# Deck-hung caisson

Deck-hung caisson for seawater lift, produced-water disposal or open-drain sump service: large-bore hollow pipe hung off a gusseted collar on the deck, blind top cover with lifting lug, padded side inlet (port inlet) and a vent nozzle (port vent), guide clamps with stand-off brackets back to jacket steel at −Z, stand-off anodes and a slotted open bottom. Origin on the caisson axis at deck level (y = 0); it rises stickUp above the deck and hangs `length` below it (intended, like a jacket).

**Standards:** ISO 19902, NORSOK P-001, ASME B16.5, DNV-RP-B401

## Installation

```bash
npx -y https://decktwin.com/cli/deck-twin-0.2.2.tgz add caisson
```

Copies `structure/caisson.tsx`, any helper files it imports and the shared `lib/` into `src/components/deck-twin/`. Needs `three`, `@react-three/fiber` and `@react-three/drei`.

## Usage

```tsx
import { Canvas } from '@react-three/fiber'
import { OrbitControls } from '@react-three/drei'
import { Stage } from './components/deck-twin/lib/stage'
import { Caisson } from './components/deck-twin/structure/caisson'

export default function Scene() {
  return (
    <Canvas shadows camera={{ position: [8, 5, 9], fov: 35 }}>
      <Stage>
        <Caisson />
      </Stage>
      <OrbitControls makeDefault />
    </Canvas>
  )
}
```

## Props

| Prop | Type | Default | Range |
| --- | --- | --- | --- |
| `nps` | `number (NPS, in)` | `24` |  |
| `length` | `number (m)` | `25` | 3 – 60 |
| `stickUp` | `number (m)` | `1.4` | 0.9 – 3 |
| `inletNps` | `number (NPS, in)` | `6` |  |
| `ventNps` | `number (NPS, in)` | `2` |  |
| `rating` | `150 \| 300 \| 600 \| 900 \| 1500 \| 2500` | `150` |  |
| `guideSpacing` | `number (m)` | `8` | 2 – 20 |
| `anodes` | `boolean` | `true` |  |
| `...group` | position, rotation, scale… |  |  |

## Ports

Flange faces in the component's local frame, metres. Origin: centre of the footprint at deck level (y = 0).

| Id | Label | Position | Direction | Size | Class |
| --- | --- | --- | --- | --- | --- |
| `inlet` | Inlet | 0.494, 0.650, 0.000 | 1, 0, 0 | 6" | 150 |
| `vent` | Vent | -0.469, 1.150, 0.000 | -1, 0, 0 | 2" | 150 |

## P&ID

A long vertical pipe or open-bottom vessel hanging from the deck through the sea-level line, with the inlet or pump column entering at the top; labelled as seawater lift, firewater, disposal or sump caisson.

ISO 10628-2 / P&ID convention for deck-hung caissons

Pumps drawn inside it are vertical-turbine-pump or diesel-firewater-pump. A riser is a pipe line (with ESDV) that continues to a subsea pipeline, not an open-ended caisson.

Caisson datasheet / structural drawing (NORSOK P-001, ISO 19902) fields and the props they set:

| Field | Prop |
| --- | --- |
| Caisson size | `nps` |
| Length | `length` |
| Stick-up above deck | `stickUp` |
| Inlet nozzle size | `inletNps` |
| Vent nozzle size | `ventNps` |
| Flange rating | `rating` |
| Guide spacing | `guideSpacing` |
| Anodes | `anodes` |

## Typical suppliers

Fabricated to project specification. The geometry is generic and sized from public standards. It is not vendor CAD.

## Source

`structure/caisson.tsx`. This is the component file only: it imports shared code, so install it with the command above rather than pasting it alone. https://decktwin.com/r/caisson.json has every file.

```tsx
// Deck-hung caisson (seawater lift, disposal or open-drain sump): pipe hung off a gusseted deck collar, flanged side inlet and vent, blind top cover, guide clamps, anodes and a slotted open bottom.
import * as THREE from 'three'
import type { Kit } from '../lib/kit'
import { KitMesh, useKit, type GroupProps } from '../lib/mesh'
import { blindFlange, nozzle } from '../lib/parts'
import { port, type Port } from '../lib/ports'
import { nozzleStandout, pipeOD, type Rating } from '../lib/standards'
import { gusset } from './_steel'

export interface CaissonProps {
  /** caisson pipe size, NPS */
  nps?: number
  /** length below the deck, m */
  length?: number
  /** caisson top above the deck, m */
  stickUp?: number
  inletNps?: number
  ventNps?: number
  rating?: Rating
  /** guide clamp spacing below the deck, m */
  guideSpacing?: number
  anodes?: boolean
}

export const defaults = {
  nps: 24,
  length: 25,
  stickUp: 1.4,
  inletNps: 6,
  ventNps: 2,
  rating: 150 as Rating,
  guideSpacing: 8,
  anodes: true,
}

type P = typeof defaults

function nozzles(p: P) {
  const R = pipeOD(p.nps) / 2
  const yIn = Math.max(0.5, p.stickUp - 0.75)
  const yV = p.stickUp - 0.25
  return {
    R,
    inlet: { base: [R, yIn, 0] as [number, number, number], face: [R + nozzleStandout(p.inletNps, p.rating), yIn, 0] as [number, number, number] },
    vent: { base: [-R, yV, 0] as [number, number, number], face: [-R - nozzleStandout(p.ventNps, p.rating), yV, 0] as [number, number, number] },
  }
}

export function ports(props: CaissonProps = {}): Port[] {
  const p = { ...defaults, ...props } as P
  const n = nozzles(p)
  return [
    port('inlet', 'Inlet', n.inlet.face, [1, 0, 0], p.inletNps, p.rating),
    port('vent', 'Vent', n.vent.face, [-1, 0, 0], p.ventNps, p.rating, 'vent'),
  ]
}

export function Caisson(props: CaissonProps & GroupProps) {
  const { nps, length, stickUp, inletNps, ventNps, rating, guideSpacing, anodes, ...group } = { ...defaults, ...props }
  const data = useKit((k) => build(k, { nps, length, stickUp, inletNps, ventNps, rating, guideSpacing, anodes }), [nps, length, stickUp, inletNps, ventNps, rating, guideSpacing, anodes])
  return (
    <group {...group}>
      <KitMesh data={data} />
    </group>
  )
}

export default Caisson

function build(k: Kit, p: P) {
  const n = nozzles(p)
  const R = n.R
  const od = 2 * R
  const wall = Math.max(0.0127, od * 0.03)
  const top = Math.max(0.9, p.stickUp)
  const bot = -Math.max(3, p.length)
  const mat = 'pipePaint'
  const growth = 'structSteelDark'
  // pipe: painted above the cellar, darker below 3 m under the deck
  k.pipe(mat, [0, top - 0.12, 0], [0, -3, 0], od, wall, 32)
  k.pipe(growth, [0, -3, 0], [0, bot, 0], od, wall, 32)
  // top: weld-neck flange and blind cover with lifting lug
  const face: [number, number, number] = [0, top, 0]
  blindFlange(k, p.nps, p.rating, face, 'y')
  k.cyl(mat, R * 1.25, 0.12, [0, top - 0.06, 0], 'y', 32)
  k.box('structSteel', [0.12, 0.1, 0.02], [0, top + 0.12, 0])
  // hang-off collar on the deck: ring plate and gussets
  k.pipe('structSteel', [0, 0, 0], [0, 0.04, 0], od + 0.5, 0.25 - 0.002, 32)
  for (let i = 0; i < 8; i++) {
    const a = (i / 8) * Math.PI * 2
    const d: [number, number, number] = [Math.cos(a), 0, Math.sin(a)]
    gusset(k, [d[0] * R, 0.04, d[2] * R], d, [0, 1, 0], 0.22, 0.35, 0.016)
  }
  // nozzles
  nozzle(k, { base: n.inlet.base, dir: [1, 0, 0], nps: p.inletNps, rating: p.rating, standout: n.inlet.face[0] - R, pad: pipeOD(p.inletNps) * 1.8 })
  nozzle(k, { base: n.vent.base, dir: [-1, 0, 0], nps: p.ventNps, rating: p.rating, standout: -n.vent.face[0] - R })
  // guide clamps with stand-off brackets to the jacket steel on -Z
  for (let y = -Math.min(p.guideSpacing, 4); y > bot + 1; y -= Math.max(2, p.guideSpacing)) {
    const m = y < -3 ? growth : mat
    k.pipe(m, [0, y - 0.25, 0], [0, y + 0.25, 0], od + 0.06, 0.028, 32)
    k.box('structSteel', [0.3, 0.3, 0.9], [0, y, -R - 0.48])
    k.box('structSteel', [0.4, 0.02, 0.4], [0, y, -R - 0.94])
  }
  // slotted bottom section and a stiffening ring at the open end
  for (let i = 0; i < 12; i++) {
    const a = (i / 12) * Math.PI * 2
    const q = new THREE.Quaternion().setFromAxisAngle(new THREE.Vector3(0, 1, 0), -a)
    for (let j = 0; j < 3; j++) k.box('pipeBore', [0.006, 0.45, 0.07], [Math.cos(a) * (R + 0.001), bot + 0.8 + j * 0.65, Math.sin(a) * (R + 0.001)], q)
  }
  k.pipe(growth, [0, bot, 0], [0, bot + 0.15, 0], od + 0.04, 0.03, 32)
  if (p.anodes)
    for (let y = -6; y > bot + 2; y -= 6) {
      k.rod('aluminium', [R + 0.16, y - 0.6, 0], [R + 0.16, y + 0.6, 0], 0.07, 8)
      for (const s of [-0.5, 0.5]) k.rod('structSteelDark', [R - 0.01, y + s, 0], [R + 0.16, y + s, 0], 0.015, 6)
    }
}
```