Use Case: Instrumentation Arrangements

Reusable, parametric instrument loops — level clusters and inline flowmeter compounds

Shipped-library note: These instrument arrangements are illustrative authoring patterns, not separately shipped templates. The shipped sewage-pumping-station template builds equivalent level clusters, flow compounds and discharge pressure transmitters inline (see its build() in the Overview). Use the patterns here to learn how to model instrument loops with the SDK.

Instrument arrangements are small but fiddly: a level measurement isn't just a transmitter, it's a primary element, a transmitter, often a high-high float backup and a duty float, each with the right signal lines and tags. Modelling them as reusable patterns means the whole cluster drops in correctly every time — and a station template (see Pumping Stations) can place them consistently.

Template	Level	Slug	Role
Level Instrument Cluster	0	level-instrument-cluster	Primary level element + transmitter + optional float backups
Inline Flowmeter Compound	0	flowmeter-compound-inline	Flowmeter on a pipe run with isolation, optional bypass + drain

---

Level 0: Level Instrument Cluster

A complete level-measurement point for a wet well or tank: a primary element, its transmitter, and optional independent float switches for high-high alarm and duty start/stop.

Parameters

Parameter	Type	Default	Options
primary_type	enum	ultrasonic	ultrasonic, radar, submersible-pressure
include_hh_float	boolean	true	independent high-high float switch
include_duty_float	boolean	true	duty start/stop float switch
tag_prefix	string	IPS01	e.g. IPS01LT

Layout

   ╔═══╗  LE   primary element (mounted above liquid)
   ║LE ║       primary_type → ultrasonic | radar | submersible-pressure
   ╚═╤═╝
     │ signal
   ( LT )      transmitter (instrument-transmitter-circle)
     │
   ─ ─ ─ ─ ─ ─ ─ ─ liquid surface ─ ─ ─ ─ ─
     ○ HH float    (include_hh_float)   → high-high alarm, independent of LT
     ○ duty float  (include_duty_float) → pump start/stop backup

What the code does

build: (p, ctx) => {
  const levelElement     = ctx.place('instrument-level-element',      { at: [0, 0], tag: `${p.tag_prefix}LE`, props: { instrument_type: p.primary_type } });
  const levelTransmitter = ctx.place('instrument-transmitter-circle', { at: [0, 2], tag: `${p.tag_prefix}LT`, props: { function_letter: 'LT', output: '4-20mA HART' } });

  // Signal line from the primary element to its transmitter (interface-ref form)
  ctx.connect({ symbol: levelElement, port: 'signal_out' }, { symbol: levelTransmitter, port: 'signal_in' });

  ctx.when(p.include_hh_float, () => {
    ctx.place('instrument-float-switch', { at: [3, 4], tag: `${p.tag_prefix}LSHH` });
  });
  ctx.when(p.include_duty_float, () => {
    ctx.place('instrument-float-switch', { at: [3, 5], tag: `${p.tag_prefix}LSL` });
  });
},

Variations from one template

Scenario	Parameters	Result
Standard wet-well level	defaults	Ultrasonic LE + LT + HH float + duty float
Foaming / scummy surface	primary_type = radar	Radar primary element (immune to foam blanket)
Submerged installation	primary_type = submersible-pressure	Hydrostatic pressure element
Continuous-only (no floats)	include_hh_float = false, include_duty_float = false	LT only — floats covered elsewhere

The independent float switches matter for functional safety: the HH float is a separate sensing path from the continuous LT, so a single transmitter failure can't disable high-level protection.

---

Level 0: Inline Flowmeter Compound

A metered section of pipe: upstream/downstream isolation, the flowmeter itself, an optional bypass (Bauer/coupling), and an optional downstream drain — the full "compound" you'd build around any in-line flow element.

Parameters

Parameter	Type	Default	Options
pipe_size	dimension	DN150	DN50 – DN600
pipe_material	enum	DI	DI, uPVC, SS316, HDPE
flowmeter_type	enum	electromagnetic	electromagnetic, ultrasonic-inline, vortex
include_bauer	boolean	true	quick-release bypass coupling for removal
include_drain_ds	boolean	true	downstream drain point
drain_size	enum	3/4" BSP	1/2", 3/4", 1" BSP
iso_valve_type	enum	gate	gate, butterfly, ball
tag_prefix	string	IPS01	e.g. IPS01FE / IPS01FT

Layout

  west ──[ISO]──┬── (FE) flow element ──(FT) transmitter ──[ISO]──┬── east
                │                                                  │
              [bypass]  (include_bauer)                         [drain] (include_drain_ds)
                                                                  ▼

What the code does

build: (p, ctx) => {
  const main = ctx.pipe('main', { size: p.pipe_size, material: p.pipe_material });
  ctx.route(main, [[0, 0], [18, 0]]);

  // Upstream isolation (valve family is parametric), placed inline on the main
  ctx.place(`valve-${p.iso_valve_type}-standard`, { at: [3, 0], on: main, tag: `${p.tag_prefix}V_01` });

  // Optional removal bypass, teed off the main (branch requires `at`)
  ctx.when(p.include_bauer, () => {
    ctx.branch(main, {
      at: [5, 0], direction: 'south', size: p.drain_size,
      components: [{ symbol: 'valve-bauer-coupling', tag: `${p.tag_prefix}V_02`, offset: [0, 2] }],
      terminator: { label: 'DRAIN' },
    });
  });

  // The metering pair: flow element (inline) + transmitter bubble (above), joined by a signal line
  const fe  = ctx.place('instrument-flow-element',       { at: [9, 0],  on: main, tag: `${p.tag_prefix}FE_01`, props: { instrument_type: p.flowmeter_type } });
  const fit = ctx.place('instrument-transmitter-circle', { at: [9, -3],           tag: `${p.tag_prefix}FIT_01`, props: { function_letter: 'FIT', output: '4-20mA HART' } });
  ctx.connect({ symbol: fe, port: 'signal_out' }, { symbol: fit, port: 'signal_in' });

  // Downstream isolation
  ctx.place(`valve-${p.iso_valve_type}-standard`, { at: [15, 0], on: main, tag: `${p.tag_prefix}V_03` });

  // Optional downstream drain
  ctx.when(p.include_drain_ds, () => {
    ctx.branch(main, {
      at: [13, 0], direction: 'south', size: p.drain_size,
      components: [{ symbol: 'valve-gate-standard', tag: `${p.tag_prefix}V_04`, offset: [0, 2] }],
      terminator: { label: 'DRAIN' },
    });
  });
},

Variations from one template

Scenario	Parameters	Result
Standard mag-flow on a rising main	defaults	Mag flowmeter, gate isolation, bypass + drain
Clean-water trunk main	flowmeter_type = ultrasonic-inline, iso_valve_type = butterfly	Clamp/inline US meter, butterfly isolation
Steam / gas service	flowmeter_type = vortex	Vortex meter
No-bypass tight install	include_bauer = false	Meter without removal spool

Variation — valve family. As in the manifold, iso_valve_type interpolates the symbol id (valve-${p.iso_valve_type}-standard), so the whole compound's isolation switches between gate / butterfly / ball in one parameter.

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Composing instruments into larger templates

These Level-0 instrument templates aren't only standalone — the Level-1 Inlet Pumping Station composes the level cluster in the wet well and the flowmeter compound on the rising main through their interface points (process_in / process_out and signal_out). Author the loop once; reuse it inside every station and treatment block.

Try it

1. Templates → Gallery → Common Arrangements → pick Level Instrument Cluster or Inline Flowmeter Compound → Place
2. Set primary_type / flowmeter_type and toggle the float / bypass / drain options
3. The loop drops in fully tagged and wired; connect its interface points to your pipe run or vessel

Related topics

• Drawing Templates Overview
• Template Language Reference — every param.* and ctx.* signature used above
• Pumping Stations — composes these instrument arrangements
• Building Process Diagrams

References

1. BS 1646 — symbolic representation for process measurement and control
2. BS 1553 — general engineering / pipework symbols
3. Independent high-level float vs. continuous transmitter (functional-safety separation)