Datasheet dimensions and outline drawings¶

A datasheet (equipment/datasheets/<TAG>.yaml, cheme schema datasheet) states the item's main dimensions, weights, materials per part and nozzle schedule in typed, optional fields, and comes with a generated outline drawing equipment/datasheets/<TAG>.svg. Every field is optional: a datasheet written before them validates unchanged.

Module	Holds
`domains/equipment/schemas/datasheet.py`	`DatasheetDimensions` (with `Support`, `ColumnSection`, `Tubes`, `Plates`, `Baseplate`), `Weights`, `Material` and its `MaterialClass`, the nozzle schedule fields of `DatasheetNozzle`
`domains/equipment/outline.py`	`outline(sheet) -> Outline` (the main sizes in metres, the drawing family), `derived_dimensions(item, model) -> (dimensions, weights)` (what the equipment list and the layout model state), `kind_of`, `head_depth`
`domains/equipment/drawing.py`	`render_outline(sheet, meta, source) -> str` (the SVG), `title_meta(config)`
`domains/equipment/datasheets.py`	the checks (`dimension_findings`, `nozzle_findings`, `drawing_findings`), `drawing_states`, `datasheet_gate`, `field_counts`
`domains/equipment/dimensions.py`	the tolerances, shared with the equipment-list check against the P&ID sizing attributes (`size_problems`)
`project/datasheets.py`	`drawings(root, tags, write)`, `datasheet_report(root)` (the viewer's index and entries), `nozzles_of(models)`
`interfaces/cli/datasheets.py`	`cheme datasheets drawing [--tag] [--write \\| --check \\| --print]`, `cheme datasheets fill --dimensions`

The fields¶

Every value is a number, text or {value, unit, assumed, source} (and may be TBD, supplier or not_applicable like any other datasheet value). Lengths are in m unless the unit says mm or cm, weights in t (kg is read too); another unit is cheme.datasheet-unit (warning) and left out of the checks and the drawing.

dimensions:
  orientation: vertical                 # of a round item's axis
  outside_diameter: {value: 4.0, unit: m, source: equipment/equipment-list.yaml dimensions.diameter}
  inside_diameter: {value: 3960, unit: mm, source: DESIGN.md D-061, assumed: true}
  tangent_length: {value: 20.0, unit: m, source: DESIGN.md D-061}
  head: {value: ellipsoidal_2_1, source: equipment/equipment-list.yaml dimensions.head}
  support: {type: skirt, height: {value: 4.0, unit: m, source: D-061}}  # base to bottom tangent
  # an item above grade: support: {type: none, elevation: 20.0, stands_on: C-3101} (an LP column
  #   on the HP column); an internal of another item with no sizes of its own: housed_in: C-3102
  sections:                             # a column: from the bottom tangent line up
    - {id: lower bed, internals: structured packing 250Y, bottom: 1.5, height: 6.0}
  overall_height: {value: 25.0, unit: m, source: equipment/equipment-list.yaml dimensions.height}
  # shell and tube: inside_diameter (shell ID), shell_passes, tubes: {count, outside_diameter,
  #   length, passes, pitch}; plate exchanger: plates: {height, width, count}; machine:
  #   baseplate: {length, width}, shaft_height; a horizontal item or a machine: axis_deg
weights: {empty: 38.0, operating: {value: supplier, unit: t, source: enquiry E-12}, test: TBD}
materials:
  shell: {value: SA-516-70, material_class: carbon_steel, standard: ASME II A}
  packing: SS 304                       # a plain value is still accepted
nozzles:
  - {name: N1, mark: N1, service: Air inlet, dn: 600, rating: PN16, facing: RF, face: side,
     orientation_deg: 180, elevation_m: 7.333, projection_m: 2.6, lines: [AIR-1002]}

material_class is one of carbon_steel, low_temperature_carbon_steel, low_alloy_steel, stainless_steel, duplex_stainless_steel, nickel_alloy, aluminium, copper_alloy, titanium, cast_iron, plastic, fibre_reinforced_plastic, lined_steel, concrete, other: the key the take-off, the LCA and the cost factor can match a part by.

Nozzle locations keep the convention of the layout (orientation_deg from site east, counter-clockwise; elevation_m above the item's base). projection_m is the flange face from the axis (a side nozzle of a vertical item) or from the surface it leaves; axial_m places a nozzle of a horizontal item or a machine along the item's own axis. mark is the drawing's mark when it differs from name.

Draft and fill: only what the files state¶

cheme datasheets draft writes dimensions and weights from the equipment list's dimensions (outside diameter, overall height or length, head and support types, the empty weight) and, where layout/plant-model.yaml exists, the tangent length and support height of its generated shell and a horizontal item's axis direction (axis_deg, the placement's angle). An item placed above grade gets its base elevation (support.elevation, the placement's z) and, when the top of exactly one other model item is at its base under its centre, that item (support.stands_on). housed_in is written by hand (the files do not state it). The model's tangent length and support height are the 3D model's proportions, not a vessel design: they are written assumed: true with a source that says so. Only the empty weight the list gives is written; the gate's require: [weights] asks for the rest.

cheme datasheets fill adds the same to every draft; cheme datasheets fill --dimensions does only that, into final datasheets too. A field is added when the sheet does not have it or rewritten when an earlier fill wrote it (source cheme datasheets fill: ...); a value written by hand, a TBD and a marker are kept, and a final sheet gets no TBD.

The outline drawing¶

cheme datasheets drawing --write writes equipment/datasheets/<TAG>.svg for every valid datasheet whose drawing is not current; --check exits 1 when one is missing or stale; without an option it lists each drawing's state; --print --tag T prints one. The drawing is generated from the datasheet alone (plus the title block fields of plant.yaml): never edit it.

A3 sheet, SVG in sheet millimetres; an elevation and a nozzle orientation (plan) view.
Vertical vessels, columns and tanks: shell, heads by type, skirt, legs or lugs, tangent lines, column sections; side nozzles at their angle and elevation, top and bottom nozzles at their offset. Horizontal vessels and shell-and-tube exchangers: side view on saddles and plan in the item's frame (north arrow from axis_deg). Machines, plate exchangers and anything else: the overall box, baseplate, shaft centre line.
The base line is labelled with what the item stands on (base on C-3101 (+20 m)), its base elevation (base +7.5 m) or base / grade. The schematic saddles (or legs) of a horizontal item move, the least distance, clear of its bottom nozzles.
An item that cannot be drawn says which dimensions. fields are missing, or, with housed_in, that it is housed in that item and has no main dimensions of its own.
The schedule shows the connected lines as the service where a nozzle gives none.
Nozzles at one angle or at one point share a label (N3, N4 270°); a label that would overlap an earlier one steps down, in the order the nozzles are listed.
Dimension lines for the stated dimensions only (* marks an assumed one). A nozzle without a location is in the schedule (marked) but not drawn; an unknown head is drawn flat with a note; saddle positions and nozzle stubs without projection_m are schematic, which the notes say.
The title block names the tag, service, class, plant, project, revision and the datasheet's fingerprint (sha256: of the YAML), not the commit: the drawing stays current across commits that do not change its datasheet. A draft carries a DRAFT marker.
Deterministic: the same datasheet gives the same bytes.

cheme validate reports a drawing that is no longer what its datasheet gives (cheme.datasheet-drawing-stale, warning). A datasheet without a drawing is not reported unless a gate requires it.

Checks¶

All warnings, each naming the datasheet, the line and the item's tag:

cheme.datasheet-dimension-mismatch: a main dimension against the equipment list's dimensions, with the tolerances of domains/equipment/dimensions.py: a size stated twice (outside diameter, an overall size, the empty weight) within SAME (5 %); an inside diameter within DIAMETER (15 %) and not above the outside one; a tangent or tube length between SHORT (50 %) and FIT (105 %) of the overall size; plates not beyond it; head and support types the same.
cheme.datasheet-dimension-layout: against layout/plant-model.yaml: the outside diameter against the model's shell, the overall sizes against the item's box, a tangent or tube length not longer than the model's extent.
cheme.datasheet-nozzle-pid: a datasheet nozzle the P&IDs do not draw on the item, a drawn one the datasheet does not list (once it lists any), a different DN or different lines (only when every P&ID loads).
cheme.datasheet-nozzle-line: a line of a nozzle that the line list does not have (one the P&ID draws there is the lines cross-check's finding).
cheme.datasheet-nozzle-duplicate, cheme.datasheet-unit: a nozzle listed twice, a unit that is not read.
cheme.datasheet-nozzle-layout (as before): nozzle locations against the layout model.

The gate¶

kind: datasheets keeps its meaning (one final, valid datasheet per listed item) and can require more at a stage with require::

- id: datasheets
  title: Datasheets with dimensions, weights and current drawings
  stage: detail
  kind: datasheets
  require: [dimensions, weights, nozzle-schedule, drawing-current]

dimensions: the main dimensions of each item's family: a diameter, the tangent length, head and support type (and the sections of a column); a shell-and-tube's shell ID and tube length, count, OD and passes; a plate exchanger's plate height, width and count; a machine's baseplate and shaft height; anything else an overall height or length. A supplier or not_applicable marker counts as given, a TBD does not.
weights: empty and operating, and the test weight of a vessel, column, tank or shell-and-tube exchanger.
nozzle-schedule: every nozzle with a DN and a face, a side nozzle with its orientation and elevation.
drawing-current: every outline drawing what cheme datasheets drawing writes.

In the viewer API¶

GET /api/datasheets?rev=: {rev, directory, datasheets: [{tag, file, valid, type, service, draft, counts: {assumed, tbd, supplier, not_applicable}, nozzles, has_dimensions, has_weights, drawing, has_drawing, drawing_current, findings: {error, warning, info}}], missing: [tags], source}; 404 without datasheets. GET /api/repo says has_datasheets.
GET /api/datasheets/{tag}?rev=: {rev, tag, file, summary, datasheet (parsed, null when it does not validate), data (the file as JSON), drawing: {file, state, current}, findings, source}.
GET /api/datasheets/{tag}.svg?rev=: the committed drawing (X-Cheme-Drawing: committed, X-Cheme-Drawing-Current: true|false), or the generated one when none is committed or with generated=true (X-Cheme-Drawing: generated); 422 for a datasheet that does not validate.

The findings are computed on a private copy of the revision's inputs (plant.yaml, the equipment and line lists, the layout model, the P&IDs, the datasheets and their drawings) and cached by their blob ids. cheme export-static exports all three for every datasheet; a datasheet whose YAML or drawing an --exclude glob matches is left out, of the index too.