978,
     1027,
     1
    ],
    [
     16,
     150,
     1467,
     1540,
     1
    ],
    [
     16,
     200,
     1956,
     2054,
     2
    ]
   ]
  }
 },
 "sheet_text": "Tri-clamp bubbler gravity caps: measure specific gravity from the lid with two dip tubes — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/tri-clamp-bubbler-gravity-caps/  (CC BY 4.0)\nBasis: Xem Studio design: the standard 1½ in solid cap with two Ø4.76 × Ø2.4 tubes whose open ends are a fixed Δh apart, each with a 4 mm hose barb; the method is hydrostatics, Δp = ρ g Δh\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Push a slow trickle of gas (the same gas as the headspace, CO₂) down both tubes; each tube's back-pressure equals the liquid head above its tip. The difference between the two is ρ g Δh, so specific gravity = Δp / (997 × 9.81 × Δh). The fill level and the headspace pressure cancel out, as long as both tips stay under the liquid.\n- Read the difference with one differential pressure sensor across the two barbs. With Δh 200 mm, water gives 1956 Pa and every 0.001 of gravity adds about 2 Pa, so pick a sensor that resolves 1 Pa or better; a longer Δh gives more signal.\n- Nothing goes in the vessel but two thin tubes: no floating hydrometer, no radio through stainless steel.\n- Every clamp face is the ISO 2852 profile used across this site: 2.85 mm rim, flat face with the gasket groove (K 1.6 deep, R3 1.2 bottom, 23° walls, P2 0.8 edges) on C2, 20° back cone. Flange C3 / groove C2 / tube OD × wall, mm: ½–¾ in 25.0 / 20.4 (derived) / 12.7–19.05 × 1.65; 1–1½ in 50.5 / 43.5 / 25.4–38.1 × 1.65; 2 in 64.0 / 56.5 / 50.8 × 1.65; 2½ in 77.5 / 70.5 / 63.5 × 1.65; 3 in 91.0 / 83.5 / 76.2 × 1.65; 4 in 119.0 / 110.0 / 101.6 × 2.11; 6 in 166.9 (6.570 in) / 156.5 / 152.4 × 2.77; 8 in 217.7 (8.570 in) / 207.0 / 203.2 × 2.77; 10 in 268.5 / 261.0 / 254.0 × 3.40; 12 in 319.3 / 311.8 / 304.8 × 3.40.\n\ndeep_tube_in  dh_mm  dp_water_pa  dp_sg_1050_pa  pa_per_0.001_sg\n12  100  978  1027  1\n12  150  1467  1540  1\n12  200  1956  2054  2\n16  100  978  1027  1\n16  150  1467  1540  1\n16  200  1956  2054  2\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- physics: Hydrostatic pressure: Δp = ρ g Δh (two bubbler tubes at a height difference Δh give the density of the liquid between them) — web — physics — https://en.wikipedia.org/wiki/Hydrostatics\n- GW Kent: Tri-clamp fittings guide: tube OD, flange OD and ID per size to 12 in; solid cap thickness — web — publisher's guide; dimensions cited — https://www.gwkent.com/triclamp-guide\n- Rubber Fab: Tri-Clamp gasket dimensional chart: gasket ID, OD and bead diameter per size (2 in bead 2.22 in / 56.50 mm, 1.5 in 1.71 / 43.50, 3 in 3.29 / 83.50) — PDF — maker chart; dimensions are facts [verify license at link] — https://shop.andersonprocess.com/media/assets/product/documents/rubber-fab-tri-clamp-dimensions.pdf\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/tri-clamp-bubbler-gravity-caps/index.json\nAPI: https://xemstudio.com/api/geometry?object=tri-clamp-bubbler-gravity-caps\n",
 "sources": [
  {
   "publisher": "physics",
   "title": "Hydrostatic pressure: Δp = ρ g Δh (two bubbler tubes at a height difference Δh give the density of the liquid between them)",
   "url": "https://en.wikipedia.org/wiki/Hydrostatics",
   "formats": [
    "web"
   ],
   "license": "physics",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "GW Kent",
   "title": "Tri-clamp fittings guide: tube OD, flange OD and ID per size to 12 in; solid cap thickness",
   "url": "https://www.gwkent.com/triclamp-guide",
   "formats": [
    "web"
   ],
   "license": "publisher's guide; dimensions cited",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Rubber Fab",
   "title": "Tri-Clamp gasket dimensional chart: gasket ID, OD and bead diameter per size (2 in bead 2.22 in / 56.50 mm, 1.5 in 1.71 / 43.50, 3 in 3.29 / 83.50)",
   "url": "https://shop.andersonprocess.com/media/assets/product/documents/rubber-fab-tri-clamp-dimensions.pdf",
   "formats": [
    "PDF"
   ],
   "license": "maker chart; dimensions are facts",
   "license_verified": false,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
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  "tolerance_mm": null
 },
 "related": [
  "tri-clamp-brewing-sensor-lids",
  "tri-clamp-dip-tube-caps",
  "tri-clamp-dished-bottom-vessels"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [],
 "faq": [
  {
   "q": "Why two tubes and not one?",
   "a": "One tube measures depth × density, so a level change looks like a gravity change; two tubes a fixed distance apart measure density alone."
  },
  {
   "q": "Which length for a 6 × 18 in vessel?",
   "a": "The 16 in cap: the deep tip sits just above the dished bottom, the shallow tip 100–200 mm higher, both under a normal fill."
  }
 ],
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}