v1.0.0 to v1.1.0
94 added, 173 removed. Audit A to A.
---
name: neqsim-utilities-specification
- version: "1.0.0"
- description: "Utility system specification — steam levels (HP/MP/LP), cooling water (CW supply/return ΔT), instrument air dryness, fuel gas composition, nitrogen purity, demineralized water, refrigeration. USE WHEN: a task requires utility duty consolidation, utility-system sizing, ESG/energy reporting, or selecting between utility levels for a process service. Pairs with neqsim-heat-integration (grand composite curve drives utility level selection) and neqsim-power-generation (HRSG/steam network)."
- last_verified: "2026-04-26"
+ version: "1.1.0"
+ description: "Select and document process utility levels and quality requirements: steam, cooling/heating media, instrument air, fuel gas, nitrogen, water and refrigeration. Use for utility design bases, consumer-to-header allocation and project specification reviews. Use neqsim-utility-design for screening calculations and neqsim-utilities-design-report for the complete report workflow."
+ last_verified: "2026-10-25"
---
- # NeqSim Utilities Specification Skill
-
- Specify and size the seven core utilities every process plant needs:
- **steam, cooling water, instrument air, fuel gas, nitrogen, demin water, refrigeration**.
- Choices are usually decided by the grand-composite curve from [`neqsim-heat-integration`](../neqsim-heat-integration/SKILL.md)
- and constrained by site standards (NORSOK U-001, IOGP S-714).
-
- ## When to Use
-
- - Consolidating heating/cooling duties into utility headers
- - Choosing **between** utility levels (LP vs MP steam, CW vs chilled water)
- - Sizing utility headers and consumers
- - Drafting utility design basis for FEED
- - ESG / energy intensity reporting (kg CO₂ per t product)
-
- Standards: **NORSOK U-001** (utility systems), **NORSOK P-002** (utility design),
- **IOGP S-714**, **ASME PTC 12** (steam quality), **ISA-7.0.01** (instrument air).
-
- ## Utility 1 — Steam (HP / MP / LP)
-
- Typical levels — pick from the grand composite curve:
-
- | Level | Pressure | Saturation T | Service |
- | ----- | --------- | ------------ | ---------------------------------------------------------- |
- | HP | 40–100 barg | 250–310 °C | Driving steam turbines, high-T reboilers |
- | MP | 10–25 barg | 180–225 °C | Reboilers, glycol regen, stripper |
- | LP | 3–6 barg | 130–160 °C | Tracing, deaerator, low-T reboilers |
- | Atmospheric | 0 barg | 100 °C | Heating coils, tank heating |
-
- **Selection rule:** pick the **lowest** level that beats the cold stream by
- ΔTmin + 10 °C margin. Lower steam = cheaper and lets HP go to power generation.
-
- **Sizing inputs:**
- - Total reboiler / heater duty per level
- - Letdown allowance (10–20% spare)
- - Network losses (3–5% per km of header)
-
- **Boiler / HRSG feed water (BFW):**
- - Conductivity < 0.3 µS/cm (per ASME PTC 12)
- - O2 < 7 ppb (deaerator + scavenger like hydrazine or carbohydrazide)
- - Hardness < 0.01 ppm (softener / RO)
-
- ## Utility 2 — Cooling Water
-
- ```
- Q_cool = ṁ_CW × cp × (T_return − T_supply)
- ```
-
- | Parameter | Tropical | Temperate | Arctic |
- | ----------------- | ------------ | ------------ | ------------- |
- | T_supply (°C) | 32 | 25 | 10 |
- | T_return (°C) | 42 | 35 | 25 |
- | ΔT design | 10 | 10 | 15 |
- | Cycles of conc. | 4–6 | 5–7 | 5–7 |
- | Velocity (tube) | 1.5–2.5 m/s | 1.5–2.5 m/s | 1.5–2.5 m/s |
- | Fouling factor | 0.0002 m²K/W | 0.0001 m²K/W | 0.0001 m²K/W |
-
- **Pinch on CW:** cooler outlet T_process must be ≥ T_supply + ΔTmin (typically 8–10 °C);
- otherwise switch to chilled water or air cooler.
-
- **Air coolers** preferred when:
- - Site lacks abundant water
- - Service T > 60 °C (CW would scale)
- - Environmental discharge restricted
-
- ## Utility 3 — Instrument Air (ISA-7.0.01)
-
- | Specification | Value |
- | -------------------- | -------------------------------- |
- | Pressure | 7–9 barg |
- | Dew point | ≤ −40 °C (atmospheric) — keep dry |
- | Particulates | ≤ 40 µm |
- | Oil content | ≤ 1 mg/m³ |
- | Header sizing | Σ users × 1.5 + 25% spare |
- | Receiver volume | 5 min @ peak demand |
- | Backup | N₂ tie-in for emergency |
-
- ## Utility 4 — Fuel Gas
-
- For gas turbines, fired heaters, flare pilots:
+ # NeqSim utilities specification
- | Spec | Typical |
- | -------------------------------- | ----------------------------- |
- | LHV (Wobbe Index variation) | < ±5% of design |
- | Pressure (turbine) | 25–35 barg |
- | H2S content | < 4 ppmv (NORSOK), < 250 mg/Nm³ (general) |
- | Liquid carryover | None — KO drum upstream |
- | C5+ dewpoint margin | ≥ 20 °C above lowest pipeline T |
- | Heating value | 30–50 MJ/Nm³ for natural gas |
+ Define the service conditions a utility must deliver at each consumer before sizing
+ its supply system. Reuse the process design basis and solved cases. Select utility
+ levels with [heat integration](../neqsim-heat-integration/SKILL.md), then use
+ [utility design](../neqsim-utility-design/SKILL.md) for screening calculations.
+ For the full report, load
+ [utilities design report](../neqsim-utilities-design-report/SKILL.md).
- Use NeqSim to build the Wobbe Index calc:
- ```java
- double LHV = fluid.getCombustionEnergy("LHV/MJ/Sm3");
- double SG = fluid.getMolarMass() / 28.96;
- double WI = LHV / Math.sqrt(SG); // Wobbe index
- ```
+ ## Establish the requirement source
- ## Utility 5 — Nitrogen
+ Read the project basis, applicable regulatory requirements, company specifications,
+ consumer datasheets and vendor operating envelopes. Use
+ [standards lookup](../neqsim-standards-lookup/SKILL.md) to verify designations,
+ editions, scope and applicability. Record each requirement's source, identifier,
+ value, unit, operating case, verification status and evidence. Resolve conflicts
+ through the project's documented precedence and deviations process.
- | Service | Purity | Pressure | Notes |
- | ---------------------- | ------------ | -------------- | ------------------------- |
- | Purging / inerting | 99.5% | 7–10 barg | Bulk N₂ ok |
- | Blanketing | 99.9% | 0.05 barg | Tank low-P |
- | Catalyst regen / sour service | 99.99% | 7 barg | Cryogenic / PSA |
- | Instrument backup | 99.5% | 7 barg | Tie-in to IA header |
+ NORSOK P-002 is a candidate process-system basis where adopted by the project;
+ instrument-air quality may invoke ISA-7.0.01 and ISO 8573-1. Applicability and
+ licensed requirements must be checked before assigning limits. Do not identify
+ NORSOK U-001 or IOGP S-714 as generic utility-system specifications, or cite
+ ASME PTC 12 as a general boiler-feedwater quality specification.
- Volume rule for vessel inerting: **5× geometric volume** at atmospheric to reach ≤ 1% O₂.
+ A public catalogue confirms scope and edition, not compliance with unavailable
+ clauses. Keep unavailable requirements as explicit gaps. Do not turn examples,
+ legacy skill tables or a screening model's defaults into mandatory design values.
- ## Utility 6 — Demineralized Water
+ ## Shared consumer and header contract
- | Service | Conductivity | Notes |
- | ------------------------ | -------------- | -------------------- |
- | BFW / HRSG | < 0.3 µS/cm | Mixed-bed polished |
- | Chemical injection make-up | < 1 µS/cm | Two-bed sufficient |
- | Wash water (GBS, sour) | Drinking water | Cl < 250 ppm |
+ For every service, define:
- ## Utility 7 — Refrigeration (Chilled Water / Propane / Mixed Refrigerant)
+ - Consumer tag, supply and return header, battery limits and physical location.
+ - Duty or flow by operating case, including duration and intermittent demand.
+ - Minimum, normal and maximum pressure, temperature and quality at the consumer;
+ distinguish these from generation conditions and mechanical design conditions.
+ - Required availability, allowable interruption, startup needs and loss-of-utility
+ response, with their requirement sources.
+ - Distribution losses, elevation and pressure drop; supply/return interactions;
+ monitoring, sampling and control requirements.
- When CW can't reach the temperature target:
+ State absolute pressure as bara and gauge pressure as barg. Convert only using an
+ explicit reference atmospheric pressure. State gas reference temperature, absolute
+ pressure, dry/wet basis and compressibility convention before using standard-volume
+ flows; do not assume `Nm3/h` and `Sm3/h` are interchangeable. Distinguish actual
+ volume, standard volume, mass and molar flow. Preserve the source unit and record
+ any conversion method. Missing demand is unknown, never an assumed zero.
- | Service | Temp range | Refrigerant |
- | ---------------- | ---------- | ------------------------------ |
- | Chilled water | 5–15 °C | NH₃ or absorption chiller |
- | Propane | −40 to 0 °C | C3 cycle (LNG, NGL recovery) |
- | Cascade / MR | < −40 °C | C3-MR, DMR (LNG) |
- | LIN / LHE | < −150 °C | Liquid N₂ / He (specialty) |
+ Choose simultaneous operating cases before consolidating loads. Do not sum
+ unrelated individual maxima as a normal demand or apply a universal diversity,
+ spare-capacity or storage factor. Separate continuous, intermittent, startup,
+ shutdown, emergency and future loads. Record every allowance once and justify it.
- For LNG see also [`neqsim-platform-modeling`](../neqsim-platform-modeling/SKILL.md).
+ ## Select levels and quality by service
- ## Pattern 1 — Utility Duty Consolidation
+ | Service | Requirements and decisions to establish |
+ |---|---|
+ | Steam and condensate | Define pressure levels from process temperature profiles, heat-integration targets and consumer requirements. Calculate saturation properties at absolute pressure; check superheat, steam quality, pressure losses and condensate backpressure. Include letdown, desuperheating, flash recovery, traps and return contamination. Set approach temperatures and margins from the project basis, not a fixed increment. |
+ | Heating water, hot oil and tracing | Define supply/return temperatures, minimum circulation, fluid properties, freeze protection, thermal stability, expansion and degradation limits. Match the required temperature grade and distinguish recovered heat from fired or electrical input. |
+ | Cooling water, seawater and air cooling | Use site climate and seasonal cases, seawater intake or cooling-tower conditions, material/corrosion constraints and discharge permits. Set return temperatures, allowable pressure drop, fouling and water chemistry from evidence. Check the complete exchanger temperature profile, including approach limits and turndown; do not select cooling medium solely from one process temperature. |
+ | Instrument and plant air | Specify delivery pressure, particles, oil and moisture separately by service and consumer. Distinguish pressure dew point at its stated measurement pressure from atmospheric dew point; never compare them without conversion. Specify quality class and test basis where adopted. Derive receiver autonomy from the essential demand during the defined failure and usable pressure range; include actuator stroking and dryer regeneration. |
+ | Fuel gas | Use the burner/turbine vendor envelope for composition, heating-value basis, Wobbe index, delivery conditions, contaminants and allowable variation. State LHV versus HHV, reference conditions and relative-density basis. Evaluate water/hydrocarbon dew points across the pressure-temperature envelope, liquid separation, filtration, heating and supply interruptions. No universal H2S limit, Wobbe tolerance or dew-point margin is assumed. |
+ | Nitrogen | Define oxygen concentration and other contaminants, purity convention, dryness, pressure and availability for each purge, inerting or blanketing service. Derive the oxygen target from the material and operating conditions, and validate the purge method, mixing/displacement assumption, leakage and measurement endpoint. Do not prescribe a universal vessel-volume multiplier. Assess supply method, storage and oxygen-deficiency hazards. |
+ | Water systems | Keep potable, service, demineralized, boiler-feed and cooling-water requirements separate. Define quality from duty, boiler pressure/regime, OEM requirements, metallurgy, corrosion/scale control and applicable health/discharge rules. State conductivity reference temperature and concentration bases. Do not prescribe a universal conductivity, dissolved-oxygen limit or chemical-treatment recipe. |
+ | Refrigeration | Select the medium/cycle against required temperature profiles, climate, refrigerant properties, safety and environmental restrictions. Check evaporator/condenser approaches, heat rejection, operating envelope and part-load performance. Identify a Carnot-fraction estimate as screening rather than a simulated or vendor-qualified cycle. |
- ```java
- double Q_HP_steam = 0, Q_MP = 0, Q_LP = 0, Q_CW = 0, Q_air = 0;
- for (ProcessEquipmentInterface eq : process.getUnitOperations()) {
- if (eq instanceof Heater) {
- double T = ((Heater) eq).getOutletStream().getTemperature("C");
- double Q = ((Heater) eq).getDuty();
- if (T > 200) Q_HP_steam += Q;
- else if (T > 130) Q_MP += Q;
- else Q_LP += Q;
- } else if (eq instanceof Cooler) {
- double T = ((Cooler) eq).getOutletStream().getTemperature("C");
- double Q = ((Cooler) eq).getDuty();
- if (T > 60) Q_air += Q; // air-cooled
- else Q_CW += Q; // CW
- }
- }
- ```
+ Do not automatically connect nitrogen to instrument air. Any backup connection
+ needs an engineered change covering equipment compatibility, asphyxiation,
+ backflow prevention, pressure control and the project's safety requirements.
- ## Pattern 2 — Utility Cost Allocation
+ For firewater, drains, vents/flare, electrical supply and other utility interfaces,
+ load the relevant specialist skill and use the agreed interface conditions.
+ Do not infer their adequacy from a heat-duty roll-up.
- ```
- $/yr = duty × hours × $/kWh
- ```
+ ## Check sizing hand-off and economics
- Typical Norwegian indicative numbers (escalate / replace per project):
+ Pass the selected levels, source requirements and simultaneous case loads to
+ `@utility-design`. Keep raw process heat and shaft-work signs distinct from
+ positive utility consumption. Confirm current NeqSim API signatures and units
+ before extracting duties. Identify internal heat recovery so neither recovered
+ heat nor utility generation is counted twice.
- | Utility | $/MWh |
- | ---------------------- | --------- |
- | HP steam | 25 |
- | MP steam | 22 |
- | LP steam | 18 |
- | Cooling water | 0.5 |
- | Air cooling (fans) | 1.5 (electricity only) |
- | Refrigeration (propane) | 50–80 |
- | Electricity | 70–100 |
+ For liquid thermal utilities, use the enthalpy rise across supply/return conditions
+ for mass-flow calculations. A constant heat-capacity approximation needs a stated
+ range and justification. Check quality and temperature feasibility before accepting
+ a calculated flow.
- ## Common Mistakes
+ Use sourced tariffs, fuel/emission factors, currency, price date and case durations
+ for annual cost and emissions. Distinguish thermal energy, shaft power and
+ purchased electrical energy, including stated efficiencies. Do not multiply every
+ peak load by full-year hours or count internal transfer energy as purchased energy.
- | Mistake | Fix |
- | -------------------------------------------------------- | -------------------------------------------------------------------- |
- | Single steam level for all heating | At least HP + LP — saves 10–25% energy via pinch |
- | CW return T close to wet-bulb | Cooling tower can't approach wet-bulb closer than 3–5 °C |
- | Sizing IA at peak demand only | Add 25% spare + receiver for valve-stroke transients |
- | Fuel gas spec without Wobbe | Burners care about Wobbe, not just LHV — vary composition tests it |
- | N₂ purge based on volume × 1 | Need 4–5 displacements to reach 99% inerting (well-mixed assumption) |
- | Demin water spec'd as drinking water | BFW conductivity < 0.3 µS/cm — drinking water is 100–500 |
+ ## Acceptance and hand-off
- ## Validation Checklist
+ - Link each consumer to one identified service/header and all applicable cases.
+ - Reconcile utility levels with temperature feasibility and consumer delivery limits.
+ - Identify source requirements and explain each unresolved or conflicting value.
+ - Keep project allowances, demand diversity, standby capacity and storage separate.
+ - Show quality and capacity checks at the limiting consumer, including loss cases.
+ - Record costs/emissions only with their assumptions and evidence.
+ - Hand over the specification register, source references, case loads and open gaps
+ to [utilities design report](../neqsim-utilities-design-report/SKILL.md).
- - [ ] Each consumer linked to a utility level / supply
- - [ ] Steam levels chosen against grand composite curve
- - [ ] CW ΔT fits site climate (10 °C temperate, 15 °C arctic)
- - [ ] IA dryness ≤ −40 °C dew point in design basis
- - [ ] Fuel-gas Wobbe variation within burner tolerance
- - [ ] Utility load summary in `results.json` under `utilities` with duty + cost
- - [ ] CO₂ intensity calculated for project ESG metric
+ Use readiness labels consistent with the main process report. Screening estimates
+ and unconfirmed requirements cannot establish detailed-design adequacy or standards
+ compliance.
- ## Related Skills
+ ## Related skills
- - [`neqsim-heat-integration`](../neqsim-heat-integration/SKILL.md) — pinch dictates utility levels
- - [`neqsim-power-generation`](../neqsim-power-generation/SKILL.md) — HRSG / steam network
- - [`neqsim-emissions-environmental`](../neqsim-ccs-hydrogen/SKILL.md) — CO₂ from utility fuel
+ - [Heat integration](../neqsim-heat-integration/SKILL.md)
+ - [Utility design](../neqsim-utility-design/SKILL.md)
+ - [Power generation](../neqsim-power-generation/SKILL.md)
+ - [Standards lookup](../neqsim-standards-lookup/SKILL.md)
+ - [Utilities design report](../neqsim-utilities-design-report/SKILL.md)